MyBatisPlus简介

1.是什么

MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

2.为什么

合理封装，简化开发

入门

1.创建数据库

2.创建工程

3.引入依赖

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.     <modelVersion>4.0.0</modelVersion>
  5.     <groupId>com.atguigu</groupId>
  6.     <artifactId>mybatisplus</artifactId>
  7.     <version>0.0.1-SNAPSHOT</version>
  8.     <name>mybatisplus</name>
  9.     <description>Demo project for Spring Boot</description>
  11.     <properties>
  12.         <java.version>1.8</java.version>
  13.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  14.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  15.         <spring-boot.version>2.2.1.RELEASE</spring-boot.version>
  16.     </properties>
  18.     <dependencies>
  19.         <dependency>
  20.             <groupId>org.springframework.boot</groupId>
  21.             <artifactId>spring-boot-starter</artifactId>
  22.         </dependency>
  24.         <dependency>
  25.             <groupId>org.springframework.boot</groupId>
  26.             <artifactId>spring-boot-starter-test</artifactId>
  27.             <scope>test</scope>
  28.             <exclusions>
  29.                 <exclusion>
  30.                     <groupId>org.junit.vintage</groupId>
  31.                     <artifactId>junit-vintage-engine</artifactId>
  32.                 </exclusion>
  33.             </exclusions>
  34.         </dependency>
  36.         <!--mybatis-plus-->
  37.         <dependency>
  38.             <groupId>com.baomidou</groupId>
  39.             <artifactId>mybatis-plus-boot-starter</artifactId>
  40.             <version>3.0.5</version>
  41.         </dependency>
  42. <!--mysql-->
  43.         <dependency>
  44.             <groupId>mysql</groupId>
  45.             <artifactId>mysql-connector-java</artifactId>
  46.         </dependency>
  48.         <!--lombok用来简化实体类-->
  49.         <dependency>
  50.             <groupId>org.projectlombok</groupId>
  51.             <artifactId>lombok</artifactId>
  52.         </dependency>
  53.     </dependencies>
  55.     <dependencyManagement>
  56.         <dependencies>
  57.             <dependency>
  58.                 <groupId>org.springframework.boot</groupId>
  59.                 <artifactId>spring-boot-dependencies</artifactId>
  60.                 <version>${spring-boot.version}</version>
  61.                 <type>pom</type>
  62.                 <scope>import</scope>
  63.             </dependency>
  64.         </dependencies>
  65.     </dependencyManagement>
  67.     <build>
  68.         <plugins>
  69.             <plugin>
  70.                 <groupId>org.apache.maven.plugins</groupId>
  71.                 <artifactId>maven-compiler-plugin</artifactId>
  72.                 <version>3.8.1</version>
  73.                 <configuration>
  74.                     <source>1.8</source>
  75.                     <target>1.8</target>
  76.                     <encoding>UTF-8</encoding>
  77.                 </configuration>
  78.             </plugin>
  79.             <plugin>
  80.                 <groupId>org.springframework.boot</groupId>
  81.                 <artifactId>spring-boot-maven-plugin</artifactId>
  82.                 <version>2.2.10.RELEASE</version>
  83.                 <configuration>
  84.                     <mainClass>com.atguigu.mpdemo.MpdemoApplication</mainClass>
  85.                 </configuration>
  86.                 <executions>
  87.                     <execution>
  88.                         <id>repackage</id>
  89.                         <goals>
  90.                             <goal>repackage</goal>
  91.                         </goals>
  92.                     </execution>
  93.                 </executions>
  94.             </plugin>
  95.         </plugins>
  96.     </build>

4.创建启动类

  1. @SpringBootApplication
  2. public class MybatisPlusApplication {
  3.     public static void main(String[] args) {
  4.         SpringApplication.run(MybatisPlusApplication.class,args);
  5.     }
  6. }

5.实现MP

(1)创建实体类

  1. @Data
  2. public class User {
  3.     private Long id;
  4.     private String name;
  5.     private Integer age;
  6.     private String email;
  7. }

(2) 创建配置文件 application.properties

  1. spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
  2. spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8
  3. spring.datasource.username=root
  4. spring.datasource.password=123123

