http://github.com/FasterXML/jackson: General data-binding functionality for Jackson: works on core streaming API (FasterXML)
  • Tatu Saloranta 
package com.fasterxml.jackson.databind.util;

import java.io.Closeable;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.*;
import java.util.*;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.PropertyName;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;

public final class ClassUtil
{
    private final static Class<?> CLS_OBJECT = Object.class;

    private final static Annotation[] NO_ANNOTATIONS = new Annotation[0];
    private final static Ctor[] NO_CTORS = new Ctor[0];

    private final static Iterator<?> EMPTY_ITERATOR = Collections.emptyIterator();

    /*
    /**********************************************************
    /* Simple factory methods
    /**********************************************************
     */

    
Since:2.7
/**
     * @since 2.7
     */
    @SuppressWarnings("unchecked")
    public static <T> Iterator<T> emptyIterator() {
        return (Iterator<T>) EMPTY_ITERATOR;
    }

    /*
    /**********************************************************
    /* Methods that deal with inheritance
    /**********************************************************
     */

    
Method that will find all sub-classes and implemented interfaces
of a given class or interface. Classes are listed in order of
precedence, starting with the immediate super-class, followed by
interfaces class directly declares to implemented, and then recursively
followed by parent of super-class and so forth.
Note that Object.class is not included in the list
regardless of whether endBefore argument is defined or not.

Params:
  • endBefore – Super-type to NOT include in results, if any; when
   encountered, will be ignored (and no super types are checked).
Since:2.7
/**
     * Method that will find all sub-classes and implemented interfaces
     * of a given class or interface. Classes are listed in order of
     * precedence, starting with the immediate super-class, followed by
     * interfaces class directly declares to implemented, and then recursively
     * followed by parent of super-class and so forth.
     * Note that <code>Object.class</code> is not included in the list
     * regardless of whether <code>endBefore</code> argument is defined or not.
     *
     * @param endBefore Super-type to NOT include in results, if any; when
     *    encountered, will be ignored (and no super types are checked).
     *
     * @since 2.7
     */
    public static List<JavaType> findSuperTypes(JavaType type, Class<?> endBefore,
            boolean addClassItself) {
        if ((type == null) || type.hasRawClass(endBefore) || type.hasRawClass(Object.class)) {
            return Collections.emptyList();
        }
        List<JavaType> result = new ArrayList<JavaType>(8);
        _addSuperTypes(type, endBefore, result, addClassItself);
        return result;
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static List<Class<?>> findRawSuperTypes(Class<?> cls, Class<?> endBefore, boolean addClassItself) {
        if ((cls == null) || (cls == endBefore) || (cls == Object.class)) {
            return Collections.emptyList();
        }
        List<Class<?>> result = new ArrayList<Class<?>>(8);
        _addRawSuperTypes(cls, endBefore, result, addClassItself);
        return result;
    }

    
Method for finding all super classes (but not super interfaces) of given class,
starting with the immediate super class and ending in the most distant one.
Class itself is included if addClassItself is true.


NOTE: mostly/only called to resolve mix-ins as that's where we do not care
about fully-resolved types, just associated annotations.

Since:2.7
/**
     * Method for finding all super classes (but not super interfaces) of given class,
     * starting with the immediate super class and ending in the most distant one.
     * Class itself is included if <code>addClassItself</code> is true.
     *<p>
     * NOTE: mostly/only called to resolve mix-ins as that's where we do not care
     * about fully-resolved types, just associated annotations.
     *
     * @since 2.7
     */
    public static List<Class<?>> findSuperClasses(Class<?> cls, Class<?> endBefore,
            boolean addClassItself) {
        List<Class<?>> result = new ArrayList<Class<?>>(8);
        if ((cls != null) && (cls != endBefore))  {
            if (addClassItself) {
                result.add(cls);
            }
            while ((cls = cls.getSuperclass()) != null) {
                if (cls == endBefore) {
                    break;
                }
                result.add(cls);
            }
        }
        return result;
    }

    @Deprecated // since 2.7
    public static List<Class<?>> findSuperTypes(Class<?> cls, Class<?> endBefore) {
        return findSuperTypes(cls, endBefore, new ArrayList<Class<?>>(8));
    }

    @Deprecated // since 2.7
    public static List<Class<?>> findSuperTypes(Class<?> cls, Class<?> endBefore, List<Class<?>> result) {
        _addRawSuperTypes(cls, endBefore, result, false);
        return result;
    }

    private static void _addSuperTypes(JavaType type, Class<?> endBefore, Collection<JavaType> result,
            boolean addClassItself)
    {
        if (type == null) {
            return;
        }
        final Class<?> cls = type.getRawClass();
        if (cls == endBefore || cls == Object.class) { return; }
        if (addClassItself) {
            if (result.contains(type)) { // already added, no need to check supers
                return;
            }
            result.add(type);
        }
        for (JavaType intCls : type.getInterfaces()) {
            _addSuperTypes(intCls, endBefore, result, true);
        }
        _addSuperTypes(type.getSuperClass(), endBefore, result, true);
    }

    private static void _addRawSuperTypes(Class<?> cls, Class<?> endBefore, Collection<Class<?>> result, boolean addClassItself) {
        if (cls == endBefore || cls == null || cls == Object.class) { return; }
        if (addClassItself) {
            if (result.contains(cls)) { // already added, no need to check supers
                return;
            }
            result.add(cls);
        }
        for (Class<?> intCls : _interfaces(cls)) {
            _addRawSuperTypes(intCls, endBefore, result, true);
        }
        _addRawSuperTypes(cls.getSuperclass(), endBefore, result, true);
    }

    /*
    /**********************************************************
    /* Class type detection methods
    /**********************************************************
     */

    
Returns:Null if class might be a bean; type String (that identifies
  why it's not a bean) if not
/**
     * @return Null if class might be a bean; type String (that identifies
     *   why it's not a bean) if not
     */
    public static String canBeABeanType(Class<?> type)
    {
        // First: language constructs that ain't beans:
        if (type.isAnnotation()) {
            return "annotation";
        }
        if (type.isArray()) {
            return "array";
        }
        if (Enum.class.isAssignableFrom(type)) {
            return "enum";
        }
        if (type.isPrimitive()) {
            return "primitive";
        }

