SpringBoot整合MybatisPlus3.X之乐观锁(十三)

主要适用场景

意图：

当要更新一条记录的时候，希望这条记录没有被别人更新

乐观锁实现方式：

• 取出记录时，获取当前version

• 更新时，带上这个version

• 执行更新时， set version = newVersion where version = oldVersion

• 如果version不对，就更新失败

乐观锁配置需要2步 记得两步

1.插件配置

spring xml:

<bean class="com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor"/>
spring boot:

@Bean
public OptimisticLockerInterceptor optimisticLockerInterceptor() {
    return new OptimisticLockerInterceptor();
}

2.注解实体字段 @Version 必须要!

@Version
private Integer version;

特别说明:

• 支持的数据类型只有:int,Integer,long,Long,Date,Timestamp,LocalDateTime

• 整数类型下 newVersion = oldVersion + 1

• newVersion 会回写到 entity 中

• 仅支持 updateById(id) 与 update(entity, wrapper) 方法

• 在 update(entity, wrapper) 方法下, wrapper 不能复用!!!

示例

示例Java代码（参考代码）

int id = 100;
int version = 2;
​
User u = new User();
u.setId(id);
u.setVersion(version);
u.setXXX(xxx);
​
if(userService.updateById(u)){
    System.out.println("Update successfully");
}else{
    System.out.println("Update failed due to modified by others");
}

示例SQL原理

update tbl_user set name = 'update',version = 3 where id = 100 and version = 2

• pom.xml

  <dependencies>
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter</artifactId>
          </dependency>
          <dependency>
              <groupId>com.baomidou</groupId>
              <artifactId>mybatis-plus-boot-starter</artifactId>
              <version>3.2.0</version>
          </dependency>
          <dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
          </dependency>
          <!-- https://mvnrepository.com/artifact/p6spy/p6spy -->
          <dependency>
              <groupId>p6spy</groupId>
              <artifactId>p6spy</artifactId>
              <version>3.8.0</version>
          </dependency>
          <dependency>
              <groupId>com.h2database</groupId>
              <artifactId>h2</artifactId>
              <scope>runtime</scope>
          </dependency>
  ​
          <dependency>
              <groupId>com.alibaba</groupId>
              <artifactId>fastjson</artifactId>
              <version>1.2.49</version>
              <scope>test</scope>
          </dependency>
          <!-- for testing -->
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-test</artifactId>
              <scope>test</scope>
          </dependency>
      </dependencies>

• 配置类

  @Configuration
  public class MybatisPlusOptLockerConfig {
  ​
      @Bean
      public OptimisticLockerInterceptor optimisticLockerInterceptor() {
          return new OptimisticLockerInterceptor();
      }
  }

• 实体类​

  @Data
  public class User {
  ​
      @TableId(value = "id", type = IdType.AUTO)
      private Long id;
      private String name;
      private Integer age;
      private String email;
      @Version
      private Integer version;
  }

• Mapper

  public interface UserMapper extends BaseMapper<User> {
  ​
  }

• 启动类

  @SpringBootApplication
  @MapperScan("com.mp.locker.mapper")  //不加在容器里面获取不了
  public class LockerApplication {
  ​
      public static void main(String[] args) {
          SpringApplication.run(LockerApplication.class, args);
      }
  ​
  }

• application.yml

  spring:
    datasource:
      driver-class-name: com.p6spy.engine.spy.P6SpyDriver
      url: jdbc:p6spy:h2:tcp://192.168.180.115:19200/~/mem/test
      username: root
      password: test

• 测试类

  @SpringBootTest
  class LockerApplicationTests {
  ​
      @Autowired(required = false)
      UserMapper userMapper;
  ​
      @Test
      public void testUpdateByIdSucc() {
          User user = new User();
          user.setAge(18);
          user.setEmail("test@baomidou.com");
          user.setName("optlocker");
          user.setVersion(1);
          userMapper.insert(user);
          Long id = user.getId();
          //INSERT INTO user ( name, version, email, age ) VALUES ( 'optlocker', 1, 'test@baomidou.com', 18 )
          User userUpdate = new User();
          userUpdate.setId(id);
          userUpdate.setAge(19);
          userUpdate.setVersion(1);
          //UPDATE user SET version=2, age=19 WHERE id=6 AND version=1
          Assert.assertEquals("Should update success", 1, userMapper.updateById(userUpdate));
          //6 optlocker   19  test@baomidou.com   2  值变成2
          Assert.assertEquals("Should version = version+1", 2, userUpdate.getVersion().intValue());
      }
  ​
      @Test
      public void testUpdateByIdFail() {
          User user = new User();
          user.setAge(18);
          user.setEmail("test@baomidou.com");
          user.setName("optlocker");
          user.setVersion(1);
          //INSERT INTO user ( name, version, email, age ) VALUES ( 'optlocker', 1, 'test@baomidou.com', 18 )
          userMapper.insert(user);
          Long id = user.getId();
  ​
          User userUpdate = new User();
          userUpdate.setId(id);
          userUpdate.setAge(19);
          userUpdate.setVersion(0);
          //UPDATE user SET version=1, age=19 WHERE id=7 AND version=0
          userMapper.updateById(userUpdate);
      }
  ​
      @Test
      public void testUpdateByIdSuccWithNoVersion() {
          User user = new User();
          user.setAge(18);
          user.setEmail("test@baomidou.com");
          user.setName("optlocker");
          user.setVersion(1);
          userMapper.insert(user);
          Long id = user.getId();
  ​
          User userUpdate = new User();
          userUpdate.setId(id);
          userUpdate.setAge(19);
          userUpdate.setVersion(null);
          Assert.assertEquals("Should update success as no version passed in", 1, userMapper.updateById(userUpdate));
          User updated = userMapper.selectById(id);
          Assert.assertEquals("Version not changed", 1, updated.getVersion().intValue());
          Assert.assertEquals("Age updated", 19, updated.getAge().intValue());
      }
  ​
      /**
       * 批量更新带乐观锁
       * <p>
       * update(et,ew) et:必须带上version的值才会触发乐观锁
       */
      @Test
      public void testUpdateByEntitySucc() {
          QueryWrapper<User> ew = new QueryWrapper<>();
          ew.eq("version", 1);
          int count = userMapper.selectCount(ew);
  ​
          User entity = new User();
          entity.setAge(28);
          entity.setVersion(1);
  ​
          Assert.assertEquals("updated records should be same", count, userMapper.update(entity, null));
          ew = new QueryWrapper<>();
          ew.eq("version", 1);
          Assert.assertEquals("No records found with version=1", 0, userMapper.selectCount(ew).intValue());
          ew = new QueryWrapper<>();
          ew.eq("version", 2);
          Assert.assertEquals("All records with version=1 should be updated to version=2", count, userMapper.selectCount(ew).intValue());
      }
  ​
  }