MyBatis之注解开发

ゝ一纸荒年。 2024-03-22 18:50 135阅读 0赞

除了XML映射方式，MyBatis还支持注解方式实现POJO对象和数据表之间的关联映射，使用注解的方式一般将SQL语句直接写到接口上。与XML的映射方式相比，基于注解的映射方式相对简单。Mybatis提供的注解有：
在这里插入图片描述

1.环境准备

1.1 数据库准备

  1. USE mybatis;
  2. # 创建一个名称为tb_worker的表
  3. CREATE TABLE  tb_worker( 
  4.      id INT PRIMARY KEY AUTO_INCREMENT,
  5.      name VARCHAR(32),
  6.      age INT,
  7.      sex VARCHAR(8),
  8.      worker_id INT UNIQUE     
  9. );
  10. # 插入2条数据
  11. INSERT INTO tb_worker(name,age,sex,worker_id)VALUES('张三',32,'女',1001);
  12. INSERT INTO tb_worker(name,age,sex,worker_id)VALUES('李四',29,'男',1002);
  13. INSERT INTO tb_worker(name,age,sex,worker_id)VALUES('王五',26,'男',1003);

1.2 Idea基础环境

1.2.1 创建annotaion module

在这里插入图片描述

1.2.2 pom.xml引入依赖

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0"
  3.          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  5.     <parent>
  6.         <artifactId>mybatis-series</artifactId>
  7.         <groupId>com.biem</groupId>
  8.         <version>1.0-SNAPSHOT</version>
  9.     </parent>
  10.     <modelVersion>4.0.0</modelVersion>
  12.     <artifactId>annotation</artifactId>
  14.     <properties>
  15.         <maven.compiler.source>8</maven.compiler.source>
  16.         <maven.compiler.target>8</maven.compiler.target>
  17.     </properties>
  19.     <dependencies>
  20.         <dependency>
  21.             <groupId>org.mybatis</groupId>
  22.             <artifactId>mybatis</artifactId>
  23.             <version>3.4.6</version>
  24.         </dependency>
  26.         <dependency>
  27.             <groupId>mysql</groupId>
  28.             <artifactId>mysql-connector-java</artifactId>
  29.             <version>8.0.18</version>
  30.         </dependency>
  32.         <dependency>
  33.             <groupId>junit</groupId>
  34.             <artifactId>junit</artifactId>
  35.             <version>4.12</version>
  36.             <scope>test</scope>
  37.         </dependency>
  39.         <dependency>
  40.             <groupId>log4j</groupId>
  41.             <artifactId>log4j</artifactId>
  42.             <version>1.2.16</version>
  43.         </dependency>
  45.         <dependency>
  46.             <groupId>org.projectlombok</groupId>
  47.             <artifactId>lombok</artifactId>
  48.             <version>1.18.16</version>
  49.         </dependency>
  50.     </dependencies>
  51. </project>

