org.apache.tools.ant.util
Class ClasspathUtils

java.lang.Object
  |
  +--org.apache.tools.ant.util.ClasspathUtils

public class ClasspathUtils
extends java.lang.Object

Offers some helper methods on the Path structure in ant.

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 class ClasspathUtils.Delegate
          Delegate that helps out any specific ProjectComponent that needs dynamic classloading.
 
Field Summary
static java.lang.String REUSE_LOADER_REF
          Name of the magic property that controls classloader reuse in Ant 1.4.
 
Constructor Summary
ClasspathUtils()
           
 
Method Summary
static java.lang.ClassLoader getClassLoaderForPath(Project p, Path path, java.lang.String loaderId)
          Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean).
static java.lang.ClassLoader getClassLoaderForPath(Project p, Path path, java.lang.String loaderId, boolean reverseLoader)
          Convenience overloaded version of getClassLoaderForPath(Project, Path, String, boolean, boolean).
static java.lang.ClassLoader getClassLoaderForPath(Project p, Path path, java.lang.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, not used before classloader that uses the passed path as it's classpath.
static java.lang.Object newInstance(java.lang.String className, java.lang.ClassLoader userDefinedLoader)
          Creates a fresh object instance of the specified classname.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

REUSE_LOADER_REF

public static final java.lang.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,
                                                          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 it's parent (which is contra the regular classloader behaviour)
Returns:
The class loader

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Path path,
                                                          java.lang.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,
                                                          java.lang.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 it's parent (which is contra the regular classloader behaviour)
Returns:
The class loader

getClassLoaderForPath

public static java.lang.ClassLoader getClassLoaderForPath(Project p,
                                                          Path path,
                                                          java.lang.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 perviously 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 it's 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.

getUniqueClassLoaderForPath

public static java.lang.ClassLoader getUniqueClassLoaderForPath(Project p,
                                                                Path path,
                                                                boolean reverseLoader)
Gets a fresh, different, not used before classloader that uses the passed path as it's 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 it's parent (which is contra the regular classloader behaviour)
Returns:
The fresh, different, not used before class loader.

newInstance

public static java.lang.Object newInstance(java.lang.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.

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


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