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## org.springframework.core
Class OverridingClassLoader

    java.lang.Object
      java.lang.ClassLoader
          org.springframework.core.DecoratingClassLoader
              org.springframework.core.OverridingClassLoader

Direct Known Subclasses:
  SimpleInstrumentableClassLoader, SimpleThrowawayClassLoader

    public class OverridingClassLoader

extends DecoratingClassLoader

`ClassLoader` that does not always delegate to the parent loader, as normal class loaders do. This enables, for example, instrumentation to be forced in the overriding ClassLoader, or a "throwaway" class loading behavior, where selected classes are temporarily loaded in the overriding ClassLoader, in order to load an instrumented version of the class in the parent ClassLoader later on.

Since:
  2.0.1
Author:
  Rod Johnson, Juergen Hoeller

Field Summary
`static String[]` | `DEFAULT_EXCLUDED_PACKAGES` Packages that are excluded by default

Constructor Summary
`OverridingClassLoader(ClassLoader parent)` Create a new OverridingClassLoader for the given class loader.

Method Summary
`protected boolean` | `isEligibleForOverriding(String className)` Determine whether the specified class is eligible for overriding by this class loader.
`protected byte[]` | `loadBytesForClass(String name)` Load the defining bytes for the given class, to be turned into a Class object through a `ClassLoader.defineClass(byte[], int, int)` call.
`protected Class` | `loadClass(String name, boolean resolve)`
`protected Class` | `loadClassForOverriding(String name)` Load the specified class for overriding purposes in this ClassLoader.
`protected InputStream` | `openStreamForClass(String name)` Open an InputStream for the specified class.
`protected byte[]` | `transformIfNecessary(String name, byte[] bytes)` Transformation hook to be implemented by subclasses.

Methods inherited from class org.springframework.core.DecoratingClassLoader
`excludeClass, excludePackage, isExcluded`

Methods inherited from class java.lang.ClassLoader
`clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findResources, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### DEFAULT_EXCLUDED_PACKAGES

    public static final String[] DEFAULT_EXCLUDED_PACKAGES

  Packages that are excluded by default

Constructor Detail

### OverridingClassLoader

    public OverridingClassLoader(ClassLoader parent)

  Create a new OverridingClassLoader for the given class loader.

  Parameters:
    `parent` - the ClassLoader to build an overriding ClassLoader for

Method Detail

### loadClass

    protected Class loadClass(String name,
                              boolean resolve)
                       throws ClassNotFoundException

  Overrides:
    `loadClass` in class `ClassLoader`
  Throws:
    `ClassNotFoundException`

### isEligibleForOverriding

    protected boolean isEligibleForOverriding(String className)

  Determine whether the specified class is eligible for overriding by this class loader.

  Parameters:
    `className` - the class name to check
  Returns:
    whether the specified class is eligible
  See Also:
    `DecoratingClassLoader.isExcluded(java.lang.String)`

### loadClassForOverriding

    protected Class loadClassForOverriding(String name)
                                    throws ClassNotFoundException

  Load the specified class for overriding purposes in this ClassLoader.

  The default implementation delegates to `ClassLoader.findLoadedClass(java.lang.String)`, `loadBytesForClass(java.lang.String)` and `ClassLoader.defineClass(byte[], int, int)`.

  Parameters:
    `name` - the name of the class
  Returns:
    the Class object, or `null` if no class defined for that name
  Throws:
    `ClassNotFoundException` - if the class for the given name couldn't be loaded

### loadBytesForClass

    protected byte[] loadBytesForClass(String name)
                                throws ClassNotFoundException

  Load the defining bytes for the given class, to be turned into a Class object through a `ClassLoader.defineClass(byte[], int, int)` call.

  The default implementation delegates to `openStreamForClass(java.lang.String)` and `transformIfNecessary(java.lang.String, byte[])`.

  Parameters:
    `name` - the name of the class
  Returns:
    the byte content (with transformers already applied), or `null` if no class defined for that name
  Throws:
    `ClassNotFoundException` - if the class for the given name couldn't be loaded

### openStreamForClass

    protected InputStream openStreamForClass(String name)

  Open an InputStream for the specified class.

  The default implementation loads a standard class file through the parent ClassLoader's `getResourceAsStream` method.

  Parameters:
    `name` - the name of the class
  Returns:
    the InputStream containing the byte code for the specified class

### transformIfNecessary

    protected byte[] transformIfNecessary(String name,
                                          byte[] bytes)

  Transformation hook to be implemented by subclasses.

  The default implementation simply returns the given bytes as-is.

  Parameters:
    `name` - the fully-qualified name of the class being transformed
    `bytes` - the raw bytes of the class
  Returns:
    the transformed bytes (never `null`; same as the input bytes if the transformation produced no changes)

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