1.2.3 创建资源

包：4个
(1) src/main/java下创建

com.biem.pojo
com.biem.mapper
com.biem.util

(2) src/test/java下创建
类：4个
(1) com.biem.pojo.Worker.java
  1. package com.biem.pojo;
  3. import lombok.AllArgsConstructor;
  4. import lombok.Data;
  5. import lombok.Getter;
  6. import lombok.NoArgsConstructor;
  8. /**
  9.  * ClassName: Worker
  10.  * Package: com.biem.pojo
  11.  * Description:
  12.  *
  13.  * @Create 2023/5/19 8:27
  14.  * @Version 1.0
  15.  */
  16. @Data
  17. //@Data ： 注在类上，提供类的get、set、equals、hashCode、canEqual、toString方法
  18. @NoArgsConstructor
  19. @AllArgsConstructor
  20. public class Worker {
  22.     private Integer id;
  23.     private String name;
  24.     private Integer age;
  25.     private String sex;
  26.     private Integer workerId;
  27. }
(2) com.biem.mapper.WorkerMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: WorkerMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 8:27
  9.  * @Version 1.0
  10.  */
  11. public interface WorkerMapper {
  13. }
(3) com.biem.util.MyBatisUtil.java
  1. package com.biem.util;
  3. import org.apache.ibatis.io.Resources;
  4. import org.apache.ibatis.session.SqlSession;
  5. import org.apache.ibatis.session.SqlSessionFactory;
  6. import org.apache.ibatis.session.SqlSessionFactoryBuilder;
  8. import java.io.IOException;
  9. import java.io.InputStream;
  11. /**
  12.  * ClassName: MybatisUtil
  13.  * Package: com.biem.util
  14.  * Description:
  15.  *
  16.  * @Create 2023/4/5 22:23
  17.  * @Version 1.0
  18.  */
  19. public class MyBatisUtil {
  21.     //利用static(静态)属于类不属于对象,且全局唯一
  22.     private static SqlSessionFactory sqlSessionFactory = null;
  23.     //利用静态块在初始化类时实例化sqlSessionFactory
  24.     static {
  26.         InputStream is= null;
  27.         try {
  29.             is = Resources.getResourceAsStream("mybatis-config.xml");
  30.             sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
  31.         } catch (IOException e) {
  33.             e.printStackTrace();
  34.             throw new ExceptionInInitializerError(e);
  35.         }
  36.     }
  38.     /**
  39.      * openSession 创建一个新的SqlSession对象
  40.      * @return SqlSession对象
  41.      */
  42.     public static SqlSession openSession(boolean autoCommit){
  44.         return sqlSessionFactory.openSession(autoCommit);
  45.     }
  47.     public static SqlSession openSession(){
  49.         return sqlSessionFactory.openSession();
  50.     }
  51.     /**
  52.      * 释放一个有效的SqlSession对象
  53.      * @param session 准备释放SqlSession对象
  54.      */
  55.     public static void closeSession(SqlSession session){
  57.         if(session != null){
  59.             session.close();
  60.         }
  61.     }
  62. }
(4) com.biem.test.WorkerTest.java
  1. package com.biem.test;
  3. /**
  4.  * ClassName: WorkerTest
  5.  * Package: com.biem.test
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 9:21
  9.  * @Version 1.0
  10.  */
  11. public class WorkerTest {
  13. }
配置：3个
(1) jdbc.properties
  1. jdbc.driver=com.mysql.cj.jdbc.Driver
  2. jdbc.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC
  3. jdbc.username=root
  4. jdbc.password=root
(2) log4j.xml
  1. <?xml version="1.0" encoding="UTF-8" ?>
  2. <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
  4. <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
  6.     <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
  7.         <param name="Encoding" value="UTF-8"/>
  8.         <layout class="org.apache.log4j.PatternLayout">
  9.             <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n"/>
  10.         </layout>
  11.     </appender>
  12.     <logger name="java.sql">
  13.         <level value="debug"/>
  14.     </logger>
  15.     <logger name="org.apache.ibatis">
  16.         <level value="info"/>
  17.     </logger>
  18.     <root>
  19.         <level value="debug"/>
  20.         <appender-ref ref="STDOUT"/>
  21.     </root>
  22. </log4j:configuration>
(3) mybatis-config.xml
  1. <?xml version="1.0" encoding="UTF-8" ?>
  2. <!DOCTYPE configuration
  3.         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  4.         "http://mybatis.org/dtd/mybatis-3-config.dtd">
  5. <configuration>
  6.     <!--引入properties文件-->
  7.     <properties resource="jdbc.properties"></properties>
  9.     <!--将下划线映射为驼峰-->
  10.     <settings>
  11.         <setting name="mapUnderscoreToCamelCase" value="true"/>
  12.     </settings>
  14.     <!--设置类型别名-->
  15.     <typeAliases>
  16.         <package name="com.biem.pojo"/>
  17.     </typeAliases>
  19.     <environments default="development">
  20.         <environment id="development">
  21.             <transactionManager type="JDBC"/>
  22.             <dataSource type="POOLED">
  23.                 <property name="driver" value="${jdbc.driver}"/>
  24.                 <property name="url" value="${jdbc.url}"/>
  25.                 <property name="username" value="${jdbc.username}"/>
  26.                 <property name="password" value="${jdbc.password}"/>
  27.             </dataSource>
  28.         </environment>
  30.     </environments>
  32.     <!-- 引入映射文件 -->
  33.     <mappers>
  34.         <package name="com.biem.mapper"/>
  35.     </mappers>
  37. </configuration>

2.常用注解

2.1 @Select注解

2.1.1 com.biem.mapper.WorkerMapper.java下添加

  1. @Select("select * from tb_worker where id=#{id}")
  2.     public Worker findWorkerById(Integer id);

2.1.2 com.biem.test.WorkerTest.java下添加

  1. @Test
  2.     public void findWorkerById(){
  4.         SqlSession session = MyBatisUtil.openSession();
  5.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  6.         System.out.println("mapper.findWorkerById(1) = " + mapper.findWorkerById(1));
  7.         session.close();
  8.     }

2.1.3 输出结果

  1. DEBUG 05-19 10:14:56,714 ==>  Preparing: select * from tb_worker where id=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 10:14:56,800 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 10:14:56,863 <==      Total: 1 (BaseJdbcLogger.java:159) 
  4. mapper.findWorkerById(1) = Worker(id=1, name=张三, age=32, sex=女, workerId=1001)

