Package javassist.util.proxy

Class ProxyFactory

  • public class ProxyFactory
extends java.lang.Object
    Factory of dynamic proxy classes.

    This factory generates a class that extends the given super class and implements the given interfaces. The calls of the methods inherited from the super class are forwarded and then invoke() is called on the method handler associated with instances of the generated class. The calls of the methods from the interfaces are also forwarded to the method handler.

    For example, if the following code is executed, 

     ProxyFactory f = new ProxyFactory();
 f.setSuperclass(Foo.class);
 f.setFilter(new MethodFilter() {
     public boolean isHandled(Method m) {
         // ignore finalize()
         return !m.getName().equals("finalize");
     }
 });
 Class c = f.createClass();
 MethodHandler mi = new MethodHandler() {
     public Object invoke(Object self, Method m, Method proceed,
                          Object[] args) throws Throwable {
         System.out.println("Name: " + m.getName());
         return proceed.invoke(self, args);  // execute the original method.
     }
 };
 Foo foo = (Foo)c.newInstance();
 ((Proxy)foo).setHandler(mi);

    Here, Method is java.lang.reflect.Method.

    Then, the following method call will be forwarded to MethodHandler mi and prints a message before executing the originally called method bar() in Foo. 

     foo.bar();

    The last three lines of the code shown above can be replaced with a call to the helper method create, which generates a proxy class, instantiates it, and sets the method handler of the instance: 

         :
 Foo foo = (Foo)f.create(new Class[0], new Object[0], mi);

    To change the method handler during runtime, execute the following code: 

     MethodHandler mi = ... ;    // alternative handler
 ((Proxy)foo).setHandler(mi);

    If setHandler is never called for a proxy instance then it will employ the default handler which proceeds by invoking the original method. The behaviour of the default handler is identical to the following handler: 

     class EmptyHandler implements MethodHandler {
     public Object invoke(Object self, Method m,
                          Method proceed, Object[] args) throws Exception {
         return proceed.invoke(self, args);
     }
 }

    A proxy factory caches and reuses proxy classes by default. It is possible to reset this default globally by setting static field useCache to false. Caching may also be configured for a specific factory by calling instance method setUseCache(boolean). It is strongly recommended that new clients of class ProxyFactory enable caching. Failure to do so may lead to exhaustion of the heap memory area used to store classes.

    Caching is automatically disabled for any given proxy factory if deprecated instance method setHandler(MethodHandler) is called. This method was used to specify a default handler which newly created proxy classes should install when they create their instances. It is only retained to provide backward compatibility with previous releases of javassist. Unfortunately,this legacy behaviour makes caching and reuse of proxy classes impossible. The current programming model expects javassist clients to set the handler of a proxy instance explicitly by calling method Proxy.setHandler(MethodHandler) as shown in the sample code above. New clients are strongly recommended to use this model rather than calling setHandler(MethodHandler).

    A proxy object generated by ProxyFactory is serializable if its super class or any of its interfaces implement java.io.Serializable. However, a serialized proxy object may not be compatible with future releases. The serialization support should be used for short-term storage or RMI.

    For compatibility with older releases serialization of proxy objects is implemented by adding a writeReplace method to the proxy class. This allows a proxy to be serialized to a conventional ObjectOutputStream and deserialized from a corresponding ObjectInputStream. However this method suffers from several problems, the most notable one being that it fails to serialize state inherited from the proxy's superclass.

    An alternative method of serializing proxy objects is available which fixes these problems. It requires inhibiting generation of the writeReplace method and instead using instances of ProxyObjectOutputStream and ProxyObjectInputStream (which are subclasses of ObjectOutputStream and ObjectInputStream) to serialize and deserialize, respectively, the proxy. These streams recognise javassist proxies and ensure that they are serialized and deserialized without the need for the proxy class to implement special methods such as writeReplace. Generation of the writeReplace method can be disabled globally by setting static field useWriteReplace to false. Alternatively, it may be configured per factory by calling instance method setUseWriteReplace(boolean).

    Since:
    3.1
    See Also:
    MethodHandler

    • Field Detail

      • superClass

        private java.lang.Class superClass

      • interfaces

        private java.lang.Class[] interfaces

      • signatureMethods

        private java.util.List signatureMethods

      • hasGetHandler

        private boolean hasGetHandler

      • signature

        private byte[] signature

      • classname

        private java.lang.String classname

      • basename

        private java.lang.String basename

      • superName

        private java.lang.String superName

      • thisClass

        private java.lang.Class thisClass

      • factoryUseCache

        private boolean factoryUseCache
        per factory setting initialised from current setting for useCache but able to be reset before each create call

      • factoryWriteReplace

        private boolean factoryWriteReplace
        per factory setting initialised from current setting for useWriteReplace but able to be reset before each create call

      • writeDirectory

        public java.lang.String writeDirectory
        If the value of this variable is not null, the class file of the generated proxy class is written under the directory specified by this variable. For example, if the value is ".", then the class file is written under the current directory. This method is for debugging.

