/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.catalina.loader;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.File;
import java.io.FilePermission;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.charset.StandardCharsets;

import javax.management.ObjectName;

import jakarta.servlet.ServletContext;

import org.apache.catalina.Context;
import org.apache.catalina.Globals;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.Loader;
import org.apache.catalina.util.LifecycleMBeanBase;
import org.apache.catalina.util.ToStringUtil;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.buf.UDecoder;
import org.apache.tomcat.util.compat.JreCompat;
import org.apache.tomcat.util.modeler.Registry;
import org.apache.tomcat.util.res.StringManager;

Classloader implementation which is specialized for handling web applications in the most efficient way, while being Catalina aware (all accesses to resources are made through WebResourceRoot). This class loader supports detection of modified Java classes, which can be used to implement auto-reload support. 

This class loader is configured via the Resources children of its Context
prior to calling start().  When a new class is required,
these Resources will be consulted first to locate the class.  If it
is not present, the system class loader will be used instead.
Author:
Craig R. McClanahan, Remy Maucherat/**
 * Classloader implementation which is specialized for handling web
 * applications in the most efficient way, while being Catalina aware (all
 * accesses to resources are made through
 * {@link org.apache.catalina.WebResourceRoot}).
 * This class loader supports detection of modified
 * Java classes, which can be used to implement auto-reload support.
 * <p>
 * This class loader is configured via the Resources children of its Context
 * prior to calling <code>start()</code>.  When a new class is required,
 * these Resources will be consulted first to locate the class.  If it
 * is not present, the system class loader will be used instead.
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 */
public class WebappLoader extends LifecycleMBeanBase implements Loader{

    private static final Log log = LogFactory.getLog(WebappLoader.class);

    // ----------------------------------------------------- Instance Variables

    
The class loader being managed by this Loader component.
/**
     * The class loader being managed by this Loader component.
     */
    private WebappClassLoaderBase classLoader = null;


    
The Context with which this Loader has been associated.
/**
     * The Context with which this Loader has been associated.
     */
    private Context context = null;


    
The "follow standard delegation model" flag that will be used to
configure our ClassLoader.
/**
     * The "follow standard delegation model" flag that will be used to
     * configure our ClassLoader.
     */
    private boolean delegate = false;


    
The Java class name of the ClassLoader implementation to be used.
This class should extend WebappClassLoaderBase, otherwise, a different
loader implementation must be used.
/**
     * The Java class name of the ClassLoader implementation to be used.
     * This class should extend WebappClassLoaderBase, otherwise, a different
     * loader implementation must be used.
     */
    private String loaderClass = ParallelWebappClassLoader.class.getName();


    
The string manager for this package.
/**
     * The string manager for this package.
     */
    protected static final StringManager sm = StringManager.getManager(WebappLoader.class);


    
The property change support for this component.
/**
     * The property change support for this component.
     */
    protected final PropertyChangeSupport support = new PropertyChangeSupport(this);


    
Classpath set in the loader.
/**
     * Classpath set in the loader.
     */
    private String classpath = null;


    // ------------------------------------------------------------- Properties

    
Return the Java class loader to be used by this Container.
/**
     * Return the Java class loader to be used by this Container.
     */
    @Override
    public ClassLoader getClassLoader() {
        return classLoader;
    }


    @Override
    public Context getContext() {
        return context;
    }


    @Override
    public void setContext(Context context) {

        if (this.context == context) {
            return;
        }

        if (getState().isAvailable()) {
            throw new IllegalStateException(sm.getString("webappLoader.setContext.ise"));
        }

        // Process this property change
        Context oldContext = this.context;
        this.context = context;
        support.firePropertyChange("context", oldContext, this.context);
    }


    
Return the "follow standard delegation model" flag used to configure
our ClassLoader.
/**
     * Return the "follow standard delegation model" flag used to configure
     * our ClassLoader.
     */
    @Override
    public boolean getDelegate() {
        return this.delegate;
    }