2.2 @Insert注解

2.2.1 com.biem.mapper.WorkerMapper.java下添加

  1. @Insert("insert into tb_worker(name, age, sex, worker_id) values(#{name}, #{age}, #{sex}, #{workerId})")
  2.     public int insertWorker(Worker worker);

2.2.2 com.biem.test.WorkerTest.java下添加

  1. @Test
  2.     public void inserWorker(){
  4.         SqlSession session = MyBatisUtil.openSession();
  5.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  6.         Worker worker = new Worker();
  7.         worker.setName("王强");
  8.         worker.setAge(36);
  9.         worker.setSex("女");
  10.         worker.setWorkerId(1004);
  11.         int result = mapper.insertWorker(worker);
  12.         session.commit();
  13.         session.close();
  14.     }

2.2.3 输出结果

  1. DEBUG 05-19 10:27:51,392 ==>  Preparing: insert into tb_worker(name, age, sex, worker_id) values(?, ?, ?, ?)  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 10:27:51,472 ==> Parameters: 王强(String), 36(Integer), 女(String), 1004(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 10:27:51,477 <==    Updates: 1 (BaseJdbcLogger.java:159)

2.3 @Update注解

2.3.1 com.biem.mapper.WorkerMapper.java下添加

  1. @Update("update tb_worker set name=#{name},age=#{age} where id = #{id}")
  2.     public int updateWorker(Worker worker);

2.3.2 com.biem.test.WorkerTest.java下添加

  1. @Test
  2.     public void updateWorker(){
  4.         SqlSession session = MyBatisUtil.openSession();
  5.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  6.         Worker worker = new Worker();
  7.         worker.setId(4);
  8.         worker.setName("王冰");
  9.         worker.setAge(36);
  10.         int result = mapper.updateWorker(worker);
  11.         if(result>0){
  13.             System.out.println("更新了"+result+"条数据");
  14.         } else {
  16.             System.out.println("更新失败");
  17.         }
  18.         session.commit();
  19.         session.close();
  20.     }

2.3.3 输出结果

  1. DEBUG 05-19 10:40:23,577 ==>  Preparing: update tb_worker set name=?,age=? where id = ?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 10:40:23,640 ==> Parameters: 王冰(String), 36(Integer), 4(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 10:40:23,645 <==    Updates: 1 (BaseJdbcLogger.java:159) 
  4. 更新了1条数据

2.4 @Delete注解

2.4.1 com.biem.mapper.WorkerMapper.java下添加

  1. @Delete("delete from tb_worker where id=#{id}")
  2.     public int deleteWorkerById(Integer id);

2.4.2 com.biem.test.WorkerTest.java下添加

  1. @Test
  2.     public void deleteWorkerById(){
  4.         SqlSession session = MyBatisUtil.openSession();
  5.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  6.         int result = mapper.deleteWorkerById(4);
  7.         if(result>0){
  9.             System.out.println("删除了"+result+"条数据");
  10.         } else {
  12.             System.out.println("删除失败");
  13.         }
  14.         session.close();
  15.     }

2.4.3 输出结果

  1. DEBUG 05-19 10:43:44,179 ==>  Preparing: delete from tb_worker where id=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 10:43:44,247 ==> Parameters: 4(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 10:43:44,251 <==    Updates: 1 (BaseJdbcLogger.java:159) 
  4. 删除了1条数据

2.5 @Param注解

@Param注解的作用是指定SQL语句中的参数，通常用于SQL语句中参数比较多的情况。

2.4.1 com.biem.mapper.WorkerMapper.java下添加

  1. //mybatis不能识别多个参数,所以多个参数会抛出，
  2.     //Cause: org.apache.ibatis.binding.BindingException: Parameter 'id' not found. Available parameters are [arg1, arg0, param1, param2]
  3.     @Select("select * from tb_worker where id=#{id} and name=#{name}")
  4.     public Worker findWorkerByIdAndName1(Integer id, String name);
  6.     @Select("select * from tb_worker where id=#{param1} and name=#{param2}")
  7.     public Worker findWorkerByIdAndName2(@Param("param1") Integer id, @Param("param2") String name);
  9.     @Select("select * from tb_worker where id=#{arg1} and name=#{arg0}")
  10.     public Worker findWorkerByIdAndName3(@Param("arg1") Integer id, @Param("arg0") String name);

