AntClassLoader (Apache Ant API)
Description: declaration: package: org.apache.tools.ant, class: AntClassLoader

# Class AntClassLoader

java.lang.Object
java.lang.ClassLoader
org.apache.tools.ant.AntClassLoader

All Implemented Interfaces:
  `Closeable, AutoCloseable, EventListener, BuildListener, SubBuildListener`

Direct Known Subclasses:
  `AntClassLoader2, AntClassLoader5, SplitClassLoader`

public class AntClassLoader extends ClassLoader implements SubBuildListener, Closeable
Used to load classes within ant with a different classpath from that used to start ant. Note that it is possible to force a class into this loader even when that class is on the system classpath by using the forceLoadClass method. Any subsequent classes loaded by that class will then use this loader rather than the system class loader.

Note that this classloader has a feature to allow loading in reverse order and for "isolation". Due to the fact that a number of methods in java.lang.ClassLoader are final (at least in java 1.4 getResources) this means that the class has to fake the given parent.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `AntClassLoader()`
  Create an Ant Class Loader
  `AntClassLoader(ClassLoader parent, boolean parentFirst)`
  Creates an empty class loader.
  `AntClassLoader(ClassLoader parent, Project project, Path classpath)`
  Create an Ant ClassLoader for a given project, with a parent classloader and an initial classpath.
  `AntClassLoader(ClassLoader parent, Project project, Path classpath, boolean parentFirst)`
  Creates a classloader for the given project using the classpath given.
  `AntClassLoader(Project project, Path classpath)`
  Creates a classloader for the given project using the classpath given.
  `AntClassLoader(Project project, Path classpath, boolean parentFirst)`
  Creates a classloader for the given project using the classpath given.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addJavaLibraries()`
  add any libraries that come with different java versions here
  `void`
  `addLoaderPackageRoot(String packageRoot)`
  Adds a package root to the list of packages which must be loaded using this loader.
  `void`
  `addPathComponent(File file)`
  Add a path component.
  `void`
  `addPathElement(String pathElement)`
  Adds an element to the classpath to be searched.
  `protected void`
  `addPathFile(File pathComponent)`
  Add a file to the path.
  `void`
  `addSystemPackageRoot(String packageRoot)`
  Adds a package root to the list of packages which must be loaded on the parent loader.
  `void`
  `buildFinished(BuildEvent event)`
  Cleans up any resources held by this classloader at the end of a build.
  `void`
  `buildStarted(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `void`
  `cleanup()`
  Cleans up any resources held by this classloader.
  `void`
  `close()`
  `protected Class<?>`
  `defineClassFromData(File container, byte[] classData, String classname)`
  Define a class given its bytes
  `protected void`
  `definePackage(File container, String className)`
  Define the package information associated with a class.
  `protected void`
  `definePackage(File container, String packageName, Manifest manifest)`
  Define the package information when the class comes from a jar with a manifest
  `Class<?>`
  `findClass(String name)`
  Searches for and load a class on the classpath of this class loader.
  `protected URL`
  `findResource(String name)`
  Finds the resource with the given name.
  `protected Enumeration<URL>`
  `findResources(String name)`
  Returns an enumeration of URLs representing all the resources with the given name by searching the class loader's classpath.
  `protected Enumeration<URL>`
  `findResources(String name, boolean skipParent)`
  Returns an enumeration of URLs representing all the resources with the given name by searching the class loader's classpath.
  `Class<?>`
  `forceLoadClass(String classname)`
  Loads a class through this class loader even if that class is available on the parent classpath.
  `Class<?>`
  `forceLoadSystemClass(String classname)`
  Loads a class through this class loader but defer to the parent class loader.
  `String`
  `getClasspath()`
  Returns the classpath this classloader will consult.
  `ClassLoader`
  `getConfiguredParent()`
  Gets the parent as has been specified in the constructor or via setParent.
  `Enumeration<URL>`
  `getNamedResources(String name)`
  Finds all the resources with the given name.
  `URL`
  `getResource(String name)`
  Finds the resource with the given name.
  `InputStream`
  `getResourceAsStream(String name)`
  Returns a stream to read the requested resource name.
  `Enumeration<URL>`
  `getResources(String name)`
  `protected URL`
  `getResourceURL(File file, String resourceName)`
  Returns the URL of a given resource in the given file which may either be a directory or a zip file.
  `static void`
  `initializeClass(Class<?> theClass)`
  Deprecated.
  since 1.6.x.
  `protected boolean`
  `isInPath(File component)`
  Indicate if the given file is in this loader's path
  `protected Class<?>`
  `loadClass(String classname, boolean resolve)`
  Loads a class with this class loader.
  `protected void`
  `log(String message, int priority)`
  Logs a message through the project object if one has been provided.
  `void`
  `messageLogged(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `static AntClassLoader`
  `newAntClassLoader(ClassLoader parent, Project project, Path path, boolean parentFirst)`
  Factory method
  `void`
  `resetThreadContextLoader()`
  Resets the current thread's context loader to its original value.
  `void`
  `setClassPath(Path classpath)`
  Set the classpath to search for classes to load.
  `void`
  `setIsolated(boolean isolated)`
  Sets whether this classloader should run in isolated mode.
  `void`
  `setParent(ClassLoader parent)`
  Set the parent for this class loader.
  `void`
  `setParentFirst(boolean parentFirst)`
  Control whether class lookup is delegated to the parent loader first or after this loader.
  `void`
  `setProject(Project project)`
  Set the project associated with this class loader
  `void`
  `setThreadContextLoader()`
  Sets the current thread's context loader to this classloader, storing the current loader value for later resetting.
  `void`
  `subBuildFinished(BuildEvent event)`
  Cleans up any resources held by this classloader at the end of a subbuild if it has been created for the subbuild's project instance.
  `void`
  `subBuildStarted(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `void`
  `targetFinished(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `void`
  `targetStarted(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `void`
  `taskFinished(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `void`
  `taskStarted(BuildEvent event)`
  Empty implementation to satisfy the BuildListener interface.
  `String`
  `toString()`
  Returns a `String` representing this loader.

