基于Spring整合mybatis的mapper生成过程

Spring整合mybatis的mapper生成过程

mapperScannerConfigurer实现了BeandifinitionRegistryPostProcessor

后置处理beanFactory时会调用其postProcessBeanDefinitionRegistry

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
   if (this.processPropertyPlaceHolders) {
     processPropertyPlaceHolders();
   }

ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
   scanner.setAddToConfig(this.addToConfig);
   scanner.setAnnotationClass(this.annotationClass);
   scanner.setMarkerInterface(this.markerInterface);
   scanner.setSqlSessionFactory(this.sqlSessionFactory);
   scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
   scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
   scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
   scanner.setResourceLoader(this.applicationContext);
   scanner.setBeanNameGenerator(this.nameGenerator);
   scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
   scanner.registerFilters();
//扫描包集合，注册mapper的beandifinition
   scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
 }

ClassPathMapperScanner#doScan

public Set<BeanDefinitionHolder> doScan(String... basePackages) {
   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 {
//会对bean信息进行一些更改和添加，如设置propertyValues，向其中添加sqlsessionFactory等属性信息等
     processBeanDefinitions(beanDefinitions);
   }

return beanDefinitions;
 }

ClassPathBeanDefinitionScanner#doScan

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
//遍历集合扫描包，获取包下的可用的mapper信息
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}

如上在进行包扫描时，会调用ClassPathBeanDefinitionScanner#doScan，进行beanDefinition的扫描和注册

执行完后调用ClassPathMapperScanner#processBeanDefinitions

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
//有省略部分

//这里有遍历所有mapper
//将所有mapper的beanClass改为了mapperFactoryBean，最后生成的bean也是该类型的，只有在用到的
//时候才会调用getObject生成mapper
     definition.setBeanClass(this.mapperFactoryBeanClass);
//接下来是添加一些MapperFactoryBean的属性信息到beandefinition里，在生成实例的时候，会根据
//此处传入的值来进行具体设置，如sqlsessionFactory
     definition.getPropertyValues().add("addToConfig", this.addToConfig);

if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
       definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));

} else if (this.sqlSessionFactory != null) {
       definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);

}

if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {

definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName));

} else if (this.sqlSessionTemplate != null) {

definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);

}
 }

确定了所有的mapper的beanDefinition为MapperFactoryBean类型后，

确定在生成的bean皆为MapperFactoryBean，在getBean时会调用MapperFactoryBean#getObject

mapperInterface是在MapperFactoryBean创建时，会调用有参构造创建实例，值是创建是

 构造方法参数的获取从mdb中

创建除了传入mapperInterface，还会在设置属性值时调用MapperFactoryBean的父类SqlSessionDaoSupport#setSqFactory 将mdb中的sqlsessionfactory传入其中

mdb的sqlsessionFactory信息来历

查看方法栈调用，可以看到在开始填充属性时会去mdb中判断是否有propertyValue，如果有就返回，这就是之前扫描mapper后ClassPathMapperScanner#processBeanDefinitions对mdb的一些设置

在创造service时，如果有@Autowire 注入mapper，在createBean时会调用getObject

mdb只有一份，可得sqlsessionfactory即只有一份，sqlsessionTemplate一个mapper一份

来源：https://blog.csdn.net/m0_47039719/article/details/123615798