        // Anything else? Seems valid, then
        return null;
    }
    
    public static String isLocalType(Class<?> type, boolean allowNonStatic)
    {
        /* As per [JACKSON-187], GAE seems to throw SecurityExceptions
         * here and there... and GAE itself has a bug, too
         * Bah. So we need to catch some wayward exceptions on GAE
         */
        try {
            final boolean isStatic = Modifier.isStatic(type.getModifiers());

            // one more: method locals, anonymous, are not good:
            // 23-Jun-2020, tatu: [databind#2758] With JDK14+ should allow
            //    local Record types, however
            if (!isStatic && hasEnclosingMethod(type)) {
                return "local/anonymous";
            }
            /* But how about non-static inner classes? Can't construct
             * easily (theoretically, we could try to check if parent
             * happens to be enclosing... but that gets convoluted)
             */
            if (!allowNonStatic) {
                if (!isStatic && getEnclosingClass(type) != null) {
                    return "non-static member class";
                }
            }
        }
        catch (SecurityException e) { }
        catch (NullPointerException e) { }
        return null;
    }

    
Method for finding enclosing class for non-static inner classes

/**
     * Method for finding enclosing class for non-static inner classes
     */
    public static Class<?> getOuterClass(Class<?> type)
    {
        // as above, GAE has some issues...
        if (!Modifier.isStatic(type.getModifiers())) {
            try {
                // one more: method locals, anonymous, are not good:
                if (hasEnclosingMethod(type)) {
                    return null;
                }
                return getEnclosingClass(type);
            } catch (SecurityException e) { }
        }
        return null;
    }

    
Helper method used to weed out dynamic Proxy types; types that do
not expose concrete method API that we could use to figure out
automatic Bean (property) based serialization.

/**
     * Helper method used to weed out dynamic Proxy types; types that do
     * not expose concrete method API that we could use to figure out
     * automatic Bean (property) based serialization.
     */
    public static boolean isProxyType(Class<?> type)
    {
        // As per [databind#57], should NOT disqualify JDK proxy:
        /*
        // Then: well-known proxy (etc) classes
        if (Proxy.isProxyClass(type)) {
            return true;
        }
        */
        String name = type.getName();
        // Hibernate uses proxies heavily as well:
        if (name.startsWith("net.sf.cglib.proxy.")
            || name.startsWith("org.hibernate.proxy.")) {
            return true;
        }
        // Not one of known proxies, nope:
        return false;
    }

    
Helper method that checks if given class is a concrete one;
that is, not an interface or abstract class.

/**
     * Helper method that checks if given class is a concrete one;
     * that is, not an interface or abstract class.
     */
    public static boolean isConcrete(Class<?> type)
    {
        int mod = type.getModifiers();
        return (mod & (Modifier.INTERFACE | Modifier.ABSTRACT)) == 0;
    }

    public static boolean isConcrete(Member member)
    {
        int mod = member.getModifiers();
        return (mod & (Modifier.INTERFACE | Modifier.ABSTRACT)) == 0;
    }
    
    public static boolean isCollectionMapOrArray(Class<?> type)
    {
        if (type.isArray()) return true;
        if (Collection.class.isAssignableFrom(type)) return true;
        if (Map.class.isAssignableFrom(type)) return true;
        return false;
    }

    public static boolean isBogusClass(Class<?> cls) {
        return (cls == Void.class || cls == Void.TYPE
                || cls == com.fasterxml.jackson.databind.annotation.NoClass.class);
    }

    
Helper method for detecting Java14-added new Record types 
Since:2.12
/**
     * Helper method for detecting Java14-added new {@code Record} types
     *
     * @since 2.12
     */
    public static boolean isRecordType(Class<?> cls) {
        Class<?> parent = cls.getSuperclass();
        return (parent != null) && "java.lang.Record".equals(parent.getName());
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static boolean isObjectOrPrimitive(Class<?> cls) {
        return (cls == CLS_OBJECT) || cls.isPrimitive();
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static boolean hasClass(Object inst, Class<?> raw) {
        // 10-Nov-2016, tatu: Could use `Class.isInstance()` if we didn't care
        //    about being exactly that type
        return (inst != null) && (inst.getClass() == raw);
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static void verifyMustOverride(Class<?> expType, Object instance,
            String method)
    {
        if (instance.getClass() != expType) {
            throw new IllegalStateException(String.format(
                    "Sub-class %s (of class %s) must override method '%s'",
                instance.getClass().getName(), expType.getName(), method));
        }
    }

    /*
    /**********************************************************
    /* Method type detection methods
    /**********************************************************
     */

    
Deprecated:Since 2.6 not used; may be removed before 3.x
/**
     * @deprecated Since 2.6 not used; may be removed before 3.x
     */
    @Deprecated // since 2.6
    public static boolean hasGetterSignature(Method m)
    {
        // First: static methods can't be getters
        if (Modifier.isStatic(m.getModifiers())) {
            return false;
        }
        // Must take no args
        Class<?>[] pts = m.getParameterTypes();
        if (pts != null && pts.length != 0) {
            return false;
        }
        // Can't be a void method
        if (Void.TYPE == m.getReturnType()) {
            return false;
        }
        // Otherwise looks ok:
        return true;
    }

    /*
    /**********************************************************
    /* Exception handling; simple re-throw
    /**********************************************************
     */

    
Helper method that will check if argument is an Error, and if so, (re)throw it; otherwise just return 
Since:2.9
/**
     * Helper method that will check if argument is an {@link Error},
     * and if so, (re)throw it; otherwise just return
     *
     * @since 2.9
     */
    public static Throwable throwIfError(Throwable t) {
        if (t instanceof Error) {
            throw (Error) t;
        }
        return t;
    }

    
Helper method that will check if argument is an RuntimeException, and if so, (re)throw it; otherwise just return 
Since:2.9
/**
     * Helper method that will check if argument is an {@link RuntimeException},
     * and if so, (re)throw it; otherwise just return
     *
     * @since 2.9
     */
    public static Throwable throwIfRTE(Throwable t) {
        if (t instanceof RuntimeException) {
            throw (RuntimeException) t;
        }
        return t;
    }

    
Helper method that will check if argument is an IOException, and if so, (re)throw it; otherwise just return 
Since:2.9
/**
     * Helper method that will check if argument is an {@link IOException},
     * and if so, (re)throw it; otherwise just return
     *
     * @since 2.9
     */
    public static Throwable throwIfIOE(Throwable t) throws IOException {
        if (t instanceof IOException) {
            throw (IOException) t;
        }
        return t;
    }

    /*
    /**********************************************************
    /* Exception handling; other
    /**********************************************************
     */
    
    
Method that can be used to find the "root cause", innermost
of chained (wrapped) exceptions.

