Day10——支持主键自增的数据库获取主键值

忘是亡心i 2023-07-04 12:49 12阅读 0赞

# 一. 问题需求 #

插入一条新的数据，立马查询这条数据。

**分析：** 插入新数据很简单，查询数据需要知道这条数据的主键值，因此我们需要在插入新数据后立马获取到并且返回它的主键值

### [前往免费下载源码][Link 1] ###

# 二. 例子 #

MyBatis中可以使用useGeneratedKeys=“true”，然后把keyProperty设置到目标属性上，如下：

EmployeeMapper.xml

<insert id="insertEmployee" parameterType="com.atguigu.mybatis.beans.Employee" useGeneratedKeys="true" keyProperty="id">
    	     insert into tbl_employee (last_name, email, gender) values (#{lastName}, #{email}, #{gender})
    	 </insert>

TestMyBatis.java

@Test
    	public void testReturnKeys() throws Exception{ 
    		SqlSessionFactory ssf = getSqlSessionFactory();
    		SqlSession session = ssf.openSession();
    		//ssf.openSession(true);带自动提交功能
    		try { 
    			EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
    			Employee employee = new Employee(null, "柴柴", "cls@sina.com", "0");
    			mapper.insertEmployee(employee);
    			
    			Integer id = employee.getId();
    			System.out.println("主键值：" + id);
    			
    			session.commit();
    			
    			
    			/** * 底层源码实现主键自增并且返回主键 */
    // 
    // Connection conn = null;
    // PreparedStatement ps = 
    // conn.prepareStatement("sql语句", PreparedStatement.RETURN_GENERATED_KEYS);
    // ps.executeUpdate();
    // ps.getGeneratedKeys();
    			
    		} finally { 
    			// TODO: handle finally clause
    			session.close();
    		}
    		
    	}
    	
    	
    	public SqlSessionFactory getSqlSessionFactory() throws Exception { 
    		String resource = "mybatis-config.xml"; 
    		InputStream inputStream = 
    				Resources.getResourceAsStream(resource); 
    		SqlSessionFactory sqlSessionFactory = 
    				new SqlSessionFactoryBuilder().build(inputStream);
    		return sqlSessionFactory;
    	}

[Link 1]: https://me.csdn.net/download/qq_40634846