    
Set the "follow standard delegation model" flag used to configure
our ClassLoader.
Params:
delegate – The new flag/**
     * Set the "follow standard delegation model" flag used to configure
     * our ClassLoader.
     *
     * @param delegate The new flag
     */
    @Override
    public void setDelegate(boolean delegate) {
        boolean oldDelegate = this.delegate;
        this.delegate = delegate;
        support.firePropertyChange("delegate", Boolean.valueOf(oldDelegate),
                                   Boolean.valueOf(this.delegate));
    }


    
Returns:
the ClassLoader class name./**
     * @return the ClassLoader class name.
     */
    public String getLoaderClass() {
        return this.loaderClass;
    }


    
Set the ClassLoader class name.
Params:
loaderClass – The new ClassLoader class name/**
     * Set the ClassLoader class name.
     *
     * @param loaderClass The new ClassLoader class name
     */
    public void setLoaderClass(String loaderClass) {
        this.loaderClass = loaderClass;
    }

    
Set the ClassLoader instance, without relying on reflection This method will also invoke setLoaderClass(String) with loaderInstance.getClass().getName() as an argument 
Params:
loaderInstance – The new ClassLoader instance to use/**
     * Set the ClassLoader instance, without relying on reflection
     * This method will also invoke {@link #setLoaderClass(String)} with
     * {@code loaderInstance.getClass().getName()} as an argument
     *
     * @param loaderInstance The new ClassLoader instance to use
     */
    public void setLoaderInstance(WebappClassLoaderBase loaderInstance) {
        this.classLoader = loaderInstance;
        setLoaderClass(loaderInstance.getClass().getName());
    }

    // --------------------------------------------------------- Public Methods

    
Add a property change listener to this component.
Params:
listener – The listener to add/**
     * Add a property change listener to this component.
     *
     * @param listener The listener to add
     */
    @Override
    public void addPropertyChangeListener(PropertyChangeListener listener) {

        support.addPropertyChangeListener(listener);

    }


    
Execute a periodic task, such as reloading, etc. This method will be
invoked inside the classloading context of this container. Unexpected
throwables will be caught and logged.
/**
     * Execute a periodic task, such as reloading, etc. This method will be
     * invoked inside the classloading context of this container. Unexpected
     * throwables will be caught and logged.
     */
    @Override
    public void backgroundProcess() {
        Context context = getContext();
        if (context != null) {
            if (context.getReloadable() && modified()) {
                ClassLoader originalTccl = Thread.currentThread().getContextClassLoader();
                try {
                    Thread.currentThread().setContextClassLoader(WebappLoader.class.getClassLoader());
                    context.reload();
                } finally {
                    Thread.currentThread().setContextClassLoader(originalTccl);
                }
            }
        }
    }


    public String[] getLoaderRepositories() {
        if (classLoader == null) {
            return new String[0];
        }
        URL[] urls = classLoader.getURLs();
        String[] result = new String[urls.length];
        for (int i = 0; i < urls.length; i++) {
            result[i] = urls[i].toExternalForm();
        }
        return result;
    }

    public String getLoaderRepositoriesString() {
        String repositories[]=getLoaderRepositories();
        StringBuilder sb=new StringBuilder();
        for (String repository : repositories) {
            sb.append(repository).append(':');
        }
        return sb.toString();
    }


    
Classpath, as set in org.apache.catalina.jsp_classpath context
property
Returns:
The classpath/**
     * Classpath, as set in org.apache.catalina.jsp_classpath context
     * property
     *
     * @return The classpath
     */
    public String getClasspath() {
        return classpath;
    }


    
Has the internal repository associated with this Loader been modified,
such that the loaded classes should be reloaded?
/**
     * Has the internal repository associated with this Loader been modified,
     * such that the loaded classes should be reloaded?
     */
    @Override
    public boolean modified() {
        return classLoader != null ? classLoader.modified() : false ;
    }


    
Remove a property change listener from this component.
Params:
listener – The listener to remove/**
     * Remove a property change listener from this component.
     *
     * @param listener The listener to remove
     */
    @Override
    public void removePropertyChangeListener(PropertyChangeListener listener) {
        support.removePropertyChangeListener(listener);
    }


