mrcode.duckprxy.impl
Class JavassistDuckPrxy

java.lang.Object
  mrcode.duckprxy.impl.JavassistDuckPrxy

All Implemented Interfaces:

DuckPrxy

public class JavassistDuckPrxy
extends java.lang.Object
implements DuckPrxy

Javassist implementation of DuckPrxy. A new class is generated for a proxy which will delegate calls to the provided delegate object. No runtime reflection is used, making it very efficient. Also, it can implement classes, not just interfaces. However, there are some down-sides:

• Some JVMs cannot garbage collect classes. In such JVM every javassist duck proxy instance will leak memory.
• Javassist cannot handle inner interfaces and classes. Hence, javassist duck proxies cannot implement inner interfaces (and inner classes, but the reflection based implementation cannot implement classes at all).

There are some rough edges: The proxy creator assumes that the delegate methods have a appropriate parameter and return types. This is not checked. You will probably get strange javassist or class loading exceptions when this assumption is not met.

Constructor Summary

JavassistDuckPrxy()

JavassistDuckPrxy(java.lang.String classNamePrefix)
Constructor to set own class name prefix.

Method Summary

protected void	addInterface(javassist.ClassPool classPool, javassist.CtClass ctClass, java.lang.Class<?> interfce, java.lang.Class<?> delegateClass, java.util.List<MethodUtils.MethodRetrieveStrategy> strategies, java.lang.reflect.Method subDelegateGetter)
protected void	addMethod(javassist.ClassPool classPool, javassist.CtClass ctClass, java.lang.reflect.Method method, java.lang.Class<?> delegateClass, java.util.List<MethodUtils.MethodRetrieveStrategy> strategies, java.lang.reflect.Method subDelegateGetter)
protected java.lang.String	createClassName(java.lang.Class<?> delegateClass, java.util.Collection<java.lang.Class<?>> interfaces)
protected javassist.CtClass	getCtClass(javassist.ClassPool classPool, java.lang.Class<?> clazz)
protected javassist.CtClass[]	getCtClass(javassist.ClassPool classPool, java.lang.Class<?>[] classes)
protected java.lang.String	getDelegateCall(java.lang.String name, java.lang.reflect.Method delegateMethod, int argsLen)
protected AbstractPrxyInvocationHandler.DelegateClassInformation	getDelegateClassInformation(java.lang.Class<?> delegateClass)
DuckArg	getDuckArg(java.lang.annotation.Annotation[] annotations)
protected java.lang.reflect.Method	getMethodDelegate(java.lang.reflect.Method method, java.lang.Class<?> delegateClass, java.util.List<MethodUtils.MethodRetrieveStrategy> strategies, java.lang.reflect.Method subDelegateGetter, java.lang.StringBuilder delegatePath)
java.lang.Class<?>	getProxyClass(java.lang.String className, java.lang.Object delegate, java.lang.Class<?> delegateClass, java.util.List<java.lang.Class<?>> allInterfaces, javassist.ClassPool classPool)
<T> T	makeProxy(java.lang.Class<T> mainInterface, java.lang.Object delegate, java.lang.Class<?>... interfaces) Creates an object that implements the defined interfaces delegating to a given object, mainly using duck typing.
protected java.util.List<MethodUtils.MethodRetrieveStrategy>	makeStrategies(java.lang.Class<?> delegateClass, AbstractPrxyInvocationHandler.DelegateClassInformation info)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JavassistDuckPrxy

public JavassistDuckPrxy()

JavassistDuckPrxy

public JavassistDuckPrxy(java.lang.String classNamePrefix)

Constructor to set own class name prefix. Normally, you do not want to override the class name prefix.

Parameters:

classNamePrefix - Override value for class name prefix.

Method Detail

makeProxy

public <T> T makeProxy(java.lang.Class<T> mainInterface,
                       java.lang.Object delegate,
                       java.lang.Class<?>... interfaces)

Description copied from interface: DuckPrxy

Creates an object that implements the defined interfaces delegating to a given object, mainly using duck typing.

Specified by:

makeProxy in interface DuckPrxy

Type Parameters:

T - The class of the main interface.

Parameters:

mainInterface - The main interface that the resulting object shall implement.

delegate - The object to delegate the calls to.

interfaces - Secondary interfaces to implement.

Returns:

An object implementing the main interface and secondary interfaces, delegating to the delegate object.

getProxyClass

public java.lang.Class<?> getProxyClass(java.lang.String className,
                                        java.lang.Object delegate,
                                        java.lang.Class<?> delegateClass,
                                        java.util.List<java.lang.Class<?>> allInterfaces,
                                        javassist.ClassPool classPool)
                                 throws javassist.CannotCompileException,
                                        javassist.NotFoundException

Throws:

javassist.CannotCompileException

javassist.NotFoundException

createClassName

protected java.lang.String createClassName(java.lang.Class<?> delegateClass,
                                           java.util.Collection<java.lang.Class<?>> interfaces)

addInterface

protected void addInterface(javassist.ClassPool classPool,
                            javassist.CtClass ctClass,
                            java.lang.Class<?> interfce,
                            java.lang.Class<?> delegateClass,
                            java.util.List<MethodUtils.MethodRetrieveStrategy> strategies,
                            java.lang.reflect.Method subDelegateGetter)
                     throws javassist.NotFoundException,
                            javassist.CannotCompileException

Throws:

javassist.NotFoundException

javassist.CannotCompileException

addMethod

protected void addMethod(javassist.ClassPool classPool,
                         javassist.CtClass ctClass,
                         java.lang.reflect.Method method,
                         java.lang.Class<?> delegateClass,
                         java.util.List<MethodUtils.MethodRetrieveStrategy> strategies,
                         java.lang.reflect.Method subDelegateGetter)
                  throws javassist.NotFoundException,
                         javassist.CannotCompileException

Throws:

javassist.NotFoundException

javassist.CannotCompileException

getMethodDelegate

protected java.lang.reflect.Method getMethodDelegate(java.lang.reflect.Method method,
                                                     java.lang.Class<?> delegateClass,
                                                     java.util.List<MethodUtils.MethodRetrieveStrategy> strategies,
                                                     java.lang.reflect.Method subDelegateGetter,
                                                     java.lang.StringBuilder delegatePath)

getDelegateCall

protected java.lang.String getDelegateCall(java.lang.String name,
                                           java.lang.reflect.Method delegateMethod,
                                           int argsLen)

getDuckArg

public DuckArg getDuckArg(java.lang.annotation.Annotation[] annotations)

getCtClass

protected javassist.CtClass getCtClass(javassist.ClassPool classPool,
                                       java.lang.Class<?> clazz)
                                throws javassist.NotFoundException

Throws:

javassist.NotFoundException

getCtClass

protected javassist.CtClass[] getCtClass(javassist.ClassPool classPool,
                                         java.lang.Class<?>[] classes)
                                  throws javassist.NotFoundException

Throws:

javassist.NotFoundException

makeStrategies

protected java.util.List<MethodUtils.MethodRetrieveStrategy> makeStrategies(java.lang.Class<?> delegateClass,
                                                                            AbstractPrxyInvocationHandler.DelegateClassInformation info)

getDelegateClassInformation

protected AbstractPrxyInvocationHandler.DelegateClassInformation getDelegateClassInformation(java.lang.Class<?> delegateClass)