1.首先获得方法A所在类的Class object，即通过Class.forName(ClassName)以及 object.newInstance()获得。

注意这里的ClassName包含类所在的包名。

2.利用刚才得到的Class object调用getDeclaredMethod(String name, Class<?>... parameterTypes)方法。前一个参数是nonpublic方法A的名字，后面的参数是包含方法A的各个参数的类型的Class Object。这样就可以得到方法A的object，原文描述为：Returns a Method object that reflects the specified declared method of the class or interface represented by this Class object。

Method A’= getDeclaredMethod(“A”,Class<?>... parameterTypesOf”A”) 也可以保留方法A原名，这里为了区分命名为A’。

3.设置方法A’的可见性A’.setAccessible(true);

4.调用A’方法，注意一定要invoke()====>A’.invoke(A所在类的Classobject, A的参数)。

对私有字段反射的主要流程

1.和私有方法的反射类似

2.利用刚才得到的Class object调用getDeclaredField(String fieldName)获取字段对象fieldObj。

3.设置字段可见性fieldObj.setAccessible(true);

4.设置字段fieldObj.set(object, value)

获取字段的值fieldObj.get(object)

    (1)写个类

    package xxx.yyy.zzzpublic class Simple {private void displayMessage(String strMsg) {System.out.println("message is:" + strMsg);}}

    (2)反射调用import java.lang.reflect.*;public class Test {public static void main(String[] args) throws ClassNotFoundException,SecurityException, NoSuchMethodException, InstantiationException,IllegalAccessException, IllegalArgumentException,InvocationTargetException {Class simpleClass = Class.forName("xxx.yyy.zzz.Simple");Object simpelObject = simpleClass.newInstance();Class[] args1 = new Class[1];args1[0] = String.class;Method simpleMethod = simpleClass.getDeclaredMethod("displayMessage",arg1);simpleMethod.setAccessible(true);String[] argments = new String[1];argments[0] = "Hello,world";simpleMethod.invoke(simpelObject, argments);}}

package org.apache.nutch.parse.html;public class TestOnly {private String[] array= new String[4];private String[] getStringArray(){return array;}private void setStringArray(String[] values){array=values;}}

它的array数据和对应的set/get方法都是私有的

package org.apache.nutch.parse.html;import org.junit.Test;import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;import static org.junit.Assert.*;public class TestOnlyTest {@Testpublic void testGetStringArray() throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException,IllegalAccessException, InstantiationException, MalformedURLException, NoSuchFieldException {Class testObj = Class.forName("org.apache.nutch.parse.html.TestOnly");Object obj = testObj.newInstance();/*test set method.*/Method setArray = testObj.getDeclaredMethod("setStringArray", new Class[]{String[].class});setArray.setAccessible(true);String[] name = {"hello", "world"};setArray.invoke(obj, new Object[]{name});/*test get method.*/Method getArray = testObj.getDeclaredMethod("getStringArray");getArray.setAccessible(true);String[] result = (String[])getArray.invoke(obj);assertEquals("hello",result[0]);assertEquals("world",result[1]);/*test private field visit.*/Field array =testObj.getDeclaredField("array");array.setAccessible(true);array.set(obj, new String[]{"come","here","baby"});result = (String[])array.get(obj);assertEquals("come",result[0]);assertEquals("here",result[1]);assertEquals("baby",result[2]);}
}

当然不用单元测试，也可以用通过打印语句来验证结果集的正确性。

    @Overridepublic ArrayList<Outlink> filterOutlinks(ArrayList<Outlink> list) {ArrayList<Outlink> filterList = new ArrayList<Outlink>();Outlink filterLink = null;for (Outlink outlink : list) {if (isCrawlOutLineUrl(outlink.getToUrl())) {try {filterLink = new Outlink(outlink.getToUrl(), "ydss");} catch (MalformedURLException e) {dMsg.warn("MalformedURLException:", e);continue;}if (!filterList.contains(filterLink)) {filterList.add(filterLink);}}}return filterList;}

其中isCrawlOutLineUrl是一个判断是否为合法出链的私有方法，具体逻辑忽略，此外用到了一个私有字段url。

//    @Testpublic void testIsCrawlOutLineUrl() throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException,IllegalAccessException, InstantiationException, NoSuchFieldException{String outLinkUrl = "http://bbs.ydss.cn/thread-199593-1-1.html";Class ypObj = Class.forName("org.apache.nutch.parse.html.YdssParser");Object yp = ypObj.newInstance();Method isCrawlOutLineUrl = ypObj.getDeclaredMethod("isCrawlOutLineUrl", new Class[]{String.class});isCrawlOutLineUrl.setAccessible(true);Field url = ypObj.getDeclaredField("url");url.setAccessible(true);url.set(yp, "http://bbs.ydss.cn/forum.php?mod=viewthread&tid=505896&extra=page%3D1%26filter%3Dauthor%26orderby%3Ddateline");assertFalse((Boolean) isCrawlOutLineUrl.invoke(yp, outLinkUrl));outLinkUrl = "http://bbs.ydss.cn/thread-505896-1-1.html";assertFalse((Boolean) isCrawlOutLineUrl.invoke(yp, outLinkUrl));}