org.springframework.instrument.classloading

## Class ReflectiveLoadTimeWeaver

- java.lang.Object
- - org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver

All Implemented Interfaces:
  LoadTimeWeaver

    public class ReflectiveLoadTimeWeaver
    extends Object
    implements LoadTimeWeaver

`LoadTimeWeaver` which uses reflection to delegate to an underlying ClassLoader with well-known transformation hooks. The underlying ClassLoader is expected to support the following weaving methods (as defined in the `LoadTimeWeaver` interface):

- `public void addTransformer(java.lang.instrument.ClassFileTransformer)`: for registering the given ClassFileTransformer on this ClassLoader
- `public ClassLoader getThrowawayClassLoader()`: for obtaining a throwaway class loader for this ClassLoader (optional; ReflectiveLoadTimeWeaver will fall back to a SimpleThrowawayClassLoader if that method isn't available)

Please note that the above methods must reside in a class that is publicly accessible, although the class itself does not have to be visible to the application's class loader.

The reflective nature of this LoadTimeWeaver is particularly useful when the underlying ClassLoader implementation is loaded in a different class loader itself (such as the application server's class loader which is not visible to the web application). There is no direct API dependency between this LoadTimeWeaver adapter and the underlying ClassLoader, just a 'loose' method contract.

This is the LoadTimeWeaver to use in combination with Spring's `TomcatInstrumentableClassLoader` for Tomcat 5.0+ as well as with the Resin application server version 3.1+.

Since:
  2.0
Author:
  Costin Leau, Juergen Hoeller
See Also:
  `addTransformer(java.lang.instrument.ClassFileTransformer)`, `getThrowawayClassLoader()`, `SimpleThrowawayClassLoader`, `TomcatInstrumentableClassLoader`

### Constructor Summary

Constructors
Constructor and Description
`ReflectiveLoadTimeWeaver()` Create a new ReflectiveLoadTimeWeaver for the current context class loader, which needs to support the required weaving methods.
`ReflectiveLoadTimeWeaver(ClassLoader classLoader)` Create a new SimpleLoadTimeWeaver for the given class loader.

### Method Summary

Methods
`void` `addTransformer(ClassFileTransformer transformer)` Add a `ClassFileTransformer` to be applied by this `LoadTimeWeaver`.
`ClassLoader` `getInstrumentableClassLoader()` Return a `ClassLoader` that supports instrumentation through AspectJ-style load-time weaving based on user-defined `ClassFileTransformers`.
`ClassLoader` `getThrowawayClassLoader()` Return a throwaway `ClassLoader`, enabling classes to be loaded and inspected without affecting the parent `ClassLoader`.

### Methods inherited from class java.lang.Object

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

### Constructor Detail

#### ReflectiveLoadTimeWeaver

    public ReflectiveLoadTimeWeaver()

Create a new ReflectiveLoadTimeWeaver for the current context class loader, which needs to support the required weaving methods.

#### ReflectiveLoadTimeWeaver

    public ReflectiveLoadTimeWeaver(ClassLoader classLoader)

Create a new SimpleLoadTimeWeaver for the given class loader.

Parameters:
  `classLoader` - the `ClassLoader` to delegate to for weaving (must support the required weaving methods).
Throws:
  `IllegalStateException` - if the supplied `ClassLoader` does not support the required weaving methods

### Method Detail

#### addTransformer

    public void addTransformer(ClassFileTransformer transformer)

Description copied from interface: `LoadTimeWeaver`
Add a `ClassFileTransformer` to be applied by this `LoadTimeWeaver`.

Specified by:
  `addTransformer` in interface `LoadTimeWeaver`
Parameters:
  `transformer` - the `ClassFileTransformer` to add

#### getInstrumentableClassLoader

    public ClassLoader getInstrumentableClassLoader()

Description copied from interface: `LoadTimeWeaver`
Return a `ClassLoader` that supports instrumentation through AspectJ-style load-time weaving based on user-defined `ClassFileTransformers`.

May be the current `ClassLoader`, or a `ClassLoader` created by this `LoadTimeWeaver` instance.

Specified by:
  `getInstrumentableClassLoader` in interface `LoadTimeWeaver`
Returns:
  the `ClassLoader` which will expose instrumented classes according to the registered transformers

#### getThrowawayClassLoader

    public ClassLoader getThrowawayClassLoader()

Description copied from interface: `LoadTimeWeaver`
Return a throwaway `ClassLoader`, enabling classes to be loaded and inspected without affecting the parent `ClassLoader`.

Should not return the same instance of the `ClassLoader` returned from an invocation of `LoadTimeWeaver.getInstrumentableClassLoader()`.

Specified by:
  `getThrowawayClassLoader` in interface `LoadTimeWeaver`
Returns:
  a temporary throwaway `ClassLoader`; should return a new instance for each call, with no existing state