  ### Methods inherited from class ClassLoader

  `clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, registerAsParallelCapable, resolveClass, resources, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners`

  ### Methods inherited from class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### AntClassLoader

    public AntClassLoader(ClassLoader parent, Project project, Path classpath)
    Create an Ant ClassLoader for a given project, with a parent classloader and an initial classpath.
    Parameters:
      `parent` - the parent for this classloader.
      `project` - The project to which this classloader is to belong.
      `classpath` - The classpath to use to load classes.
    Since:
      Ant 1.7.

  - ### AntClassLoader

    public AntClassLoader()
    Create an Ant Class Loader

  - ### AntClassLoader

    public AntClassLoader(Project project, Path classpath)
    Creates a classloader for the given project using the classpath given.
    Parameters:
      `project` - The project to which this classloader is to belong. Must not be `null`.
      `classpath` - The classpath to use to load the classes. This is combined with the system classpath in a manner determined by the value of ${build.sysclasspath}. May be `null`, in which case no path elements are set up to start with.

  - ### AntClassLoader

    public AntClassLoader(ClassLoader parent, Project project, Path classpath, boolean parentFirst)
    Creates a classloader for the given project using the classpath given.
    Parameters:
      `parent` - The parent classloader to which unsatisfied loading attempts are delegated. May be `null`, in which case the classloader which loaded this class is used as the parent.
      `project` - The project to which this classloader is to belong. Must not be `null`.
      `classpath` - the classpath to use to load the classes. May be `null`, in which case no path elements are set up to start with.
      `parentFirst` - If `true`, indicates that the parent classloader should be consulted before trying to load the a class through this loader.

  - ### AntClassLoader

    public AntClassLoader(Project project, Path classpath, boolean parentFirst)
    Creates a classloader for the given project using the classpath given.
    Parameters:
      `project` - The project to which this classloader is to belong. Must not be `null`.
      `classpath` - The classpath to use to load the classes. May be `null`, in which case no path elements are set up to start with.
      `parentFirst` - If `true`, indicates that the parent classloader should be consulted before trying to load the a class through this loader.

  - ### AntClassLoader

    public AntClassLoader(ClassLoader parent, boolean parentFirst)
    Creates an empty class loader. The classloader should be configured with path elements to specify where the loader is to look for classes.
    Parameters:
      `parent` - The parent classloader to which unsatisfied loading attempts are delegated. May be `null`, in which case the classloader which loaded this class is used as the parent.
      `parentFirst` - If `true`, indicates that the parent classloader should be consulted before trying to load the a class through this loader.

