Java基础之代理原理与用法详解

static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h)

public interface StduentInterface {
 public int insertStudent(Student student);
}

public class StudentDAO implements StduentInterface {
 @Override
 public int insertStudent(Student student) {
  // 以下这段代码是业务逻辑
  return null == student ? 0 : 1;
 }
}

public class StudentStaticProxyDAO {
 private StudentDAO studentDAO;
 public StudentStaticProxyDAO(StudentDAO studentDAO) {
  this.studentDAO = studentDAO;
 }
 public int insertStudent(Student student) {
  Logger.info("开始插入一个学生记录： " + student.toString());
  int number = studentDAO.insertStudent(student);
  Logger.info("插入 " + number + " 条学生记录");
  return number;
 }
}

public class LoggerDynamicProxy implements InvocationHandler{
 private Object target;
 public LoggerDynamicProxy(Object obj) {
  this.target = obj;
 }
 /**
  * 动态代理类中的 invoke 方法
  *
  * 三个参数的意义：
  *
  * proxy ：代理对象
  * method : 委托类中要调用的方法
  * args ：method 方法的参数
  */
 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  Logger.info("before 业务方法调用之前");
  Object obj = method.invoke(target, args);
  Logger.info("before 业务方法调用之前");
  return obj;
 }
}

public class ProxyTest {
 public static void main(String[] args) {
  /**
   * 基础组件准备
   */
  StudentDAO studentDao = new StudentDAO();
  Student student = new Student(100000);
  StudentStaticProxyDAO studentProxyDAO = new StudentStaticProxyDAO(studentDao);
  /**
   * 测试委托类的功能
   */
  System.out.println(studentDao.insertStudent(student));
  /**
   * 测试静态代理类的功能
   */
  System.out.println(studentProxyDAO.insertStudent(student));
  /**
   * 测试动态代理类的功能
   */
  StduentInterface newProxyInstance = (StduentInterface)Proxy.newProxyInstance(studentDao.getClass().getClassLoader(),
    studentDao.getClass().getInterfaces(),
    new LoggerDynamicProxy(studentDao));
  int insertStudent = newProxyInstance.insertStudent(student);
  System.out.println(insertStudent);
}