Mybatis-Spring（1）BeanDefinition

将Mybatis中的Mapper注册到Spring的ApplicationContext中，受Spring的生命周期管理。

Mapper扫描注解，用法

@Configuration
@MapperScan("org.mybatis.spring.sample.mapper")

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MapperScannerRegistrar.class)
public @interface MapperScan

这里，注意到@MapperScan其中包装了一个注解：@Import(MapperScannerRegistrar.class)

@Import处理的环节：AbstractApplicationContext.refresh()

@Override
public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
	............
	　　try {
		............
		// Invoke factory processors registered as beans in the context.
		invokeBeanFactoryPostProcessors(beanFactory);
		............
	　　}
	}
}

@Import解析并且将BeanDefiniton注册环节：ConfigurationClassPostProcessor.processConfigBeanDefinitions

/**
 * Build and validate a configuration model based on the registry of
 * {@link Configuration} classes.
 */
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
	List<BeanDefinitionHolder> configCandidates = new ArrayList<BeanDefinitionHolder>();
	//1、所有的BeanDefiniton的name
	String[] candidateNames = registry.getBeanDefinitionNames();

	for (String beanName : candidateNames) {
		............
		//2、将所有的@Configuration的类放入configCandidates中
		else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
			configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
		}
	}
	............
	Set<BeanDefinitionHolder> candidates = new LinkedHashSet<BeanDefinitionHolder>(configCandidates);
	do {
		//3、解析所有的@Configuration类里面所有的注解（@Bean、@Profile、@Import、@ImportResource、@ComponentScan、@Lazy、@PropertySource）
		parser.parse(candidates);
		............
　　　　　　　　　　Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(parser.getConfigurationClasses());
		............
		//4、通过解析成的configClasses，将所有的配置转化成BeanDefinition
		this.reader.loadBeanDefinitions(configClasses);
		............
	}
	while (!candidates.isEmpty());
	............
}

下面我们看下MapperScannerRegistrar做了哪些事情

registerBeanDefinitions：注册Bean

public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

	// MapperScan配置的注解数据
    AnnotationAttributes annoAttrs = AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);

    Class<? extends Annotation> annotationClass = annoAttrs.getClass("annotationClass");
    if (!Annotation.class.equals(annotationClass)) {
	  // 设置需要注册的annotationClass
      scanner.setAnnotationClass(annotationClass);
    }
    Class<?> markerInterface = annoAttrs.getClass("markerInterface");
    if (!Class.class.equals(markerInterface)) {
      // 设置需要注册的markerInterface
	  scanner.setMarkerInterface(markerInterface);
    }

    Class<? extends BeanNameGenerator> generatorClass = annoAttrs.getClass("nameGenerator");
    if (!BeanNameGenerator.class.equals(generatorClass)) {
      // 设置自定义的BeanNameGenerator
	  scanner.setBeanNameGenerator(BeanUtils.instantiateClass(generatorClass));
    }

    Class<? extends MapperFactoryBean> mapperFactoryBeanClass = annoAttrs.getClass("factoryBean");
    if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) {
      // 设置自定义的MapperFactoryBean.class
	  scanner.setMapperFactoryBean(BeanUtils.instantiateClass(mapperFactoryBeanClass));
    }
	// 设置sqlSessionTemplateRef的值到sqlSessionTemplateBeanName
    scanner.setSqlSessionTemplateBeanName(annoAttrs.getString("sqlSessionTemplateRef"));
	// 设置sqlSessionTemplateRef的值到sqlSessionFactoryBeanName
    scanner.setSqlSessionFactoryBeanName(annoAttrs.getString("sqlSessionFactoryRef"));

    List<String> basePackages = new ArrayList<String>();
    for (String pkg : annoAttrs.getStringArray("value")) {
      if (StringUtils.hasText(pkg)) {
        // 设置basePackages
		basePackages.add(pkg);
      }
    }
    for (String pkg : annoAttrs.getStringArray("basePackages")) {
      if (StringUtils.hasText(pkg)) {
        // 设置basePackages
		basePackages.add(pkg);
      }
    }
    for (Class<?> clazz : annoAttrs.getClassArray("basePackageClasses")) {
      // 设置basePackages
	  basePackages.add(ClassUtils.getPackageName(clazz));
    }
	// 根据annotationClass和markerInterface,设置addIncludeFilter
    scanner.registerFilters();
	// 开始扫描
    scanner.doScan(StringUtils.toStringArray(basePackages));
  }

scanner.doScan:扫描

@Override
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
    // 调用ClassPathBeanDefinitionScanner.doScan，将包下所有的类都注册到容器中
    Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
    if (beanDefinitions.isEmpty()) {
        logger.warn("No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration.");
    } else {
	// 为了beanDefinitions信息，1、让这些接口类可以被MapperFactoryBean动态代理 2、设置对应的SqlSession到被代理的对象中
        processBeanDefinitions(beanDefinitions);
    }
    return beanDefinitions;
}

processBeanDefinitions：处理BeanDefiniton

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    GenericBeanDefinition definition;
    for (BeanDefinitionHolder holder : beanDefinitions) {
		definition = (GenericBeanDefinition) holder.getBeanDefinition();
		...........
		// the mapper interface is the original class of the bean
		// but, the actual class of the bean is MapperFactoryBean
		// 设置接口作为构造器入参，后面看MapperFactoryBean的构造器，就能理解这是干嘛的了
		definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59
		// 将MapperFactoryBean.class作为Mapper的类，是为了让Sprintg感知，这个Bean的实例是要通过定义的FactoryBean来创建的
		definition.setBeanClass(this.mapperFactoryBean.getClass());
		...........
		// 设置sqlSessionFactoryBeanName（sqlSessionFactoryRef的值）的运行时bean引用
		definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
		// 设置sqlSessionTemplateBeanName（sqlSessionTemplateRef的值）的运行时bean引用
		definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
        ...........
    }
}