Mybatis整合springboot原理分析，MybatisAutoConfiguration，AutoConfiguredMapperScannerRegistrar
本章需要参考之前的两篇博客：
- Mybatis整合spring原理分析，SqlSessionFactoryBean，MapperScan，MapperScannerRegistrar，MapperScannerConfigurer
- springboot自动装配原理，底层源码分析，条件注解实现机制
从之前springboot自动装配原理，在资源目录下应该存在META-INF/spring.factories文件，查看mybatis-spring-boot-autoconfigure模块，其下该文件内容如下：
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.mybatis.spring.boot.autoconfigure.MybatisLanguageDriverAutoConfiguration,\
org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration
其中，MybatisLanguageDriverAutoConfiguration内容如下：
// MybatisLanguageDriverAutoConfiguration.java
@Configuration
@ConditionalOnClass(LanguageDriver.class)
public class MybatisLanguageDriverAutoConfiguration {
private static final String CONFIGURATION_PROPERTY_PREFIX = "mybatis.scripting-language-driver";
/**
* Configuration class for mybatis-freemarker 1.1.x or under.
*/
@Configuration
@ConditionalOnClass(FreeMarkerLanguageDriver.class)
@ConditionalOnMissingClass("org.mybatis.scripting.freemarker.FreeMarkerLanguageDriverConfig")
public static class LegacyFreeMarkerConfiguration {
@Bean
@ConditionalOnMissingBean
FreeMarkerLanguageDriver freeMarkerLanguageDriver() {
return new FreeMarkerLanguageDriver();
}
}
/**
* Configuration class for mybatis-freemarker 1.2.x or above.
*/
@Configuration
@ConditionalOnClass({
FreeMarkerLanguageDriver.class, FreeMarkerLanguageDriverConfig.class })
public static class FreeMarkerConfiguration {
@Bean
@ConditionalOnMissingBean
FreeMarkerLanguageDriver freeMarkerLanguageDriver(FreeMarkerLanguageDriverConfig config) {
return new FreeMarkerLanguageDriver(config);
}
@Bean
@ConditionalOnMissingBean
@ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".freemarker")
public FreeMarkerLanguageDriverConfig freeMarkerLanguageDriverConfig() {
return FreeMarkerLanguageDriverConfig.newInstance();
}
}
/**
* Configuration class for mybatis-velocity 2.0 or under.
*/
@Configuration
@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() {
return new org.mybatis.scripting.velocity.Driver();
}
}
/**
* Configuration class for mybatis-velocity 2.1.x or above.
*/
@Configuration
@ConditionalOnClass({
VelocityLanguageDriver.class, VelocityLanguageDriverConfig.class })
public static class VelocityConfiguration {
@Bean
@ConditionalOnMissingBean
VelocityLanguageDriver velocityLanguageDriver(VelocityLanguageDriverConfig config) {
return new VelocityLanguageDriver(config);
}
@Bean
@ConditionalOnMissingBean
@ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".velocity")
public VelocityLanguageDriverConfig velocityLanguageDriverConfig() {
return VelocityLanguageDriverConfig.newInstance();
}
}
@Configuration
@ConditionalOnClass(ThymeleafLanguageDriver.class)
public static class ThymeleafConfiguration {
@Bean
@ConditionalOnMissingBean
ThymeleafLanguageDriver thymeleafLanguageDriver(ThymeleafLanguageDriverConfig config) {
return new ThymeleafLanguageDriver(config);
}
@Bean
@ConditionalOnMissingBean
@ConfigurationProperties(CONFIGURATION_PROPERTY_PREFIX + ".thymeleaf")
public ThymeleafLanguageDriverConfig thymeleafLanguageDriverConfig() {
return ThymeleafLanguageDriverConfig.newInstance();
}
}
可以看到，这个类主要就是注入一个LanguageDriver实现，主要逻辑在MybatisAutoConfiguration:
// MybatisAutoConfiguration.java
@org.springframework.context.annotation.Configuration
@ConditionalOnClass({
SqlSessionFactory.class, SqlSessionFactoryBean.class })
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter({
DataSourceAutoConfiguration.class, MybatisLanguageDriverAutoConfiguration.class })
public class MybatisAutoConfiguration implements InitializingBean {
...
