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Mybatis复杂查询的实现

开发者 https://www.devze.com 2024-09-27 10:33 出处:网络 作者: 雪顶猫的鳄
目录一、环境搭建1.1 建表1.2 导入依赖1.3 创建实体类1.3.1 Student 实体类1.3.2 Teacher 实体类1.4 创建Mapper接口1.4.1 StudentMapper 接口1.4.2 TeacherMapper 接口1.5 创建Mapper.XML文件1.5.1 namespace 绑定St
目录
  • 一、环境搭建
    • 1.1 建表
    • 1.2 导入依赖
    • 1.3 创建实体类
      • 1.3.1 Student 实体类
      • 1.3.2 Teacher 实体类
    • 1.4 创建Mapper接口
      • 1.4.1 StudentMapper 接口
      • 1.4.2 TeacherMapper 接口
    • 1.5 创建Mapper.XML文件
      • 1.5.1 namespace 绑定StudentMapper接口
      • 1.5.2 namespace 绑定TeacherMapper接口
    • 1.6 核心配置文件中注册Mapper.xml文件
      • 1.7 测试
      • 二、多对一复杂查询
        • 2.1 按照查询嵌套处理
          • 2.1.1 编写接口方法
          • 2.1.2 编写sql标签
          • 2.1.3 测试
          • 2.1.4 测试结果
        • 2.2 按照结果嵌套处理
          • 2.2.1 编写接口方法
          • 2.2.2 编写sql标签
          • 2.2.3 测试
          • 2.2.4 测试结果
      • 三、一对多复杂查询
        • 3.1 按照结果嵌套查询
          • 3.1.1 学生实体类
          • 3.1.2 教师实体类
          • 3.1.3 编写接口
          • 3.1.4 编写TeacherMapper1.xml文件
          • 3.1.5 测试
          • 3.1.6 测试结果
        • 3.2 根据查询嵌套处理
          • 3.2.1 编写接口
          • 3.2.2 编写TeacherMapper1.xml文件
          • 3.2.3 测试
          • 3.2.4 测试结果

      一、环境搭建

      1.1 建表

      CREATE TABLE `teacher` (
        `id` INT(10) NOT NULL,
        `name` VARCHAR(30) DEFAULT NULL,
        PRIMARY KEY (`id`)
      ) ENGINE=INNODB DEFAULT CHARSET=utf8
      
      INSERT INTO teacher(`id`, `name`) VALUES (1, '乔丹'); 
      INSERT INTO teacher(`id`, `name`) VALUES (2, '科比'); 
      INSERT INTO teacher(`id`, `name`) VALUES (1, '垫脚哥'); 
      
      CREATE TABLE `student` (
        `id` INT(10) NOT NULL,
        `name` VARCHAR(30) DEFAULT NULL,
        `tid` INT(10) DEFAULT NULL,
        PRIMARY KEY (`id`),
        KEY `fktid` (`tid`),
        CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
      ) ENGINE=INNODB DEFAULT CHARSET=utf8
      
      INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('1', '杜兰特', '1'); 
      INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('2', '德罗赞', '1'); 
      INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('3', '詹姆斯', '1'); 
      INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('4', '卡子哥', '1'); 
      INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('5', '乔治', '1');
      

      1.2 导入依赖

      <dependencies>
          <dependency>
              <groupId>log4j</groupId>
              <artifactId>log4j</artifactId>
              <version>1.2.16</version>
          </dependency>
      	<dependency>
      	    <groupId>org.myBATis</groupId>
      	    <artifactId>mybatis</artifactId>
      	    <version>3.5.2</version>
      	</dependency>
      	<dependency>
      	    <groupId>mysql</groupId>
      	    <artifactId>mysql-connector-Java</artifactId>
      	    <version>5.1.47</version>
      	</dependency>
      	<dependency>
      	    <groupId>junit</groupId>
      	    <artifactId>junit</artifactId>
      	    <version>4.12</version>
      	</dependency>
          <dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
              <version>1.18.12</version>
              <scope>provided</scope>
          </dependency>
      </dependencies>
      