- ## Method Details

  - ### setProject

    public void setProject(Project project)
    Set the project associated with this class loader
    Parameters:
      `project` - the project instance

  - ### setClassPath

    public void setClassPath(Path classpath)
    Set the classpath to search for classes to load. This should not be changed once the classloader starts to server classes
    Parameters:
      `classpath` - the search classpath consisting of directories and jar/zip files.

  - ### setParent

    public void setParent(ClassLoader parent)
    Set the parent for this class loader. This is the class loader to which this class loader will delegate to load classes
    Parameters:
      `parent` - the parent class loader.

  - ### setParentFirst

    public void setParentFirst(boolean parentFirst)
    Control whether class lookup is delegated to the parent loader first or after this loader. Use with extreme caution. Setting this to false violates the class loader hierarchy and can lead to Linkage errors
    Parameters:
      `parentFirst` - if true, delegate initial class search to the parent classloader.

  - ### log

    protected void log(String message, int priority)
    Logs a message through the project object if one has been provided.
    Parameters:
      `message` - The message to log. Should not be `null`.
      `priority` - The logging priority of the message.

  - ### setThreadContextLoader

    public void setThreadContextLoader()
    Sets the current thread's context loader to this classloader, storing the current loader value for later resetting.

  - ### resetThreadContextLoader

    public void resetThreadContextLoader()
    Resets the current thread's context loader to its original value.

  - ### addPathElement

    public void addPathElement(String pathElement) throws BuildException
    Adds an element to the classpath to be searched.
    Parameters:
      `pathElement` - The path element to add. Must not be `null`.
    Throws:
      `BuildException` - if the given path element cannot be resolved against the project.

  - ### addPathComponent

    public void addPathComponent(File file)
    Add a path component. This simply adds the file, unlike addPathElement it does not open jar files and load files from their CLASSPATH entry in the manifest file.
    Parameters:
      `file` - the jar file or directory to add.

  - ### addPathFile

    protected void addPathFile(File pathComponent) throws IOException
    Add a file to the path. Reads the manifest, if available, and adds any additional class path jars specified in the manifest.
    Parameters:
      `pathComponent` - the file which is to be added to the path for this class loader
    Throws:
      `IOException` - if data needed from the file cannot be read.

  - ### getClasspath

    public String getClasspath()
    Returns the classpath this classloader will consult.
    Returns:
      the classpath used for this classloader, with elements separated by the path separator for the system.

  - ### setIsolated

    public void setIsolated(boolean isolated)
    Sets whether this classloader should run in isolated mode. In isolated mode, classes not found on the given classpath will not be referred to the parent class loader but will cause a ClassNotFoundException.
    Parameters:
      `isolated` - Whether or not this classloader should run in isolated mode.

  - ### initializeClass

    @Deprecated public static void initializeClass(Class<?> theClass)
    Deprecated.
    since 1.6.x. Use Class.forName with initialize=true instead.
    Forces initialization of a class in a JDK 1.1 compatible, albeit hacky way.
    Parameters:
      `theClass` - The class to initialize. Must not be `null`.

  - ### addSystemPackageRoot

    public void addSystemPackageRoot(String packageRoot)
    Adds a package root to the list of packages which must be loaded on the parent loader. All subpackages are also included.
    Parameters:
      `packageRoot` - The root of all packages to be included. Should not be `null`.

  - ### addLoaderPackageRoot

    public void addLoaderPackageRoot(String packageRoot)
    Adds a package root to the list of packages which must be loaded using this loader. All subpackages are also included.
    Parameters:
      `packageRoot` - The root of all packages to be included. Should not be `null`.

  - ### forceLoadClass

    public Class<?> forceLoadClass(String classname) throws ClassNotFoundException
    Loads a class through this class loader even if that class is available on the parent classpath. This ensures that any classes which are loaded by the returned class will use this classloader.
    Parameters:
      `classname` - The name of the class to be loaded. Must not be `null`.
    Returns:
      the required Class object
    Throws:
      `ClassNotFoundException` - if the requested class does not exist on this loader's classpath.

  - ### forceLoadSystemClass

    public Class<?> forceLoadSystemClass(String classname) throws ClassNotFoundException
    Loads a class through this class loader but defer to the parent class loader. This ensures that instances of the returned class will be compatible with instances which have already been loaded on the parent loader.
    Parameters:
      `classname` - The name of the class to be loaded. Must not be `null`.
    Returns:
      the required Class object
    Throws:
      `ClassNotFoundException` - if the requested class does not exist on this loader's classpath.

