hardcore java 学习5 反射

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 ########## */