2.4.2 com.biem.test.WorkerTest.java下添加

  1. @Test
  2.     public void findWorkerByIdAndName1(){
  4.         SqlSession session = MyBatisUtil.openSession();
  5.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  6.         System.out.println("mapper.findWorkerByIdAndName1(1,\"张三\") = " + mapper.findWorkerByIdAndName1(1, "张三"));
  7.         session.close();
  8.     }
  10.     @Test
  11.     public void findWorkerByIdAndName2(){
  13.         SqlSession session = MyBatisUtil.openSession();
  14.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  15.         System.out.println("mapper.findWorkerByIdAndName2(1,\"张三\") = " + mapper.findWorkerByIdAndName2(1, "张三"));
  16.         session.close();
  17.     }
  19.     @Test
  20.     public void findWorkerByIdAndName3(){
  22.         SqlSession session = MyBatisUtil.openSession();
  23.         WorkerMapper mapper = session.getMapper(WorkerMapper.class);
  24.         System.out.println("mapper.findWorkerByIdAndName3(1,\"张三\") = " + mapper.findWorkerByIdAndName3(1, "张三"));
  25.         session.close();
  26.     }

2.4.3 输出结果

(1) findWorkerByIdAndName1结果
  1. org.apache.ibatis.exceptions.PersistenceException: 
  2. ### Error querying database.  Cause: org.apache.ibatis.binding.BindingException: Parameter 'id' not found. Available parameters are [arg1, arg0, param1, param2]
  3. ### Cause: org.apache.ibatis.binding.BindingException: Parameter 'id' not found. Available parameters are [arg1, arg0, param1, param2]
  5.     at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
  6.     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
  7.     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
  8.     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
  9.     at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:83)
  10.     at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
  11.     at com.sun.proxy.$Proxy9.findWorkerByIdAndName1(Unknown Source)
  12.     at com.biem.test.WorkerTest.findWorkerByIdAndName1(WorkerTest.java:79)
  13.     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  14.     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  15.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  16.     at java.lang.reflect.Method.invoke(Method.java:498)
  17.     at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
  18.     at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  19.     at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
  20.     at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
  21.     at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
  22.     at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
  23.     at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
  24.     at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
  25.     at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
  26.     at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
  27.     at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
  28.     at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
  29.     at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
  30.     at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
  31.     at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
  32.     at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
  33.     at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
  34.     at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
  35.     at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
  36.     at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
  37. Caused by: org.apache.ibatis.binding.BindingException: Parameter 'id' not found. Available parameters are [arg1, arg0, param1, param2]
  38.     at org.apache.ibatis.binding.MapperMethod$ParamMap.get(MapperMethod.java:204)
  39.     at org.apache.ibatis.reflection.wrapper.MapWrapper.get(MapWrapper.java:45)
  40.     at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:122)
  41.     at org.apache.ibatis.executor.BaseExecutor.createCacheKey(BaseExecutor.java:219)
  42.     at org.apache.ibatis.executor.CachingExecutor.createCacheKey(CachingExecutor.java:146)
  43.     at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:82)
  44.     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
  45.     ... 30 more
(2) findWorkerByIdAndName2结果
  1. DEBUG 05-19 14:21:20,200 ==>  Preparing: select * from tb_worker where id=? and name=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 14:21:20,280 ==> Parameters: 1(Integer), 张三(String) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 14:21:20,334 <==      Total: 1 (BaseJdbcLogger.java:159) 
  4. mapper.findWorkerByIdAndName2(1,"张三") = Worker(id=1, name=张三, age=32, sex=女, workerId=1001)
(3) findWorkerByIdAndName3结果
  1. DEBUG 05-19 14:23:33,639 ==>  Preparing: select * from tb_worker where id=? and name=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 14:23:33,703 ==> Parameters: 1(Integer), 张三(String) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 14:23:33,754 <==      Total: 1 (BaseJdbcLogger.java:159) 
  4. mapper.findWorkerByIdAndName3(1,"张三") = Worker(id=1, name=张三, age=32, sex=女, workerId=1001)

