MyBatis动态SQL foreach标签实现批量插入

需求:查出给定id的记录:

<select id="getEmpsByConditionForeach" resultType="com.test.beans.Employee">
        SELECT * FROM tb1_emplyee WHERE id IN
        <foreach collection="list" item="item_id" separator="," open="(" close=")">
            #{item_id}
        </foreach>
</select>

关于foreach标签,有几个属性应该注意一下:

collection：指定要遍历的集合：
list类型的参数会特殊处理封装在map中，map的key就叫list
item：将当前遍历出的元素赋值给指定的变量
separator:每个元素之间的分隔符
open：遍历出所有结果拼接一个开始的字符
close:遍历出所有结果拼接一个结束的字符
index:索引。遍历list的时候是index就是索引，item就是当前值
遍历map的时候index表示的就是map的key，item就是map的值
#{变量名}就能取出变量的值也就是当前遍历出的元素

测试方法:

@Test
    public void testDynamicSqlTest() throws IOException{
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        //1、获取到的SqlSession不会自动提交数据
        SqlSession openSession = sqlSessionFactory.openSession();
        try
        {
                EmployeeMapperDymanicSQL mapper=openSession.getMapper(EmployeeMapperDymanicSQL.class);
                /*Employee employee=new Employee(1,"lili",null,"1");*/
                List<Employee> emps=mapper.getEmpsByConditionForeach(Arrays.asList(1,2,3,4));
                for (Employee e:emps){
                    System.out.println(e);
                }

        }
        finally {
            openSession.close();
        }
    }

foreach标签也可以实现实现批量插入(删除)数据:

这里以批量插入数据为例:

<insert id="addEmps">
        INSERT INTO tb1_emplyee(last_name,email,gender,d_id)
        VALUES
        <foreach collection="emps" item="emp" separator=",">
            (#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})
        </foreach>
</insert>

对应的接口:

public void addEmps(@Param("emps")List<Employee> emps);

测试方法

@Test
    public void testBatchSave() throws IOException{
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        //1、获取到的SqlSession不会自动提交数据
        SqlSession openSession = sqlSessionFactory.openSession();
        try
        {
            EmployeeMapperDymanicSQL mapper=openSession.getMapper(EmployeeMapperDymanicSQL.class);
            List<Employee> emps=new ArrayList<Employee>();
            emps.add(new Employee(null,"Eminem","Eminem@126.com","1",new Department(1)));
            emps.add(new Employee(null,"2Pac","2Pac@126.com","1",new Department(1)));
            mapper.addEmps(emps);
            openSession.commit();
        }
        finally {
            openSession.close();
        }

    }