MyBatis图文并茂讲解注解开发一对一查询

目录

• MyBatis的注解实现复杂映射开发
• 一对一查询
• 一对一查询的模型
• 一对一查询的语句
• 创建PersonMapper接口
• 使用注解配置Mapper
• 测试类
• 一对一配置总结

MyBatis的注解实现复杂映射开发

实现复杂关系映射之前我们可以在映射文件中通过配置来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

一对一查询

一对一查询的模型

一对一查询的需求：查询一个用户信息，与此同时查询出该用户对应的身份证信息

一对一查询的语句

创建数据库：

-- ----------------------------
-- Table structure for card
-- ----------------------------
DROP TABLE IF EXISTS `card`;
CREATE TABLE `card`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `number` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  `pid` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `cp_fk`(`pid`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 4 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of card
-- ----------------------------
INSERT INTO `card` VALUES (1, '12345', 1);
INSERT INTO `card` VALUES (2, '23456', 2);
INSERT INTO `card` VALUES (3, '34567', 3);
-- ----------------------------
-- Table structure for classes
-- ----------------------------
DROP TABLE IF EXISTS `classes`;
CREATE TABLE `classes`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `NAME` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 3 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of classes
-- ----------------------------
INSERT INTO `classes` VALUES (1, '极地一班');
INSERT INTO `classes` VALUES (2, '极地二班');
-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `NAME` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 3 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES (1, '语文');
INSERT INTO `course` VALUES (2, '数学');
-- ----------------------------
-- Table structure for person
-- ----------------------------
DROP TABLE IF EXISTS `person`;
CREATE TABLE `person`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `NAME` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  `age` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 4 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of person
-- ----------------------------
INSERT INTO `person` VALUES (1, '张三', 23);
INSERT INTO `person` VALUES (2, '李四', 24);
INSERT INTO `person` VALUES (3, '王五', 25);
-- ----------------------------
-- Table structure for stu_cr
-- ----------------------------
DROP TABLE IF EXISTS `stu_cr`;
CREATE TABLE `stu_cr`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `sid` int(11) NULL DEFAULT NULL,
  `cid` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `sc_fk1`(`sid`) USING BTREE,
  INDEX `sc_fk2`(`cid`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 5 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Fixed;
-- ----------------------------
-- Records of stu_cr
-- ----------------------------
INSERT INTO `stu_cr` VALUES (1, 1, 1);
INSERT INTO `stu_cr` VALUES (2, 1, 2);
INSERT INTO `stu_cr` VALUES (3, 2, 1);
INSERT INTO `stu_cr` VALUES (4, 2, 2);
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `NAME` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  `age` int(11) NULL DEFAULT NULL,
  `cid` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `cs_fk`(`cid`) USING BTREE
) ENGINE = MyISAM AUTO_INCREMENT = 5 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '张三', 23, 1);
INSERT INTO `student` VALUES (2, '李四', 24, 1);
INSERT INTO `student` VALUES (3, '王五', 25, 2);
INSERT INTO `student` VALUES (4, '赵六', 26, 2);
SET FOREIGN_KEY_CHECKS = 1;

对应的sql语句：

SELECT * FROM card；
SELECT * FROM person WHERE id=#{id};

创建PersonMapper接口

public interface PersonMapper {
    //根据id查询
    @Select("SELECT * FROM person WHERE id=#{id}")
    public abstract Person selectById(Integer id);
}

使用注解配置Mapper

public interface CardMapper {
    //查询全部
    @Select("SELECT * FROM card")
    @Results({
            @Result(column = "id",property = "id"),
            @Result(column = "number",property = "number"),
            @Result(
                    property = "p",             // 被包含对象的变量名
                    javaType = Person.class,    // 被包含对象的实际数据类型
                    column = "pid",             // 根据查询出的card表中的pid字段来查询person表
                    /*
                        one、@One 一对一固定写法
                        select属性：指定调用哪个接口中的哪个方法
                     */
                    one = @One(select = "com.yyl.one_to_one.PersonMapper.selectById")
            )
    })
    public abstract List<Card> selectAll();
}

测试类

public class Test01 {
    @Test
    public void selectAll() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取CardMapper接口的实现类对象
        CardMapper mapper = sqlSession.getMapper(CardMapper.class);
        //5.调用实现类对象中的方法，接收结果
        List<Card> list = mapper.selectAll();
        //6.处理结果
        for (Card card : list) {
            System.out.println(card);
        }
        //7.释放资源
        sqlSession.close();
        is.close();
    }
}

运行结果如下：

一对一配置总结

到此这篇关于MyBatis图文并茂讲解注解开发一对一查询的文章就介绍到这了,更多相关MyBatis一对一查询内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！