      1.3 创建实体类

      1.3.1 Student 实体类

      @Data
      @NoArgsConstructor
      public class Student {
          private int id;
          private String name;
          //学生要关联一个老师
          private Teacher teacher;
          }
      

      1.3.2 Teacher 实体类

      @Data
      public class Teacher {
          private int id;
          private String name;
          }
      

      1.4 创建Mapper接口

      1.4.1 StudentMapper 接口

      public interface StudentMapper {
      }
      

      1.4.2 TeacherMapper 接口

      public interface TeacherMapper {
          @Select("select *from teacher where id=#{tid}")
          Teacher getTeacher(@Param("tid") int id);
          }
      

      1.5 创建Mapper.xml文件

      1.5.1 namespace 绑定StudentMapper接口

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
              "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      
      <mapper namespace="com.kuang.dao.StudentMapper">
      
      </mapper>
      

      1.5.2 namespace 绑定TeacherMapper接口

      <?xml ver编程客栈sion="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"        "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.kuang.dao.TeacherMapper">   </mapper>
      

      1.6 核心配置文件中注册Mapper.xml文件

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE configuration
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
              "http://mybatis.org/dtd/mybatis-3-config.dtd">
      
      <configuration>
      
          <properties resource="db.properties"/>
          <settings>
              <setting name="logImpl" value="STDOUT_LOGGING"/>
          </settings>
          <typeAliases>
             <package name="com.kuang.pojo"/>
             <!-- <typeAlias type="com.kuang.pojo.User" alias="User"/>-->
          </typeAliases>
      
          <environments default="development">
              <environment id="development">
                  <transactionManager type="JDBC"/>
                  <dataSource type="POOLED">
                      <property name="driver" value="${driver}"/>
                      <property name="url" value="${url}"/>
                      <property name="username" value="${username}"/>
                      <property name="password" value="${password}"/>
                  </dataSource>
              </environment>
          </environments>
      
          <mappers>
              <mapper class="com.kuang.dao.TeacherMapper"/>
              <mapper class="com.kuang.dao.StudentMapper"/>
          </mappers>
      
      </configuration>
      

      1.7 测试

      @Test
      public void getTeacher(){
          SqlSession sqlSession = MybatisUtils.getSqlSession();    TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
          Teacher teacher = mapper.getTeacher(1);    
          System.out.println(teacher);    
          sqlSession.close();
          }
      

      测试结果

      Mybatis复杂查询的实现

      二、多对一复杂查询

      2.1 按照查询嵌套处理

      2.1.1 编写接口方法

      public interface StudentMapper {
       //查询所有的学生信息,以及对应的老师信息 
       List<Student> getStudent();
       }
      

      2.1.2 编写sql标签

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"        
              "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      <mapper namespace="com.kuang.dao.StudentMapper">   
               <select id="getStudent" resultMap="StudentTeacher">
                   select *from student;
               </select>
               <resultMap id="StudentTeacher" type="Student">
                   <result property="id" column="id"/>
                   <result property="name" column="name"/>
                   <!--复杂的属性:我们要单独处理 对象:association 集合:collection -->        
                   <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/>   
               </resultMap>
               <select id="getTeacher" resultType="Teacher" >
                   select *from teacher where id=#{id}    
               </select>
      </mapper>
      

      2.1.3 测试

      @Test
      public void testStudent(){
         //第一步获取sqlsession对象
         SqlSession sqlSession = MybatisUtils.getSqlSession();
         StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
         List<Student> studentList = mapper.getStudent();
         for (Student student : studentList) {
             System.out.println(student);
         }
         sqlSession.close();
      }
      

      2.1.4 测试结果

      Mybatis复杂查询的实现

      2.2 按照结果嵌套处理

      2.2.1 编写接口方法

      public interface StudentMapper {
       //查询所有的学生信息,以及对应的老师信息
       List<Student> getStudent2();
      }
      

      2.2.2 编写sql标签

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"        
              编程客栈"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      <mapper namespace="com.kuang.dao.StudentMapper">        
              <!--按照结果嵌套查询-->
              <select id="getStudent2" resultMap="StudentTeacher2">
                      select s.id sid,s.name sname,t.name tname
                      from student s,teacher t
                      where s.tid =t.id;
              </select>
              <resultMap id="StudentTeacher2" type="Student">
                      <result property="id" column="sid" />
                      <result property="name" column="sname" />
                      <association property="teacher" javaType="Teacher">            
                          <result property="name" column="tname"/>
                      </association>           
              </resultMap>
      </mapper>
      android

