org.apache.tools.ant.util

Class ClasspathUtils

java.lang.Object

org.apache.tools.ant.util.ClasspathUtils

public class ClasspathUtils
extends Object

Offers some helper methods on the Path structure in ant.

The basic idea behind this utility class is to use it from inside the different Ant objects (and user defined objects) that need classLoading for their operation. Normally those would have a setClasspathRef() {for the @classpathref} and/or a createClasspath() {for the nested <classpath>} Typically one would have in your Ant Task or DataType

 ClasspathUtils.Delegate cpDelegate;

 public void init() {
     this.cpDelegate = ClasspathUtils.getDelegate(this);
     super.init();
 }

 public void setClasspathRef(Reference r) {
     this.cpDelegate.setClasspathRef(r);
 }

 public Path createClasspath() {
     return this.cpDelegate.createClasspath();
 }

 public void setClassname(String fqcn) {
     this.cpDelegate.setClassname(fqcn);
 }
 

At execution time, when you actually need the classloading you can just:

     Object o = this.cpDelegate.newInstance();
 

Since:

Ant 1.6

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ClasspathUtils.Delegate Delegate that helps out any specific ProjectComponent that needs dynamic classloading.

Field Summary

Fields

Modifier and Type	Field and Description
static String	REUSE_LOADER_REF Name of the magic property that controls classloader reuse in Ant 1.4.

Constructor Summary

Constructors

Constructor and Description
ClasspathUtils()

Method Summary

Modifier and Type	Method and Description
static java.lang.ClassLoader	getClassLoaderForPath(Project p, Path path, String loaderId) Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean).
static java.lang.ClassLoader	getClassLoaderForPath(Project p, Path path, String loaderId, boolean reverseLoader) Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean, boolean).
static java.lang.ClassLoader	getClassLoaderForPath(Project p, Path path, String loaderId, boolean reverseLoader, boolean reuseLoader) Gets a classloader that loads classes from the classpath defined in the path argument.
static java.lang.ClassLoader	getClassLoaderForPath(Project p, Reference ref) Convenience overloaded version of getClassLoaderForPath(Project, Reference, boolean).
static java.lang.ClassLoader	getClassLoaderForPath(Project p, Reference ref, boolean reverseLoader) Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean).
static ClasspathUtils.Delegate	getDelegate(ProjectComponent component) Obtains a delegate that helps out with classic classpath configuration.
static java.lang.ClassLoader	getUniqueClassLoaderForPath(Project p, Path path, boolean reverseLoader) Gets a fresh, different, previously unused classloader that uses the passed path as its classpath.
static Object	newInstance(String className, java.lang.ClassLoader userDefinedLoader) Creates a fresh object instance of the specified classname.
static Object	newInstance(String className, java.lang.ClassLoader userDefinedLoader, Class expectedType) Creates a fresh object instance of the specified classname.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

REUSE_LOADER_REF

public static final String REUSE_LOADER_REF

Name of the magic property that controls classloader reuse in Ant 1.4.

See Also:

Constant Field Values

Constructor Detail

ClasspathUtils

public ClasspathUtils()

Method Detail

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Path path,
                                                          String loaderId)

Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean).

Assumes the logical 'false' for the reverseLoader.

Parameters:

p - current Ant project

path - the path

loaderId - the loader id string

Returns:

The class loader

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Path path,
                                                          String loaderId,
                                                          boolean reverseLoader)

Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean, boolean).

Sets value for 'reuseLoader' to true if the magic property has been set.

Parameters:

p - the project

path - the path

loaderId - the loader id string

reverseLoader - if set to true this new loader will take precedence over its parent (which is contra the regular classloader behaviour)

Returns:

The class loader

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Path path,
                                                          String loaderId,
                                                          boolean reverseLoader,
                                                          boolean reuseLoader)

Gets a classloader that loads classes from the classpath defined in the path argument.

Based on the setting of the magic property 'ant.reuse.loader' this will try to reuse the previously created loader with that id, and of course store it there upon creation.

Parameters:

p - Ant Project where the handled components are living in.

path - Path object to be used as classpath for this classloader

loaderId - identification for this Loader,

reverseLoader - if set to true this new loader will take precedence over its parent (which is contra the regular classloader behaviour)

reuseLoader - if true reuse the loader if it is found

Returns:

ClassLoader that uses the Path as its classpath.

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Reference ref)

Convenience overloaded version of getClassLoaderForPath(Project, Reference, boolean).

Assumes the logical 'false' for the reverseLoader.

Parameters:

p - the project

ref - the reference

Returns:

The class loader

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Reference ref,
                                                          boolean reverseLoader)

Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean).

Delegates to the other one after extracting the referenced Path from the Project. This checks also that the passed Reference is pointing to a Path all right.

Parameters:

p - current Ant project

ref - Reference to Path structure

reverseLoader - if set to true this new loader will take precedence over its parent (which is contra the regular classloader behaviour)

Returns:

The class loader

getDelegate

public static ClasspathUtils.Delegate getDelegate(ProjectComponent component)

Obtains a delegate that helps out with classic classpath configuration.

Parameters:

component - your projectComponent that needs the assistence

Returns:

the helper, delegate.

See Also:

ClasspathUtils.Delegate

getUniqueClassLoaderForPath

public static java.lang.ClassLoader getUniqueClassLoaderForPath(Project p,
                                                                Path path,
                                                                boolean reverseLoader)

Gets a fresh, different, previously unused classloader that uses the passed path as its classpath.

This method completely ignores the ant.reuse.loader magic property and should be used with caution.

Parameters:

p - Ant Project where the handled components are living in.

path - the classpath for this loader

reverseLoader - if set to true this new loader will take precedence over its parent (which is contra the regular classloader behaviour)

Returns:

The fresh, different, previously unused class loader.

newInstance

public static Object newInstance(String className,
                                 java.lang.ClassLoader userDefinedLoader)

Creates a fresh object instance of the specified classname.

This uses the userDefinedLoader to load the specified class, and then makes an instance using the default no-argument constructor.

Parameters:

className - the full qualified class name to load.

userDefinedLoader - the classloader to use.

Returns:

The fresh object instance

Throws:

BuildException - when loading or instantiation failed.

newInstance

public static Object newInstance(String className,
                                 java.lang.ClassLoader userDefinedLoader,
                                 Class expectedType)

Creates a fresh object instance of the specified classname.

This uses the userDefinedLoader to load the specified class, and then makes an instance using the default no-argument constructor.

Parameters:

className - the full qualified class name to load.

userDefinedLoader - the classloader to use.

expectedType - the Class that the result should be assignment compatible with. (No ClassCastException will be thrown in case the result of this method is casted to the expectedType)

Returns:

The fresh object instance

Throws:

BuildException - when loading or instantiation failed.

Since:

Ant 1.7