  - ### getResourceAsStream

    public InputStream getResourceAsStream(String name)
    Returns a stream to read the requested resource name.
    Overrides:
      `getResourceAsStream` in class `ClassLoader`
    Parameters:
      `name` - The name of the resource for which a stream is required. Must not be `null`.
    Returns:
      a stream to the required resource or `null` if the resource cannot be found on the loader's classpath.

  - ### getResource

    public URL getResource(String name)
    Finds the resource with the given name. A resource is some data (images, audio, text, etc) that can be accessed by class code in a way that is independent of the location of the code.
    Overrides:
      `getResource` in class `ClassLoader`
    Parameters:
      `name` - The name of the resource for which a stream is required. Must not be `null`.
    Returns:
      a URL for reading the resource, or `null` if the resource could not be found or the caller doesn't have adequate privileges to get the resource.

  - ### getNamedResources

    public Enumeration<URL> getNamedResources(String name) throws IOException
    Finds all the resources with the given name. A resource is some data (images, audio, text, etc) that can be accessed by class code in a way that is independent of the location of the code.
    Parameters:
      `name` - name of the resource
    Returns:
      possible URLs as enumeration
    Throws:
      `IOException` - if something goes wrong
    Since:
      Ant 1.8.0
    See Also:
      - `findResources(String, boolean)`

  - ### findResource

    protected URL findResource(String name)
    Finds the resource with the given name.
    Overrides:
      `findResource` in class `ClassLoader`
    Parameters:
      `name` - The resource name
    Returns:
      A `URL` object for reading the resource, or `null` if the resource could not be found

  - ### findResources

    protected Enumeration<URL> findResources(String name) throws IOException
    Returns an enumeration of URLs representing all the resources with the given name by searching the class loader's classpath.
    Overrides:
      `findResources` in class `ClassLoader`
    Parameters:
      `name` - The resource name to search for. Must not be `null`.
    Returns:
      an enumeration of URLs for the resources
    Throws:
      `IOException` - if I/O errors occurs (can't happen)

  - ### findResources

    protected Enumeration<URL> findResources(String name, boolean skipParent) throws IOException
    Returns an enumeration of URLs representing all the resources with the given name by searching the class loader's classpath.
    Parameters:
      `name` - The resource name to search for. Must not be `null`.
      `skipParent` - whether to skip searching the parent first - will be false if the method is invoked from `getResources(String)` or `getNamedResources(String)` and true if the method is invoked from `findResources(String)`.
    Returns:
      an enumeration of URLs for the resources
    Throws:
      `IOException` - if I/O errors occurs (can't happen)

  - ### getResourceURL

    protected URL getResourceURL(File file, String resourceName)
    Returns the URL of a given resource in the given file which may either be a directory or a zip file.
    Parameters:
      `file` - The file (directory or jar) in which to search for the resource. Must not be `null`.
      `resourceName` - The name of the resource for which a stream is required. Must not be `null`.
    Returns:
      a stream to the required resource or `null` if the resource cannot be found in the given file object.

  - ### loadClass

    protected Class<?> loadClass(String classname, boolean resolve) throws ClassNotFoundException
    Loads a class with this class loader. This class attempts to load the class in an order determined by whether or not the class matches the system/loader package lists, with the loader package list taking priority. If the classloader is in isolated mode, failure to load the class in this loader will result in a ClassNotFoundException.
    Overrides:
      `loadClass` in class `ClassLoader`
    Parameters:
      `classname` - The name of the class to be loaded. Must not be `null`.
      `resolve` - `true` if all classes upon which this class depends are to be loaded.
    Returns:
      the required Class object
    Throws:
      `ClassNotFoundException` - if the requested class does not exist on the system classpath (when not in isolated mode) or this loader's classpath.

  - ### defineClassFromData

    protected Class<?> defineClassFromData(File container, byte[] classData, String classname) throws IOException
    Define a class given its bytes
    Parameters:
      `container` - the container from which the class data has been read may be a directory or a jar/zip file.
      `classData` - the bytecode data for the class
      `classname` - the name of the class
    Returns:
      the Class instance created from the given data
    Throws:
      `IOException` - if the class data cannot be read.

  - ### definePackage

    protected void definePackage(File container, String className) throws IOException
    Define the package information associated with a class.
    Parameters:
      `container` - the file containing the class definition.
      `className` - the class name of for which the package information is to be determined.
    Throws:
      `IOException` - if the package information cannot be read from the container.