/**
     * Method that can be used to find the "root cause", innermost
     * of chained (wrapped) exceptions.
     */
    public static Throwable getRootCause(Throwable t)
    {
        while (t.getCause() != null) {
            t = t.getCause();
        }
        return t;
    }

    
Method that works like by calling getRootCause and then either throwing it (if instanceof IOException), or return. 
Since:2.8
/**
     * Method that works like by calling {@link #getRootCause} and then
     * either throwing it (if instanceof {@link IOException}), or
     * return.
     *
     * @since 2.8
     */
    public static Throwable throwRootCauseIfIOE(Throwable t) throws IOException {
        return throwIfIOE(getRootCause(t));
    }

    
Method that will wrap 't' as an IllegalArgumentException if it is a checked exception; otherwise (runtime exception or error) throw as is 
/**
     * Method that will wrap 't' as an {@link IllegalArgumentException} if it
     * is a checked exception; otherwise (runtime exception or error) throw as is
     */
    public static void throwAsIAE(Throwable t) {
        throwAsIAE(t, t.getMessage());
    }

    
Method that will wrap 't' as an IllegalArgumentException (and with specified message) if it is a checked exception; otherwise (runtime exception or error) throw as is 
/**
     * Method that will wrap 't' as an {@link IllegalArgumentException} (and with
     * specified message) if it
     * is a checked exception; otherwise (runtime exception or error) throw as is
     */
    public static void throwAsIAE(Throwable t, String msg)
    {
        throwIfRTE(t);
        throwIfError(t);
        throw new IllegalArgumentException(msg, t);
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static <T> T throwAsMappingException(DeserializationContext ctxt,
            IOException e0) throws JsonMappingException {
        if (e0 instanceof JsonMappingException) {
            throw (JsonMappingException) e0;
        }
        JsonMappingException e = JsonMappingException.from(ctxt, e0.getMessage());
        e.initCause(e0);
        throw e;
    }

    
Method that will locate the innermost exception for given Throwable; and then wrap it as an IllegalArgumentException if it is a checked exception; otherwise (runtime exception or error) throw as is 
/**
     * Method that will locate the innermost exception for given Throwable;
     * and then wrap it as an {@link IllegalArgumentException} if it
     * is a checked exception; otherwise (runtime exception or error) throw as is
     */
    public static void unwrapAndThrowAsIAE(Throwable t)
    {
        throwAsIAE(getRootCause(t));
    }

    
Method that will locate the innermost exception for given Throwable; and then wrap it as an IllegalArgumentException if it is a checked exception; otherwise (runtime exception or error) throw as is 
/**
     * Method that will locate the innermost exception for given Throwable;
     * and then wrap it as an {@link IllegalArgumentException} if it
     * is a checked exception; otherwise (runtime exception or error) throw as is
     */
    public static void unwrapAndThrowAsIAE(Throwable t, String msg)
    {
        throwAsIAE(getRootCause(t), msg);
    }

    
Helper method that encapsulate logic in trying to close output generator
in case of failure; useful mostly in forcing flush()ing as otherwise
error conditions tend to be hard to diagnose. However, it is often the
case that output state may be corrupt so we need to be prepared for
secondary exception without masking original one.

Since:2.8
/**
     * Helper method that encapsulate logic in trying to close output generator
     * in case of failure; useful mostly in forcing flush()ing as otherwise
     * error conditions tend to be hard to diagnose. However, it is often the
     * case that output state may be corrupt so we need to be prepared for
     * secondary exception without masking original one.
     *
     * @since 2.8
     */
    public static void closeOnFailAndThrowAsIOE(JsonGenerator g, Exception fail)
        throws IOException
    {
        /* 04-Mar-2014, tatu: Let's try to prevent auto-closing of
         *    structures, which typically causes more damage.
         */
        g.disable(JsonGenerator.Feature.AUTO_CLOSE_JSON_CONTENT);
        try {
            g.close();
        } catch (Exception e) {
            fail.addSuppressed(e);
        }
        throwIfIOE(fail);
        throwIfRTE(fail);
        throw new RuntimeException(fail);
    }

    
Helper method that encapsulate logic in trying to close given Closeable in case of failure; useful mostly in forcing flush()ing as otherwise error conditions tend to be hard to diagnose. However, it is often the case that output state may be corrupt so we need to be prepared for secondary exception without masking original one. 
Since:2.8
/**
     * Helper method that encapsulate logic in trying to close given {@link Closeable}
     * in case of failure; useful mostly in forcing flush()ing as otherwise
     * error conditions tend to be hard to diagnose. However, it is often the
     * case that output state may be corrupt so we need to be prepared for
     * secondary exception without masking original one.
     *
     * @since 2.8
     */
    public static void closeOnFailAndThrowAsIOE(JsonGenerator g,
            Closeable toClose, Exception fail)
        throws IOException
    {
        if (g != null) {
            g.disable(JsonGenerator.Feature.AUTO_CLOSE_JSON_CONTENT);
            try {
                g.close();
            } catch (Exception e) {
                fail.addSuppressed(e);
            }
        }
        if (toClose != null) {
            try {
                toClose.close();
            } catch (Exception e) {
                fail.addSuppressed(e);
            }
        }
        throwIfIOE(fail);
        throwIfRTE(fail);
        throw new RuntimeException(fail);
    }

    /*
    /**********************************************************
    /* Instantiation
    /**********************************************************
     */

    
Method that can be called to try to create an instantiate of
specified type. Instantiation is done using default no-argument
constructor.

