一个简单的Java反编译实例

1、目标对象

package com.leiht.reflect.decompile;

public class Entity {
	public void method1() {
		System.out.println("-------------Method1-----------");
	}
	public void method2(String str) {
		System.out.println("-------------Method2-----------" + str);
	}
}

2、反编译实现类

package com.leiht.reflect.decompile;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class ClassLoaderExpand extends ClassLoader {
	
	public Class<?> getClass(String classFileName, String className) {
		byte[] data = loadClassData(classFileName);
		Class<?> clazz = this.defineClass(className, data, 0, data.length);
	    return clazz;
	}
	
	/*
	 * 读取xxxx.clsss文件为byte[]数组
	 */
	private byte[] loadClassData(String classFileName) {
		
		FileInputStream fis = null;
		byte[] result = null;
		ByteArrayOutputStream bos = null;
		try{
			fis = new FileInputStream(new File(classFileName));
			bos = new ByteArrayOutputStream();
			int i;
			while((i = fis.read()) != -1) {
				bos.write(i);
			}
			result = bos.toByteArray();
		}catch(Exception e) {
			e.printStackTrace();
		}finally {
			if(fis != null) {
				try {
					fis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if(bos != null) {
				try {
					bos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		
		return result;
	}
}

3、测试类

package com.leiht.reflect.decompile;

import java.lang.reflect.Method;

public class ClassLoaderExpandTest {
	public static void main(String[] args) throws Exception {
		ClassLoaderExpand cle = new ClassLoaderExpand();

		String classFileName = "D:\\J2SEProject\\Reflect\\bin\\com\\leiht\\reflect\\decompile\\Entity.class";
		
		//测试了一下，不传这个className也没问题
		String className = "com.leiht.reflect.decompile.Entity";
		
		Class<?> clazz = cle.getClass(classFileName, className);
		
		System.out.println(clazz);
		
		Method method1 = clazz.getMethod("method1");
		Method method2 = clazz.getMethod("method2", String.class);
		
		method1.invoke(clazz.newInstance());
		method2.invoke(clazz.newInstance(), "雷洪太");
	}
}