https://github.com/spring-projects/spring-framework: Spring Core (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.convert;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;


Context about a type to convert from or to.

Author:Keith Donald, Andy Clement, Juergen Hoeller, Phillip Webb, Sam Brannen, Stephane Nicoll
Since:3.0
/**
 * Context about a type to convert from or to.
 *
 * @author Keith Donald
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Phillip Webb
 * @author Sam Brannen
 * @author Stephane Nicoll
 * @since 3.0
 */
@SuppressWarnings("serial")
public class TypeDescriptor implements Serializable {

	private static final Annotation[] EMPTY_ANNOTATION_ARRAY = new Annotation[0];

	private static final Map<Class<?>, TypeDescriptor> commonTypesCache = new HashMap<>(32);

	private static final Class<?>[] CACHED_COMMON_TYPES = {
			boolean.class, Boolean.class, byte.class, Byte.class, char.class, Character.class,
			double.class, Double.class, float.class, Float.class, int.class, Integer.class,
			long.class, Long.class, short.class, Short.class, String.class, Object.class};

	static {
		for (Class<?> preCachedClass : CACHED_COMMON_TYPES) {
			commonTypesCache.put(preCachedClass, valueOf(preCachedClass));
		}
	}


	private final Class<?> type;

	private final ResolvableType resolvableType;

	private final AnnotatedElementAdapter annotatedElement;


	
Create a new type descriptor from a MethodParameter. 
Use this constructor when a source or target conversion point is a
constructor parameter, method parameter, or method return value.

Params:
  • methodParameter – the method parameter
/**
	 * Create a new type descriptor from a {@link MethodParameter}.
	 * <p>Use this constructor when a source or target conversion point is a
	 * constructor parameter, method parameter, or method return value.
	 * @param methodParameter the method parameter
	 */
	public TypeDescriptor(MethodParameter methodParameter) {
		this.resolvableType = ResolvableType.forMethodParameter(methodParameter);
		this.type = this.resolvableType.resolve(methodParameter.getNestedParameterType());
		this.annotatedElement = new AnnotatedElementAdapter(methodParameter.getParameterIndex() == -1 ?
				methodParameter.getMethodAnnotations() : methodParameter.getParameterAnnotations());
	}

	
Create a new type descriptor from a Field. 
Use this constructor when a source or target conversion point is a field.

Params:
  • field – the field
/**
	 * Create a new type descriptor from a {@link Field}.
	 * <p>Use this constructor when a source or target conversion point is a field.
	 * @param field the field
	 */
	public TypeDescriptor(Field field) {
		this.resolvableType = ResolvableType.forField(field);
		this.type = this.resolvableType.resolve(field.getType());
		this.annotatedElement = new AnnotatedElementAdapter(field.getAnnotations());
	}

	
Create a new type descriptor from a Property. 
Use this constructor when a source or target conversion point is a
property on a Java class.

Params:
  • property – the property
/**
	 * Create a new type descriptor from a {@link Property}.
	 * <p>Use this constructor when a source or target conversion point is a
	 * property on a Java class.
	 * @param property the property
	 */
	public TypeDescriptor(Property property) {
		Assert.notNull(property, "Property must not be null");
		this.resolvableType = ResolvableType.forMethodParameter(property.getMethodParameter());
		this.type = this.resolvableType.resolve(property.getType());
		this.annotatedElement = new AnnotatedElementAdapter(property.getAnnotations());
	}

	
Create a new type descriptor from a ResolvableType. 
This constructor is used internally and may also be used by subclasses
that support non-Java languages with extended type systems. It is public
as of 5.1.4 whereas it was protected before.

Params:
  • resolvableType – the resolvable type
  • type – the backing type (or null if it should get resolved)
  • annotations – the type annotations
Since:4.0
/**
	 * Create a new type descriptor from a {@link ResolvableType}.
	 * <p>This constructor is used internally and may also be used by subclasses
	 * that support non-Java languages with extended type systems. It is public
	 * as of 5.1.4 whereas it was protected before.
	 * @param resolvableType the resolvable type
	 * @param type the backing type (or {@code null} if it should get resolved)
	 * @param annotations the type annotations
	 * @since 4.0
	 */
	public TypeDescriptor(ResolvableType resolvableType, @Nullable Class<?> type, @Nullable Annotation[] annotations) {
		this.resolvableType = resolvableType;
		this.type = (type != null ? type : resolvableType.toClass());
		this.annotatedElement = new AnnotatedElementAdapter(annotations);
	}


	
Variation of getType() that accounts for a primitive type by returning its object wrapper type. 
This is useful for conversion service implementations that wish to
normalize to object-based types and not work with primitive types directly.

/**
	 * Variation of {@link #getType()} that accounts for a primitive type by
	 * returning its object wrapper type.
	 * <p>This is useful for conversion service implementations that wish to
	 * normalize to object-based types and not work with primitive types directly.
	 */
	public Class<?> getObjectType() {
		return ClassUtils.resolvePrimitiveIfNecessary(getType());
	}

	
The type of the backing class, method parameter, field, or property
described by this TypeDescriptor.