Params:
  • canFixAccess – Whether it is possible to try to change access
  rights of the default constructor (in case it is not publicly
  accessible) or not.
Throws:
  • IllegalArgumentException – If instantiation fails for any reason;
   except for cases where constructor throws an unchecked exception
   (which will be passed as is)
/**
     * Method that can be called to try to create an instantiate of
     * specified type. Instantiation is done using default no-argument
     * constructor.
     *
     * @param canFixAccess Whether it is possible to try to change access
     *   rights of the default constructor (in case it is not publicly
     *   accessible) or not.
     *
     * @throws IllegalArgumentException If instantiation fails for any reason;
     *    except for cases where constructor throws an unchecked exception
     *    (which will be passed as is)
     */
    public static <T> T createInstance(Class<T> cls, boolean canFixAccess)
        throws IllegalArgumentException
    {
        Constructor<T> ctor = findConstructor(cls, canFixAccess);
        if (ctor == null) {
            throw new IllegalArgumentException("Class "+cls.getName()+" has no default (no arg) constructor");
        }
        try {
            return ctor.newInstance();
        } catch (Exception e) {
            ClassUtil.unwrapAndThrowAsIAE(e, "Failed to instantiate class "+cls.getName()+", problem: "+e.getMessage());
            return null;
        }
    }

    public static <T> Constructor<T> findConstructor(Class<T> cls, boolean forceAccess)
        throws IllegalArgumentException
    {
        try {
            Constructor<T> ctor = cls.getDeclaredConstructor();
            if (forceAccess) {
                checkAndFixAccess(ctor, forceAccess);
            } else {
                // Has to be public...
                if (!Modifier.isPublic(ctor.getModifiers())) {
                    throw new IllegalArgumentException("Default constructor for "+cls.getName()+" is not accessible (non-public?): not allowed to try modify access via Reflection: cannot instantiate type");
                }
            }
            return ctor;
        } catch (NoSuchMethodException e) {
            ;
        } catch (Exception e) {
            ClassUtil.unwrapAndThrowAsIAE(e, "Failed to find default constructor of class "+cls.getName()+", problem: "+e.getMessage());
        }
        return null;
    }

    /*
    /**********************************************************
    /* Class name, description access
    /**********************************************************
     */

    
Since:2.9
/**
     * @since 2.9
     */
    public static Class<?> classOf(Object inst) {
        if (inst == null) {
            return null;
        }
        return inst.getClass();
    }
    
    
Since:2.9
/**
     * @since 2.9
     */
    public static Class<?> rawClass(JavaType t) {
        if (t == null) {
            return null;
        }
        return t.getRawClass();
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static <T> T nonNull(T valueOrNull, T defaultValue) {
        return (valueOrNull == null) ? defaultValue : valueOrNull;
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static String nullOrToString(Object value) {
        if (value == null) {
            return null;
        }
        return value.toString();
    }

    
Since:2.9
/**
     * @since 2.9
     */
    public static String nonNullString(String str) {
        if (str == null) {
            return "";
        }
        return str;
    }

    
Returns either quoted value (with double-quotes) -- if argument non-null
String -- or String NULL (no quotes) (if null).

Since:2.9
/**
     * Returns either quoted value (with double-quotes) -- if argument non-null
     * String -- or String NULL (no quotes) (if null).
     *
     * @since 2.9
     */
    public static String quotedOr(Object str, String forNull) {
        if (str == null) {
            return forNull;
        }
        return String.format("\"%s\"", str);
    }

    /*
    /**********************************************************
    /* Type name, name, desc handling methods
    /**********************************************************
     */

    
Helper method used to construct appropriate description
when passed either type (Class) or an instance; in latter
case, class of instance is to be used.

/**
     * Helper method used to construct appropriate description
     * when passed either type (Class) or an instance; in latter
     * case, class of instance is to be used.
     */
    public static String getClassDescription(Object classOrInstance)
    {
        if (classOrInstance == null) {
            return "unknown";
        }
        Class<?> cls = (classOrInstance instanceof Class<?>) ?
            (Class<?>) classOrInstance : classOrInstance.getClass();
        return nameOf(cls);
    }

    
Helper method to create and return "backticked" description of given resolved type (or, "null" if null passed), similar to return vaue of getClassDescription(Object). 
Params:
  • fullType – Fully resolved type or null
Returns:String description of type including generic type parameters, surrounded
  by backticks, if type passed; or string "null" if {code null} passed
Since:2.10
/**
     * Helper method to create and return "backticked" description of given
     * resolved type (or, {@code "null"} if {@code null} passed), similar
     * to return vaue of {@link #getClassDescription(Object)}.
     *
     * @param fullType Fully resolved type or null
     * @return String description of type including generic type parameters, surrounded
     *   by backticks, if type passed; or string "null" if {code null} passed
     *
     * @since 2.10
     */
    public static String getTypeDescription(JavaType fullType)
    {
        if (fullType == null) {
            return "[null]";
        }
        StringBuilder sb = new StringBuilder(80).append('`');
        sb.append(fullType.toCanonical());
        return sb.append('`').toString();
    }

    
Helper method used to construct appropriate description
when passed either type (Class) or an instance; in latter
case, class of instance is to be used.

Since:2.9
/**
     * Helper method used to construct appropriate description
     * when passed either type (Class) or an instance; in latter
     * case, class of instance is to be used.
     *
     * @since 2.9
     */
    public static String classNameOf(Object inst) {
        if (inst == null) {
            return "[null]";
        }
        Class<?> raw = (inst instanceof Class<?>) ? (Class<?>) inst : inst.getClass();
        return nameOf(raw);
    }

    
Returns either `cls.getName()` (if `cls` not null),
or "[null]" if `cls` is null.

