Custom ID Generator

MyBatis-Plus provides a flexible custom ID generator feature, allowing developers to tailor ID generation strategies according to business needs. Starting from version 3.3.0, it defaults to using the snowflake algorithm combined with a UUID without hyphens as the ID generation method.

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

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 auto-conversion. Requires exact matching, e.g., if it returns Long, the entity primary key cannot be defined as Integer.
nextUUID	ASSIGN_UUID	String	Defaults to generating UUID without hyphens.

How to Customize

MyBatis-Plus offers multiple ways to implement custom ID generators. Below 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 a distributed ID generation service based on the business key
        long id = ...; // Invoke distributed ID generation logic
        // Return the generated ID value
        return id;
    }
}

Method 2: Use a 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 to generate primary key IDs for database tables, whereas KeyGenerator is an interface in the MyBatis framework used to generate key values when executing SQL statements, typically for generating auto-incremented primary keys or obtaining newly generated IDs after INSERT statements.

IdentifierGenerator focuses more 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 is generally recommended to use IdentifierGenerator for generating primary key IDs, as it integrates more tightly with MyBatis-Plus, offering greater convenience and functionality.