JDBC基础学习之事务控制(四)

一、现象

 二、事务的概念

三、事务特征

 四、事务的类型

五、示例

       5.1情况1：正常删除人员信息，删除用户信息是有异常，虽然将事务设置为手动提交，但仍然不能控制一致性，原因是他们进行操作时是两个Connection.

package com.zlt.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.zlt.jdbc.util.DBUtil;

public class Test5 {

	public static void main(String[] args) {

		deletePersonById(1);
		deleteUserByPid(1);
	}
	
	
	/**
	 * 根据人员ID删除人员信息
	 * @param id
	 * @return reuslt :-1,删除失败;非-1，删除成功
	 */
	public static int deletePersonById(int id){
		int result = 0;
		Connection conn = null;
		PreparedStatement pstmt = null;
		
		try {
			conn  = DBUtil.getConnection();
			conn.setAutoCommit(false);//将事务设为手动提交
			String sql = "delete from t_person where id = ?" ;
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			result = pstmt.executeUpdate();
			conn.commit();//提交事务
		} catch (SQLException e) {
			e.printStackTrace();
			result = -1;
			try {
				conn.rollback();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}//事务回滚
		}finally{
			DBUtil.close(pstmt);
			DBUtil.close(conn);
		}
		return result;
	}
	
	
	
	/**
	 * 根据人员ID删除用户信息
	 * @param pid 人员ID
	 * @return 
	 */
	public static int deleteUserByPid(int pid){
		Connection conn = null;
		PreparedStatement pstmt = null;
		int result = 0;
		try {
			conn  = DBUtil.getConnection();
			conn.setAutoCommit(false);
			String sql = "delete from user where pid = ?";
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, pid);
			Integer.parseInt("123a");
			result = pstmt.executeUpdate();
			conn.commit();
		} catch (SQLException e) {
			e.printStackTrace();
			result = -1;
			try {
				conn.rollback();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}finally{
			DBUtil.close(pstmt);
			DBUtil.close(conn);
		}
		return result;
	}

}

   5.2改进事务控制，将两个方法的Connection控制在一个Connection

package com.zlt.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.zlt.jdbc.util.DBUtil;

public class Test5 {

	public static void main(String[] args) {
		
		Connection conn = null;
		try{
			conn = DBUtil.getConnection();
			conn.setAutoCommit(false);//将事务设为手动提交
			deletePersonById(conn,1);
			deleteUserByPid(conn,1);
			conn.commit();//提交事务
		}catch(Exception e){
			try {
				conn.rollback();//事务回滚
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}finally{
			DBUtil.close(conn);
		}
	}
	
	
	/**
	 * 根据人员ID删除人员信息
	 * @param id
	 * @return reuslt :-1,删除失败;非-1，删除成功
	 */
	public static int deletePersonById(Connection conn,int id){
		int result = 0;
		PreparedStatement pstmt = null;
		
		try {
			String sql = "delete from t_person where id = ?" ;
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			result = pstmt.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
			result = -1;
		}
		return result;
	}
	
	
	
	/**
	 * 根据人员ID删除用户信息
	 * @param pid 人员ID
	 * @return 
	 */
	public static int deleteUserByPid(Connection conn,int pid){
		PreparedStatement pstmt = null;
		int result = 0;
		try {
			String sql = "delete from user where pid = ?";
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, pid);
			Integer.parseInt("123a");
			result = pstmt.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
			result = -1;
		}
		return result;
	}
}

    以上示例代码虽然进行的改进但是事务还是没有控制住,只有一张表中的数据被删除了，由于在deleteUserByPid方法中出现了异常没有往上抛，被底下把异常Catch了，当然一般持久化异常都是SQLException,此处我们为了做实验才catch Exception异常

    5.3小结

 最后的代码：方法deleteUserByPid虽然有异常，但方法deletePersonById中也未删除数据，说明进行了事务回滚

package com.zlt.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.zlt.jdbc.util.DBUtil;

public class Test5 {

	public static void main(String[] args) {
		
		Connection conn = null;
		try{
			conn = DBUtil.getConnection();
			conn.setAutoCommit(false);//将事务设为手动提交
			deletePersonById(conn,1);
			deleteUserByPid(conn,1);
			conn.commit();//提交事务
		}catch(Exception e){
			try {
				conn.rollback();//事务回滚
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}finally{
			DBUtil.close(conn);
		}
	}
	
	
	/**
	 * 根据人员ID删除人员信息
	 * @param id
	 * @return reuslt :-1,删除失败;非-1，删除成功
	 */
	public static int deletePersonById(Connection conn,int id) throws SQLException{
		int result = 0;
		PreparedStatement pstmt = null;
		
		try {
			String sql = "delete from t_person where id = ?" ;
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			result = pstmt.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
			result = -1;
			throw new SQLException();
		}
		return result;
	}
	
	
	
	/**
	 * 根据人员ID删除用户信息
	 * @param pid 人员ID
	 * @return 
	 */
	public static int deleteUserByPid(Connection conn,int pid) throws SQLException{
		PreparedStatement pstmt = null;
		int result = 0;
		try {
			String sql = "delete from user where pid = ?";
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, pid);
			Integer.parseInt("123a");
			result = pstmt.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
			result = -1;
			throw new SQLException();
		}
		return result;
	}

}

    5.4 遗留的问题

         1）JDBC有大量重复的地方
         2）随着功能模块的增加维护越来越不方面，因此将数据库操作的那层抽象出来，DAO层
         3）流行的持久层开源框架：Mybatis与Hibernate