Since:2.9
/**
     * Returns either `cls.getName()` (if `cls` not null),
     * or "[null]" if `cls` is null.
     *
     * @since 2.9
     */
    public static String nameOf(Class<?> cls) {
        if (cls == null) {
            return "[null]";
        }
        int index = 0;
        while (cls.isArray()) {
            ++index;
            cls = cls.getComponentType();
        }
        String base = cls.isPrimitive() ? cls.getSimpleName() : cls.getName();
        if (index > 0) {
            StringBuilder sb = new StringBuilder(base);
            do {
                sb.append("[]");
            } while (--index > 0);
            base = sb.toString();
        }
        return backticked(base);
    }

    
Returns either single-quoted (apostrophe) 'named.getName()' (if named not null), or "[null]" if named is null. 

NOTE: before 2.12 returned "backticked" version instead of single-quoted name; changed
to be compatible with most existing quoting usage within databind

Since:2.9
/**
     * Returns either single-quoted (apostrophe) {@code 'named.getName()'} (if {@code named} not null),
     * or "[null]" if {@code named} is null.
     *<p>
     * NOTE: before 2.12 returned "backticked" version instead of single-quoted name; changed
     * to be compatible with most existing quoting usage within databind
     *
     * @since 2.9
     */
    public static String nameOf(Named named) {
        if (named == null) {
            return "[null]";
        }
        return apostrophed(named.getName());
    }

    
Returns either single-quoted (apostrophe) 'name' (if name not null), or "[null]" if name is null. 
Since:2.12
/**
     * Returns either single-quoted (apostrophe) {@code 'name'} (if {@code name} not null),
     * or "[null]" if {@code name} is null.
     *
     * @since 2.12
     */
    public static String name(String name) {
        if (name == null) {
            return "[null]";
        }
        return apostrophed(name);
    }
    
    
Returns either single-quoted (apostrophe) 'name' (if name not null), or "[null]" if name is null. 
Since:2.12
/**
     * Returns either single-quoted (apostrophe) {@code 'name'} (if {@code name} not null),
     * or "[null]" if {@code name} is null.
     *
     * @since 2.12
     */
    public static String name(PropertyName name) {
        if (name == null) {
            return "[null]";
        }
        // 26-Aug-2020, tatu: Should we consider namespace somehow?
        return apostrophed(name.getSimpleName());
    }

    /*
    /**********************************************************
    /* Other escaping, description access
    /**********************************************************
     */

    
Returns either `text` (backtick-quoted) or [null]. 
Since:2.9
/**
     * Returns either {@code `text`} (backtick-quoted) or {@code [null]}.
     *
     * @since 2.9
     */
    public static String backticked(String text) {
        if (text == null) {
            return "[null]";
        }
        return new StringBuilder(text.length()+2).append('`').append(text).append('`').toString();
    }

    
Returns either 'text' (single-quoted) or [null]. 
Since:2.9
/**
     * Returns either {@code 'text'} (single-quoted) or {@code [null]}.
     *
     * @since 2.9
     */
    public static String apostrophed(String text) {
        if (text == null) {
            return "[null]";
        }
        return new StringBuilder(text.length()+2).append('\'').append(text).append('\'').toString();
    }

    
Helper method that returns Throwable.getMessage() for all other exceptions except for JsonProcessingException, for which getOriginalMessage() is returned instead. Method is used to avoid accidentally including trailing location information twice in message when wrapping exceptions. 
Since:2.9.7
/**
     * Helper method that returns {@link Throwable#getMessage()} for all other exceptions
     * except for {@link JsonProcessingException}, for which {@code getOriginalMessage()} is
     * returned instead.
     * Method is used to avoid accidentally including trailing location information twice
     * in message when wrapping exceptions.
     *
     * @since 2.9.7
     */
    public static String exceptionMessage(Throwable t) {
        if (t instanceof JsonProcessingException) {
            return ((JsonProcessingException) t).getOriginalMessage();
        }
        return t.getMessage();
    }
    
    /*
    /**********************************************************
    /* Primitive type support
    /**********************************************************
     */
    
    
Helper method used to get default value for wrappers used for primitive types
(0 for Integer etc)

/**
     * Helper method used to get default value for wrappers used for primitive types
     * (0 for Integer etc)
     */
    public static Object defaultValue(Class<?> cls)
    {
        if (cls == Integer.TYPE) {
            return Integer.valueOf(0);
        }
        if (cls == Long.TYPE) {
            return Long.valueOf(0L);
        }
        if (cls == Boolean.TYPE) {
            return Boolean.FALSE;
        }
        if (cls == Double.TYPE) {
            return Double.valueOf(0.0);
        }
        if (cls == Float.TYPE) {
            return Float.valueOf(0.0f);
        }
        if (cls == Byte.TYPE) {
            return Byte.valueOf((byte) 0);
        }
        if (cls == Short.TYPE) {
            return Short.valueOf((short) 0);
        }
        if (cls == Character.TYPE) {
            return '\0';
        }
        throw new IllegalArgumentException("Class "+cls.getName()+" is not a primitive type");
    }

    
Helper method for finding wrapper type for given primitive type (why isn't
there one in JDK?)

/**
     * Helper method for finding wrapper type for given primitive type (why isn't
     * there one in JDK?)
     */
    public static Class<?> wrapperType(Class<?> primitiveType)
    {
        if (primitiveType == Integer.TYPE) {
            return Integer.class;
        }
        if (primitiveType == Long.TYPE) {
            return Long.class;
        }
        if (primitiveType == Boolean.TYPE) {
            return Boolean.class;
        }
        if (primitiveType == Double.TYPE) {
            return Double.class;
        }
        if (primitiveType == Float.TYPE) {
            return Float.class;
        }
        if (primitiveType == Byte.TYPE) {
            return Byte.class;
        }
        if (primitiveType == Short.TYPE) {
            return Short.class;
        }
        if (primitiveType == Character.TYPE) {
            return Character.class;
        }
        throw new IllegalArgumentException("Class "+primitiveType.getName()+" is not a primitive type");
    }

    
Method that can be used to find primitive type for given class if (but only if)
it is either wrapper type or primitive type; returns `null` if type is neither.

