ClassTransformer (Jakarta Persistence API documentation)

```
public interface ClassTransformer
```
A persistence provider supplies an instance of this interface to the PersistenceUnitInfo.addTransformer(jakarta.persistence.spi.ClassTransformer) 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(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer)`	Invoked when a class is being loaded or redefined.

- Method Detail
  - transform
```
byte[] transform(ClassLoader loader,
                 String className,
                 Class<?> classBeingRedefined,
                 ProtectionDomain protectionDomain,
                 byte[] classfileBuffer)
          throws TransformerException
```
    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:
    
    TransformerException - if the input does not represent a well-formed class file