AntClassLoader (Apache Ant API)

org.apache.tools.ant
Class AntClassLoader


java.lang.Object

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  +--java.lang.ClassLoader

        |

        +--org.apache.tools.ant.AntClassLoader

All Implemented Interfaces:
BuildListener, java.util.EventListener

public class AntClassLoader
extends java.lang.ClassLoader
implements BuildListener

Used to load classes within ant with a different claspath 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.

Author:
Conor MacNeill
, Jesse Glick , Magesh Umasankar

Constructor Summary
AntClassLoader(java.lang.ClassLoader parent, boolean parentFirst)
          Creates an empty class loader.
AntClassLoader(java.lang.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
 void addLoaderPackageRoot(java.lang.String packageRoot)
          Adds a package root to the list of packages which must be loaded using this loader.
 void addPathElement(java.lang.String pathElement)
          Adds an element to the classpath to be searched.
 void addSystemPackageRoot(java.lang.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.
 java.lang.Class findClass(java.lang.String name)
          Searches for and load a class on the classpath of this class loader.
protected  java.util.Enumeration findResources(java.lang.String name)
          Returns an enumeration of URLs representing all the resources with the given name by searching the class loader's classpath.
 java.lang.Class forceLoadClass(java.lang.String classname)
          Loads a class through this class loader even if that class is available on the parent classpath.
 java.lang.Class forceLoadSystemClass(java.lang.String classname)
          Loads a class through this class loader but defer to the parent class loader.
 java.lang.String getClasspath()
          Returns the classpath this classloader will consult.
 java.net.URL getResource(java.lang.String name)
          Finds the resource with the given name.
 java.io.InputStream getResourceAsStream(java.lang.String name)
          Returns a stream to read the requested resource name.
static void initializeClass(java.lang.Class theClass)
          Forces initialization of a class in a JDK 1.1 compatible, albeit hacky way.
protected  java.lang.Class loadClass(java.lang.String classname, boolean resolve)
          Loads a class with this class loader.
protected  void log(java.lang.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.
 void resetThreadContextLoader()
          Resets the current thread's context loader to its original value.
 void setIsolated(boolean isolated)
          Sets whether this classloader should run in isolated mode.
 void setThreadContextLoader()
          Sets the current thread's context loader to this classloader, storing the current loader value for later resetting.
 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.
 
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findResource, findSystemClass, getPackage, getPackages, getParent, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

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(java.lang.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(java.lang.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 Detail

log


protected void log(java.lang.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(java.lang.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.

getClasspath


public java.lang.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


public static void initializeClass(java.lang.Class theClass)
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(java.lang.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(java.lang.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 java.lang.Class forceLoadClass(java.lang.String classname)
                               throws java.lang.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:
java.lang.ClassNotFoundException - if the requested class does not exist on this loader's classpath.

forceLoadSystemClass


public java.lang.Class forceLoadSystemClass(java.lang.String classname)
                                     throws java.lang.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 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:
java.lang.ClassNotFoundException - if the requested class does not exist on this loader's classpath.

getResourceAsStream


public java.io.InputStream getResourceAsStream(java.lang.String name)
Returns a stream to read the requested resource name.

Overrides:
getResourceAsStream in class java.lang.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 java.net.URL getResource(java.lang.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 java.lang.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.

findResources


protected java.util.Enumeration findResources(java.lang.String name)
                                       throws java.io.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 java.lang.ClassLoader
Parameters:
name - The resource name to search for. Must not be null.
Returns:
an enumeration of URLs for the resources
Throws:
java.io.IOException - if I/O errors occurs (can't happen)

loadClass


protected java.lang.Class loadClass(java.lang.String classname,
                                    boolean resolve)
                             throws java.lang.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 java.lang.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:
java.lang.ClassNotFoundException - if the requested class does not exist on the system classpath (when not in isolated mode) or this loader's classpath.

findClass


public java.lang.Class findClass(java.lang.String name)
                          throws java.lang.ClassNotFoundException
Searches for and load a class on the classpath of this class loader.

Overrides:
findClass in class java.lang.ClassLoader
Parameters:
name - The name of the class to be loaded. Must not be null.
Returns:
the required Class object
Throws:
java.lang.ClassNotFoundException - if the requested class does not exist on this loader's classpath.

cleanup


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


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()

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.getPriority()


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