JavaWeb:业务层两种事务管理方式

￡神魔★判官ぃ 2022-03-28 08:46 349阅读 0赞

### 业务层事务管理 ###

*  事务管理
 *   *  DAO层事务管理
     *  Service层事务管理
     *  事务管理要加在哪里？
 *  例子：转账
 *   *  View、Servlet和Domain代码
     *   *  事务控制第一种方法：传递Service传递一个Connection给Dao层
         *  事务控制第二种方法：使用ThreadLocal
     *  使用DBUtils的事务控制：传递相同Connection
     *  Hibernate事务管理：ThreadLocal

# 事务管理 #

## DAO层事务管理 ##

dao层一般完成单个数据库操作，使用Connection可以控制单个事务的提交，回滚。

## Service层事务管理 ##

service层一般完成一定的业务逻辑，需要使用多个dao的操作组合完成。所以这些操作要么全部完成要么全部不做。也就是一个事务。

## 事务管理要加在哪里？ ##

答：Service层，控制整个业务逻辑的隔离性。

# 例子：转账 #

## View、Servlet和Domain代码 ##

View层：

Domain:

private Integer id;
    	private String name;
    	private Double money;
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public Double getMoney() {
    		return money;
    	}
    	public void setMoney(Double money) {
    		this.money = money;
    	}
    
    }

Jdbc工具类：

static ComboPooledDataSource dataSource = null;
    	static{
    		dataSource=new ComboPooledDataSource();
    	}
    	
    	public static Connection getConnection() throws SQLException{
    		return dataSource.getConnection();
    	}
    	
    	public static DataSource getDataSource(){
    		return dataSource;
    	}
    	public static void close(Connection con,PreparedStatement ps,ResultSet rs){
    		if(rs!=null){
    			try {
    				rs.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		if(ps!=null){
    			try {
    				ps.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		
    		if(con!=null){
    			try {
    				con.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    	}
    	
    	public static void main(String[] args) throws SQLException {
    		System.out.println(new JDBCUtils().getConnection());
    	}
    
    	public static void startTransaction() {
    		startTransaction();
    		
    	}

Servlet层：调用业务层的服务进行转账

public class AccountServlet extends HttpServlet {
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		String from = request.getParameter("from");
    		String to = request.getParameter("to");
    		request.setCharacterEncoding("utf-8");//post乱码
    		Double money = Double.parseDouble(request.getParameter("money"));
    		
    		//处理数据
    		AccountService service = new AccountService();
    		try {
    			service.transfer(from ,to ,money);
    		} catch (SQLException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    
    	/**
    	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doGet(request, response);
    	}
    
    }

### 事务控制第一种方法：传递Service传递一个Connection给Dao层 ###

Service层分析：分别调用Dao层的两个方法，完成一个事务，一个事务必须使用同一个Connection设置自动提交false，在业务层完成事务的提交/回滚。

* 事务管理第一种解决办法：向下传递Connection
    	 * @param from
    	 * @param to
    	 * @param money
    	 * @throws SQLException
    	 */
    	public void transfer(String from, String to, Double money) throws SQLException {
    		AccountDao accountDao = new AccountDao();
    		//方法1：业务层获得Connection 传给dao
    		Connection conn = null;
    		
    		try {
    			conn= JDBCUtils.getConnection();
    			conn.setAutoCommit(false);
    			accountDao.transferOut(from,money,conn);
    			int i=1/0;
    			accountDao.transferIn(to,money,conn);
    		} catch (Exception e) {
    			System.out.println("rollback");
    			conn.rollback();
    			e.printStackTrace();
    		}
    		conn.commit();
    	}

对应Dao层代码：接收Service层的Connection

* 第一种：传递Connection
    	 * @param from
    	 * @param money
    	 * @param conn
    	 * @throws SQLException
    	 *//*
    	public void transferOut(String from, Double money, Connection conn) throws SQLException {
    		
    		//Connection conn = null;
    		PreparedStatement ps=null;
    		try{
    			//conn = JDBCUtils.getConnection();
    			String sql = "update account set money = money-? where name =?";
    			ps = (PreparedStatement) conn.prepareStatement(sql);
    			ps.setDouble(1, money);
    			ps.setString(2, from);
    			ps.executeUpdate();
    		}catch (Exception e) {
    			e.printStackTrace();
    		}finally {
    			ps.close();
    			//conn.close();
    		}
    	}
    
    	public void transferIn(String to, Double money, Connection conn) throws SQLException {
    		//Connection conn = null;
    		PreparedStatement ps=null;
    		try{
    			//conn = JDBCUtils.getConnection();
    			String sql = "update account set money = money+? where name =?";
    			ps = conn.prepareStatement(sql);
    			ps.setDouble(1, money);
    			ps.setString(2, to);
    			ps.executeUpdate();
    		}catch (Exception e) {
    			e.printStackTrace();
    		}finally {
    			ps.close();
    			//conn.close();
    		}
    	}

### 事务控制第二种方法：使用ThreadLocal ###

ThreadLocal使用Map<key,value>将一个变量与线程绑定，key是线程，value是与绑定线程的变量。将Connection作为变量与线程绑定，就保证了在执行Service时，每个线程在执行每个Dao操作时，获取同一个Connection。  
Service层代码：

* 事务管理，使用ThreadLocal
    	 * @param from
    	 * @param to
    	 * @param money
    	 * @throws SQLException 
    	 */
    	public void transfer2(String from, String to, Double money) throws SQLException {
    		AccountDao accountDao = new AccountDao();
    		Connection conn = null;
    		try {
    			conn= JDBCUtils2.getConnection();
    			JDBCUtils2.startTransaction();
    			accountDao.transferOut(from,money);
    			//int i=1/0;
    			accountDao.transferIn(to,money);
    		} catch (Exception e) {
    			System.out.println("rollback");
    			JDBCUtils2.rollBackTranaction();
    			e.printStackTrace();
    		}
    		JDBCUtils2.commitTransaction();
    	}