Returns primitive types as-is. See getObjectType() for a variation of this operation that resolves primitive types to their corresponding Object types if necessary. 
See Also:
/**
	 * The type of the backing class, method parameter, field, or property
	 * described by this TypeDescriptor.
	 * <p>Returns primitive types as-is. See {@link #getObjectType()} for a
	 * variation of this operation that resolves primitive types to their
	 * corresponding Object types if necessary.
	 * @see #getObjectType()
	 */
	public Class<?> getType() {
		return this.type;
	}

	
Return the underlying ResolvableType. 
Since:4.0
/**
	 * Return the underlying {@link ResolvableType}.
	 * @since 4.0
	 */
	public ResolvableType getResolvableType() {
		return this.resolvableType;
	}

	
Return the underlying source of the descriptor. Will return a Field, MethodParameter or Type depending on how the TypeDescriptor was constructed. This method is primarily to provide access to additional type information or meta-data that alternative JVM languages may provide. 
Since:4.0
/**
	 * Return the underlying source of the descriptor. Will return a {@link Field},
	 * {@link MethodParameter} or {@link Type} depending on how the {@link TypeDescriptor}
	 * was constructed. This method is primarily to provide access to additional
	 * type information or meta-data that alternative JVM languages may provide.
	 * @since 4.0
	 */
	public Object getSource() {
		return this.resolvableType.getSource();
	}

	
Narrows this TypeDescriptor by setting its type to the class of the provided value. 
If the value is null, no narrowing is performed and this TypeDescriptor is returned unchanged. 
Designed to be called by binding frameworks when they read property, field, or method return values. Allows such frameworks to narrow a TypeDescriptor built from a declared property, field, or method return value type. For example, a field declared as java.lang.Object would be narrowed to java.util.HashMap if it was set to a java.util.HashMap value. The narrowed TypeDescriptor can then be used to convert the HashMap to some other type. Annotation and nested type context is preserved by the narrowed copy. 
Params:
  • value – the value to use for narrowing this type descriptor
Returns:this TypeDescriptor narrowed (returns a copy with its type updated to the
class of the provided value)
/**
	 * Narrows this {@link TypeDescriptor} by setting its type to the class of the
	 * provided value.
	 * <p>If the value is {@code null}, no narrowing is performed and this TypeDescriptor
	 * is returned unchanged.
	 * <p>Designed to be called by binding frameworks when they read property, field,
	 * or method return values. Allows such frameworks to narrow a TypeDescriptor built
	 * from a declared property, field, or method return value type. For example, a field
	 * declared as {@code java.lang.Object} would be narrowed to {@code java.util.HashMap}
	 * if it was set to a {@code java.util.HashMap} value. The narrowed TypeDescriptor
	 * can then be used to convert the HashMap to some other type. Annotation and nested
	 * type context is preserved by the narrowed copy.
	 * @param value the value to use for narrowing this type descriptor
	 * @return this TypeDescriptor narrowed (returns a copy with its type updated to the
	 * class of the provided value)
	 */
	public TypeDescriptor narrow(@Nullable Object value) {
		if (value == null) {
			return this;
		}
		ResolvableType narrowed = ResolvableType.forType(value.getClass(), getResolvableType());
		return new TypeDescriptor(narrowed, value.getClass(), getAnnotations());
	}

	
Cast this TypeDescriptor to a superclass or implemented interface preserving annotations and nested type context. 
Params:
  • superType – the super type to cast to (can be null)
Throws:
Returns:a new TypeDescriptor for the up-cast type
Since:3.2
/**
	 * Cast this {@link TypeDescriptor} to a superclass or implemented interface
	 * preserving annotations and nested type context.
	 * @param superType the super type to cast to (can be {@code null})
	 * @return a new TypeDescriptor for the up-cast type
	 * @throws IllegalArgumentException if this type is not assignable to the super-type
	 * @since 3.2
	 */
	@Nullable
	public TypeDescriptor upcast(@Nullable Class<?> superType) {
		if (superType == null) {
			return null;
		}
		Assert.isAssignable(superType, getType());
		return new TypeDescriptor(getResolvableType().as(superType), superType, getAnnotations());
	}

	
Return the name of this type: the fully qualified class name.

/**
	 * Return the name of this type: the fully qualified class name.
	 */
	public String getName() {
		return ClassUtils.getQualifiedName(getType());
	}

	
Is this type a primitive type?

/**
	 * Is this type a primitive type?
	 */
	public boolean isPrimitive() {
		return getType().isPrimitive();
	}

	
Return the annotations associated with this type descriptor, if any.

Returns:the annotations, or an empty array if none
/**
	 * Return the annotations associated with this type descriptor, if any.
	 * @return the annotations, or an empty array if none
	 */
	public Annotation[] getAnnotations() {
		return this.annotatedElement.getAnnotations();
	}

	
Determine if this type descriptor has the specified annotation.

As of Spring Framework 4.2, this method supports arbitrary levels
of meta-annotations.

Params:
  • annotationType – the annotation type
Returns:true if the annotation is present
/**
	 * Determine if this type descriptor has the specified annotation.
	 * <p>As of Spring Framework 4.2, this method supports arbitrary levels
	 * of meta-annotations.
	 * @param annotationType the annotation type
	 * @return <tt>true</tt> if the annotation is present
	 */
	public boolean hasAnnotation(Class<? extends Annotation> annotationType) {
		if (this.annotatedElement.isEmpty()) {
			// Shortcut: AnnotatedElementUtils would have to expect AnnotatedElement.getAnnotations()
			// to return a copy of the array, whereas we can do it more efficiently here.
			return false;
		}
		return AnnotatedElementUtils.isAnnotated(this.annotatedElement, annotationType);
	}

	
Obtain the annotation of the specified annotationType that is on this type descriptor. 
As of Spring Framework 4.2, this method supports arbitrary levels of meta-annotations.

