org.apache.tools.ant.util

Class 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
static classClasspathUtils.Delegate
Delegate that helps out any specific ProjectComponent that needs dynamic classloading.
Field Summary
static StringREUSE_LOADER_REF
Name of the magic property that controls classloader reuse in Ant 1.4.
Method Summary
static ClassLoadergetClassLoaderForPath(Project p, Reference ref)
Convenience overloaded version of {@link #getClassLoaderForPath(Project, Reference, boolean)}.
static ClassLoadergetClassLoaderForPath(Project p, Reference ref, boolean reverseLoader)
Convenience overloaded version of {@link #getClassLoaderForPath(Project, Path, String, boolean)}.
static ClassLoadergetClassLoaderForPath(Project p, Path path, String loaderId)
Convenience overloaded version of {@link #getClassLoaderForPath(Project, Path, String, boolean)}.
static ClassLoadergetClassLoaderForPath(Project p, Path path, String loaderId, boolean reverseLoader)
Convenience overloaded version of {@link #getClassLoaderForPath(Project, Path, String, boolean, boolean)}.
static ClassLoadergetClassLoaderForPath(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 ClasspathUtils.DelegategetDelegate(ProjectComponent component)
Obtains a delegate that helps out with classic classpath configuration.
static ClassLoadergetUniqueClassLoaderForPath(Project p, Path path, boolean reverseLoader)
Gets a fresh, different, previously unused classloader that uses the passed path as its classpath.
static ObjectnewInstance(String className, ClassLoader userDefinedLoader)
Creates a fresh object instance of the specified classname.
static ObjectnewInstance(String className, ClassLoader userDefinedLoader, Class expectedType)
Creates a fresh object instance of the specified classname.

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.

Method Detail

getClassLoaderForPath

public static ClassLoader getClassLoaderForPath(Project p, Reference ref)
Convenience overloaded version of {@link #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 ClassLoader getClassLoaderForPath(Project p, Reference ref, boolean reverseLoader)
Convenience overloaded version of {@link #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

getClassLoaderForPath

public static ClassLoader getClassLoaderForPath(Project p, Path path, String loaderId)
Convenience overloaded version of {@link #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 ClassLoader getClassLoaderForPath(Project p, Path path, String loaderId, boolean reverseLoader)
Convenience overloaded version of {@link #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 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.

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: Delegate

getUniqueClassLoaderForPath

public static 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, 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, 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