public interface MyService {
  void test01();
  void test02(String s);
}
public class MyServiceImpl implements MyService {
  @Override
  public void test01() {
    System.out.println("test01");
  }
  @Override
  public void test02(String s) {
    System.out.println(s);
  }
}
public class Main {
  public static void main(String[] args) {
    MyServiceImpl target = new MyServiceImpl();
    }
}

package com.dmz.proxy;
import com.dmz.proxy.target.MyService;
/**
 * 静态代理
 */
public class StaticProxy implements MyService {
  private MyService target;
  public StaticProxy(MyService target) {
    this.target = target;
  }
  @Override
  public void test01() {
    System.out.println("proxy print log for test01");
    target.test01();
  }
  @Override
  public void test02(String s) {
    System.out.println("proxy print log for test02");
    target.test02(s);
  }
}

public class ProxyUtil {
  /**
   * @param target 目标对象
   * @return 代理对象
   */
  public static Object newInstance(Object target) {
    Object proxy = null;
        // 开始拼接字符串
    Class targetInf = target.getClass().getInterfaces()[0];
    Method[] methods = targetInf.getDeclaredMethods();
    String line = System.lineSeparator();
    String tab = "\t";
    String infName = targetInf.getSimpleName();
    String content = "";
    String packageContent = "package com.dmz.proxy;" + line;
    String importContent = "import " + targetInf.getName() + ";" + line;
    String clazzFirstLineContent = "public class $Proxy implements " + infName + "{" + line;
    String filedContent = tab + "private " + infName + " target;" + line;
    String constructorContent = tab + "public $Proxy (" + infName + " target){" + line
        + tab + tab + "this.target =target;"
        + line + tab + "}" + line;
    String methodContent = "";
    for (Method method : methods) {
      String returnTypeName = method.getReturnType().getSimpleName();
      String methodName = method.getName();
      // Sting.class String.class
      Class args[] = method.getParameterTypes();
      String argsContent = "";
      String paramsContent = "";
      int flag = 0;
      for (Class arg : args) {
        String temp = arg.getSimpleName();
        //String
        //String p0,Sting p1,
        argsContent += temp + " p" + flag + ",";
        paramsContent += "p" + flag + ",";
        flag++;
      }
      if (argsContent.length() > 0) {
        argsContent = argsContent.substring(0, argsContent.lastIndexOf(",") - 1);
        paramsContent = paramsContent.substring(0, paramsContent.lastIndexOf(",") - 1);
      }
      methodContent += tab + "public " + returnTypeName + " " + methodName + "(" + argsContent + ") {" + line
          + tab + tab + "System.out.println(\"proxy print log for " + methodName + "\");" + line
          + tab + tab + "target." + methodName + "(" + paramsContent + ");" + line
          + tab + "}" + line;
    }
    content = packageContent + importContent + clazzFirstLineContent + filedContent + constructorContent + methodContent + "}";
    //字符串拼接结束
        // 开始生成.java文件
    File file = new File("g:\\com\\dmz\\proxy\\$Proxy.java");
    try {
      if (!file.exists()) {
        file.createNewFile();
      }
      FileWriter fw = new FileWriter(file);
      fw.write(content);
      fw.flush();
      fw.close();
    // .java文件生成结束
        // 开始进行编译   
      JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
      StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null, null, null);
      Iterable units = fileMgr.getJavaFileObjects(file);
      JavaCompiler.CompilationTask t = compiler.getTask(null, fileMgr, null, null, null, units);
      t.call();
      fileMgr.close();
    // 编译结束，生成.class文件
      // 从G盘中加载class文件
      URL[] urls = new URL[]{new URL("file:G:\\\\")};
      URLClassLoader urlClassLoader = new URLClassLoader(urls);
      // 加载
      Class clazz = urlClassLoader.loadClass("com.dmz.proxy.$Proxy");
            // 加载结束
            // 构造代理对象
      Constructor constructor = clazz.getConstructor(targetInf);
      proxy = constructor.newInstance(target);
    } catch (Exception e) {
      e.printStackTrace();
    }
    return proxy;
  }
}

public class Main {
    public static void main(String[] args) {
        MyServiceImpl target = new MyServiceImpl();
        MyService o = ((MyService) ProxyUtil.newInstance(target));
        o.test01();
        o.test02("test02");
    }
}