(3)添加mapper接口

  1. @Repository
  2. public interface UserMapper extends BaseMapper<User> {
  3. }

(4) 启动类添加注解

  1. @SpringBootApplication
  2. @MapperScan("com.atguigu.mybatisplus.mapper")
  3. public class MybatisPlusApplication {
  4.     public static void main(String[] args) {
  5.         SpringApplication.run(MybatisPlusApplication.class,args);
  6.     }
  7. }

(5) 测试

  1. @SpringBootTest
  2. public class MybatisPlusApplicationTest {
  4.     @Autowired
  5.     private UserMapper userMapper;
  8.     @Test
  9.     public void getAll(){
  10.         List<User> users = userMapper.selectList(null);
  11.         users.forEach(System.out::println);
  12.    }
  14. }

MP配置日志输出

  1. #mybatis日志
  2. mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

MP添加信息+主键策略

1.添加用户信息

  1. @Test
  2. public void addUser(){
  3.     User user = new User();
  4.     user.setName("zhang3");
  5.     user.setAge(33);
  6.     user.setEmail("zhang3@qq.com");
  7.     userMapper.insert(user);
  8. }

2.主键策略

(1)策略 => 自增 , UUID : 随机字符串 , Redis , MP生成 , AUTO : 自动 , INPUT : 手动输入 , NONE : 不使用 , ID_WORKER : 根据算法生成全局序列(数字) , ID_WORKER_STR : 根据算法生成全局序列(字符串)

3.MP修改数据

  1. @Test
  2. public void updateUser(){
  3.     User user = new User();
  4.     user.setId(1366632417028227073L);
  5.     user.setName("zhang3UPUP");
  6.     userMapper.updateById(user);
  7. }

4.MP实现自动填充

  1. 1修改表字段
  2. 在User表中添加datetime类型的新的字段 create_time、update_time
  4. 2、增加实体字段
  5. （1）增加字段
  6. private Date createTime;
  7. private Date updateTime;
  8. （2）添加注解
  9. @TableField(fill = FieldFill.INSERT)
  10. private Date createTime;
  11. @TableField(fill = FieldFill.INSERT_UPDATE)
  12. private Date updateTime;
  14. 3、添加控制器
  15. @Component
  16. public class MyMetaObjectHandler  implements MetaObjectHandler {
  17.     @Override
  18.     public void insertFill(MetaObject metaObject) {
  19.         this.setFieldValByName("createTime",new Date(),metaObject);
  20.         this.setFieldValByName("updateTime",new Date(),metaObject);
  21.     }
  23.    @Override
  24.     public void updateFill(MetaObject metaObject) {
  25.         this.setFieldValByName("updateTime",new Date(),metaObject);
  26.     }
  27. }

5.乐观锁

MP实现乐观锁

(1)增加字段

数据库增加字段 version

(2)添加注解实现自动填充

@TableField(fill = FieldFill.INSERT)

private Integer version;

(3)添加乐观锁注解

@Version

@TableField(fill = FieldFill.INSERT)

private Integer version;

(4)添加插件

  1. @Configuration
  2. @EnableTransactionManagement
  3. @MapperScan("com.atguigu.mybatisplus.mapper")
  4. public class MybatisPlusConfig {
  5.     /**
  6.      * 乐观锁插件
  7.      */
  8.     @Bean
  9.     public OptimisticLockerInterceptor optimisticLockerInterceptor() {
  10.         return new OptimisticLockerInterceptor();
  11.     }
  13. }

(5) 测试

要想用到乐观锁,就必须先实现 => 先查询后修改

  1. @Test
  2. public void updateUser(){
  3.     User user = userMapper.selectById(1366652515570946050L);
  4.     user.setName("wang5");
  5.     userMapper.updateById(user);
  6. }

MP实现基本查询

1.根据id查询

User user = userMapper.selsectById(xxxxxxxx);

2.根据集合查询

  1. public void  selectByIds(){
  2.     List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));
  3.     users.forEach(System.out::println);
  4. }

