自定义classloader

MapleClassLoader

package com.maple;import java.io.*;public class MapleClassLoader extends ClassLoader {    private String path = "E:\\Workspaces\\loader\\target\\classes\\";    public MapleClassLoader(String path){        this.path = path ;    }    public MapleClassLoader(ClassLoader parent,String path){        super(parent);        this.path = path;    }    /*@Override    protected Class
     findClass(String name) throws ClassNotFoundException {        byte[] data = loadClassData(name);        return defineClass(name,data,0,data.length);    }*/    /*private byte[] loadClassData(String name) {        try {            name = name.replaceAll(".", "\\");            FileInputStream is = new FileInputStream(new File(path + name + ".class"));            ByteArrayOutputStream bos = new ByteArrayOutputStream();            int b;            while ((b = is.read()) != -1) {                bos.write(b);            }            return bos.toByteArray();        } catch (Exception e) {            e.printStackTrace();        }        return null;    }*/    @Override    public Class
     loadClass(String name) throws ClassNotFoundException {        try {            String fileName = name.replaceAll("\\.", "\\/");            FileInputStream is;            try {                is = new FileInputStream(new File(path + fileName + ".class"));            } catch (Exception e) {                is = null;            }            if (is == null) {                return super.loadClass(name);            }            ByteArrayOutputStream bos = new ByteArrayOutputStream();            int b;            while ((b = is.read()) != -1) {                bos.write(b);            }            byte[] data = bos.toByteArray();            return defineClass(name, data, 0, data.length);        } catch (Exception e) {            throw new ClassNotFoundException(name);        }    }}

测试

public class Demo1 {    public static void main(String[] args) throws Exception {        MapleClassLoader mc = new MapleClassLoader(Thread.currentThread().getContextClassLoader(),"E:\\Workspaces\\loader\\target\\classes\\");        Object obj = (Object)mc.loadClass("com.maple.Demo1").newInstance();        System.out.println("load: "+ obj.getClass());        System.out.println("local: "+ Demo1.NUM);        System.out.println(obj instanceof Demo1);    }    private static int NUM = 1;    private static Integer addNum(){        return NUM++;    }}

测试结果

load: class com.maple.Demo1local: 1false

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优化版ClassLoader

package com.maple.cl;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.net.URL;import java.net.URLClassLoader;/** * App Class Loader * * @author craneding * @date 16/1/28 */public class AppClassLoader extends ClassLoader {    private String path = "E:\\Workspaces\\loader\\target\\classes\\";    public AppClassLoader(String path) {        super(ClassLoader.getSystemClassLoader());        this.path = path;    }    public AppClassLoader(ClassLoader parent,String path) {        super(parent);        this.path = path;    }    @Override    public Class
     loadClass(String name) throws ClassNotFoundException {        if (name.startsWith("com.maple.test.S") || name.startsWith("com.isuwang.org.apache.thrift") || name.startsWith("com.isuwang.dapeng.transaction.api")                || name.startsWith("com.google.gson"))            return ClassLoaderManager.shareClassLoader.loadClass(name);        try {            Class
     c = findLoadedClass(name);            if(c==null){                String fileName = name.replaceAll("\\.", "\\/");                FileInputStream is;                try {                    is = new FileInputStream(new File(path + fileName + ".class"));                } catch (Exception e) {                    is = null;                }                if (is == null) {                    return super.loadClass(name);                }                ByteArrayOutputStream bos = new ByteArrayOutputStream();                int b;                while ((b = is.read()) != -1) {                    bos.write(b);                }                byte[] data = bos.toByteArray();                return defineClass(name, data, 0, data.length);            }            return c;        } catch (Exception e) {            throw new ClassNotFoundException(name);        }    }}