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
....
}
@Bean
@ConditionalOnMissingBean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
ExecutorType executorType = this.properties.getExecutorType();
if (executorType != null) {
return new SqlSessionTemplate(sqlSessionFactory, executorType);
} else {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
@org.springframework.context.annotation.Configuration
@Import(AutoConfiguredMapperScannerRegistrar.class)
@ConditionalOnMissingBean({
MapperFactoryBean.class, MapperScannerConfigurer.class })
public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {
@Override
public void afterPropertiesSet() {
logger.debug(
"Not found configuration for registering mapper bean using @MapperScan, MapperFactoryBean and MapperScannerConfigurer.");
}
}
public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar {
private BeanFactory beanFactory;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
if (!AutoConfigurationPackages.has(this.beanFactory)) {
logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.");
return;
}
logger.debug("Searching for mappers annotated with @Mapper");
List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
if (logger.isDebugEnabled()) {
packages.forEach(pkg -> logger.debug("Using auto-configuration base package '{}'", pkg));
}
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
builder.addPropertyValue("processPropertyPlaceHolders", true);
builder.addPropertyValue("annotationClass", Mapper.class);
builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(packages));
BeanWrapper beanWrapper = new BeanWrapperImpl(MapperScannerConfigurer.class);
Set<String> propertyNames = Stream.of(beanWrapper.getPropertyDescriptors()).map(PropertyDescriptor::getName)
.collect(Collectors.toSet());
if (propertyNames.contains("lazyInitialization")) {
// Need to mybatis-spring 2.0.2+
builder.addPropertyValue("lazyInitialization", "${mybatis.lazy-initialization:false}");
}
if (propertyNames.contains("defaultScope")) {
// Need to mybatis-spring 2.0.6+
builder.addPropertyValue("defaultScope", "${mybatis.mapper-default-scope:}");
}
registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());
}
@Override
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
}
下面我们逐一说明。
- 首先是该Enable起作用是当前环境下存在
SqlSessionFactory.class, SqlSessionFactoryBean.class这两个类，还记得之前分析mybatis和spring整合的，就是通过SqlSessionFactoryBean,这就表示需要引入mybatis-spring依赖，而SqlSessionFactory则是mybatis本身的依赖，即pom需要引入mybatis和mybatis-spring这两个依赖MybatisAutoConfiguration才会起作用 - 获取
SqlSessionFactory，如果当前IOC容器没有SqlSessionFactory类型的bean，则这里会创建一个 - 创建
SqlSessionTemplate，如果当前IOC容器没有SqlSessionTemplate类型bean，则这里会创建一个 - 如果当前IOC容器没有
MapperFactoryBean.class, MapperScannerConfigurer.class这两个bean，则会通过：
org.springframework.context.annotation.Configuration
@Import(AutoConfiguredMapperScannerRegistrar.class)
@ConditionalOnMissingBean({
MapperFactoryBean.class, MapperScannerConfigurer.class })
public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean
通过AutoConfiguredMapperScannerRegistrar导入，其通过实现registerBeanDefinitions方法，将MapperScannerConfigurer这个类注入到了IOC容器中，还记得之前mybatis整合spring的时候怎么用到这个类的吗？这个就是众多的Mapper转成MapperFactory注入到了IOC容器中，至此，借助mybatis-spring，mybatis-springboot将SqlSessionFactoryBean和众多的Mapper都注入到IOC容器中，大家就可以愉快的使用了。
是不是感觉很简单，其实如果看了前面的两篇，这块理解起来就没什么难度了。