  - ### definePackage

    protected void definePackage(File container, String packageName, Manifest manifest)
    Define the package information when the class comes from a jar with a manifest
    Parameters:
      `container` - the jar file containing the manifest
      `packageName` - the name of the package being defined.
      `manifest` - the jar's manifest

  - ### findClass

    public Class<?> findClass(String name) throws ClassNotFoundException
    Searches for and load a class on the classpath of this class loader.
    Overrides:
      `findClass` in class `ClassLoader`
    Parameters:
      `name` - The name of the class to be loaded. Must not be `null`.
    Returns:
      the required Class object
    Throws:
      `ClassNotFoundException` - if the requested class does not exist on this loader's classpath.

  - ### isInPath

    protected boolean isInPath(File component)
    Indicate if the given file is in this loader's path
    Parameters:
      `component` - the file which is to be checked
    Returns:
      true if the file is in the class path

  - ### cleanup

    public void cleanup()
    Cleans up any resources held by this classloader. Any open archive files are closed.

  - ### getConfiguredParent

    public ClassLoader getConfiguredParent()
    Gets the parent as has been specified in the constructor or via setParent.
    Returns:
      classloader
    Since:
      Ant 1.8.0

  - ### buildStarted

    public void buildStarted(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `buildStarted` in interface `BuildListener`
    Parameters:
      `event` - the buildStarted event

  - ### buildFinished

    public void buildFinished(BuildEvent event)
    Cleans up any resources held by this classloader at the end of a build.
    Specified by:
      `buildFinished` in interface `BuildListener`
    Parameters:
      `event` - the buildFinished event
    See Also:
      - `BuildEvent.getException()`

  - ### subBuildFinished

    public void subBuildFinished(BuildEvent event)
    Cleans up any resources held by this classloader at the end of a subbuild if it has been created for the subbuild's project instance.
    Specified by:
      `subBuildFinished` in interface `SubBuildListener`
    Parameters:
      `event` - the buildFinished event
    Since:
      Ant 1.6.2
    See Also:
      - `BuildEvent.getException()`

  - ### subBuildStarted

    public void subBuildStarted(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `subBuildStarted` in interface `SubBuildListener`
    Parameters:
      `event` - the buildStarted event
    Since:
      Ant 1.6.2

  - ### targetStarted

    public void targetStarted(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `targetStarted` in interface `BuildListener`
    Parameters:
      `event` - the targetStarted event
    See Also:
      - `BuildEvent.getTarget()`

  - ### targetFinished

    public void targetFinished(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `targetFinished` in interface `BuildListener`
    Parameters:
      `event` - the targetFinished event
    See Also:
      - `BuildEvent.getException()`

  - ### taskStarted

    public void taskStarted(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `taskStarted` in interface `BuildListener`
    Parameters:
      `event` - the taskStarted event
    See Also:
      - `BuildEvent.getTask()`

  - ### taskFinished

    public void taskFinished(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `taskFinished` in interface `BuildListener`
    Parameters:
      `event` - the taskFinished event
    See Also:
      - `BuildEvent.getException()`

  - ### messageLogged

    public void messageLogged(BuildEvent event)
    Empty implementation to satisfy the BuildListener interface.
    Specified by:
      `messageLogged` in interface `BuildListener`
    Parameters:
      `event` - the messageLogged event
    See Also:
      - `BuildEvent.getMessage()`
      - `BuildEvent.getException()`
      - `BuildEvent.getPriority()`

  - ### addJavaLibraries

    public void addJavaLibraries()
    add any libraries that come with different java versions here

  - ### toString

    public String toString()
    Returns a `String` representing this loader.
    Overrides:
      `toString` in class `Object`
    Returns:
      the path that this classloader has.

  - ### getResources

    public Enumeration<URL> getResources(String name) throws IOException
    Overrides:
      `getResources` in class `ClassLoader`
    Throws:
      `IOException`

  - ### close

    public void close()
    Specified by:
      `close` in interface `AutoCloseable`
    Specified by:
      `close` in interface `Closeable`

  - ### newAntClassLoader

    public static AntClassLoader newAntClassLoader(ClassLoader parent, Project project, Path path, boolean parentFirst)
    Factory method
    Parameters:
      `parent` - ClassLoader
      `project` - Project
      `path` - Path
      `parentFirst` - boolean
    Returns:
      AntClassLoader