Params:
  • annotationType – the annotation type
Returns:the annotation, or null if no such annotation exists on this type descriptor
/**
	 * Obtain the annotation of the specified {@code annotationType} that is on this type descriptor.
	 * <p>As of Spring Framework 4.2, this method supports arbitrary levels of meta-annotations.
	 * @param annotationType the annotation type
	 * @return the annotation, or {@code null} if no such annotation exists on this type descriptor
	 */
	@Nullable
	public <T extends Annotation> T getAnnotation(Class<T> annotationType) {
		if (this.annotatedElement.isEmpty()) {
			// Shortcut: AnnotatedElementUtils would have to expect AnnotatedElement.getAnnotations()
			// to return a copy of the array, whereas we can do it more efficiently here.
			return null;
		}
		return AnnotatedElementUtils.getMergedAnnotation(this.annotatedElement, annotationType);
	}

	
Returns true if an object of this type descriptor can be assigned to the location
described by the given type descriptor.

For example, valueOf(String.class).isAssignableTo(valueOf(CharSequence.class)) returns true because a String value can be assigned to a CharSequence variable. On the other hand, valueOf(Number.class).isAssignableTo(valueOf(Integer.class)) returns false because, while all Integers are Numbers, not all Numbers are Integers. 
For arrays, collections, and maps, element and key/value types are checked if declared.
For example, a List<String> field value is assignable to a Collection<CharSequence>
field, but List<Number> is not assignable to List<Integer>.

See Also:
Returns:true if this type is assignable to the type represented by the provided type descriptor
/**
	 * Returns true if an object of this type descriptor can be assigned to the location
	 * described by the given type descriptor.
	 * <p>For example, {@code valueOf(String.class).isAssignableTo(valueOf(CharSequence.class))}
	 * returns {@code true} because a String value can be assigned to a CharSequence variable.
	 * On the other hand, {@code valueOf(Number.class).isAssignableTo(valueOf(Integer.class))}
	 * returns {@code false} because, while all Integers are Numbers, not all Numbers are Integers.
	 * <p>For arrays, collections, and maps, element and key/value types are checked if declared.
	 * For example, a List&lt;String&gt; field value is assignable to a Collection&lt;CharSequence&gt;
	 * field, but List&lt;Number&gt; is not assignable to List&lt;Integer&gt;.
	 * @return {@code true} if this type is assignable to the type represented by the provided
	 * type descriptor
	 * @see #getObjectType()
	 */
	public boolean isAssignableTo(TypeDescriptor typeDescriptor) {
		boolean typesAssignable = typeDescriptor.getObjectType().isAssignableFrom(getObjectType());
		if (!typesAssignable) {
			return false;
		}
		if (isArray() && typeDescriptor.isArray()) {
			return isNestedAssignable(getElementTypeDescriptor(), typeDescriptor.getElementTypeDescriptor());
		}
		else if (isCollection() && typeDescriptor.isCollection()) {
			return isNestedAssignable(getElementTypeDescriptor(), typeDescriptor.getElementTypeDescriptor());
		}
		else if (isMap() && typeDescriptor.isMap()) {
			return isNestedAssignable(getMapKeyTypeDescriptor(), typeDescriptor.getMapKeyTypeDescriptor()) &&
				isNestedAssignable(getMapValueTypeDescriptor(), typeDescriptor.getMapValueTypeDescriptor());
		}
		else {
			return true;
		}
	}

	private boolean isNestedAssignable(@Nullable TypeDescriptor nestedTypeDescriptor,
			@Nullable TypeDescriptor otherNestedTypeDescriptor) {

		return (nestedTypeDescriptor == null || otherNestedTypeDescriptor == null ||
				nestedTypeDescriptor.isAssignableTo(otherNestedTypeDescriptor));
	}

	
Is this type a Collection type? 
/**
	 * Is this type a {@link Collection} type?
	 */
	public boolean isCollection() {
		return Collection.class.isAssignableFrom(getType());
	}

	
Is this type an array type?

/**
	 * Is this type an array type?
	 */
	public boolean isArray() {
		return getType().isArray();
	}

	
If this type is an array, returns the array's component type. If this type is a Stream, returns the stream's component type. If this type is a Collection and it is parameterized, returns the Collection's element type. If the Collection is not parameterized, returns null indicating the element type is not declared. 
Throws:
Returns:the array component type or Collection element type, or null if this type is a Collection but its element type is not parameterized
/**
	 * If this type is an array, returns the array's component type.
	 * If this type is a {@code Stream}, returns the stream's component type.
	 * If this type is a {@link Collection} and it is parameterized, returns the Collection's element type.
	 * If the Collection is not parameterized, returns {@code null} indicating the element type is not declared.
	 * @return the array component type or Collection element type, or {@code null} if this type is a
	 * Collection but its element type is not parameterized
	 * @throws IllegalStateException if this type is not a {@code java.util.Collection} or array type
	 */
	@Nullable
	public TypeDescriptor getElementTypeDescriptor() {
		if (getResolvableType().isArray()) {
			return new TypeDescriptor(getResolvableType().getComponentType(), null, getAnnotations());
		}
		if (Stream.class.isAssignableFrom(getType())) {
			return getRelatedIfResolvable(this, getResolvableType().as(Stream.class).getGeneric(0));
		}
		return getRelatedIfResolvable(this, getResolvableType().asCollection().getGeneric(0));
	}