Since:2.7
/**
     * Method that can be used to find primitive type for given class if (but only if)
     * it is either wrapper type or primitive type; returns `null` if type is neither.
     *
     * @since 2.7
     */
    public static Class<?> primitiveType(Class<?> type)
    {
        if (type.isPrimitive()) {
            return type;
        }
        
        if (type == Integer.class) {
            return Integer.TYPE;
        }
        if (type == Long.class) {
            return Long.TYPE;
        }
        if (type == Boolean.class) {
            return Boolean.TYPE;
        }
        if (type == Double.class) {
            return Double.TYPE;
        }
        if (type == Float.class) {
            return Float.TYPE;
        }
        if (type == Byte.class) {
            return Byte.TYPE;
        }
        if (type == Short.class) {
            return Short.TYPE;
        }
        if (type == Character.class) {
            return Character.TYPE;
        }
        return null;
    }

    /*
    /**********************************************************
    /* Access checking/handling methods
    /**********************************************************
     */

    
Equivalent to call:

  checkAndFixAccess(member, false);



Deprecated:Since 2.7 call variant that takes boolean flag.
/**
     * Equivalent to call:
     *<pre>
     *   checkAndFixAccess(member, false);
     *</pre>
     *
     * @deprecated Since 2.7 call variant that takes boolean flag.
     */
    @Deprecated
    public static void checkAndFixAccess(Member member) {
        checkAndFixAccess(member, false);
    }

    
Method that is called if a Member may need forced access, to force a field, method or constructor to be accessible: this is done by calling AccessibleObject.setAccessible(boolean). 
Params:
  • member – Accessor to call setAccessible() on.
  • force – Whether to always try to make accessor accessible (true),
  or only if needed as per access rights (false)
Since:2.7
/**
     * Method that is called if a {@link Member} may need forced access,
     * to force a field, method or constructor to be accessible: this
     * is done by calling {@link AccessibleObject#setAccessible(boolean)}.
     * 
     * @param member Accessor to call <code>setAccessible()</code> on.
     * @param force Whether to always try to make accessor accessible (true),
     *   or only if needed as per access rights (false)
     *
     * @since 2.7
     */
    public static void checkAndFixAccess(Member member, boolean force)
    {
        // We know all members are also accessible objects...
        AccessibleObject ao = (AccessibleObject) member;

        /* 14-Jan-2009, tatu: It seems safe and potentially beneficial to
         *   always to make it accessible (latter because it will force
         *   skipping checks we have no use for...), so let's always call it.
         */
        try {
            if (force || 
                    (!Modifier.isPublic(member.getModifiers())
                            || !Modifier.isPublic(member.getDeclaringClass().getModifiers()))) {
                ao.setAccessible(true);
            }
        } catch (SecurityException se) {
            // 17-Apr-2009, tatu: Related to [JACKSON-101]: this can fail on platforms like
            // Google App Engine); so let's only fail if we really needed it...
            if (!ao.isAccessible()) {
                Class<?> declClass = member.getDeclaringClass();
                throw new IllegalArgumentException("Cannot access "+member+" (from class "+declClass.getName()+"; failed to set access: "+se.getMessage());
            }
        }
    }

    /*
    /**********************************************************
    /* Enum type detection
    /**********************************************************
     */

    
Helper method that encapsulates reliable check on whether given raw type "is an Enum", that is, is or extends Enum. 
Since:2.10.1
/**
     * Helper method that encapsulates reliable check on whether
     * given raw type "is an Enum", that is, is or extends {@link java.lang.Enum}.
     *
     * @since 2.10.1
     */
    public static boolean isEnumType(Class<?> rawType) {
        return Enum.class.isAssignableFrom(rawType);
    }

    
Helper method that can be used to dynamically figure out enumeration type of given EnumSet, without having access to its declaration. Code is needed to work around design flaw in JDK. 
/**
     * Helper method that can be used to dynamically figure out
     * enumeration type of given {@link EnumSet}, without having
     * access to its declaration.
     * Code is needed to work around design flaw in JDK.
     */
    public static Class<? extends Enum<?>> findEnumType(EnumSet<?> s)
    {
        // First things first: if not empty, easy to determine
        if (!s.isEmpty()) {
            return findEnumType(s.iterator().next());
        }
        // Otherwise need to locate using an internal field
        return EnumTypeLocator.instance.enumTypeFor(s);
    }

    
Helper method that can be used to dynamically figure out enumeration type of given EnumSet, without having access to its declaration. Code is needed to work around design flaw in JDK. 
/**
     * Helper method that can be used to dynamically figure out
     * enumeration type of given {@link EnumSet}, without having
     * access to its declaration.
     * Code is needed to work around design flaw in JDK.
     */
    public static Class<? extends Enum<?>> findEnumType(EnumMap<?,?> m)
    {
        if (!m.isEmpty()) {
            return findEnumType(m.keySet().iterator().next());
        }
        // Otherwise need to locate using an internal field
        return EnumTypeLocator.instance.enumTypeFor(m);
    }

    
Helper method that can be used to dynamically figure out formal
enumeration type (class) for given enumeration. This is either
class of enum instance (for "simple" enumerations), or its
superclass (for enums with instance fields or methods)

/**
     * Helper method that can be used to dynamically figure out formal
     * enumeration type (class) for given enumeration. This is either
     * class of enum instance (for "simple" enumerations), or its
     * superclass (for enums with instance fields or methods)
     */
    public static Class<? extends Enum<?>> findEnumType(Enum<?> en)
    {
        // enums with "body" are sub-classes of the formal type
        return en.getDeclaringClass();
    }

    
Helper method that can be used to dynamically figure out formal
enumeration type (class) for given class of an enumeration value.
This is either class of enum instance (for "simple" enumerations),
or its superclass (for enums with instance fields or methods)

/**
     * Helper method that can be used to dynamically figure out formal
     * enumeration type (class) for given class of an enumeration value.
     * This is either class of enum instance (for "simple" enumerations),
     * or its superclass (for enums with instance fields or methods)
     */
    @SuppressWarnings("unchecked")
    public static Class<? extends Enum<?>> findEnumType(Class<?> cls)
    {
        // enums with "body" are sub-classes of the formal type
        if (cls.getSuperclass() != Enum.class) {
            cls = cls.getSuperclass();
        }
        return (Class<? extends Enum<?>>) cls;
    }

    
A method that will look for the first Enum value annotated with the given Annotation.