JDBCUtils2:保证获得的Connection是与当前线程绑定的Conn

static ComboPooledDataSource dataSource = null;
    	static final ThreadLocal<Connection> tl=new ThreadLocal<Connection>();
    	//连接与线程绑定ThreadLocal的Map里放的是<Thread,Connection>
    	static{
    		dataSource=new ComboPooledDataSource();
    	}
    	
    	public static Connection getConnection() throws SQLException{
    		Connection conn = null;
    		if(tl.get()==null){
    			conn = dataSource.getConnection();
    			tl.set(conn); //获取线程时连接放入线程
    		}
    		return tl.get();//取出线程绑定的连接
    		
    	}
    	
    	public static DataSource getDataSource(){
    		return dataSource;
    	}
    	
    	public static void close(Connection con,PreparedStatement ps,ResultSet rs){
    		if(rs!=null){
    			try {
    				rs.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		if(ps!=null){
    			try {
    				ps.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		
    		if(con!=null){
    			try {
    				con.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    	}
    
    	public static void startTransaction() throws SQLException {
    		Connection conn = null;
    		conn = tl.get();
    		if(conn==null){
    			conn=dataSource.getConnection();
    			tl.set(conn);
    		}
    		conn.setAutoCommit(false);//线程绑定的连接设置不自动提交
    		
    	}
    	
    	public static void commitTransaction() throws SQLException{
    		Connection connection = tl.get();
    		connection.commit();   ///线程绑定的连接提交事务
    	}
    	
    	public static  void  rollBackTranaction() throws SQLException{
    		Connection connection = tl.get();
    		connection.rollback();//线程绑定的连接回滚
    	}
    }

Dao层代码：获得的链接是与当前线程绑定的Connection

public void transferOut(String from, Double money) throws SQLException {
    		Connection conn = null;
    		PreparedStatement ps=null;
    		try{
    			conn = JDBCUtils2.getConnection();
    			String sql = "update account set money = money-? where name =?";
    			ps = (PreparedStatement) conn.prepareStatement(sql);
    			ps.setDouble(1, money);
    			ps.setString(2, from);
    			ps.executeUpdate();
    		}catch (Exception e) {
    			e.printStackTrace();
    		}finally {
    			ps.close();
    			//conn.close();
    		}
    	}
    	public void transferIn(String to, Double money) throws SQLException {
    		/*//没有事务管理dbutils时这样用
    		 * QueryRunner query=new QueryRunner(JDBCUtils.getDataSource());
    		String sql = "update account set money = money+? where name =?";
    		query.update(sql,money,to);
    		*/
    
    		Connection conn = null;
    		PreparedStatement ps=null;
    		try{
    			conn = JDBCUtils2.getConnection();
    			String sql = "update account set money = money+? where name =?";
    			ps = conn.prepareStatement(sql);
    			ps.setDouble(1, money);
    			ps.setString(2, to);
    			ps.executeUpdate();
    		}catch (Exception e) {
    			e.printStackTrace();
    		}finally {
    			ps.close();
    			//conn.close();
    		}
    	}

## 使用DBUtils的事务控制：传递相同Connection ##

Service层：传递普通Connection给dao层

* 事务管理，使用Dbutils和第一种类似，都是传递Connection
    	 * @param from
    	 * @param to
    	 * @param money
    	 * @throws SQLException 
    	 */
    	public void transfer(String from, String to, Double money) throws SQLException {
    		AccountDao accountDao = new AccountDao();
    		Connection conn = null;
    		try {
    			conn= JDBCUtils.getConnection();
    			conn.setAutoCommit(false);
    			accountDao.transferOut(from,money,conn);
    			int i=1/0;
    			accountDao.transferIn(to,money,conn);
    		} catch (Exception e) {
    			System.out.println("rollback");
    			DbUtils.rollbackAndClose(conn);
    			e.printStackTrace();
    		}
    		DbUtils.commitAndCloseQuietly(conn);
    	}

dao层使用DBUtils进行数据库操作：

* 第一种：DButils
    	 * @param from
    	 * @param money
    	 * @param conn
    	 * @throws SQLException
    	 */
    	public void transferOut(String from, Double money, Connection conn) throws SQLException {
    		//有事务管理dbutils时这样用
    		QueryRunner query=new QueryRunner();
    		String sql = "update account set money = money-? where name =?";
    		//传Connection
    		query.update(conn,sql,money,from);
    		
    	}
    
    	public void transferIn(String to, Double money, Connection conn) throws SQLException {
    		//有事务管理dbutils时这样用
    		QueryRunner query=new QueryRunner();
    		String sql = "update account set money = money+? where name =?";
    		//传Connection
    		query.update(conn,sql,money,to);
    	}

## Hibernate事务管理：ThreadLocal ##

Hibernate使用ThreadLocal管理事务，程序员不必编写代码进行控制，只需要在核心配置文件里配置即可设置对应的事务管理级别

<property name="hibernate.current_session_context_class">thread</property>

Hibernate工具类里通过SessionFactory的getCurrentSession()获得与线程绑定的Connection,不再配置文件里配置是使用不了这个方法的。

public static  Session getCurrentSeesion(){
    		//xml配置以后才可以使用
    		return factory.getCurrentSession();
    	}

Hibernate使用：

Session session = HibernateUtils.getCurrentSeesion();
    		Transaction transaction = session.beginTransaction();
    		Customer c= new  Customer();
    		c.setCust_name("王");
    		session.save(c);
    		transaction.commit();
    		//不要关闭session，线程结束会自动关闭