        The default value is null.

      • OBJECT_TYPE

        private static final java.lang.Class OBJECT_TYPE

      • FILTER_SIGNATURE_FIELD

        private static final java.lang.String FILTER_SIGNATURE_FIELD
        See Also:
        Constant Field Values

      • FILTER_SIGNATURE_TYPE

        private static final java.lang.String FILTER_SIGNATURE_TYPE
        See Also:
        Constant Field Values

      • NULL_INTERCEPTOR_HOLDER

        private static final java.lang.String NULL_INTERCEPTOR_HOLDER
        See Also:
        Constant Field Values

      • DEFAULT_INTERCEPTOR

        private static final java.lang.String DEFAULT_INTERCEPTOR
        See Also:
        Constant Field Values

      • HANDLER_TYPE

        private static final java.lang.String HANDLER_TYPE

      • HANDLER_SETTER_TYPE

        private static final java.lang.String HANDLER_SETTER_TYPE

      • HANDLER_GETTER_TYPE

        private static final java.lang.String HANDLER_GETTER_TYPE

      • SERIAL_VERSION_UID_FIELD

        private static final java.lang.String SERIAL_VERSION_UID_FIELD
        See Also:
        Constant Field Values

      • SERIAL_VERSION_UID_TYPE

        private static final java.lang.String SERIAL_VERSION_UID_TYPE
        See Also:
        Constant Field Values

      • SERIAL_VERSION_UID_VALUE

        private static final long SERIAL_VERSION_UID_VALUE
        See Also:
        Constant Field Values

      • useCache

        public static volatile boolean useCache
        If true, a generated proxy class is cached and it will be reused when generating the proxy class with the same properties is requested. The default value is true. Note that this value merely specifies the initial setting employed by any newly created proxy factory. The factory setting may be overwritten by calling factory instance method setUseCache(boolean)
        Since:
        3.4

      • useWriteReplace

        public static volatile boolean useWriteReplace
        If true, a generated proxy class will implement method writeReplace enabling serialization of its proxies to a conventional ObjectOutputStream. this (default) setting retains the old javassist behaviour which has the advantage that it retains compatibility with older releases and requires no extra work on the part of the client performing the serialization. However, it has the disadvantage that state inherited from the superclasses of the proxy is lost during serialization. if false then serialization/deserialization of the proxy instances will preserve all fields. However, serialization must be performed via a ProxyObjectOutputStream and deserialization must be via ProxyObjectInputStream. Any attempt to serialize proxies whose class was created with useWriteReplace set to false via a normal ObjectOutputStream will fail. Note that this value merely specifies the initial setting employed by any newly created proxy factory. The factory setting may be overwritten by calling factory instance method setUseWriteReplace(boolean)
        Since:
        3.4

      • proxyCache

        private static java.util.WeakHashMap proxyCache

      • hexDigits

        private static char[] hexDigits

      • classLoaderProvider

        public static ProxyFactory.ClassLoaderProvider classLoaderProvider
        A provider used by createClass() for obtaining a class loader. get() on this ClassLoaderProvider object is called to obtain a class loader.

        The value of this field can be updated for changing the default implementation.

        Example: 

         ProxyFactory.classLoaderProvider = new ProxyFactory.ClassLoaderProvider() {
     public ClassLoader get(ProxyFactory pf) {
         return Thread.currentThread().getContextClassLoader();
     }
 };
        Since:
        3.4

      • nameGenerator

        public static ProxyFactory.UniqueName nameGenerator
        A unique class name generator. Replacing this generator changes the algorithm to generate a unique name. The get method does not have to be a synchronized method since the access to this field is mutually exclusive and thus thread safe.

      • sorter

        private static java.util.Comparator sorter

      • HANDLER_GETTER_KEY

        private static final java.lang.String HANDLER_GETTER_KEY
        See Also:
        Constant Field Values

    • Constructor Detail

      • ProxyFactory

        public ProxyFactory()
        Constructs a factory of proxy class.

