使用Filter实现事务

r囧r小猫 2023-10-12 08:17 5阅读 0赞

一、创建Filter，在web.xml中拦截所有请求进行过滤

<filter>
        <display-name>TransactionFilter</display-name>
        <filter-name>TransactionFilter</filter-name>
        <filter-class>com.atguigu.filter.TransactionFilter</filter-class>
      </filter>
      <filter-mapping>
        <filter-name>TransactionFilter</filter-name>
        <url-pattern>/*</url-pattern>
      </filter-mapping>

二、使用线程管理一个Connection

import java.sql.Connection;
    import java.sql.SQLException;
    import java.util.Properties;
    
    import javax.sql.DataSource;
    
    import com.alibaba.druid.pool.DruidDataSourceFactory;
    
    /** * 获取连接和释放连接的工具类 * * @author Chunsheng Zhang * */
    public class JDBCUtils { 
    	private static DataSource dataSource;
    
    	// 创建一个管理Connection的线程
    	private static ThreadLocal<Connection> threadLocal = new ThreadLocal<>();
    
    	static { 
    		try { 
    			// 1、读取druip.properties文件
    			Properties pro = new Properties();
    			pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
    
    			// 2、连接连接池
    			dataSource = DruidDataSourceFactory.createDataSource(pro);
    		} catch (Exception e) { 
    			e.printStackTrace();
    		}
    	}
    
    	// 获取连接
    	public static Connection getConnection() { 
    		// 从当前线程获取connection
    		Connection connection = threadLocal.get();
    		try { 
    			// 如果Connection为空的话，创建一个connection，并将该connection放到该线程当中
    			if (connection == null) { 
    				connection = dataSource.getConnection();
    				threadLocal.set(connection);
    			}
    		} catch (SQLException e) { 
    			e.printStackTrace();
    		}
    		return connection;
    	}
    
    	// 释放连接
    	public static void releaseConnection() { 
    		// 从当前线程获取Connection
    		Connection connection = threadLocal.get();
    		if (connection != null) { 
    			try { 
    				connection.close();
    				// 将connection从当前线程中移除，释放线程
    				threadLocal.remove();
    			} catch (SQLException e) { 
    				e.printStackTrace();
    			}
    		}
    	}
    }

三、在Filter实现类中实现事务（底层异常都向上抛给该实现类统一处理：为了回滚数据）

import java.io.IOException;
    import java.sql.Connection;
    import java.sql.SQLException;
    
    import javax.servlet.FilterChain;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.atguigu.util.JDBCUtils;
    
    public class TransactionFilter extends HttpFilter { 
    
    	@Override
    	public void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
    			throws IOException, ServletException { 
    		// 获得Connection对象
    		Connection connection = JDBCUtils.getConnection();
    		try { 
    			// 开启事务，将默认的自动提交改为false
    			connection.setAutoCommit(false);
    			// 放行，执行相应代码
    			chain.doFilter(req, res);
    			// 如果无异常的话，执行到这一步就都成功了，所以提交事务
    			connection.commit();
    		} catch (Exception e) { 
    			// 处理异常
    			try { 
    				// 若有异常则回滚数据
    				connection.rollback();
    			} catch (SQLException e1) { 
    				e1.printStackTrace();
    			}
    			e.printStackTrace();
    			res.sendRedirect(req.getContextPath()+"/pages/error/transaction_error.jsp");
    		} finally { 
    			// 关闭事务
    			JDBCUtils.releaseConnection();
    		}
    	}
    
    }