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/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later,
 * or the Apache License Version 2.0.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist.tools.reflect;

import java.lang.reflect.*;
import java.util.Arrays;
import java.io.Serializable;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

/**
 * A runtime class metaobject.
 *
 * 

A ClassMetaobject is created for every * class of reflective objects. It can be used to hold values * shared among the reflective objects of the same class. * *

To obtain a class metaobject, calls _getClass() * on a reflective object. For example, * *

ClassMetaobject cm = ((Metalevel)reflectiveObject)._getClass();
 * 
* * @see javassist.tools.reflect.Metaobject * @see javassist.tools.reflect.Metalevel */ public class ClassMetaobject implements Serializable { /** * The base-level methods controlled by a metaobject * are renamed so that they begin with * methodPrefix "_m_". */ static final String methodPrefix = "_m_"; static final int methodPrefixLen = 3; private Class javaClass; private Constructor[] constructors; private Method[] methods; /** * Specifies how a java.lang.Class object is loaded. * *

If true, it is loaded by: *

Thread.currentThread().getContextClassLoader().loadClass()
*

If false, it is loaded by Class.forName(). * The default value is false. */ public static boolean useContextClassLoader = false; /** * Constructs a ClassMetaobject. * * @param params params[0] is the name of the class * of the reflective objects. */ public ClassMetaobject(String[] params) { try { javaClass = getClassObject(params[0]); } catch (ClassNotFoundException e) { throw new RuntimeException("not found: " + params[0] + ", useContextClassLoader: " + Boolean.toString(useContextClassLoader), e); } constructors = javaClass.getConstructors(); methods = null; } private void writeObject(ObjectOutputStream out) throws IOException { out.writeUTF(javaClass.getName()); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { javaClass = getClassObject(in.readUTF()); constructors = javaClass.getConstructors(); methods = null; } private Class getClassObject(String name) throws ClassNotFoundException { if (useContextClassLoader) return Thread.currentThread().getContextClassLoader() .loadClass(name); else return Class.forName(name); } /** * Obtains the java.lang.Class representing this class. */ public final Class getJavaClass() { return javaClass; } /** * Obtains the name of this class. */ public final String getName() { return javaClass.getName(); } /** * Returns true if obj is an instance of this class. */ public final boolean isInstance(Object obj) { return javaClass.isInstance(obj); } /** * Creates a new instance of the class. * * @param args the arguments passed to the constructor. */ public final Object newInstance(Object[] args) throws CannotCreateException { int n = constructors.length; for (int i = 0; i < n; ++i) { try { return constructors[i].newInstance(args); } catch (IllegalArgumentException e) { // try again } catch (InstantiationException e) { throw new CannotCreateException(e); } catch (IllegalAccessException e) { throw new CannotCreateException(e); } catch (InvocationTargetException e) { throw new CannotCreateException(e); } } throw new CannotCreateException("no constructor matches"); } /** * Is invoked when static fields of the base-level * class are read and the runtime system intercepts it. * This method simply returns the value of the field. * *

Every subclass of this class should redefine this method. */ public Object trapFieldRead(String name) { Class jc = getJavaClass(); try { return jc.getField(name).get(null); } catch (NoSuchFieldException e) { throw new RuntimeException(e.toString()); } catch (IllegalAccessException e) { throw new RuntimeException(e.toString()); } } /** * Is invoked when static fields of the base-level * class are modified and the runtime system intercepts it. * This method simply sets the field to the given value. * *

