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  • Mybatis的map用法

    当Mybatis传过来的值是map类型的时候,有两种处理方法

    1、将数值装入类封装起来

    public interface IStudentDao {
    
        // 根据姓名和年龄查询
        List<Student> selectStudentsByCondition(Map<String, Object> map);
    
        // 根据姓名和年龄查询
        List<Student> selectStudentsByCondition2(String name,int age);
    }

    2、map有动态加载,所以不用impl,只需dao 的抽象方法和id名称一样就可以

    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    <!--为了防止多个mapper.xml相同的id名所以namespace改为对应的到的包路径-->
    <mapper namespace="com.liuya.demo.mybatis.dysnamic.dao.IStudentDao">
        <!-- 配置数据库和实体类的字段 -->
        <resultMap id="studentMapper" type="Student">
            <id column="T_ID" property="id"/>
            <result column="T_NAME" property="name"/>
            <result column="T_AGE" property="age"/>
            <result column="T_SCORE" property="score"/>
        </resultMap>
    
        <!-- 根据姓氏模糊查询 -->
        <select id="selectStudentsByCondition" resultMap="studentMapper">
            select T_NAME,T_AGE,T_SCORE
            from STUDENT
            where T_NAME like '%' #{nameCon} '%'
            AND T_AGE > #{ageCon}
            AND T_SCORE > #{student1.score }
        </select>
    
        <!-- 根据姓氏模糊查询,#{}大括号里是索引
              #{}中可以放什么内容?
              (1)参数对象的属性
              (2)随意内容,此时的#{}是占位符
              (3)参数为map时的key
              (4)参数为map时,若key所对应的value为对象,则可将对象的属性放入
              (5)参数的索引号
        -->
        <select id="selectStudentsByCondition2" resultMap="studentMapper">
            select T_NAME,T_AGE,T_SCORE
            from STUDENT
            where T_NAME like '%' #{0} '%'
            AND T_AGE > #{1}
        </select>
    
    
    </mapper>

    3、对其测试

    public class MyTest {
    
        private IStudentDao idao;
        private SqlSession sqlSession;
    
        @Before
        public void before() {
            sqlSession = MybatisUtil.getSqlSession();
            idao = sqlSession.getMapper(IStudentDao.class);
        }
    
        @After
        public void after() {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    
    
        // 查询一个姓张的,年龄大于24,并且成绩比田七高的学生
        @Test
        public void testSelectStudentsByCondition() {
            System.out.println("开始查询学生");
            Student student1 = new Student("",21,66);
    
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("nameCon","张");
            map.put("ageCon",24);
            map.put("student1",student1);
    
            List<Student> students = idao.selectStudentsByCondition(map);
            for (Student student : students) {
                System.out.println(student);
            }
            System.out.println("查询学生成功");
        }
    
        // 查询一个姓张的,年龄大于24,并且成绩比田七高的学生
        @Test
        public void testSelectStudentsByCondition2() {
            System.out.println("开始查询学生");
    
            List<Student> students = idao.selectStudentsByCondition2("张",24);
            for (Student student : students) {
                System.out.println(student);
            }
            System.out.println("查询学生成功");
        }
    }
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  • 原文地址:https://www.cnblogs.com/liuyangfirst/p/7470503.html
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