jrunx.util
Class DynamicClassLoader

java.lang.Object
  |
  +--java.lang.ClassLoader
        |
        +--java.security.SecureClassLoader
              |
              +--java.net.URLClassLoader
                    |
                    +--jrunx.util.JRunURLClassLoader
                          |
                          +--jrunx.resource.ResourceURLClassLoader
                                |
                                +--jrunx.util.DynamicClassLoader

public class DynamicClassLoader

extends ResourceURLClassLoader

This class is a URLClassLoader that does automatic reloading and automatic compilation. The class provides the following:

• the ability to reload a Class when a dependent class changes (servlet/JSP/Tag handler)
• the ability to compile a class for a java file when needed and possible
• the ability to track relationships between classes such that steps can be taken to insure that ClassCastExceptions aren't possible
• minimal disruption by only reloading necessary classes and leaving unaffected classes alone

To use this class, you can not simply create an instance and load the class you wish to use it on. Instead, you must call loadClass() on the class each time you wish to check if it needs to be reloaded, usually called when the class is to be instantiated.

We use a classloader within this classloader to actually load the classes. We get a new classloader when:

• the class we're trying to load changes
• a class referenced in the class we're trying to load changes

Note that the old ClassLoader still exists, we just no longer have a reference to it. It will stay around until all objects that were defined with it have been garbage collected.

From 12.7 of Java Lang. Spec.:
Reloading may not be transparent if, for example, the class has:

• static variables (whose state would be lost)
• static initializers (which may have side effects)
• native methods (which may retain static state)

Author:

Tom Reilly, Brian Deitte

Constructor Summary

DynamicClassLoader(java.net.URL[] urls)

DynamicClassLoader(java.net.URL[] urls, boolean compile)

DynamicClassLoader(java.net.URL[] urls, java.lang.ClassLoader parent, boolean compile)

Method Summary

static java.lang.String	convertSlashName(java.lang.String name)
protected java.lang.Class	findClass(java.lang.String name)
static java.util.Set	getClassDependencies(java.lang.Class cls)
static jrunx.util.ClassConstantPool	read(java.io.InputStream stream)

Methods inherited from class jrunx.resource.ResourceURLClassLoader

findResource

Methods inherited from class jrunx.util.JRunURLClassLoader

addURL, classloaders, classloaders, definePackage, loadClass, loadClass, setLoadFrom, toString

Methods inherited from class java.net.URLClassLoader

definePackage, findResources, getPermissions, getURLs, newInstance, newInstance

Methods inherited from class java.security.SecureClassLoader

defineClass

Methods inherited from class java.lang.ClassLoader

defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, resolveClass, setSigners

Methods inherited from class java.lang.Object

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

Constructor Detail

DynamicClassLoader

public DynamicClassLoader(java.net.URL[] urls)

DynamicClassLoader

public DynamicClassLoader(java.net.URL[] urls,
                          boolean compile)

DynamicClassLoader

public DynamicClassLoader(java.net.URL[] urls,
                          java.lang.ClassLoader parent,
                          boolean compile)

Method Detail

findClass

protected java.lang.Class findClass(java.lang.String name)
                             throws java.lang.ClassNotFoundException

Overrides:

findClass in class JRunURLClassLoader

getClassDependencies

public static java.util.Set getClassDependencies(java.lang.Class cls)

read

public static jrunx.util.ClassConstantPool read(java.io.InputStream stream)
                                         throws java.io.IOException

convertSlashName

public static java.lang.String convertSlashName(java.lang.String name)