	
If this type is a Collection or an array, creates a element TypeDescriptor from the provided collection or array element. 
Narrows the elementType property to the class of the provided collection or array element. For example, if this describes a java.util.List&lt;java.lang.Number&lt; and the element argument is an java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer. If this describes a java.util.List&lt;?&gt; and the element argument is an java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well. 
Annotation and nested type context will be preserved in the narrowed
TypeDescriptor that is returned.

Params:
  • element – the collection or array element
Throws:
See Also:
Returns:a element type descriptor, narrowed to the type of the provided element
/**
	 * If this type is a {@link Collection} or an array, creates a element TypeDescriptor
	 * from the provided collection or array element.
	 * <p>Narrows the {@link #getElementTypeDescriptor() elementType} property to the class
	 * of the provided collection or array element. For example, if this describes a
	 * {@code java.util.List&lt;java.lang.Number&lt;} and the element argument is an
	 * {@code java.lang.Integer}, the returned TypeDescriptor will be {@code java.lang.Integer}.
	 * If this describes a {@code java.util.List&lt;?&gt;} and the element argument is an
	 * {@code java.lang.Integer}, the returned TypeDescriptor will be {@code java.lang.Integer}
	 * as well.
	 * <p>Annotation and nested type context will be preserved in the narrowed
	 * TypeDescriptor that is returned.
	 * @param element the collection or array element
	 * @return a element type descriptor, narrowed to the type of the provided element
	 * @throws IllegalStateException if this type is not a {@code java.util.Collection}
	 * or array type
	 * @see #narrow(Object)
	 */
	@Nullable
	public TypeDescriptor elementTypeDescriptor(Object element) {
		return narrow(element, getElementTypeDescriptor());
	}

	
Is this type a Map type? 
/**
	 * Is this type a {@link Map} type?
	 */
	public boolean isMap() {
		return Map.class.isAssignableFrom(getType());
	}

	
If this type is a Map and its key type is parameterized, returns the map's key type. If the Map's key type is not parameterized, returns null indicating the key type is not declared. 
Throws:
Returns:the Map key type, or null if this type is a Map but its key type is not parameterized
/**
	 * If this type is a {@link Map} and its key type is parameterized,
	 * returns the map's key type. If the Map's key type is not parameterized,
	 * returns {@code null} indicating the key type is not declared.
	 * @return the Map key type, or {@code null} if this type is a Map
	 * but its key type is not parameterized
	 * @throws IllegalStateException if this type is not a {@code java.util.Map}
	 */
	@Nullable
	public TypeDescriptor getMapKeyTypeDescriptor() {
		Assert.state(isMap(), "Not a [java.util.Map]");
		return getRelatedIfResolvable(this, getResolvableType().asMap().getGeneric(0));
	}

	
If this type is a Map, creates a mapKey TypeDescriptor from the provided map key. 
Narrows the mapKeyType property to the class of the provided map key. For example, if this describes a java.util.Map&lt;java.lang.Number, java.lang.String&lt; and the key argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer. If this describes a java.util.Map&lt;?, ?&gt; and the key argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well. 
Annotation and nested type context will be preserved in the narrowed
TypeDescriptor that is returned.

Params:
  • mapKey – the map key
Throws:
See Also:
Returns:the map key type descriptor
/**
	 * If this type is a {@link Map}, creates a mapKey {@link TypeDescriptor}
	 * from the provided map key.
	 * <p>Narrows the {@link #getMapKeyTypeDescriptor() mapKeyType} property
	 * to the class of the provided map key. For example, if this describes a
	 * {@code java.util.Map&lt;java.lang.Number, java.lang.String&lt;} and the key
	 * argument is a {@code java.lang.Integer}, the returned TypeDescriptor will be
	 * {@code java.lang.Integer}. If this describes a {@code java.util.Map&lt;?, ?&gt;}
	 * and the key argument is a {@code java.lang.Integer}, the returned
	 * TypeDescriptor will be {@code java.lang.Integer} as well.
	 * <p>Annotation and nested type context will be preserved in the narrowed
	 * TypeDescriptor that is returned.
	 * @param mapKey the map key
	 * @return the map key type descriptor
	 * @throws IllegalStateException if this type is not a {@code java.util.Map}
	 * @see #narrow(Object)
	 */
	@Nullable
	public TypeDescriptor getMapKeyTypeDescriptor(Object mapKey) {
		return narrow(mapKey, getMapKeyTypeDescriptor());
	}