3.基于注解的关联查询

MyBatis注解不仅仅可以实现增删改查，MyBatis还提供了一系列注解@Results、@Result、@One、@Many等注解实现关联查询。

3.1 一对一查询

MyBatis使用@One注解实现数据表的一对一查询

3.1.1 环境准备

3.1.1.1 数据库准备
  1. USE mybatis;
  2. # 创建一个名称为tb_idcard的表
  3. CREATE TABLE  tb_idcard( 
  4.      id INT PRIMARY KEY AUTO_INCREMENT,
  5.      CODE VARCHAR(18)
  6. );
  7. # 插入2条数据
  8. INSERT INTO tb_idcard(CODE) VALUES('152221198711020624');
  9. INSERT INTO tb_idcard(CODE) VALUES('152201199008150317');
  10. # 创建一个名称为tb_person的表
  11. CREATE TABLE tb_person( 
  12.      id INT PRIMARY KEY AUTO_INCREMENT,
  13.      name VARCHAR(32),
  14.      age INT,
  15.      sex VARCHAR(8),
  16.      card_id INT UNIQUE,     
  17.      FOREIGN KEY(card_id) REFERENCES tb_idcard(id)
  18. );
  19. # 插入2条数据
  20. INSERT INTO tb_person(name,age,sex,card_id) VALUES('Rose',22,'女',1);
  21. INSERT INTO tb_person(name,age,sex,card_id) VALUES('jack',23,'男',2);
3.1.1.2 实体类准备
3.1.1.2.1 IdCard.java
  1. package com.biem.pojo;
  3. import lombok.AllArgsConstructor;
  4. import lombok.Data;
  5. import lombok.NoArgsConstructor;
  7. /**
  8.  * ClassName: IdCard
  9.  * Package: com.biem.pojo
  10.  * Description:
  11.  *
  12.  * @Create 2023/5/19 14:44
  13.  * @Version 1.0
  14.  */
  15. @Data
  16. @NoArgsConstructor
  17. @AllArgsConstructor
  18. public class IdCard {
  20.     private Integer id;                 //主键id
  21.     private String code;                //身份证号码
  22. }
3.1.1.2.2 Person.java
  1. package com.biem.pojo;
  3. import lombok.AllArgsConstructor;
  4. import lombok.Data;
  5. import lombok.NoArgsConstructor;
  7. /**
  8.  * ClassName: Person
  9.  * Package: com.biem.pojo
  10.  * Description:
  11.  *
  12.  * @Create 2023/5/19 14:44
  13.  * @Version 1.0
  14.  */
  15. @Data
  16. @NoArgsConstructor
  17. @AllArgsConstructor
  18. public class Person {
  20.     private Integer id;          //主键id
  21.     private String name;         //姓名
  22.     private Integer age;         //年龄
  23.     private String sex;          //性别
  24.     private IdCard card;        //人员关联的证件
  25. }
3.1.1.3 接口类准备
3.1.1.3.1 IdCardMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: IdCardMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 14:48
  9.  * @Version 1.0
  10.  */
  11. public interface IdCardMapper {
  13. }
3.1.1.3.2 PersonMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: PersonMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 14:49
  9.  * @Version 1.0
  10.  */
  11. public interface PersonMapper {
  13. }

3.1.2 案例测试

根据id查询 Peson对象

3.1.2.1 接口类添加

3.1.2.1.1 IdCardMapper.java
  1. @Select("select * from tb_idcard where id=#{id}")
  2.     public IdCard findIdCardById(int id);
3.1.2.1.2 PersonMapper.java
  1. @Select("select * from tb_person where id=#{id}")
  2.     @Results(
  3.             {
  4.     @Result(column = "card_id",
  5.                      property = "card",
  6.                      one = @One(select = "com.biem.mapper.IdCardMapper.findIdCardById"))})
  7.     Person findPersonById(int id);

3.1.2.2 添加测试类

com.biem.test.PersonTest.java

  1. package com.biem.test;
  3. import com.biem.mapper.PersonMapper;
  4. import com.biem.pojo.Person;
  5. import com.biem.util.MyBatisUtil;
  6. import org.apache.ibatis.session.SqlSession;
  7. import org.junit.Test;
  9. /**
  10.  * ClassName: PersonTest
  11.  * Package: com.biem.test
  12.  * Description:
  13.  *
  14.  * @Create 2023/5/19 14:54
  15.  * @Version 1.0
  16.  */
  17. public class PersonTest {
  20.     @Test
  21.     public void findPersonById(){
  23.         SqlSession session = MyBatisUtil.openSession();
  24.         PersonMapper mapper = session.getMapper(PersonMapper.class);
  25.         Person person = mapper.findPersonById(1);
  26.         System.out.println("person = " + person);
  27.         session.close();
  28.     }
  29. }

3.1.2.3 运行结果

  1. DEBUG 05-19 14:57:14,273 ==>  Preparing: select * from tb_person where id=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 14:57:14,372 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 14:57:14,421 ====>  Preparing: select * from tb_idcard where id=?  (BaseJdbcLogger.java:159) 
  4. DEBUG 05-19 14:57:14,421 ====> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  5. DEBUG 05-19 14:57:14,440 <====      Total: 1 (BaseJdbcLogger.java:159) 
  6. DEBUG 05-19 14:57:14,443 <==      Total: 1 (BaseJdbcLogger.java:159) 
  7. person = Person(id=1, name=Rose, age=22, sex=女, card=IdCard(id=1, code=152221198711020624))