If there's more than one value annotated, the first one found will be returned. Which one exactly is used is undetermined.

Params:
  • enumClass – The Enum class to scan for a value with the given annotation
  • annotationClass – The annotation to look for.
Throws:
Returns:the Enum value annotated with the given Annotation or null if none is found.
Since:2.8
/**
     * A method that will look for the first Enum value annotated with the given Annotation.
     * <p>
     * If there's more than one value annotated, the first one found will be returned. Which one exactly is used is undetermined.
     *
     * @param enumClass The Enum class to scan for a value with the given annotation
     * @param annotationClass The annotation to look for.
     * @return the Enum value annotated with the given Annotation or {@code null} if none is found.
     * @throws IllegalArgumentException if there's a reflection issue accessing the Enum
     * @since 2.8
     */
    public static <T extends Annotation> Enum<?> findFirstAnnotatedEnumValue(Class<Enum<?>> enumClass, Class<T> annotationClass)
    {
        Field[] fields = enumClass.getDeclaredFields();
        for (Field field : fields) {
            if (field.isEnumConstant()) {
                Annotation defaultValueAnnotation = field.getAnnotation(annotationClass);
                if (defaultValueAnnotation != null) {
                    final String name = field.getName();
                    for (Enum<?> enumValue : enumClass.getEnumConstants()) {
                        if (name.equals(enumValue.name())) {
                            return enumValue;
                        }
                    }
                }
            }
        }
        return null;
    }

    /*
    /**********************************************************************
    /* Methods for detecting special class categories
    /**********************************************************************
     */

    
Method that can be called to determine if given Object is the default implementation Jackson uses; as opposed to a custom serializer installed by a module or calling application. Determination is done using JacksonStdImpl annotation on handler (serializer, deserializer etc) class. 

NOTE: passing `null` is legal, and will result in true
being returned.

/**
     * Method that can be called to determine if given Object is the default
     * implementation Jackson uses; as opposed to a custom serializer installed by
     * a module or calling application. Determination is done using
     * {@link JacksonStdImpl} annotation on handler (serializer, deserializer etc)
     * class.
     *<p>
     * NOTE: passing `null` is legal, and will result in <code>true</code>
     * being returned.
     */
    public static boolean isJacksonStdImpl(Object impl) {
        return (impl == null) || isJacksonStdImpl(impl.getClass());
    }

    public static boolean isJacksonStdImpl(Class<?> implClass) {
        return (implClass.getAnnotation(JacksonStdImpl.class) != null);
    }

    
Accessor for checking whether given Class is under Java package of java.* or javax.* (including all sub-packages). 
 Added since some aspects of handling need to be changed for JDK types (and possibly some extensions under javax.?): for example, forcing of access will not work well for future JDKs (12 and later). 
 Note: in Jackson 2.11 only returned true for java.* (and not javax.*); was changed in 2.12. 
Since:2.11
/**
     * Accessor for checking whether given {@code Class} is under Java package
     * of {@code java.*} or {@code javax.*} (including all sub-packages).
     *<p>
     * Added since some aspects of handling need to be changed for JDK types (and
     * possibly some extensions under {@code javax.}?): for example, forcing of access
     * will not work well for future JDKs (12 and later).
     *<p>
     * Note: in Jackson 2.11 only returned true for {@code java.*} (and not {@code javax.*});
     * was changed in 2.12.
     *
     * @since 2.11
     */
    public static boolean isJDKClass(Class<?> rawType) {
        final String clsName = rawType.getName();
        return clsName.startsWith("java.") || clsName.startsWith("javax.");
    }

    /*
    /**********************************************************
    /* Access to various Class definition aspects; possibly
    /* cacheable; and attempts was made in 2.7.0 - 2.7.7; however
    /* unintented retention (~= memory leak) wrt [databind#1363]
    /* resulted in removal of caching
    /**********************************************************
     */

    public static boolean isNonStaticInnerClass(Class<?> cls) {
        return !Modifier.isStatic(cls.getModifiers())
                && (getEnclosingClass(cls) != null);
    }

    
Since:2.7
Deprecated:Since 2.12 (just call methods directly or check class name)
/**
     * @since 2.7
     *
     * @deprecated Since 2.12 (just call methods directly or check class name)
     */
    @Deprecated // since 2.12
    public static String getPackageName(Class<?> cls) {
        Package pkg = cls.getPackage();
        return (pkg == null) ? null : pkg.getName();
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static boolean hasEnclosingMethod(Class<?> cls) {
        return !isObjectOrPrimitive(cls) && (cls.getEnclosingMethod() != null);
    }

    
Deprecated:since 2.11 (just call Class method directly)
/**
     * @deprecated since 2.11 (just call Class method directly)
     */
    @Deprecated
    public static Field[] getDeclaredFields(Class<?> cls) {
        return cls.getDeclaredFields();
    }

    
Deprecated:since 2.11 (just call Class method directly)
/**
     * @deprecated since 2.11 (just call Class method directly)
     */
    @Deprecated
    public static Method[] getDeclaredMethods(Class<?> cls) {
        return cls.getDeclaredMethods();
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static Annotation[] findClassAnnotations(Class<?> cls) {
        if (isObjectOrPrimitive(cls)) {
            return NO_ANNOTATIONS;
        }
        return cls.getDeclaredAnnotations();
    }

    
Helper method that gets methods declared in given class; usually a simple thing,
but sometimes (as per [databind#785]) more complicated, depending on classloader
setup.

