ClassTransformer (EclipseLink 2.7.15, API Reference)

```
public interface ClassTransformer
```
A persistence provider supplies an instance of this interface to the PersistenceUnitInfo.addTransformer method. The supplied transformer instance will get called to transform entity class files when they are loaded or redefined. The transformation occurs before the class is defined by the JVM.

Since:

1.0

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`byte[]`	`transform(java.lang.ClassLoader loader, java.lang.String className, java.lang.Class<?> classBeingRedefined, java.security.ProtectionDomain protectionDomain, byte[] classfileBuffer)`	Invoked when a class is being loaded or redefined.

- Method Detail
  - transform
```
byte[] transform(java.lang.ClassLoader loader,
                 java.lang.String className,
                 java.lang.Class<?> classBeingRedefined,
                 java.security.ProtectionDomain protectionDomain,
                 byte[] classfileBuffer)
          throws java.lang.instrument.IllegalClassFormatException
```
    Invoked when a class is being loaded or redefined. The implementation of this method may transform the supplied class file and return a new replacement class file.
    
    Parameters:
    
    loader - the defining loader of the class to be transformed, may be null if the bootstrap loader
    
    className - the name of the class in the internal form of fully qualified class and interface names
    
    classBeingRedefined - if this is a redefine, the class being redefined, otherwise null
    
    protectionDomain - the protection domain of the class being defined or redefined
    
    classfileBuffer - the input byte buffer in class file format - must not be modified
    
    Returns:
    
    a well-formed class file buffer (the result of the transform), or null if no transform is performed
    
    Throws:
    
    java.lang.instrument.IllegalClassFormatException - if the input does not represent a well-formed class file