MyBatis-Plus乐观锁失效的常见原因及解决方案

@Configuration
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 必须添加乐观锁插件
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return interceptor;
    }
}

import com.baomidou.mybatisplus.annotation.Version;

public class User {
    // 正确标注版本号字段
    @Version
    private Integer version;

    // 其他字段...
}

-- 确保 version 字段有初始值
ALTER TABLE user ADD COLUMN version INT NOT NULL DEFAULT 1;

// 错误方式：直接构造新对象
User user = new User();
user.setId(1L);
user.setName("New Name");
userMapper.updateById(user); // version 未传递，乐观锁失效

// 正确方式：先查询数据
User user = userMapper.selectById(1L); // 查询当前数据（包含 version）
user.setName("New Name");
userMapper.updateById(user); // 自动处理 version 递增

<!-- 正确方式：显式添加 version 条件 -->
<update id="updateUser">
    UPDATE user
    SET name = #{name}, version = version + 1
    WHERE id = #{id} AND version = #{version}
</update>

@Transactional
public void updateData(Long id, String newName) {
    User user = userMapper.selectById(id); // 查询数据
    user.setName(newName);
    userMapper.updateById(user); // 事务提交后版本号递增
}

@Test
public void testOptimisticLock() {
    User user1 = userMapper.selectById(1L); // version=1
    User user2 = userMapper.selectById(1L); // version=1

    user1.setName("Thread 1");
    userMapper.updateById(user1); // version 变为 2

    user2.setName("Thread 2");
    try {
        userMapper.updateById(user2); // 此处应抛出 OptimisticLockException
    } catch (OptimisticLockException e) {
        System.out.println("乐观锁生效，更新失败");
    }
}

// 正确类型
@Version
private Integer version; // 或 Long/LocalDateTime

// 错误类型
@Version
private String version; // 类型不匹配，乐观锁失效

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.7</version>
</dependency>

CREATE TABLE user (
    id BIGINT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(100),
    version INT NOT NULL DEFAULT 1 -- 初始化版本号
);

import com.baomidou.mybatisplus.annotation.*;

@TableName("user")
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;

    private String name;

    @Version
    private Integer version; // 版本号字段

    // Getter & Setter
}

@Configuration
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return interceptor;
    }
}

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    @Transactional
    public void updateUser(Long id, String newName) {
        User user = userMapper.selectById(id); // 查询当前数据
        user.setName(newName);
        int result = userMapper.updateById(user); // 自动处理 version
        if (result == 0) {
            throw new OptimisticLockException("乐观锁更新失败");
        }
    }
}

@TableField("ver")
@Version
private Integer version;

UpdateWrapper<User> wrapper = new UpdateWrapper<>();
wrapper.eq("id", 1L).eq("version", user.getVersion());
user.setVersion(user.getVersion() + 1);
userMapper.update(user, wrapper);