    
Return a String representation of this component.
/**
     * Return a String representation of this component.
     */
    @Override
    public String toString() {
        return ToStringUtil.toString(this, context);
    }


    
Start associated ClassLoader and implement the requirements of LifecycleBase.startInternal(). 
Throws:
LifecycleException – if this component detects a fatal error
 that prevents this component from being used/**
     * Start associated {@link ClassLoader} and implement the requirements
     * of {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    @Override
    protected void startInternal() throws LifecycleException {

        if (log.isDebugEnabled())
            log.debug(sm.getString("webappLoader.starting"));

        if (context.getResources() == null) {
            log.info(sm.getString("webappLoader.noResources", context));
            setState(LifecycleState.STARTING);
            return;
        }

        // Construct a class loader based on our current repositories list
        try {

            classLoader = createClassLoader();
            classLoader.setResources(context.getResources());
            classLoader.setDelegate(this.delegate);

            // Configure our repositories
            setClassPath();

            setPermissions();

            classLoader.start();

            String contextName = context.getName();
            if (!contextName.startsWith("/")) {
                contextName = "/" + contextName;
            }
            ObjectName cloname = new ObjectName(context.getDomain() + ":type=" +
                    classLoader.getClass().getSimpleName() + ",host=" +
                    context.getParent().getName() + ",context=" + contextName);
            Registry.getRegistry(null, null)
                .registerComponent(classLoader, cloname, null);

        } catch (Throwable t) {
            t = ExceptionUtils.unwrapInvocationTargetException(t);
            ExceptionUtils.handleThrowable(t);
            throw new LifecycleException(sm.getString("webappLoader.startError"), t);
        }

        setState(LifecycleState.STARTING);
    }


    
Stop associated ClassLoader and implement the requirements of LifecycleBase.stopInternal(). 
Throws:
LifecycleException – if this component detects a fatal error
 that prevents this component from being used/**
     * Stop associated {@link ClassLoader} and implement the requirements
     * of {@link org.apache.catalina.util.LifecycleBase#stopInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    @Override
    protected void stopInternal() throws LifecycleException {

        if (log.isDebugEnabled())
            log.debug(sm.getString("webappLoader.stopping"));

        setState(LifecycleState.STOPPING);

        // Remove context attributes as appropriate
        ServletContext servletContext = context.getServletContext();
        servletContext.removeAttribute(Globals.CLASS_PATH_ATTR);

        // Throw away our current class loader if any
        if (classLoader != null) {
            try {
                classLoader.stop();
            } finally {
                classLoader.destroy();
            }

            // classLoader must be non-null to have been registered
            try {
                String contextName = context.getName();
                if (!contextName.startsWith("/")) {
                    contextName = "/" + contextName;
                }
                ObjectName cloname = new ObjectName(context.getDomain() + ":type=" +
                        classLoader.getClass().getSimpleName() + ",host=" +
                        context.getParent().getName() + ",context=" + contextName);
                Registry.getRegistry(null, null).unregisterComponent(cloname);
            } catch (Exception e) {
                log.warn(sm.getString("webappLoader.stopError"), e);
            }
        }


        classLoader = null;
    }


    // ------------------------------------------------------- Private Methods

    
Create associated classLoader.
/**
     * Create associated classLoader.
     */
    private WebappClassLoaderBase createClassLoader()
        throws Exception {

        if (classLoader != null) {
            return classLoader;
        }

        if (ParallelWebappClassLoader.class.getName().equals(loaderClass)) {
            return new ParallelWebappClassLoader(context.getParentClassLoader());
        }

        Class<?> clazz = Class.forName(loaderClass);
        WebappClassLoaderBase classLoader = null;

        ClassLoader parentClassLoader = context.getParentClassLoader();