3.简单查询

  1.   @Test
  2. public void selectByMap(){
  3.   Map<String,Object> map = new HashMap<>();
  4.     map.put("name","wang5");
  5.     map.put("age",55);
  6.     List<User> users = userMapper.selectByMap(map);
  7.     users.forEach(System.out::println);
  8. }

分页查询

(1)添加插件

  1. /**
  2.  * 分页插件
  3.  */
  4. @Bean
  5. public PaginationInterceptor paginationInterceptor() {
  6.     return new PaginationInterceptor();
  7. }

(2)实现分页

  1. @Test
  2. public void selectByPage(){
  3.     Page<User> page = new Page<>(1,3);
  4.     //IPage<User> userIPage = userMapper.selectPage(page, null);
  5.     userMapper.selectPage(page, null);
  6.     List<User> records = page.getRecords();
  7.     records.forEach(System.out::println);
  8.     System.out.println(page.getCurrent());
  9.     System.out.println(page.getPages());
  10.     System.out.println(page.getSize());
  11.     System.out.println(page.getTotal());
  12.     System.out.println(page.hasNext());
  13.     System.out.println(page.hasPrevious());
  14. }

MP实现删除数据

1.根据id删除

  1. @Test
  2. public void  delUser(){
  3.     int i = userMapper.deleteById(1366652515570946050L);
  4.     System.out.println(i);
  5. }

2.批量删除

  1.  @Test
  2. public void  delUsers(){
  3.  int i = userMapper.deleteBatchIds(Arrays.asList(1366632417028227073L,1366640077500923905L));
  4.     System.out.println(i);
  5. }

逻辑删除

  • 物理删除:真实删除,将对应数据从数据库中删除,之后查询不到此条被删除的数据
  • 逻辑删除:假删除,将数据中代表是否被删除字段修改为”被删除状态”,之后在数据库中仍然能看到此条数据记录

(1) 修改表 添加字段

deleted tinyint 0 (0为存在,1为删除)

(2)添加注解,实现自动填充

  1. @TableField(fill = fieldFill.INSERT)
  2. private Integer deleted;
  3. this.setFieldValByName("deleted",0,metaObject);

(3)添加逻辑删除注解

  1. @TableLogic
  2. @TableField(fill = fieldFill.INSERT)
  3. private Integer deleted;

(4) 添加配置

mybatis-plus.global-config.db-config.logic-delete-value=1
 mybatis-plus.global-config.db-config.logic-not-delete-value=0

(5)添加插件

  1. @Bean
  2. public ISqlInjector sqlInjector() {
  3.     return new LogicSqlInjector();
  4. }

MP实现条件查询

（1） eq 等于 = eq(“name”, “老王”)—->name = ‘老王’

  1.         ne 不等于 <> ne("name", "老王")--->name <> '老王'

（2） ge 等于 >= ge(“age”, 18)--->age >= 18

  1.         gt 大于 > gt("age", 18)`--->`age > 18
  3.         le  小于等于<= le("age", 18)`--->`age <= 18
  5.         lt 小于 < lt("age", 18)`--->`age < 18

（3） like LIKE ‘%值%’

  1.         like("name", "王")--->name like '%王%'

（4） between BETWEEN 值1 AND 值2

  1.          between("age", 18, 30)`--->`age between 18 and 30

（5） orderByDesc ORDER BY 字段, … DESC

（6） select 设置查询字段

  1.         orderByDesc("id", "name")--->order by id DESC,name DESC

测试

  1. @Test
  2.     public void selectByInfo(){
  3.         QueryWrapper<User> wrapper = new QueryWrapper<>();
  4. //        （1）  eq、ne
  5.         //wrapper.eq("name","zhang3");
  6. //（2）  ge、gt、le、lt
  7.         //wrapper.ge("age",18);
  8. //（3）  like
  9.         //wrapper.like("name","J");
  10. //（4）  between
  11.         //wrapper.between("age",18,28);
  12. //（5）  orderByDesc
  13.         wrapper.orderByDesc("age");
  14. //（6）  select
  15.         wrapper.select("id","name","age");
  16.         List<User> users = userMapper.selectList(wrapper);
  17.         users.forEach(System.out::println);
  18.     }