Having fun with Javassist

Transcript

1. Having fun with Javassist
2. whoami Anton Arhipov @antonarhipov
4. @Entity
 @Table(name  =  "owners")
 public  class  Owner  extends  Person  {
        @Column(name  =  "address")
        @NotEmpty
        private  String  address;
 
        @Column(name  =  "city")
        @NotEmpty
        private  String  city;
 
        @Column(name  =  "telephone")
        @NotEmpty
        @Digits(fraction  =  0,  integer  =  10)
        private  String  telephone;
 
        @OneToMany(cascade  =  CascadeType.ALL,                                  mappedBy  =  "owner")
        private  Set<Pet>  pets;  
5. public  class  JavassistLazyInitializer                  extends  BasicLazyInitializer                  implements  MethodHandler  {   final  JavassistLazyInitializer  instance              =  new  JavassistLazyInitializer(…);   
 ProxyFactory  factory  =  new  ProxyFactory();
 factory.setSuperclass(interfaces.length  ==  1?persistentClass:null);
 factory.setInterfaces(interfaces);
 factory.setFilter(FINALIZE_FILTER);   
 Class  cl  =  factory.createClass();
 final  HibernateProxy  proxy  =  (HibernateProxy)  cl.newInstance();
 ((ProxyObject)proxy).setHandler(instance);
 instance.constructed  =  true;
 return  proxy;  
6. public  class  JavassistLazyInitializer                  extends  BasicLazyInitializer                  implements  MethodHandler  {   final  JavassistLazyInitializer  instance              =  new  JavassistLazyInitializer(…);   
 ProxyFactory  factory  =  new  ProxyFactory();
 factory.setSuperclass(interfaces.length  ==  1?persistentClass:null);
 factory.setInterfaces(interfaces);
 factory.setFilter(FINALIZE_FILTER);   
 Class  cl  =  factory.createClass();
 final  HibernateProxy  proxy  =  (HibernateProxy)  cl.newInstance();
 ((ProxyObject)proxy).setHandler(instance);
 instance.constructed  =  true;
 return  proxy;   Generates proxy!
7. The main use case for bytecode generation in Java framewoks is to generate proxies
9. Agenda Javassist -javaagent basics … and little bit about о JRebel
10. Javassist www.javassist.org
11. CtPool CtClass CtClass CtClass CtClass CtField CtMethod CtConst CtMethod insertBefore insertAfter instrument Almost like Java Reflection API :)
12. https://github.com/antonarhipov/jpoint Ex1, Ex2, Ex3
13. Java Agent
14. Java Agent import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentation inst) throws Exception { inst.addTransformer(new ClassFileTransformer { // here be code }); } } META-INF/MANIFEST.MF Premain-Class: Agent $> java –javaagent:agent.jar application.Main
15. ClassFileTransformer new ClassFileTransformer() { public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); // here we can do all the things to ‘ct’ return ct.toBytecode(); } }
16. new ClassFileTransformer() { public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); // here we can do all the things to ‘ct’ return ct.toBytecode(); } } ClassFileTransformer
17. new ClassFileTransformer() { public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); // here we can do all the things to ‘ct’ return ct.toBytecode(); } } ClassFileTransformer
18. new ClassFileTransformer() { public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); // here we can do all the things to ‘ct’ return ct.toBytecode(); } } ClassFileTransformer
24. https://github.com/zeroturnaround/callspy
25. Javassist in
26. JRebel core Spring plugin Hibernate plugin EJB plugin
27. JRebel core Spring plugin Hibernate plugin EJB plugin Reloads classes
28. JRebel core Spring plugin Hibernate plugin EJB plugin Notifies plugins
29. JRebel core Spring plugin Hibernate plugin EJB plugin Refresh configurations
30. JRebel core Javassist lives here Spring plugin Hibernate plugin EJB plugin
31. Spring Hibernate OpenEJB JRebel core Spring plugin Hibernate plugin EJB plugin
32. https://github.com/antonarhipov/jpoint HowItWorks
33. Your task Javassist
34. https://speakerdeck.com/antonarhipov http://www.slideshare.net/arhan @antonarhipov anton@zeroturnaround.com