package com.zkn.newlearn.classloader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
/**
*
* @author zkn
*
*/
public class ClassLoaderTest01 extends ClassLoader {
/**
* 路径
*/
private String path = "";
/**
* 后缀名
*/
private String className = ".class";
private String name = "";
private ClassLoader loader = null;
@Override
protected Class<?> findClass(String name) {
byte[] b =loadClassData(name);
if(b != null && b.length > 0)
return defineClass(name, b, 0, b.length);
return this.getClass();
}
@SuppressWarnings("null")
private byte[] loadClassData(String names) {
names = names.replace(".", "\\");
String clazzName = path + names + className;
InputStream is = null;
ByteArrayOutputStream baos = null;
byte[] bytes = new byte[0];
int i = 0;
try{
is = new FileInputStream(new File(clazzName));
baos = new ByteArrayOutputStream();
while(-1!=(i = is.read())){
baos.write(i);
}
bytes = baos.toByteArray();
}catch(Exception e){
e.printStackTrace();
}finally{
try{
if(is != null)
is.close();
if(baos != null)
baos.close();
}catch(Exception ee){
ee.printStackTrace();
}
}
return bytes;
}
public ClassLoaderTest01(String name) {
super();
this.name = name;
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return " "+name;
}
public ClassLoaderTest01(String name, ClassLoader loader) {
super(loader);
this.name = name;
this.loader = loader;
}
public static void main(String[] args) throws Exception{
ClassLoaderTest01 loader1 = new ClassLoaderTest01("loader1");
loader1.setPath("D:\\log4j\\sys\\");
ClassLoaderTest01 loader2 = new ClassLoaderTest01("loader2",loader1);
loader2.setPath("D:\\log4j\\common\\");
ClassLoaderTest01 loader3 = new ClassLoaderTest01("loader3",null);
loader3.setPath("D:\\log4j\\common\\");
try{
test(loader2,"com.zkn.newlearn.classloader.Parent");
}catch(Exception e){
loader2 = new ClassLoaderTest01("loader02");
loader2.setPath("D:\\log4j\\common\\");
test(loader2,"com.zkn.newlearn.classloader.Parent");
}
test(loader3,"com.zkn.newlearn.classloader.Parent");
}
private static void test(ClassLoader loader,String name)
throws ClassNotFoundException, InstantiationException,
IllegalAccessException {
Class clazz = null;
try{
clazz = loader.loadClass(name);
}catch(Exception e){
e.printStackTrace();
}
clazz.newInstance();
}
}
package com.zkn.newlearn.classloader;
/**
*
* @author zkn
*
*/
public class Parent {
public static int i = 1;
public Parent(){
new Dog();
System.out.println("Parent类加载器为："+Parent.class.getClassLoader());
}
}
package com.zkn.newlearn.classloader;
/**
*
* @author pc
*
*/
public class Dog {
public Dog(){
System.out.println("Dog 类 ： 类加载器为--"+ Dog.class.getClassLoader());
}
}
ClassLoaderTest01在sys下面：
1、如果Parent类在common下面，由子类加载，即loader2来加载。
<img src="https://img-blog.csdn.net/20160122230640800?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />
2、如果Parent类在sys下面
由父类加载器加载，即loader1来加载。
<img src="https://img-blog.csdn.net/20160122230703769?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />
如果Parent在系统目录下
<img src="https://img-blog.csdn.net/20160122230726426?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />
对于loader3，无论Parent类在哪目录下，Parent类始终由loader3来加载。
