Optimistic Lock Plugin

Optimistic locking is a concurrency control mechanism used to ensure that when updating a record, it hasn’t been modified by other transactions. MyBatis-Plus provides the OptimisticLockerInnerInterceptor plugin, making it simple to implement optimistic locking in your applications.

How Optimistic Locking Works

The implementation of optimistic locking typically involves the following steps:

1. When reading a record, retrieve the current version number.
2. When updating the record, pass this version number along.
3. When performing the update operation, set the condition version = newVersion where version = oldVersion.
4. If the version numbers don’t match, the update fails.

Configuring the Optimistic Lock Plugin

To use the optimistic lock plugin, you need to perform two configuration steps:

1. Configure the Plugin

Spring XML Configuration

<bean id="optimisticLockerInnerInterceptor" class="com.baomidou.mybatisplus.extension.plugins.inner.OptimisticLockerInnerInterceptor"/>

<bean id="mybatisPlusInterceptor" class="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor">
    <property name="interceptors">
        <list>
            <ref bean="optimisticLockerInnerInterceptor"/>
        </list>
    </property>
</bean>

Spring Boot Annotation Configuration

@Configuration
@MapperScan("Modify as needed")
public class MybatisPlusConfig {

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

2. Add @Version Annotation to Entity Field

In your entity class, add the @Version annotation to the field representing the version number:

import com.baomidou.mybatisplus.annotation.Version;

public class YourEntity {
    @Version
    private Integer version;
    // Other fields...
}

Important Notes

• Supported data types include: int, Integer, long, Long, Date, Timestamp, LocalDateTime.
• For integer types, newVersion is calculated as oldVersion + 1.
• newVersion is automatically written back to the entity object.
• Supported built-in methods: updateById(entity), update(entity, wrapper), saveOrUpdate(entity), insertOrUpdate(entity) (version >= 3.5.7).
• Custom update methods will also execute optimistic lock logic if they meet the parameter conditions of built-in methods. For example, a custom myUpdate(entity) method is equivalent to updateById(entity) and will extract parameters for optimistic lock population, but the update implementation needs to be handled manually.
• In the update(entity, wrapper) method, the wrapper cannot be reused.

Example

Here’s a complete Spring Boot configuration example:

@Configuration
@MapperScan("com.yourpackage.mapper")
public class MybatisPlusConfig {

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

With the above configuration and the @Version annotation in your entity class, you can easily implement optimistic locking in your MyBatis-Plus application, effectively preventing data conflicts during concurrent updates.