    • Method Detail

      • isUseCache

        public boolean isUseCache()
        test whether this factory uses the proxy cache
        Returns:
        true if this factory uses the proxy cache otherwise false

      • setUseCache

        public void setUseCache​(boolean useCache)
        configure whether this factory should use the proxy cache
        Parameters:
        useCache - true if this factory should use the proxy cache and false if it should not use the cache
        Throws:
        java.lang.RuntimeException - if a default interceptor has been set for the factory

      • isUseWriteReplace

        public boolean isUseWriteReplace()
        test whether this factory installs a writeReplace method in created classes
        Returns:
        true if this factory installs a writeReplace method in created classes otherwise false

      • setUseWriteReplace

        public void setUseWriteReplace​(boolean useWriteReplace)
        configure whether this factory should add a writeReplace method to created classes
        Parameters:
        useWriteReplace - true if this factory should add a writeReplace method to created classes and false if it should not add a writeReplace method

      • isProxyClass

        public static boolean isProxyClass​(java.lang.Class cl)
        determine if a class is a javassist proxy class
        Parameters:
        cl -
        Returns:
        true if the class is a javassist proxy class otherwise false

      • setSuperclass

        public void setSuperclass​(java.lang.Class clazz)
        Sets the super class of a proxy class.

      • getSuperclass

        public java.lang.Class getSuperclass()
        Obtains the super class set by setSuperclass().
        Since:
        3.4

      • setInterfaces

        public void setInterfaces​(java.lang.Class[] ifs)
        Sets the interfaces of a proxy class.

      • getInterfaces

        public java.lang.Class[] getInterfaces()
        Obtains the interfaces set by setInterfaces.
        Since:
        3.4

      • setFilter

        public void setFilter​(MethodFilter mf)
        Sets a filter that selects the methods that will be controlled by a handler.

      • createClass

        public java.lang.Class createClass()
        Generates a proxy class using the current filter.

      • createClass

        public java.lang.Class createClass​(MethodFilter filter)
        Generates a proxy class using the supplied filter.

      • createClass

        java.lang.Class createClass​(byte[] signature)
        Generates a proxy class with a specific signature. access is package local so ProxyObjectInputStream can use this
        Parameters:
        signature -
        Returns:

      • createClass1

        private java.lang.Class createClass1()

      • getKey

        public java.lang.String getKey​(java.lang.Class superClass,
                               java.lang.Class[] interfaces,
                               byte[] signature,
                               boolean useWriteReplace)

      • createClass2

        private void createClass2​(java.lang.ClassLoader cl)

      • createClass3

        private void createClass3​(java.lang.ClassLoader cl)

      • setField

        private void setField​(java.lang.String fieldName,
                      java.lang.Object value)

      • getFilterSignature

        static byte[] getFilterSignature​(java.lang.Class clazz)

      • getField

        private static java.lang.Object getField​(java.lang.Class clazz,
                                         java.lang.String fieldName)

      • getHandler

        public static MethodHandler getHandler​(Proxy p)
        Obtains the method handler of the given proxy object.
        Parameters:
        p - a proxy object.
        Returns:
        the method handler.
        Since:
        3.16

      • getClassLoader

        protected java.lang.ClassLoader getClassLoader()

      • getClassLoader0

        protected java.lang.ClassLoader getClassLoader0()

      • getDomain

        protected java.security.ProtectionDomain getDomain()

      • create

        public java.lang.Object create​(java.lang.Class[] paramTypes,
                               java.lang.Object[] args,
                               MethodHandler mh)
                        throws java.lang.NoSuchMethodException,
                               java.lang.IllegalArgumentException,
                               java.lang.InstantiationException,
                               java.lang.IllegalAccessException,
                               java.lang.reflect.InvocationTargetException
        Creates a proxy class and returns an instance of that class.
        Parameters:
        paramTypes - parameter types for a constructor.
        args - arguments passed to a constructor.
        mh - the method handler for the proxy class.
        Throws:
        java.lang.NoSuchMethodException
        java.lang.IllegalArgumentException
        java.lang.InstantiationException
        java.lang.IllegalAccessException
        java.lang.reflect.InvocationTargetException
        Since:
        3.4

      • create

        public java.lang.Object create​(java.lang.Class[] paramTypes,
                               java.lang.Object[] args)
                        throws java.lang.NoSuchMethodException,
                               java.lang.IllegalArgumentException,
                               java.lang.InstantiationException,
                               java.lang.IllegalAccessException,
                               java.lang.reflect.InvocationTargetException
        Creates a proxy class and returns an instance of that class.
        Parameters:
        paramTypes - parameter types for a constructor.
        args - arguments passed to a constructor.
        Throws:
        java.lang.NoSuchMethodException
        java.lang.IllegalArgumentException
        java.lang.InstantiationException
        java.lang.IllegalAccessException
        java.lang.reflect.InvocationTargetException

      • setHandler

        public void setHandler​(MethodHandler mi)
        Deprecated.
        since 3.12 use of this method is incompatible with proxy class caching. instead clients should call method Proxy.setHandler(MethodHandler) to set the handler for each newly created proxy instance. calling this method will automatically disable caching of classes created by the proxy factory.
        Sets the default invocation handler. This invocation handler is shared among all the instances of a proxy class unless another is explicitly specified.