	
If this type is a Map and its value type is parameterized, returns the map's value type. 
If the Map's value type is not parameterized, returns null indicating the value type is not declared. 
Throws:
Returns:the Map value type, or null if this type is a Map but its value type is not parameterized
/**
	 * If this type is a {@link Map} and its value type is parameterized,
	 * returns the map's value type.
	 * <p>If the Map's value type is not parameterized, returns {@code null}
	 * indicating the value type is not declared.
	 * @return the Map value type, or {@code null} if this type is a Map
	 * but its value type is not parameterized
	 * @throws IllegalStateException if this type is not a {@code java.util.Map}
	 */
	@Nullable
	public TypeDescriptor getMapValueTypeDescriptor() {
		Assert.state(isMap(), "Not a [java.util.Map]");
		return getRelatedIfResolvable(this, getResolvableType().asMap().getGeneric(1));
	}

	
If this type is a Map, creates a mapValue TypeDescriptor from the provided map value. 
Narrows the mapValueType property to the class of the provided map value. For example, if this describes a java.util.Map&lt;java.lang.String, java.lang.Number&lt; and the value argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer. If this describes a java.util.Map&lt;?, ?&gt; and the value argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well. 
Annotation and nested type context will be preserved in the narrowed
TypeDescriptor that is returned.

Params:
  • mapValue – the map value
Throws:
See Also:
Returns:the map value type descriptor
/**
	 * If this type is a {@link Map}, creates a mapValue {@link TypeDescriptor}
	 * from the provided map value.
	 * <p>Narrows the {@link #getMapValueTypeDescriptor() mapValueType} property
	 * to the class of the provided map value. For example, if this describes a
	 * {@code java.util.Map&lt;java.lang.String, java.lang.Number&lt;} and the value
	 * argument is a {@code java.lang.Integer}, the returned TypeDescriptor will be
	 * {@code java.lang.Integer}. If this describes a {@code java.util.Map&lt;?, ?&gt;}
	 * and the value argument is a {@code java.lang.Integer}, the returned
	 * TypeDescriptor will be {@code java.lang.Integer} as well.
	 * <p>Annotation and nested type context will be preserved in the narrowed
	 * TypeDescriptor that is returned.
	 * @param mapValue the map value
	 * @return the map value type descriptor
	 * @throws IllegalStateException if this type is not a {@code java.util.Map}
	 * @see #narrow(Object)
	 */
	@Nullable
	public TypeDescriptor getMapValueTypeDescriptor(Object mapValue) {
		return narrow(mapValue, getMapValueTypeDescriptor());
	}

	@Nullable
	private TypeDescriptor narrow(@Nullable Object value, @Nullable TypeDescriptor typeDescriptor) {
		if (typeDescriptor != null) {
			return typeDescriptor.narrow(value);
		}
		if (value != null) {
			return narrow(value);
		}
		return null;
	}

	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof TypeDescriptor)) {
			return false;
		}
		TypeDescriptor otherDesc = (TypeDescriptor) other;
		if (getType() != otherDesc.getType()) {
			return false;
		}
		if (!annotationsMatch(otherDesc)) {
			return false;
		}
		if (isCollection() || isArray()) {
			return ObjectUtils.nullSafeEquals(getElementTypeDescriptor(), otherDesc.getElementTypeDescriptor());
		}
		else if (isMap()) {
			return (ObjectUtils.nullSafeEquals(getMapKeyTypeDescriptor(), otherDesc.getMapKeyTypeDescriptor()) &&
					ObjectUtils.nullSafeEquals(getMapValueTypeDescriptor(), otherDesc.getMapValueTypeDescriptor()));
		}
		else {
			return true;
		}
	}

	private boolean annotationsMatch(TypeDescriptor otherDesc) {
		Annotation[] anns = getAnnotations();
		Annotation[] otherAnns = otherDesc.getAnnotations();
		if (anns == otherAnns) {
			return true;
		}
		if (anns.length != otherAnns.length) {
			return false;
		}
		if (anns.length > 0) {
			for (int i = 0; i < anns.length; i++) {
				if (!annotationEquals(anns[i], otherAnns[i])) {
					return false;
				}
			}
		}
		return true;
	}

	private boolean annotationEquals(Annotation ann, Annotation otherAnn) {
		// Annotation.equals is reflective and pretty slow, so let's check identity and proxy type first.
		return (ann == otherAnn || (ann.getClass() == otherAnn.getClass() && ann.equals(otherAnn)));
	}

	@Override
	public int hashCode() {
		return getType().hashCode();
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder();
		for (Annotation ann : getAnnotations()) {
			builder.append("@").append(ann.annotationType().getName()).append(' ');
		}
		builder.append(getResolvableType().toString());
		return builder.toString();
	}


	
Create a new type descriptor for an object.

Use this factory method to introspect a source object before asking the
conversion system to convert it to some another type.

If the provided object is null, returns null, else calls valueOf(Class<?>) to build a TypeDescriptor from the object's class. 
Params:
  • source – the source object
Returns:the type descriptor
/**
	 * Create a new type descriptor for an object.
	 * <p>Use this factory method to introspect a source object before asking the
	 * conversion system to convert it to some another type.
	 * <p>If the provided object is {@code null}, returns {@code null}, else calls
	 * {@link #valueOf(Class)} to build a TypeDescriptor from the object's class.
	 * @param source the source object
	 * @return the type descriptor
	 */
	@Nullable
	public static TypeDescriptor forObject(@Nullable Object source) {
		return (source != null ? valueOf(source.getClass()) : null);
	}

	
Create a new type descriptor from the given type.

Use this to instruct the conversion system to convert an object to a
specific target type, when no type location such as a method parameter or
field is available to provide additional conversion context.

