org.springframework.instrument.classloading

## Class InstrumentationLoadTimeWeaver

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

- All Implemented Interfaces:
    LoadTimeWeaver

      public class InstrumentationLoadTimeWeaver
      extends Object
      implements LoadTimeWeaver

  `LoadTimeWeaver` relying on VM `Instrumentation`.

  Start the JVM specifying the Java agent to be used, like as follows:

  `-javaagent:path/to/org.springframework.instrument.jar`

  where `org.springframework.instrument.jar` is a JAR file containing the `InstrumentationSavingAgent` class, as shipped with Spring.

  In Eclipse, for example, set the "Run configuration"'s JVM args to be of the form:

  `-javaagent:${project_loc}/lib/org.springframework.instrument.jar`

  Since:
    2.0
  Author:
    Rod Johnson, Juergen Hoeller
  See Also:
    `InstrumentationSavingAgent`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `InstrumentationLoadTimeWeaver()` Create a new InstrumentationLoadTimeWeaver for the default ClassLoader.
    `InstrumentationLoadTimeWeaver(ClassLoader classLoader)` Create a new InstrumentationLoadTimeWeaver for the given ClassLoader.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addTransformer(ClassFileTransformer transformer)` Add a `ClassFileTransformer` to be applied by this `LoadTimeWeaver`.
    `ClassLoader` | `getInstrumentableClassLoader()` We have the ability to weave the current class loader when starting the JVM in this way, so the instrumentable class loader will always be the current loader.
    `ClassLoader` | `getThrowawayClassLoader()` This implementation always returns a `SimpleThrowawayClassLoader`.
    `static boolean` | `isInstrumentationAvailable()` Check whether an Instrumentation instance is available for the current VM.
    `void` | `removeTransformers()` Remove all registered transformers, in inverse order of registration.

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

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

- - ### Constructor Detail

    - #### InstrumentationLoadTimeWeaver

          public InstrumentationLoadTimeWeaver()

      Create a new InstrumentationLoadTimeWeaver for the default ClassLoader.

    - #### InstrumentationLoadTimeWeaver

          public InstrumentationLoadTimeWeaver(ClassLoader classLoader)

      Create a new InstrumentationLoadTimeWeaver for the given ClassLoader.
      Parameters:
        `classLoader` - the ClassLoader that registered transformers are supposed to apply to

  - ### 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()

      We have the ability to weave the current class loader when starting the JVM in this way, so the instrumentable class loader will always be the current loader.
      Specified by:
        `getInstrumentableClassLoader` in interface `LoadTimeWeaver`
      Returns:
        the `ClassLoader` which will expose instrumented classes according to the registered transformers

    - #### getThrowawayClassLoader

          public ClassLoader getThrowawayClassLoader()

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

    - #### removeTransformers

          public void removeTransformers()

      Remove all registered transformers, in inverse order of registration.

    - #### isInstrumentationAvailable

          public static boolean isInstrumentationAvailable()

      Check whether an Instrumentation instance is available for the current VM.
      See Also:
        `getInstrumentation()`