MyBatis圖文并茂講解注解開發(fā)一對一查詢

更新時間：2022年07月06日 08:53:54 作者：流楚丶格念

這篇文章主要介紹了SpringBoot中Mybatis注解一對一查詢的實(shí)現(xiàn)示例，有需要的朋友可以借鑒參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪

MyBatis的注解實(shí)現(xiàn)復(fù)雜映射開發(fā)

實(shí)現(xiàn)復(fù)雜關(guān)系映射之前我們可以在映射文件中通過配置來實(shí)現(xiàn)，使用注解開發(fā)后，我們可以使用@Results注解，@Result注解，@One注解，@Many注解組合完成復(fù)雜關(guān)系的配置

一對一查詢

一對一查詢的模型

一對一查詢的需求：查詢一個用戶信息，與此同時查詢出該用戶對應(yīng)的身份證信息

一對一查詢的語句

創(chuàng)建數(shù)據(jù)庫：

-- ----------------------------
-- 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, '極地一班');
INSERT INTO `classes` VALUES (2, '極地二班');
-- ----------------------------
-- 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, '語文');
INSERT INTO `course` VALUES (2, '數(shù)學(xué)');
-- ----------------------------
-- 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, '張三', 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, '張三', 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, '趙六', 26, 2);
SET FOREIGN_KEY_CHECKS = 1;

對應(yīng)的sql語句：

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

創(chuàng)建PersonMapper接口

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

使用注解配置Mapper

public interface CardMapper {
    //查詢?nèi)?
    @Select("SELECT * FROM card")
    @Results({
            @Result(column = "id",property = "id"),
            @Result(column = "number",property = "number"),
            @Result(
                    property = "p",             // 被包含對象的變量名
                    javaType = Person.class,    // 被包含對象的實(shí)際數(shù)據(jù)類型
                    column = "pid",             // 根據(jù)查詢出的card表中的pid字段來查詢person表
                    /*
                        one、@One 一對一固定寫法
                        select屬性：指定調(diào)用哪個接口中的哪個方法
                     */
                    one = @One(select = "com.yyl.one_to_one.PersonMapper.selectById")
            )
    })
    public abstract List<Card> selectAll();
}

測試類

public class Test01 {
    @Test
    public void selectAll() throws Exception{
        //1.加載核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.獲取SqlSession工廠對象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通過工廠對象獲取SqlSession對象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.獲取CardMapper接口的實(shí)現(xiàn)類對象
        CardMapper mapper = sqlSession.getMapper(CardMapper.class);
        //5.調(diào)用實(shí)現(xiàn)類對象中的方法，接收結(jié)果
        List<Card> list = mapper.selectAll();
        //6.處理結(jié)果
        for (Card card : list) {
            System.out.println(card);
        }
        //7.釋放資源
        sqlSession.close();
        is.close();
    }
}

運(yùn)行結(jié)果如下：

一對一配置總結(jié)

注解	說明
@Results	封裝映射關(guān)系的父注解。 Result[] value()：定義了 Result 數(shù)組
@Result	封裝映射關(guān)系的子注解。 column 屬性：查詢出的表中字段名稱 property 屬性：實(shí)體對象中的屬性名稱 javaType 屬性：被包含對象的數(shù)據(jù)類型 one 屬性：一對一查詢固定屬性
@One	一對一查詢的注解。 select 屬性：指定調(diào)用某個接口中的方法