Custom ID Generator

MyBatis-Plus provides flexible custom ID generator functionality, allowing developers to customize ID generation strategies according to business requirements. Starting from version 3.3.0, it uses the Snowflake algorithm combined with a UUID without hyphens as the default ID generation method.

Comparison of Built-in Primary Key Generation Strategies in MyBatis-Plus

Method	Primary Key Strategy	Primary Key Type	Description
nextId	ASSIGN_ID	Long,Integer,String	Supports automatic conversion to String type, but numeric types do not support automatic conversion. Precise matching is required, e.g., if it returns Long, the entity primary key cannot be defined as Integer.
nextUUID	ASSIGN_UUID	String	Default UUID generation without hyphens.

How to Customize

MyBatis-Plus provides multiple ways to implement custom ID generators. Here are some example projects and configuration methods.

Spring Boot Integration

Method 1: Declare as a Bean for Spring to Scan and Inject

@Component
public class CustomIdGenerator implements IdentifierGenerator {
    @Override
    public Long nextId(Object entity) {
        // Use the entity class name as a business key, or extract parameters to generate a business key
        String bizKey = entity.getClass().getName();
        // Call the distributed ID generation service based on the business key
        long id = ...; // Call distributed ID generation logic
        // Return the generated ID value
        return id;
    }
}

Method 2: Use Configuration Class

@Bean
public IdentifierGenerator idGenerator() {
    return new CustomIdGenerator();
}

Method 3: Customize via MybatisPlusPropertiesCustomizer

@Bean
public MybatisPlusPropertiesCustomizer plusPropertiesCustomizer() {
    return plusProperties -> plusProperties.getGlobalConfig().setIdentifierGenerator(new CustomIdGenerator());
}

Spring Integration

Method 1: XML Configuration

<bean name="customIdGenerator" class="com.example.CustomIdGenerator"/>
<bean id="globalConfig" class="com.baomidou.mybatisplus.core.config.GlobalConfig">
    <property name="identifierGenerator" ref="customIdGenerator"/>
</bean>

Method 2: Annotation Configuration

@Bean
public GlobalConfig globalConfig() {
    GlobalConfig conf = new GlobalConfig();
    conf.setIdentifierGenerator(new CustomIdGenerator());
    return conf;
}

Differences from KeyGenerator

MyBatis-Plus’s IdentifierGenerator is primarily used for generating primary key IDs for database tables. In contrast, KeyGenerator is an interface within the MyBatis framework used for generating key values when executing SQL statements, typically for generating auto-incrementing primary keys or retrieving newly generated IDs after INSERT statements.

IdentifierGenerator focuses more specifically on primary key ID generation, while KeyGenerator is more general-purpose and can be used for various key-value generation scenarios. When using MyBatis-Plus, it’s generally recommended to use IdentifierGenerator for generating primary key IDs because it integrates more tightly with MyBatis-Plus and offers more convenience and functionality.

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