Every subclass of this class should redefine this method. */ public void trapFieldWrite(String name, Object value) { Class jc = getJavaClass(); try { jc.getField(name).set(null, value); } catch (NoSuchFieldException e) { throw new RuntimeException(e.toString()); } catch (IllegalAccessException e) { throw new RuntimeException(e.toString()); } } /** * Invokes a method whose name begins with * methodPrefix "_m_" and the identifier. * * @exception CannotInvokeException if the invocation fails. */ static public Object invoke(Object target, int identifier, Object[] args) throws Throwable { Method[] allmethods = target.getClass().getMethods(); int n = allmethods.length; String head = methodPrefix + identifier; for (int i = 0; i < n; ++i) if (allmethods[i].getName().startsWith(head)) { try { return allmethods[i].invoke(target, args); } catch (java.lang.reflect.InvocationTargetException e) { throw e.getTargetException(); } catch (java.lang.IllegalAccessException e) { throw new CannotInvokeException(e); } } throw new CannotInvokeException("cannot find a method"); } /** * Is invoked when static methods of the base-level * class are called and the runtime system intercepts it. * This method simply executes the intercepted method invocation * with the original parameters and returns the resulting value. * *

Every subclass of this class should redefine this method. */ public Object trapMethodcall(int identifier, Object[] args) throws Throwable { try { Method[] m = getReflectiveMethods(); return m[identifier].invoke(null, args); } catch (java.lang.reflect.InvocationTargetException e) { throw e.getTargetException(); } catch (java.lang.IllegalAccessException e) { throw new CannotInvokeException(e); } } /** * Returns an array of the methods defined on the given reflective * object. This method is for the internal use only. */ public final Method[] getReflectiveMethods() { if (methods != null) return methods; Class baseclass = getJavaClass(); Method[] allmethods = baseclass.getDeclaredMethods(); int n = allmethods.length; int[] index = new int[n]; int max = 0; for (int i = 0; i < n; ++i) { Method m = allmethods[i]; String mname = m.getName(); if (mname.startsWith(methodPrefix)) { int k = 0; for (int j = methodPrefixLen;; ++j) { char c = mname.charAt(j); if ('0' <= c && c <= '9') k = k * 10 + c - '0'; else break; } index[i] = ++k; if (k > max) max = k; } } methods = new Method[max]; for (int i = 0; i < n; ++i) if (index[i] > 0) methods[index[i] - 1] = allmethods[i]; return methods; } /** * Returns the java.lang.reflect.Method object representing * the method specified by identifier. * *

Note that the actual method returned will be have an altered, * reflective name i.e. _m_2_... * * @param identifier the identifier index * given to trapMethodcall() etc. * @see Metaobject#trapMethodcall(int,Object[]) * @see #trapMethodcall(int,Object[]) */ public final Method getMethod(int identifier) { return getReflectiveMethods()[identifier]; } /** * Returns the name of the method specified * by identifier. */ public final String getMethodName(int identifier) { String mname = getReflectiveMethods()[identifier].getName(); int j = ClassMetaobject.methodPrefixLen; for (;;) { char c = mname.charAt(j++); if (c < '0' || '9' < c) break; } return mname.substring(j); } /** * Returns an array of Class objects representing the * formal parameter types of the method specified * by identifier. */ public final Class[] getParameterTypes(int identifier) { return getReflectiveMethods()[identifier].getParameterTypes(); } /** * Returns a Class objects representing the * return type of the method specified by identifier. */ public final Class getReturnType(int identifier) { return getReflectiveMethods()[identifier].getReturnType(); } /** * Returns the identifier index of the method, as identified by its * original name. * *

This method is useful, in conjuction with * {@link ClassMetaobject#getMethod(int)}, to obtain a quick reference * to the original method in the reflected class (i.e. not the proxy * method), using the original name of the method. * *

Written by Brett Randall and Shigeru Chiba. * * @param originalName The original name of the reflected method * @param argTypes array of Class specifying the method signature * @return the identifier index of the original method * @throws NoSuchMethodException if the method does not exist * * @see ClassMetaobject#getMethod(int) */ public final int getMethodIndex(String originalName, Class[] argTypes) throws NoSuchMethodException { Method[] mthds = getReflectiveMethods(); for (int i = 0; i < mthds.length; i++) { if (mthds[i] == null) continue; // check name and parameter types match if (getMethodName(i).equals(originalName) && Arrays.equals(argTypes, mthds[i].getParameterTypes())) return i; } throw new NoSuchMethodException("Method " + originalName + " not found"); } }





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