3.2 一对多查询

MyBatis使用@Many注解实现数据表的一对多关联查询，@Many注解的作用等同于XML配登文件中的元素。

3.2.1 环境准备

3.2.1.1 数据库准备
  1. USE mybatis;
  2. # 创建一个名称为tb_user的表
  3. CREATE TABLE tb_user (
  4.   id int(32) PRIMARY KEY AUTO_INCREMENT,
  5.   username varchar(32),
  6.   address varchar(256)
  7.  );
  8. # 插入3条数据
  9. INSERT INTO tb_user VALUES ('1', '小明', '北京');
  10. INSERT INTO tb_user VALUES ('2', '李华', '上海');
  11. INSERT INTO tb_user VALUES ('3', '李刚', '上海');
  12. # 创建一个名称为tb_orders的表
  13. CREATE TABLE tb_orders (
  14.   id int(32) PRIMARY KEY AUTO_INCREMENT,
  15.   number varchar(32) NOT NULL,
  16.   user_id int(32) NOT NULL,
  17.   FOREIGN KEY(user_id) REFERENCES tb_user(id)
  18. );
  19. # 插入3条数据
  20. INSERT INTO tb_orders VALUES ('1', '1000011', '1');
  21. INSERT INTO tb_orders VALUES ('2', '1000012', '1');
  22. INSERT INTO tb_orders VALUES ('3', '1000013', '2');
3.2.1.2 实体类准备
3.2.1.2.2 Orders.java
  1. package com.biem.pojo;
  3. /**
  4.  * ClassName: Orders
  5.  * Package: com.biem.pojo
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 15:09
  9.  * @Version 1.0
  10.  */
  11. @Data
  12. @NoArgsConstructor
  13. @AllArgsConstructor
  14. public class Orders {
  16.     private Integer id;                //订单id
  17.     private String number;            //订单编号
  18. }
3.2.1.2.2 User.java
  1. import lombok.NoArgsConstructor;
  3. /**
  4.  * ClassName: User
  5.  * Package: com.biem.pojo
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 15:05
  9.  * @Version 1.0
  10.  */
  11. @Data
  12. @NoArgsConstructor
  13. @AllArgsConstructor
  14. public class User {
  16.     private Integer id;                 // 用户编号
  17.     private String username;           // 用户姓名
  18.     private String address;            // 用户地址
  19.     private List<Orders> ordersList; //用户关联的订单
  20. }
3.2.1.3 接口类准备
3.2.1.3.1 UserMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: UserMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 15:11
  9.  * @Version 1.0
  10.  */
  11. public interface UserMapper {
  13. }
3.2.1.3.2 OrdersMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: OrdersMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 15:11
  9.  * @Version 1.0
  10.  */
  11. public interface OrdersMapper {
  13. }

3.2.2 案例测试

3.2.2.1 接口类添加
3.2.2.1.1 OrdersMapper.java
  1. @Select("select * from tb_orders where user_id=#{id} ")
  2.     @Results({
  3.     @Result(id = true, column = "id", property = "id"),
  4.             @Result(column = "number", property = "number")
  5.     })
  6.     public List<Orders> findOrdersByUserId(int user_id);
3.2.2.1.2 UserMapper.java
  1. @Select("select * from tb_user where id=#{id} ")
  2.     @Results({
  3.     @Result(id = true, column = "id", property = "id"),
  4.             @Result(column = "username", property = "username"),
  5.             @Result(column = "address", property = "address"),
  6.             @Result(column = "id", property = "ordersList",
  7.                     many = @Many(select =
  8.                             "com.biem.mapper.OrdersMapper.findOrdersByUserId"))})
  9.     User findUserById(int id);
3.2.2.2 测试类添加
  1. package com.biem.test;
  3. import com.biem.mapper.UserMapper;
  4. import com.biem.pojo.User;
  5. import com.biem.util.MyBatisUtil;
  6. import org.apache.ibatis.session.SqlSession;
  7. import org.junit.Test;
  9. /**
  10.  * ClassName: UserTest
  11.  * Package: com.biem.test
  12.  * Description:
  13.  *
  14.  * @Create 2023/5/19 15:16
  15.  * @Version 1.0
  16.  */
  17. public class UserTest {
  20.     @Test
  21.     public void findUserById(){
  23.         SqlSession session = MyBatisUtil.openSession();
  24.         UserMapper mapper = session.getMapper(UserMapper.class);
  25.         User user = mapper.findUserById(1);
  26.         System.out.println("user = " + user);
  27.         session.close();
  28.     }
  29. }
3.2.2.3 结果输出
  1. DEBUG 05-19 15:20:50,932 ==>  Preparing: select * from tb_user where id=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 15:20:51,004 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 15:20:51,056 ====>  Preparing: select * from tb_orders where user_id=?  (BaseJdbcLogger.java:159) 
  4. DEBUG 05-19 15:20:51,056 ====> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  5. DEBUG 05-19 15:20:51,060 <====      Total: 2 (BaseJdbcLogger.java:159) 
  6. DEBUG 05-19 15:20:51,064 <==      Total: 1 (BaseJdbcLogger.java:159) 
  7. user = User(id=1, username=小明, address=北京, ordersList=[Orders(id=1, number=1000011), Orders(id=2, number=1000012)])

