Auto-Configuration

/**
 * Auto-configuration for MyBatis that contributes SqlSessionFactory and SqlSessionTemplate.
 * Automatically configures mapper scanning when @MapperScan is not used.
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter({DataSourceAutoConfiguration.class, MybatisLanguageDriverAutoConfiguration.class})
public class MybatisAutoConfiguration implements InitializingBean {
    
    /**
     * Constructor accepting all required dependencies and customizers
     */
    public MybatisAutoConfiguration(
        MybatisProperties properties,
        ObjectProvider<Interceptor[]> interceptorsProvider,
        ObjectProvider<TypeHandler[]> typeHandlersProvider,
        ObjectProvider<LanguageDriver[]> languageDriversProvider,
        ResourceLoader resourceLoader,
        ObjectProvider<DatabaseIdProvider> databaseIdProvider,
        ObjectProvider<List<ConfigurationCustomizer>> configurationCustomizersProvider,
        ObjectProvider<List<SqlSessionFactoryBeanCustomizer>> sqlSessionFactoryBeanCustomizers
    );
    
    /**
     * Creates the main SqlSessionFactory bean with auto-configuration
     * @param dataSource the DataSource to use
     * @return configured SqlSessionFactory
     * @throws Exception if configuration fails
     */
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception;
    
    /**
     * Creates the SqlSessionTemplate bean for database operations
     * @param sqlSessionFactory the SqlSessionFactory to use
     * @return configured SqlSessionTemplate
     */
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory);
    
    /** Validates configuration after properties are set */
    @Override
    public void afterPropertiesSet();
}

/**
 * Auto-configuration for MyBatis scripting language drivers including
 * FreeMarker, Velocity, and Thymeleaf support
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(LanguageDriver.class)
public class MybatisLanguageDriverAutoConfiguration {
    
    private static final String CONFIGURATION_PROPERTY_PREFIX = "mybatis.scripting-language-driver";
    
    /**
     * Configuration for legacy FreeMarker language driver (version 1.1.x and under)
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass(FreeMarkerLanguageDriver.class)
    @ConditionalOnMissingClass("org.mybatis.scripting.freemarker.FreeMarkerLanguageDriverConfig")
    public static class LegacyFreeMarkerConfiguration {
        @Bean
        @ConditionalOnMissingBean
        FreeMarkerLanguageDriver freeMarkerLanguageDriver();
    }
    
    /**
     * Configuration for FreeMarker language driver (version 1.2.x+)
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({FreeMarkerLanguageDriver.class, FreeMarkerLanguageDriverConfig.class})
    public static class FreeMarkerConfiguration {
        @Bean
        @ConditionalOnMissingBean
        FreeMarkerLanguageDriver freeMarkerLanguageDriver(FreeMarkerLanguageDriverConfig config);
        
        @Bean
        @ConditionalOnMissingBean
        @ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".freemarker")
        public FreeMarkerLanguageDriverConfig freeMarkerLanguageDriverConfig();
    }
    
    /**
     * Configuration for legacy Velocity language driver (version 2.0 and under)
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass(org.mybatis.scripting.velocity.Driver.class)
    @ConditionalOnMissingClass("org.mybatis.scripting.velocity.VelocityLanguageDriverConfig")
    @SuppressWarnings("deprecation")
    public static class LegacyVelocityConfiguration {
        @Bean
        @ConditionalOnMissingBean
        org.mybatis.scripting.velocity.Driver velocityLanguageDriver();
    }
    
    /**
     * Configuration for Velocity language driver (version 2.1.x+)
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({VelocityLanguageDriver.class, VelocityLanguageDriverConfig.class})
    public static class VelocityConfiguration {
        @Bean
        @ConditionalOnMissingBean
        VelocityLanguageDriver velocityLanguageDriver(VelocityLanguageDriverConfig config);
        
        @Bean
        @ConditionalOnMissingBean
        @ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".velocity")
        public VelocityLanguageDriverConfig velocityLanguageDriverConfig();
    }
    
    /**
     * Configuration for Thymeleaf language driver
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass(ThymeleafLanguageDriver.class)
    public static class ThymeleafConfiguration {
        @Bean
        @ConditionalOnMissingBean
        ThymeleafLanguageDriver thymeleafLanguageDriver(ThymeleafLanguageDriverConfig config);
        