Generally prefer use of forObject(Object) for constructing type descriptors from source objects, as it handles the null object case. 
Params:
  • type – the class (may be null to indicate Object.class)
Returns:the corresponding type descriptor
/**
	 * Create a new type descriptor from the given type.
	 * <p>Use this to instruct the conversion system to convert an object to a
	 * specific target type, when no type location such as a method parameter or
	 * field is available to provide additional conversion context.
	 * <p>Generally prefer use of {@link #forObject(Object)} for constructing type
	 * descriptors from source objects, as it handles the {@code null} object case.
	 * @param type the class (may be {@code null} to indicate {@code Object.class})
	 * @return the corresponding type descriptor
	 */
	public static TypeDescriptor valueOf(@Nullable Class<?> type) {
		if (type == null) {
			type = Object.class;
		}
		TypeDescriptor desc = commonTypesCache.get(type);
		return (desc != null ? desc : new TypeDescriptor(ResolvableType.forClass(type), null, null));
	}

	
Create a new type descriptor from a Collection type. 
Useful for converting to typed Collections.

For example, a List<String> could be converted to a List<EmailAddress> by converting to a targetType built with this method. The method call to construct such a TypeDescriptor would look something like: collection(List.class, TypeDescriptor.valueOf(EmailAddress.class)); 
Params:
  • collectionType – the collection type, which must implement Collection.
  • elementTypeDescriptor – a descriptor for the collection's element type,
used to convert collection elements
Returns:the collection type descriptor
/**
	 * Create a new type descriptor from a {@link java.util.Collection} type.
	 * <p>Useful for converting to typed Collections.
	 * <p>For example, a {@code List<String>} could be converted to a
	 * {@code List<EmailAddress>} by converting to a targetType built with this method.
	 * The method call to construct such a {@code TypeDescriptor} would look something
	 * like: {@code collection(List.class, TypeDescriptor.valueOf(EmailAddress.class));}
	 * @param collectionType the collection type, which must implement {@link Collection}.
	 * @param elementTypeDescriptor a descriptor for the collection's element type,
	 * used to convert collection elements
	 * @return the collection type descriptor
	 */
	public static TypeDescriptor collection(Class<?> collectionType, @Nullable TypeDescriptor elementTypeDescriptor) {
		Assert.notNull(collectionType, "Collection type must not be null");
		if (!Collection.class.isAssignableFrom(collectionType)) {
			throw new IllegalArgumentException("Collection type must be a [java.util.Collection]");
		}
		ResolvableType element = (elementTypeDescriptor != null ? elementTypeDescriptor.resolvableType : null);
		return new TypeDescriptor(ResolvableType.forClassWithGenerics(collectionType, element), null, null);
	}

	
Create a new type descriptor from a Map type. 
Useful for converting to typed Maps.

For example, a Map<String, String> could be converted to a Map<Id, EmailAddress>
by converting to a targetType built with this method:
The method call to construct such a TypeDescriptor would look something like:

map(Map.class, TypeDescriptor.valueOf(Id.class), TypeDescriptor.valueOf(EmailAddress.class));



Params:
  • mapType – the map type, which must implement Map
  • keyTypeDescriptor – a descriptor for the map's key type, used to convert map keys
  • valueTypeDescriptor – the map's value type, used to convert map values
Returns:the map type descriptor
/**
	 * Create a new type descriptor from a {@link java.util.Map} type.
	 * <p>Useful for converting to typed Maps.
	 * <p>For example, a Map&lt;String, String&gt; could be converted to a Map&lt;Id, EmailAddress&gt;
	 * by converting to a targetType built with this method:
	 * The method call to construct such a TypeDescriptor would look something like:
	 * <pre class="code">
	 * map(Map.class, TypeDescriptor.valueOf(Id.class), TypeDescriptor.valueOf(EmailAddress.class));
	 * </pre>
	 * @param mapType the map type, which must implement {@link Map}
	 * @param keyTypeDescriptor a descriptor for the map's key type, used to convert map keys
	 * @param valueTypeDescriptor the map's value type, used to convert map values
	 * @return the map type descriptor
	 */
	public static TypeDescriptor map(Class<?> mapType, @Nullable TypeDescriptor keyTypeDescriptor,
			@Nullable TypeDescriptor valueTypeDescriptor) {

		Assert.notNull(mapType, "Map type must not be null");
		if (!Map.class.isAssignableFrom(mapType)) {
			throw new IllegalArgumentException("Map type must be a [java.util.Map]");
		}
		ResolvableType key = (keyTypeDescriptor != null ? keyTypeDescriptor.resolvableType : null);
		ResolvableType value = (valueTypeDescriptor != null ? valueTypeDescriptor.resolvableType : null);
		return new TypeDescriptor(ResolvableType.forClassWithGenerics(mapType, key, value), null, null);
	}

	
Create a new type descriptor as an array of the specified type.