3.3 多对多查询

表与表之间的多对多关联关系通常使用一个中间表来维护,tb_orders和商品表 tb_product为例，这两个表之间的关联关系使用了一个中间表 b_ordersitem 来维护，需要数据库的三个表格

3.3.1 环境准备

3.3.1.1 数据库准备
  1. USE mybatis;
  3. CREATE TABLE tb_orders (
  4.   id int(32) PRIMARY KEY AUTO_INCREMENT,
  5.   number varchar(32) NOT NULL,
  6.   user_id int(32) NOT NULL,
  7.   FOREIGN KEY(user_id) REFERENCES tb_user(id)
  8. );
  9. # 插入3条数据
  10. INSERT INTO tb_orders VALUES ('1', '1000011', '1');
  11. INSERT INTO tb_orders VALUES ('2', '1000012', '1');
  12. INSERT INTO tb_orders VALUES ('3', '1000013', '2');
  14. # 创建一个名称为tb_product的表
  15. CREATE TABLE tb_product (
  16.   id INT(32) PRIMARY KEY AUTO_INCREMENT,
  17.   NAME VARCHAR(32),
  18.   price DOUBLE 
  19.  );
  20. # 插入3条数据
  21. INSERT INTO tb_product VALUES ('1', 'Java基础入门', '44.5');
  22. INSERT INTO tb_product VALUES ('2', 'Java Web程序开发入门', '38.5');
  23. INSERT INTO tb_product VALUES ('3', 'SSM框架整合实战', '50');
  24. # 创建一个名称为tb_ordersitem 的中间表
  25. CREATE TABLE tb_ordersitem (
  26.     id INT(32) PRIMARY KEY AUTO_INCREMENT,
  27.     orders_id INT(32),
  28.     product_id INT(32),
  29.     FOREIGN KEY(orders_id) REFERENCES tb_orders(id),
  30. FOREIGN KEY(product_id) REFERENCES tb_product(id)
  31. );
  32. # 插入3条数据
  33. INSERT INTO tb_ordersitem  VALUES ('1', '1', '1');
  34. INSERT INTO tb_ordersitem  VALUES ('2', '1', '3');
  35. INSERT INTO tb_ordersitem  VALUES ('3', '3', '3');
3.3.1.2 实体类准备

Product.java

  1. package com.biem.pojo;
  3. import lombok.AllArgsConstructor;
  4. import lombok.Data;
  5. import lombok.NoArgsConstructor;
  7. import java.util.List;
  9. /**
  10.  * ClassName: Product
  11.  * Package: com.biem.pojo
  12.  * Description:
  13.  *
  14.  * @Create 2023/5/19 15:26
  15.  * @Version 1.0
  16.  */
  17. @Data
  18. @NoArgsConstructor
  19. @AllArgsConstructor
  20. public class Product {
  22.     private Integer id;                //商品id
  23.     private String name;                //商品名称
  24.     private Double price;                //商品单价
  25.     private List<Orders> orders;        //与订单关联的属性
  26. }

Orders.java修改为

  1. package com.biem.pojo;
  3. import lombok.AllArgsConstructor;
  4. import lombok.Data;
  5. import lombok.NoArgsConstructor;
  7. import java.util.List;
  9. /**
  10.  * ClassName: Orders
  11.  * Package: com.biem.pojo
  12.  * Description:
  13.  *
  14.  * @Create 2023/5/19 15:09
  15.  * @Version 1.0
  16.  */
  17. @Data
  18. @NoArgsConstructor
  19. @AllArgsConstructor
  20. public class Orders {
  22.     private Integer id;                //订单id
  23.     private String number;            //订单编号
  24.     //关联商品集合属性
  25.     private List<Product> productList;
  26. }
3.3.1.1 接口类准备
3.3.1.1.1 OrdersMapper.java为以下代码，暂时不用修改
  1. package com.biem.mapper;
  3. import com.biem.pojo.Orders;
  4. import org.apache.ibatis.annotations.Result;
  5. import org.apache.ibatis.annotations.Results;
  6. import org.apache.ibatis.annotations.Select;
  8. import java.util.List;
  10. /**
  11.  * ClassName: OrdersMapper
  12.  * Package: com.biem.mapper
  13.  * Description:
  14.  *
  15.  * @Create 2023/5/19 15:11
  16.  * @Version 1.0
  17.  */
  18. public interface OrdersMapper {
  21.     @Select("select * from tb_orders where user_id=#{id} ")
  22.     @Results({
  23.     @Result(id = true, column = "id", property = "id"),
  24.             @Result(column = "number", property = "number")
  25.     })
  26.     public List<Orders> findOrdersByUserId(int user_id);
  27. }
3.3.1.1.2 ProductMapper.java
  1. package com.biem.mapper;
  3. /**
  4.  * ClassName: ProductMapper
  5.  * Package: com.biem.mapper
  6.  * Description:
  7.  *
  8.  * @Create 2023/5/19 15:28
  9.  * @Version 1.0
  10.  */
  11. public interface ProductMapper {
  13. }

