Optimistic Lock Plugin

Optimistic locking is a concurrency control mechanism designed to ensure that a record has not been modified by other transactions when updating it. MyBatis-Plus provides the OptimisticLockerInnerInterceptor plugin, making it straightforward to implement optimistic locking in 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 (version).
2. When updating the record, pass this version number along.
3. During the update operation, set the condition version = newVersion where version = oldVersion.
4. If the version numbers do not match, the update fails.

Configuring the Optimistic Lock Plugin

To use the optimistic lock plugin, two configuration steps are required:

1. Configuring the Plugin

Spring XML Approach

<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 Approach

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

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

2. Adding the @Version Annotation to Entity Class Fields

In the 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...
}

Notes

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

Example

Below is 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 the entity class, you can easily implement optimistic locking in MyBatis-Plus applications, effectively preventing data conflicts during concurrent updates.