        Class<?>[] argTypes = { ClassLoader.class };
        Object[] args = { parentClassLoader };
        Constructor<?> constr = clazz.getConstructor(argTypes);
        classLoader = (WebappClassLoaderBase) constr.newInstance(args);

        return classLoader;
    }


    
Configure associated class loader permissions.
/**
     * Configure associated class loader permissions.
     */
    private void setPermissions() {

        if (!Globals.IS_SECURITY_ENABLED)
            return;
        if (context == null)
            return;

        // Tell the class loader the root of the context
        ServletContext servletContext = context.getServletContext();

        // Assigning permissions for the work directory
        File workDir =
            (File) servletContext.getAttribute(ServletContext.TEMPDIR);
        if (workDir != null) {
            try {
                String workDirPath = workDir.getCanonicalPath();
                classLoader.addPermission
                    (new FilePermission(workDirPath, "read,write"));
                classLoader.addPermission
                    (new FilePermission(workDirPath + File.separator + "-",
                                        "read,write,delete"));
            } catch (IOException e) {
                // Ignore
            }
        }

        for (URL url : context.getResources().getBaseUrls()) {
           classLoader.addPermission(url);
        }
    }


    
Set the appropriate context attribute for our class path.  This
is required only because Jasper depends on it.
/**
     * Set the appropriate context attribute for our class path.  This
     * is required only because Jasper depends on it.
     */
    private void setClassPath() {

        // Validate our current state information
        if (context == null)
            return;
        ServletContext servletContext = context.getServletContext();
        if (servletContext == null)
            return;

        StringBuilder classpath = new StringBuilder();

        // Assemble the class path information from our class loader chain
        ClassLoader loader = getClassLoader();

        if (delegate && loader != null) {
            // Skip the webapp loader for now as delegation is enabled
            loader = loader.getParent();
        }

        while (loader != null) {
            if (!buildClassPath(classpath, loader)) {
                break;
            }
            loader = loader.getParent();
        }

        if (delegate) {
            // Delegation was enabled, go back and add the webapp paths
            loader = getClassLoader();
            if (loader != null) {
                buildClassPath(classpath, loader);
            }
        }

        this.classpath = classpath.toString();

        // Store the assembled class path as a servlet context attribute
        servletContext.setAttribute(Globals.CLASS_PATH_ATTR, this.classpath);
    }


    private boolean buildClassPath(StringBuilder classpath, ClassLoader loader) {
        if (loader instanceof URLClassLoader) {
            URL repositories[] = ((URLClassLoader) loader).getURLs();
            for (URL url : repositories) {
                String repository = url.toString();
                if (repository.startsWith("file://"))
                    repository = UDecoder.URLDecode(repository.substring(7), StandardCharsets.UTF_8);
                else if (repository.startsWith("file:"))
                    repository = UDecoder.URLDecode(repository.substring(5), StandardCharsets.UTF_8);
                else
                    continue;
                if (repository == null)
                    continue;
                if (classpath.length() > 0)
                    classpath.append(File.pathSeparator);
                classpath.append(repository);
            }
        } else if (loader == ClassLoader.getSystemClassLoader()){
            // Java 9 onwards. The internal class loaders no longer extend
            // URLCLassLoader
            String cp = System.getProperty("java.class.path");
            if (cp != null && cp.length() > 0) {
                if (classpath.length() > 0) {
                    classpath.append(File.pathSeparator);
                }
                classpath.append(cp);
            }
            return false;
        } else {
            // Ignore Graal "unknown" classloader
            if (!JreCompat.isGraalAvailable()) {
                log.info(sm.getString("webappLoader.unknownClassLoader", loader, loader.getClass()));
            }
            return false;
        }
        return true;
    }

    @Override
    protected String getDomainInternal() {
        return context.getDomain();
    }


    @Override
    protected String getObjectNameKeyProperties() {

        StringBuilder name = new StringBuilder("type=Loader");

        name.append(",host=");
        name.append(context.getParent().getName());

        name.append(",context=");

        String contextName = context.getName();
        if (!contextName.startsWith("/")) {
            name.append('/');
        }
        name.append(contextName);

        return name.toString();
    }
}