For example to create a Map<String,String>[] use: 
TypeDescriptor.array(TypeDescriptor.map(Map.class, TypeDescriptor.value(String.class), TypeDescriptor.value(String.class)));



Params:
  • elementTypeDescriptor – the TypeDescriptor of the array element or null
Returns:an array TypeDescriptor or null if elementTypeDescriptor is null
Since:3.2.1
/**
	 * Create a new type descriptor as an array of the specified type.
	 * <p>For example to create a {@code Map<String,String>[]} use:
	 * <pre class="code">
	 * TypeDescriptor.array(TypeDescriptor.map(Map.class, TypeDescriptor.value(String.class), TypeDescriptor.value(String.class)));
	 * </pre>
	 * @param elementTypeDescriptor the {@link TypeDescriptor} of the array element or {@code null}
	 * @return an array {@link TypeDescriptor} or {@code null} if {@code elementTypeDescriptor} is {@code null}
	 * @since 3.2.1
	 */
	@Nullable
	public static TypeDescriptor array(@Nullable TypeDescriptor elementTypeDescriptor) {
		if (elementTypeDescriptor == null) {
			return null;
		}
		return new TypeDescriptor(ResolvableType.forArrayComponent(elementTypeDescriptor.resolvableType),
				null, elementTypeDescriptor.getAnnotations());
	}

	
Create a type descriptor for a nested type declared within the method parameter.

For example, if the methodParameter is a List<String> and the nesting level is 1, the nested type descriptor will be String.class. 
If the methodParameter is a List<List<String>> and the nesting level is 2, the nested type descriptor will also be a String.class. 
If the methodParameter is a Map<Integer, String> and the nesting level is 1, the nested type descriptor will be String, derived from the map value. 
If the methodParameter is a List<Map<Integer, String>> and the nesting level is 2, the nested type descriptor will be String, derived from the map value. 
Returns null if a nested type cannot be obtained because it was not declared. For example, if the method parameter is a List<?>, the nested type descriptor returned will be null. 
Params:
  • methodParameter – the method parameter with a nestingLevel of 1
  • nestingLevel – the nesting level of the collection/array element or
map key/value declaration within the method parameter
Throws:
Returns:the nested type descriptor at the specified nesting level, or null if it could not be obtained
/**
	 * Create a type descriptor for a nested type declared within the method parameter.
	 * <p>For example, if the methodParameter is a {@code List<String>} and the
	 * nesting level is 1, the nested type descriptor will be String.class.
	 * <p>If the methodParameter is a {@code List<List<String>>} and the nesting
	 * level is 2, the nested type descriptor will also be a String.class.
	 * <p>If the methodParameter is a {@code Map<Integer, String>} and the nesting
	 * level is 1, the nested type descriptor will be String, derived from the map value.
	 * <p>If the methodParameter is a {@code List<Map<Integer, String>>} and the
	 * nesting level is 2, the nested type descriptor will be String, derived from the map value.
	 * <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
	 * For example, if the method parameter is a {@code List<?>}, the nested type
	 * descriptor returned will be {@code null}.
	 * @param methodParameter the method parameter with a nestingLevel of 1
	 * @param nestingLevel the nesting level of the collection/array element or
	 * map key/value declaration within the method parameter
	 * @return the nested type descriptor at the specified nesting level,
	 * or {@code null} if it could not be obtained
	 * @throws IllegalArgumentException if the nesting level of the input
	 * {@link MethodParameter} argument is not 1, or if the types up to the
	 * specified nesting level are not of collection, array, or map types
	 */
	@Nullable
	public static TypeDescriptor nested(MethodParameter methodParameter, int nestingLevel) {
		if (methodParameter.getNestingLevel() != 1) {
			throw new IllegalArgumentException("MethodParameter nesting level must be 1: " +
					"use the nestingLevel parameter to specify the desired nestingLevel for nested type traversal");
		}
		return nested(new TypeDescriptor(methodParameter), nestingLevel);
	}

	
Create a type descriptor for a nested type declared within the field.

For example, if the field is a List<String> and the nesting level is 1, the nested type descriptor will be String.class. 
If the field is a List<List<String>> and the nesting level is 2, the nested type descriptor will also be a String.class. 
If the field is a Map<Integer, String> and the nesting level is 1, the nested type descriptor will be String, derived from the map value. 
If the field is a List<Map<Integer, String>> and the nesting level is 2, the nested type descriptor will be String, derived from the map value. 
Returns null if a nested type cannot be obtained because it was not declared. For example, if the field is a List<?>, the nested type descriptor returned will be null. 
Params:
  • field – the field
  • nestingLevel – the nesting level of the collection/array element or
map key/value declaration within the field
Throws:
Returns:the nested type descriptor at the specified nesting level, or null if it could not be obtained
/**
	 * Create a type descriptor for a nested type declared within the field.
	 * <p>For example, if the field is a {@code List<String>} and the nesting
	 * level is 1, the nested type descriptor will be {@code String.class}.
	 * <p>If the field is a {@code List<List<String>>} and the nesting level is
	 * 2, the nested type descriptor will also be a {@code String.class}.
	 * <p>If the field is a {@code Map<Integer, String>} and the nesting level
	 * is 1, the nested type descriptor will be String, derived from the map value.
	 * <p>If the field is a {@code List<Map<Integer, String>>} and the nesting
	 * level is 2, the nested type descriptor will be String, derived from the map value.
	 * <p>Returns {@code null} if a nested type cannot be obtained because it was not
	 * declared. For example, if the field is a {@code List<?>}, the nested type
	 * descriptor returned will be {@code null}.
	 * @param field the field
	 * @param nestingLevel the nesting level of the collection/array element or
	 * map key/value declaration within the field
	 * @return the nested type descriptor at the specified nesting level,
	 * or {@code null} if it could not be obtained
	 * @throws IllegalArgumentException if the types up to the specified nesting
	 * level are not of collection, array, or map types
	 */
	@Nullable
	public static TypeDescriptor nested(Field field, int nestingLevel) {
		return nested(new TypeDescriptor(field), nestingLevel);
	}

	
Create a type descriptor for a nested type declared within the property.

