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coderzyjcoderzyj
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Merge remote-tracking branch 'origin/master'
2 parents 00f4b44 + 66e5c9d commit 8ec49db

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‎java-classloader/java-classloader.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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</component>
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</module>

‎java-classloader/src/com/zyj/test/Demo01.java

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package com.zyj.test;
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/**
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* 版权声明：CopyRight (c) 2018 ucarinc. All Rights Reserved.
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*
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* @author : 张勇杰
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* @date : 2018/12/3 16:16
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* @Version : v1.0
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* @description
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**/
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public class Demo01 {
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public static void main(String[] args) {
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System.out.println(ClassLoader.getSystemClassLoader());
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System.out.println(ClassLoader.getSystemClassLoader().getParent());
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System.out.println(ClassLoader.getSystemClassLoader().getParent().getParent());
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System.out.println(System.getProperty("java.class" + ".path"));
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String a = "zyj";
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System.out.println(a.getClass().getClassLoader());
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}
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}

‎java-classloader/src/com/zyj/test/Demo02.java

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package com.zyj.test;
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/**
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* 版权声明：CopyRight (c) 2018 ucarinc. All Rights Reserved.
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*
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* @author : 张勇杰
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* @date : 2018/12/6 15:08
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* @Version : v1.0
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* @description
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**/
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public class Demo02 {
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public static void main(String[] args) throws ClassNotFoundException {
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FileSystemClassLoader loader = new FileSystemClassLoader("d:/myjava");
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FileSystemClassLoader loader1 = new FileSystemClassLoader("d:/myjava");
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Class<?> c = loader.loadClass("com.zyj.test.HelloWorld");
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Class<?> c1 = loader.loadClass("com.zyj.test.HelloWorld");
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Class<?> c2 = loader1.loadClass("com.zyj.test.HelloWorld");
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Class c3 = loader.loadClass("java.lang.String");
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System.out.println(c.hashCode());
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System.out.println(c1.hashCode());
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System.out.println(c2.hashCode());
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System.out.println(c3.hashCode());
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//JVM认为被同一个加载器加载的同一个类是相同的类
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}
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}

‎java-classloader/src/com/zyj/test/FileSystemClassLoader.java

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package com.zyj.test;
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import java.io.*;
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/**
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* 版权声明：CopyRight (c) 2018 ucarinc. All Rights Reserved.
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*
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* @author : 张勇杰
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* @date : 2018/12/6 14:47
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* @Version : v1.0
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* @description
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**/
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public class FileSystemClassLoader extends ClassLoader {
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//d:/myjava/com/zyj/test/User.class -->com.zyj.test.User
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private String rootDir;
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public FileSystemClassLoader(String rootDir){
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this.rootDir = rootDir;
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}
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@Override
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protected Class<?> findClass(String name) throws ClassNotFoundException {
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Class<?> c = findLoadedClass(name);
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//应该先查询有没有加载过这个类，如果已经加载，则返回已经加载好的类。如果没有，则加载新的类
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if(c != null){
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return c;
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}else{
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ClassLoader parent = this.getParent();
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System.out.println(parent);
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//委派给父类加载
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try {
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c = parent.loadClass(name);
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}catch (Exception e){
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}
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if(c != null){
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return c;
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}else{
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byte[] classData = getClassData(name);
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if(classData == null){
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throw new ClassNotFoundException();
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}else{
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c = defineClass(name,classData,0,classData.length);
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}
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}
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}
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return c;
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}
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private byte[] getClassData(String className){
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String path = rootDir + "/"+className.replace(".","/")+".class";
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//IOUtils,可以使用他将流中的数据转成字节数组
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InputStream is = null;
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ByteArrayOutputStream baos = new ByteArrayOutputStream();
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try {
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is = new FileInputStream(path);
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byte[] buffer = new byte[1024];
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int temp = 0;
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while((temp = is.read(buffer))!= -1){
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baos.write(buffer,0,temp);
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}
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return baos.toByteArray();
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} catch (Exception e) {
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e.printStackTrace();
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return null;
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}finally {
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if(is != null){
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try {
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is.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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if (baos != null) {
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try {
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baos.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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}
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}

‎java-classloader/src/com/zyj/test/Test02.java

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package com.zyj.test;
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/**
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* 版权声明：CopyRight (c) 2018 ucarinc. All Rights Reserved.
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*
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* @author : 张勇杰
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* @date : 2018/12/6 15:52
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* @Version : v1.0
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* @description
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**/
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public class Test02 extends Test1 {
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@Override
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protected String test01() throws Exception {
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return "我才是返回值";
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}
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public static void main(String[] args) {
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Test02 test02 = new Test02();
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try {
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System.out.println(test02.test02());
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

‎java-classloader/src/com/zyj/test/Test1.java

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package com.zyj.test;
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/**
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* 版权声明：CopyRight (c) 2018 ucarinc. All Rights Reserved.
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*
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* @author : 张勇杰
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* @date : 2018/12/6 15:51
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* @Version : v1.0
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* @description
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**/
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public abstract class Test1 {
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protected String test01() throws Exception {
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throw new Exception("666");
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}
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protected String test02() throws Exception{
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String c = test01();
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return c;
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}
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}

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