3.3.2 案例测试

3.3.2.1 接口类添加
3.3.2.1.1 ProductMapper.java修改
  1. package com.biem.mapper;
  3. import com.biem.pojo.Product;
  4. import org.apache.ibatis.annotations.Select;
  6. import java.util.List;
  8. /**
  9.  * ClassName: ProductMapper
  10.  * Package: com.biem.mapper
  11.  * Description:
  12.  *
  13.  * @Create 2023/5/19 15:28
  14.  * @Version 1.0
  15.  */
  16. public interface ProductMapper {
  18.     @Select("select * from tb_product where id in (select product_id from " +
  19.             "tb_ordersitem where orders_id = #{id} )")
  20.     public List<Product> findProductByOrdersId(int orders_id);
  21. }
3.3.2.1.2 OrdersMapper修改为
  1. package com.biem.mapper;
  3. import com.biem.pojo.Orders;
  4. import org.apache.ibatis.annotations.Many;
  5. import org.apache.ibatis.annotations.Result;
  6. import org.apache.ibatis.annotations.Results;
  7. import org.apache.ibatis.annotations.Select;
  9. import java.util.List;
  11. /**
  12.  * ClassName: OrdersMapper
  13.  * Package: com.biem.mapper
  14.  * Description:
  15.  *
  16.  * @Create 2023/5/19 15:11
  17.  * @Version 1.0
  18.  */
  19. public interface OrdersMapper {
  22.     @Select("select * from tb_orders where user_id=#{id} ")
  23.     @Results({
  24.     @Result(id = true, column = "id", property = "id"),
  25.             @Result(column = "number", property = "number")
  26.     })
  27.     public List<Orders> findOrdersByUserId(int user_id);
  30.     @Select("select * from tb_orders where id=#{id} ")
  31.     @Results({
  32.     @Result(id = true, column = "id", property = "id"),
  33.             @Result(column = "number", property = "number"),
  34.             @Result(column = "id", property = "productList",
  35.                     many = @Many(select =
  36.                             "com.biem.mapper.ProductMapper.findProductByOrdersId"))})
  37.     public Orders findOrdersById(int id);
  38. }
3.3.2.2 测试类添加
  1. package com.biem.test;
  3. import com.biem.mapper.OrdersMapper;
  4. import com.biem.pojo.Orders;
  5. import com.biem.util.MyBatisUtil;
  6. import org.apache.ibatis.session.SqlSession;
  7. import org.junit.Test;
  9. /**
  10.  * ClassName: OrdersTest
  11.  * Package: com.biem.test
  12.  * Description:
  13.  *
  14.  * @Create 2023/5/19 15:32
  15.  * @Version 1.0
  16.  */
  17. public class OrdersTest {
  19.     @Test
  20.     public void findOrdersById(){
  22.         SqlSession session = MyBatisUtil.openSession();
  23.         OrdersMapper mapper = session.getMapper(OrdersMapper.class);
  24.         Orders orders = mapper.findOrdersById(1);
  25.         System.out.println("orders = " + orders);
  26.         session.close();
  27.     }
  28. }
3.3.2.3 结果输出
  1. DEBUG 05-19 15:34:18,076 ==>  Preparing: select * from tb_orders where id=?  (BaseJdbcLogger.java:159) 
  2. DEBUG 05-19 15:34:18,147 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  3. DEBUG 05-19 15:34:18,192 ====>  Preparing: select * from tb_product where id in (select product_id from tb_ordersitem where orders_id = ? )  (BaseJdbcLogger.java:159) 
  4. DEBUG 05-19 15:34:18,192 ====> Parameters: 1(Integer) (BaseJdbcLogger.java:159) 
  5. DEBUG 05-19 15:34:18,217 <====      Total: 2 (BaseJdbcLogger.java:159) 
  6. DEBUG 05-19 15:34:18,217 <==      Total: 1 (BaseJdbcLogger.java:159) 
  7. orders = Orders(id=1, number=1000011, productList=[Product(id=1, name=Java基础入门, price=44.5, orders=null), Product(id=3, name=SSM框架整合实战, price=50.0, orders=null)])

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