For example, if the property is a List<String> and the nesting level is 1, the nested type descriptor will be String.class. 
If the property is a List<List<String>> and the nesting level is 2, the nested type descriptor will also be a String.class. 
If the property is a Map<Integer, String> and the nesting level is 1, the nested type descriptor will be String, derived from the map value. 
If the property is a List<Map<Integer, String>> and the nesting level is 2, the nested type descriptor will be String, derived from the map value. 
Returns null if a nested type cannot be obtained because it was not declared. For example, if the property is a List<?>, the nested type descriptor returned will be null. 
Params:
  • property – the property
  • nestingLevel – the nesting level of the collection/array element or
map key/value declaration within the property
Throws:
Returns:the nested type descriptor at the specified nesting level, or null if it could not be obtained
/**
	 * Create a type descriptor for a nested type declared within the property.
	 * <p>For example, if the property is a {@code List<String>} and the nesting
	 * level is 1, the nested type descriptor will be {@code String.class}.
	 * <p>If the property is a {@code List<List<String>>} and the nesting level
	 * is 2, the nested type descriptor will also be a {@code String.class}.
	 * <p>If the property is a {@code Map<Integer, String>} and the nesting level
	 * is 1, the nested type descriptor will be String, derived from the map value.
	 * <p>If the property is a {@code List<Map<Integer, String>>} and the nesting
	 * level is 2, the nested type descriptor will be String, derived from the map value.
	 * <p>Returns {@code null} if a nested type cannot be obtained because it was not
	 * declared. For example, if the property is a {@code List<?>}, the nested type
	 * descriptor returned will be {@code null}.
	 * @param property the property
	 * @param nestingLevel the nesting level of the collection/array element or
	 * map key/value declaration within the property
	 * @return the nested type descriptor at the specified nesting level, or
	 * {@code null} if it could not be obtained
	 * @throws IllegalArgumentException if the types up to the specified nesting
	 * level are not of collection, array, or map types
	 */
	@Nullable
	public static TypeDescriptor nested(Property property, int nestingLevel) {
		return nested(new TypeDescriptor(property), nestingLevel);
	}

	@Nullable
	private static TypeDescriptor nested(TypeDescriptor typeDescriptor, int nestingLevel) {
		ResolvableType nested = typeDescriptor.resolvableType;
		for (int i = 0; i < nestingLevel; i++) {
			if (Object.class == nested.getType()) {
				// Could be a collection type but we don't know about its element type,
				// so let's just assume there is an element type of type Object...
			}
			else {
				nested = nested.getNested(2);
			}
		}
		if (nested == ResolvableType.NONE) {
			return null;
		}
		return getRelatedIfResolvable(typeDescriptor, nested);
	}

	@Nullable
	private static TypeDescriptor getRelatedIfResolvable(TypeDescriptor source, ResolvableType type) {
		if (type.resolve() == null) {
			return null;
		}
		return new TypeDescriptor(type, null, source.getAnnotations());
	}


	
Adapter class for exposing a TypeDescriptor's annotations as an AnnotatedElement, in particular to AnnotatedElementUtils. 
See Also:
/**
	 * Adapter class for exposing a {@code TypeDescriptor}'s annotations as an
	 * {@link AnnotatedElement}, in particular to {@link AnnotatedElementUtils}.
	 * @see AnnotatedElementUtils#isAnnotated(AnnotatedElement, Class)
	 * @see AnnotatedElementUtils#getMergedAnnotation(AnnotatedElement, Class)
	 */
	private class AnnotatedElementAdapter implements AnnotatedElement, Serializable {

		@Nullable
		private final Annotation[] annotations;

		public AnnotatedElementAdapter(@Nullable Annotation[] annotations) {
			this.annotations = annotations;
		}

		@Override
		public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
			for (Annotation annotation : getAnnotations()) {
				if (annotation.annotationType() == annotationClass) {
					return true;
				}
			}
			return false;
		}

		@Override
		@Nullable
		@SuppressWarnings("unchecked")
		public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
			for (Annotation annotation : getAnnotations()) {
				if (annotation.annotationType() == annotationClass) {
					return (T) annotation;
				}
			}
			return null;
		}

		@Override
		public Annotation[] getAnnotations() {
			return (this.annotations != null ? this.annotations : EMPTY_ANNOTATION_ARRAY);
		}

		@Override
		public Annotation[] getDeclaredAnnotations() {
			return getAnnotations();
		}

		public boolean isEmpty() {
			return ObjectUtils.isEmpty(this.annotations);
		}

		@Override
		public boolean equals(Object other) {
			return (this == other || (other instanceof AnnotatedElementAdapter &&
					Arrays.equals(this.annotations, ((AnnotatedElementAdapter) other).annotations)));
		}

		@Override
		public int hashCode() {
			return Arrays.hashCode(this.annotations);
		}

		@Override
		public String toString() {
			return TypeDescriptor.this.toString();
		}
	}

}