Since:2.9
/**
     * Helper method that gets methods declared in given class; usually a simple thing,
     * but sometimes (as per [databind#785]) more complicated, depending on classloader
     * setup.
     *
     * @since 2.9
     */
    public static Method[] getClassMethods(Class<?> cls)
    {
        try {
            return cls.getDeclaredMethods();
        } catch (final NoClassDefFoundError ex) {
            // One of the methods had a class that was not found in the cls.getClassLoader.
            // Maybe the developer was nice and has a different class loader for this context.
            final ClassLoader loader = Thread.currentThread().getContextClassLoader();
            if (loader == null){
                // Nope... this is going to end poorly
                throw ex;
            }
            final Class<?> contextClass;
            try {
                contextClass = loader.loadClass(cls.getName());
            } catch (ClassNotFoundException e) {
                ex.addSuppressed(e);
                throw ex;
            }
            return contextClass.getDeclaredMethods(); // Cross fingers
        }
    }
    
    
Since:2.7
/**
     * @since 2.7
     */
    public static Ctor[] getConstructors(Class<?> cls) {
        // Note: can NOT skip abstract classes as they may be used with mix-ins
        // and for regular use shouldn't really matter.
        if (cls.isInterface() || isObjectOrPrimitive(cls)) {
            return NO_CTORS;
        }
        Constructor<?>[] rawCtors = cls.getDeclaredConstructors();
        final int len = rawCtors.length;
        Ctor[] result = new Ctor[len];
        for (int i = 0; i < len; ++i) {
            result[i] = new Ctor(rawCtors[i]);
        }
        return result;
    }

    // // // Then methods that do NOT cache access but were considered
    // // // (and could be added to do caching if it was proven effective)

    
Since:2.7
/**
     * @since 2.7
     */
    public static Class<?> getDeclaringClass(Class<?> cls) {
        return isObjectOrPrimitive(cls) ? null : cls.getDeclaringClass();
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static Type getGenericSuperclass(Class<?> cls) {
        return cls.getGenericSuperclass();
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static Type[] getGenericInterfaces(Class<?> cls) {
        return cls.getGenericInterfaces();
    }

    
Since:2.7
/**
     * @since 2.7
     */
    public static Class<?> getEnclosingClass(Class<?> cls) {
        // Caching does not seem worthwhile, as per profiling
        return isObjectOrPrimitive(cls) ? null : cls.getEnclosingClass();
    }

    private static Class<?>[] _interfaces(Class<?> cls) {
        return cls.getInterfaces();
    }

    /*
    /**********************************************************
    /* Helper classes
    /**********************************************************
     */

    
Inner class used to contain gory details of how we can determine details of instances of common JDK types like EnumMaps. 
/**
     * Inner class used to contain gory details of how we can determine
     * details of instances of common JDK types like {@link EnumMap}s.
     */
    private static class EnumTypeLocator
    {
        final static EnumTypeLocator instance = new EnumTypeLocator();

        private final Field enumSetTypeField;
        private final Field enumMapTypeField;
    	
        private EnumTypeLocator() {
            //JDK uses following fields to store information about actual Enumeration
            // type for EnumSets, EnumMaps...
    	        enumSetTypeField = locateField(EnumSet.class, "elementType", Class.class);
    	        enumMapTypeField = locateField(EnumMap.class, "elementType", Class.class);
        }

        @SuppressWarnings("unchecked")
        public Class<? extends Enum<?>> enumTypeFor(EnumSet<?> set)
        {
            if (enumSetTypeField != null) {
                return (Class<? extends Enum<?>>) get(set, enumSetTypeField);
            }
            throw new IllegalStateException("Cannot figure out type for EnumSet (odd JDK platform?)");
        }

        @SuppressWarnings("unchecked")
        public Class<? extends Enum<?>> enumTypeFor(EnumMap<?,?> set)
        {
            if (enumMapTypeField != null) {
                return (Class<? extends Enum<?>>) get(set, enumMapTypeField);
            }
            throw new IllegalStateException("Cannot figure out type for EnumMap (odd JDK platform?)");
        }
    	
        private Object get(Object bean, Field field)
        {
            try {
                return field.get(bean);
            } catch (Exception e) {
                throw new IllegalArgumentException(e);
            }
        }
    	
        private static Field locateField(Class<?> fromClass, String expectedName, Class<?> type)
        {
            Field found = null;
    	        // First: let's see if we can find exact match:
            Field[] fields = fromClass.getDeclaredFields();
    	        for (Field f : fields) {
    	            if (expectedName.equals(f.getName()) && f.getType() == type) {
    	                found = f;
    	                break;
    	            }
    	        }
    	        // And if not, if there is just one field with the type, that field
    	        if (found == null) {
    	            for (Field f : fields) {
    	                if (f.getType() == type) {
    	                    // If more than one, can't choose
    	                    if (found != null) return null;
    	                    found = f;
    	                }
    	            }
    	        }
    	        if (found != null) { // it's non-public, need to force accessible
    	            try {
    	                found.setAccessible(true);
    	            } catch (Throwable t) { }
    	        }
    	        return found;
        }
    }

    /*
    /**********************************************************
    /* Helper classed used for caching
    /**********************************************************
     */

    
Value class used for caching Constructor declarations; used because
caching done by JDK appears to be somewhat inefficient for some use cases.

Since:2.7
/**
     * Value class used for caching Constructor declarations; used because
     * caching done by JDK appears to be somewhat inefficient for some use cases.
     *
     * @since 2.7
     */
    public final static class Ctor
    {
        public final Constructor<?> _ctor;

        private transient Annotation[] _annotations;

        private transient Annotation[][] _paramAnnotations;
        
        private int _paramCount = -1;
        
        public Ctor(Constructor<?> ctor) {
            _ctor = ctor;
        }

        public Constructor<?> getConstructor() {
            return _ctor;
        }

        public int getParamCount() {
            int c = _paramCount;
            if (c < 0) {
                c = _ctor.getParameterTypes().length;
                _paramCount = c;
            }
            return c;
        }

        public Class<?> getDeclaringClass() {
            return _ctor.getDeclaringClass();
        }

        public Annotation[] getDeclaredAnnotations() {
            Annotation[] result = _annotations;
            if (result == null) {
                result = _ctor.getDeclaredAnnotations();
                _annotations = result;
            }
            return result;
        }

        public  Annotation[][] getParameterAnnotations() {
            Annotation[][] result = _paramAnnotations;
            if (result == null) {
                result = _ctor.getParameterAnnotations();
                _paramAnnotations = result;
            }
            return result;
        }
    }
}