      2.2.3 测试

      @Test
      public void testStudent2(){
         SqlSession sqlSession = MybatisUtils.getSqlSession();
         StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
         List<Student> studentList = mapper.getStudent2();
         for (Student student : studentList) {
             System.out.println(student);
         }
         sqlSession.close();
      }
      

      2.2.4 测试结果

      Mybatis复杂查询的实现

      三、一对多复杂查询

      3.1 按照结果嵌套查询

      3.1.1 学生实体类

      @Data
      public class Student1 {
          private int id;
          private String name;
          private int tid;
          }
      

      3.1.2 教师实体类

      @Data
      public class Teacher1 {
          private int id;
          private String name;
          //一个老师对应多个学生
          private List<Student1> studentqwxdYifoPis;
          }
      

      3.1.3 编写接口

      public interface TeacherMapper1 {
         //获取指定老师下的所有学生及老师的信息   
         Teacher1 getTeacher2(@Param("tid") int id);
         }
      

      3.1.4 编写TeacherMapper1.xml文件

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
              "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      
      <mapper namespace="com.kuang.dao.TeacherMapper1">
          <select id="getTeacher1" resultType="Teacher1">
              select *from mybatis.teacher;
          </select>
          <!--按照结果嵌套查询-->
          <select id="getTeacher2" resultMap="TeacherStudent1">
             select s.id sid,s.name sname,t.name tname,t.id tid
             from student s,teacher t
             where s.tid = t.id and t.id = #{tid};
          </select>
      
          <resultMap id="TeacherStudent1" type="Teacher1">
              <result property="id" column="tid"/>
              <result property="name" column="tname"/>
              <!--复杂的属性:我们要单独处理 对象:association 集合:collection -->
              <!--javaType="" 指定属性的类型  集合中的泛型信息我们使用ofType获取-->
              <collection property="student1s" ofType="Student1" javaType="java.util.List" >
                  <result property="id" column="sid"/>
                  <result property="name" column="sname"/>
                  <result property="tid" column="tid"/>
              </collection>
          </resultMap>
      </mapper>
      

      3.1.5 测试

      @Test
      public void test2() {
         SqlSession sqlSession = MybatisUtils.getSqlSession();
         TeacherMapper1 mapper = sqlSession.getMapper(TeacherMapper1.class);
         Teacher1 teacher = 编程mapper.getTeacher2(1);
         System.out.println(teacher);
      }
      

      3.1.6 测试结果

      Mybatis复杂查询的实现

      3.2 根据查询嵌套处理

      3.2.1 编写接口

      public interface TeacherMapper1 {
         //获取指定老师下的所有学生及老师的信息
         Teacher1 getTeacher3(@Param("tid") int id);
      }
      

      3.2.2 编写TeacherMapper1.xml文件

      <?xml version="1.0" encoding="UTF-8" ?>
      <!DOCTYPE mapper
              PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
              "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
      
      <mapper namespace="com.kuang.dao.TeacherMapper1">
      
          <select id="getTeacher3" resultType="com.kuang.pojo.Teacher1" resultMap="TeacherStudent2">
              select *from mybatis.teacher where id = #{tid};
          </select>
          
          <resultMap id="TeacherStudent2" type="Teacher1">
              <collection property="student1s" javaType="ArrayList" ofType="Student1" select="getStudentByTeacherId" column="id"/>
          </resultMap>
          
          <select id="getStudentByTeacherId" resultType="Student1">
              select *from mybatis.student where id = #{tid}
          </select>
      </mapper>
      

      3.2.3 测试

      @Test
      public void test2() {
         SqlSession sqlSession = MybatisUtils.getSqlSession();
         TeacherMapper1 mapper = sqlSession.getMapper(TeacherMapper1.class);
         Teacher1 teacher = mapper.getTeacher3(1);
         System.out.println(teacher);
      }
      

      3.2.4 测试结果

      Mybatis复杂查询的实现

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