设计模式之 动态代理 - ThreadLocal实现事务管理

 

动态代理:JDK动态代理只能对实现了接口的类进入代理,采用JDK动态代理必须实现InvocationHandler接口,采用Proxy 类创建相应的代理类.

下面使用Model2(MVC)使用代理事务查询用户基本信息,使用DB2数据库:

建立表:
create table T_USER
(
   USER_ID              VARCHAR(10)            not null,
   USER_NAME            VARCHAR(30)            not null,
   PASSWORD             VARCHAR(20)            not null,
   CONTACT_TEL          VARCHAR(30),
   EMAIL                VARCHAR(30),
   CREATE_DATE          DATE,
   constraint P_KEY_1 primary key (USER_ID)
);

初始化数据:
insert into t_user(user_id, user_name, password) values('root', '系统管理员', 'root');

 

ConnectionManager :数据库连接管理类,实现对数据库连接和事务的管理.

package gd.hz.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectionManager {
	private ConnectionManager() {
	}

	private static ThreadLocal<Connection> threadConn = new ThreadLocal<Connection>();

	// 获取数据库连接
	public static Connection getConnection() {
		Connection conn = threadConn.get();
		if (conn == null) {
			try {
				Class.forName("com.ibm.db2.jcc.DB2Driver");
				conn = DriverManager.getConnection(
						"jdbc:db2://127.0.0.1:50000/DRP", "db2admin", "619100");
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			threadConn.set(conn);
		}
		return conn;
	}

	// 设置事务手动提交
	public static void benigTransction(Connection conn) {
		try {
			if (conn != null) {
				if (conn.getAutoCommit()) {
					conn.setAutoCommit(false);
				}
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 提交事务
	public static void endTransction(Connection conn) {
		try {
			if (conn != null) {
				if (!conn.getAutoCommit()) {
					conn.commit();
				}
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 设置Connection的原始状态
	public static void recoverTransction(Connection conn) {
		try {
			if (conn != null) {
				if (conn.getAutoCommit()) {
					conn.setAutoCommit(false);
				} else {
					conn.setAutoCommit(true);
				}
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 发生异常回滚事务
	public static void rollback(Connection conn) {
		try {
			if (conn != null) {
				conn.rollback();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 关闭连接,并将其从当前线程删除
	public static void close() {
		Connection conn = threadConn.get();
		if (conn != null) {
			try {
				conn.close();
				conn = null;
				threadConn.remove();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

 

 

Model:

package gd.hz.model;

import java.util.Date;

//用户实体类
public class User {
	// 用户ID
	private String id;
	// 用户名称
	private String name;
	// 登陆密码
	private String password;
	// 联系电话
	private String contact_tel;
	// 电子邮件
	private String email;
	// 用户创建日期
	private Date create_date;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getContact_tel() {
		return contact_tel == null ? "" : contact_tel;
	}

	public void setContact_tel(String contact_tel) {
		this.contact_tel = contact_tel;
	}

	public String getEmail() {
		return email == null ? "" : email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public Date getCreate_date() {
		return create_date;
	}

	public void setCreate_date(Date create_date) {
		this.create_date = create_date;
	}
}

 

DAO接口:

package gd.hz.dao;

import gd.hz.model.User;

import java.sql.SQLException;

public interface UserDAO {
	public User selUser(String id) throws SQLException;
}

 

DAO实现类:

package gd.hz.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import gd.hz.model.User;
import gd.hz.util.ConnectionManager;

public class UserDAOImpl implements UserDAO {
	// 根据ID查询用户
	public User selUser(String id) throws SQLException {
		ResultSet resu = null;
		String sql = "SELECT * FROM DB2ADMIN.T_USER WHERE USER_ID = ?";
		Connection conn = ConnectionManager.getConnection();
		PreparedStatement pstat = conn.prepareStatement(sql);
		User user = null;
		try {
			pstat.setString(1, id);
			resu = pstat.executeQuery();
			if (resu.next()) {
				user = getUser(resu);
			}
		} finally {
			if (resu != null) {
				resu.close();
			}
			if (pstat != null) {
				pstat.close();
			}
		}
		return user;
	}

	// 获取用户
	private User getUser(ResultSet resu) throws SQLException {
		User user = new User();
		user.setId(resu.getString("USER_ID"));
		user.setName(resu.getString("USER_NAME"));
		user.setPassword(resu.getString("PASSWORD"));
		user.setContact_tel(resu.getString("CONTACT_TEL"));
		user.setEmail(resu.getString("EMAIL"));
		user.setCreate_date(resu.getTimestamp("CREATE_DATE"));
		return user;
	}
}

 

Manager接口:

package gd.hz.manager;

import gd.hz.model.User;

public interface UserManager {
	public User findUser(String id) throws Exception;
}

 

Manager实现类:

package gd.hz.manager;

import java.sql.SQLException;

import gd.hz.dao.UserDAO;
import gd.hz.dao.UserDAOImpl;
import gd.hz.model.User;

public class UserManagerImpl implements UserManager {
	private UserDAO userDAO = null;

	public UserManagerImpl() {
		userDAO = new UserDAOImpl();
	}

	public User findUser(String id) throws SQLException {
		return userDAO.selUser(id);
	}
}

 

创建代理类:

package gd.hz.util;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;

//Manager代理类
public class TransctionProxy implements InvocationHandler {
	private Object obj = null;

	// obj:需要代理的类
	public Object newProxyInstance(Object obj) {
		this.obj = obj;
		return Proxy.newProxyInstance(this.obj.getClass().getClassLoader(),
				this.obj.getClass().getInterfaces(), this);
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		// 用于接收参数
		Object param = null;
		// 如果是以下方法开头,则代理事务
		if (method.getName().startsWith("add")
				|| method.getName().startsWith("modify")
				|| method.getName().startsWith("find")
				|| method.getName().startsWith("del")) {
			Connection conn = ConnectionManager.getConnection();
			try {
				// 手动提交事务
				ConnectionManager.benigTransction(conn);
				param = method.invoke(obj, args);
				// 提交事务
				ConnectionManager.endTransction(conn);
			} catch (Exception e) {
				// 回滚事务
				ConnectionManager.rollback(conn);
				if (e instanceof InvocationTargetException) {
					InvocationTargetException inv = (InvocationTargetException) e;
					throw inv.getTargetException();
				} else {
					throw new Exception("操作失败!");
				}
			} finally {
				// 还原状态
				ConnectionManager.recoverTransction(conn);
				ConnectionManager.close();
			}
		}
		return param;
	}
}

 

测试:

package gd.hz.util;

import gd.hz.manager.UserManager;
import gd.hz.manager.UserManagerImpl;
import gd.hz.model.User;

public class Test {
	public static void main(String[] args) throws Exception {
		TransctionProxy transctionProxy = new TransctionProxy();

		// //产生代理对象
		UserManager userManager = (UserManager) transctionProxy
				.newProxyInstance(new UserManagerImpl());
		User user = userManager.findUser("root");
		System.out.println("用户名:" + user.getName());
	}
}