      • makeProxyName

        private static java.lang.String makeProxyName​(java.lang.String classname)

      • checkClassAndSuperName

        private void checkClassAndSuperName()

      • allocateClassName

        private void allocateClassName()

      • makeSortedMethodList

        private void makeSortedMethodList()

      • computeSignature

        private void computeSignature​(MethodFilter filter)

      • installSignature

        private void installSignature​(byte[] signature)

      • testBit

        private boolean testBit​(byte[] signature,
                        int idx)

      • setBit

        private void setBit​(byte[] signature,
                    int idx)

      • setInterfaces

        private static void setInterfaces​(ClassFile cf,
                                  java.lang.Class[] interfaces,
                                  java.lang.Class proxyClass)

      • callFind2Methods

        private static void callFind2Methods​(Bytecode code,
                                     java.lang.String superMethod,
                                     java.lang.String thisMethod,
                                     int index,
                                     java.lang.String desc,
                                     int classVar,
                                     int arrayVar)
        Parameters:
        thisMethod - might be null.

      • isBridge

        private static boolean isBridge​(java.lang.reflect.Method m)

      • makeUniqueName

        private static java.lang.String makeUniqueName​(java.lang.String name,
                                               java.util.List sortedMethods)

      • makeUniqueName0

        private static boolean makeUniqueName0​(java.lang.String name,
                                       java.util.Iterator it)

      • isVisible

        private static boolean isVisible​(int mod,
                                 java.lang.String from,
                                 java.lang.reflect.Member meth)
        Returns true if the method is visible from the package.
        Parameters:
        mod - the modifiers of the method.

      • getPackageName

        private static java.lang.String getPackageName​(java.lang.String name)

      • getMethods

        private java.util.HashMap getMethods​(java.lang.Class superClass,
                                     java.lang.Class[] interfaceTypes)

      • getMethods

        private void getMethods​(java.util.HashMap hash,
                        java.lang.Class clazz,
                        java.util.Set visitedClasses)

      • isOverloaded

        private static boolean isOverloaded​(int index,
                                    java.lang.reflect.Method[] methods)

      • keyToDesc

        private static java.lang.String keyToDesc​(java.lang.String key,
                                          java.lang.reflect.Method m)

      • makeConstructor

        private static MethodInfo makeConstructor​(java.lang.String thisClassName,
                                          java.lang.reflect.Constructor cons,
                                          ConstPool cp,
                                          java.lang.Class superClass,
                                          boolean doHandlerInit)

      • makeDelegator

        private MethodInfo makeDelegator​(java.lang.reflect.Method meth,
                                 java.lang.String desc,
                                 ConstPool cp,
                                 java.lang.Class declClass,
                                 java.lang.String delegatorName)

      • invokespecialTarget

        private java.lang.Class invokespecialTarget​(java.lang.Class declClass)

      • makeForwarder

        private static MethodInfo makeForwarder​(java.lang.String thisClassName,
                                        java.lang.reflect.Method meth,
                                        java.lang.String desc,
                                        ConstPool cp,
                                        java.lang.Class declClass,
                                        java.lang.String delegatorName,
                                        int index,
                                        java.util.ArrayList forwarders)
        Parameters:
        delegatorName - null if the original method is abstract.

      • setThrows

        private static void setThrows​(MethodInfo minfo,
                              ConstPool cp,
                              java.lang.reflect.Method orig)

      • setThrows

        private static void setThrows​(MethodInfo minfo,
                              ConstPool cp,
                              java.lang.Class[] exceptions)

      • addLoadParameters

        private static int addLoadParameters​(Bytecode code,
                                     java.lang.Class[] params,
                                     int offset)

      • addLoad

        private static int addLoad​(Bytecode code,
                           int n,
                           java.lang.Class type)

      • addReturn

        private static int addReturn​(Bytecode code,
                             java.lang.Class type)

      • makeParameterList

        private static void makeParameterList​(Bytecode code,
                                      java.lang.Class[] params)

      • makeWrapper

        private static int makeWrapper​(Bytecode code,
                               java.lang.Class type,
                               int regno)

      • addUnwrapper

        private static void addUnwrapper​(Bytecode code,
                                 java.lang.Class type)