hardcore java 学习5 反射

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反射有很强大的能力。可以对一个未知的类调用其中的方法。就好象是从镜子里看人，而不是直观的进行。

现在很多优秀的框架、语言都借助反射的力量。

对未知类的方法调用：

/* *     file: MethodInfoDemo.java *  package: oreilly.hcj.reflection * * This software is granted under the terms of the Common Public License, * CPL, which may be found at the following URL: * http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm * * Copyright(c) 2003-2005 by the authors indicated in the @author tags. * All Rights are Reserved by the various authors. *########## DO NOT EDIT ABOVE THIS LINE ########## */package oreilly.hcj.reflection;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import oreilly.hcj.bankdata.Gender;import oreilly.hcj.bankdata.Person;/**   * Demonstrates how to get simple method information. * * @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a> * @version $Revision: 1.3 $ */public class MethodInfoDemo {/**  * __UNDOCUMENTED__ * * @param obj __UNDOCUMENTED__ * * @throws IllegalAccessException __UNDOCUMENTED__ * @throws InvocationTargetException __UNDOCUMENTED__ */public static void emptyStrings(final Object obj)    throws IllegalAccessException, InvocationTargetException {final String PREFIX = "set";  //$NON-NLS-1$Method[] methods = obj.getClass()                  .getMethods();for (int idx = 0; idx < methods.length; idx++) {if (methods[idx].getName()                .startsWith(PREFIX)) {if (methods[idx].getParameterTypes()[0] == String.class) {methods[idx].invoke(obj, new Object[] { new String() });}}}}/**  * Demo method. * * @param args Command line arguments. */public static void main(final String[] args) {Person p = new Person();p.setFirstName("Robert");p.setLastName("Simmons");p.setGender(Gender.MALE);p.setTaxID("123abc456");printMethodInfo(p);try {System.out.println("==> " + p.getFirstName());emptyStrings(p);System.out.println("==> " + p.getFirstName());} catch (final Exception ex) {ex.printStackTrace();}}/**  * __UNDOCUMENTED__ * * @param obj __UNDOCUMENTED__ */public static void printMethodInfo(final Object obj) {Class type = obj.getClass();final Method[] methods = type.getMethods();for (int idx = 0; idx < methods.length; idx++) {System.out.println(methods[idx]);}}}/* ########## End of File ########## */