        @Bean
        @ConditionalOnMissingBean
        @ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".thymeleaf")
        public ThymeleafLanguageDriverConfig thymeleafLanguageDriverConfig();
    }
}

/**
 * Automatic mapper scanner that registers all @Mapper annotated interfaces
 * when no explicit mapper configuration is provided
 */
public static class AutoConfiguredMapperScannerRegistrar 
    implements BeanFactoryAware, EnvironmentAware, ImportBeanDefinitionRegistrar {
    
    /**
     * Registers mapper scanner configuration when auto-configuration packages are available
     */
    @Override
    public void registerBeanDefinitions(
        AnnotationMetadata importingClassMetadata, 
        BeanDefinitionRegistry registry
    );
    
    @Override
    public void setBeanFactory(BeanFactory beanFactory);
    
    @Override
    public void setEnvironment(Environment environment);
}

/**
 * Configuration that triggers automatic mapper scanning when no explicit
 * mapper configuration is found
 */
@Configuration(proxyBeanMethods = false)
@Import(AutoConfiguredMapperScannerRegistrar.class)
@ConditionalOnMissingBean({MapperFactoryBean.class, MapperScannerConfigurer.class})
public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {
    @Override
    public void afterPropertiesSet();
}

// Only when MyBatis classes are on classpath
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})

// Only when exactly one DataSource bean exists
@ConditionalOnSingleCandidate(DataSource.class)

// Only creates beans if they don't already exist
@ConditionalOnMissingBean

// Only scans for mappers if no explicit mapper configuration exists
@ConditionalOnMissingBean({MapperFactoryBean.class, MapperScannerConfigurer.class})

@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
    SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
    
    // 1. Set DataSource
    factory.setDataSource(dataSource);
    
    // 2. Configure VFS (defaults to SpringBootVFS)
    if (properties.getConfiguration() == null || properties.getConfiguration().getVfsImpl() == null) {
        factory.setVfs(SpringBootVFS.class);
    }
    
    // 3. Set configuration location if specified
    if (StringUtils.hasText(this.properties.getConfigLocation())) {
        factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
    }
    
    // 4. Apply core configuration
    applyConfiguration(factory);
    
    // 5. Set configuration properties
    if (this.properties.getConfigurationProperties() != null) {
        factory.setConfigurationProperties(this.properties.getConfigurationProperties());
    }
    
    // 6. Add interceptors
    if (!ObjectUtils.isEmpty(this.interceptors)) {
        factory.setPlugins(this.interceptors);
    }
    
    // 7. Set database ID provider
    if (this.databaseIdProvider != null) {
        factory.setDatabaseIdProvider(this.databaseIdProvider);
    }
    
    // 8. Configure type aliases
    if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
        factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
    }
    
    // 9. Set type handlers
    if (!ObjectUtils.isEmpty(this.typeHandlers)) {
        factory.setTypeHandlers(this.typeHandlers);
    }
    
    // 10. Configure mapper locations
    Resource[] mapperLocations = this.properties.resolveMapperLocations();
    if (!ObjectUtils.isEmpty(mapperLocations)) {
        factory.setMapperLocations(mapperLocations);
    }
    
    // 11. Configure scripting language drivers
    if (!ObjectUtils.isEmpty(this.languageDrivers)) {
        factory.setScriptingLanguageDrivers(this.languageDrivers);
    }
    
    // 12. Apply SqlSessionFactoryBean customizers
    applySqlSessionFactoryBeanCustomizers(factory);
    
    // 13. Build and return SqlSessionFactory
    return factory.getObject();
}

@SpringBootApplication(exclude = {MybatisAutoConfiguration.class})
public class Application {
    // Auto-configuration disabled - manual configuration required
}

@Configuration
@AutoConfigureBefore(MybatisAutoConfiguration.class)
public class CustomMybatisAutoConfiguration {
    
    @Bean
    @Primary
    public DataSource customDataSource() {
        // Custom DataSource that will be used by MyBatis auto-configuration
        return new HikariDataSource();
    }
    
    @Bean
    public Interceptor customInterceptor() {
        // Custom interceptor that will be automatically registered
        return new AuditInterceptor();
    }
}

@Configuration
public class MyBatisOverrides {
    
    // This will prevent auto-configuration from creating SqlSessionTemplate
    @Bean
    @Primary
    public SqlSessionTemplate customSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        return new CustomSqlSessionTemplate(sqlSessionFactory);
    }
}