Javassist

Javassist (Java programming assistant) is a Java library providing a means to manipulate the Java bytecode of an application.^[1] In this sense Javassist provides the support for structural reflection, i.e. the ability to change the implementation of a class at run time.

Bytecode manipulation is performed at load-time through a provided class loader.

Uses

Javassist can be used for the following:

• For specifying the bytecode using source code – can compile a fragment of source text online (e.g., just a single statement)
• For Aspect Oriented Programming (AOP) – can introduce new methods into a class and insert before/after/around advice at both the caller and callee sides
• For reflection at runtime – can use a metaobject that controls method calls on base-level objects
• For remote method invocation – can call a method on a remote object running on a web server, an alternative to Java RMI that does not need a stub compiler such as rmic

References

See also

• ObjectWeb ASM
• Byte Code Engineering Library

External links

• Javassist project home
• javassist at JBoss Labs