使用动态代理实现数据库事务（转）

数据库sql：

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)
);

insert into t_user(user_id, user_name, password) values('root', '系统管理员', 'root');

ConnectionManager.java(数据库连接管理)

package dynamicProxyTransaction;

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();
            }
        }
    }
}

User.java(实体类)

package dynamicProxyTransaction;

import java.util.Date;

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;
        }
}

UserDAO.java(用户相关的数据库操作)

package dynamicProxyTransaction;

import java.sql.SQLException;

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

UserDAOImpl.java(UserDAO实现类)

package dynamicProxyTransaction;

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

public class UserDAOImpl implements UserDAO {
    @Override
    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;
        }
}

UserManager.java(用户管理功能定义)

package dynamicProxyTransaction;

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

UserManagerImpl.java(UserManager实现类)

package dynamicProxyTransaction;

import java.sql.SQLException;

public class UserManagerImpl implements UserManager {
    // 这个和我以前写的不一样： 我都是写在每个方法中，写成属性应该好一点，减少创建对象的次数
    private UserDAO userDAO = null; 

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

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

TransactionProxy.java(代理实现)

package dynamicProxyTransaction;

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

public class TransactionProxy 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;
    }
}

Test.java(测试)

package dynamicProxyTransaction;

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

        // //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());
    }
    
}

原文地址：http://itindex.net/detail/44008-java-%E4%BB%A3%E7%90%86-threadlocal