AutoConfiguredMapperScannerRegistrar
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { logger.debug("Searching for mappers annotated with @Mapper"); ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry); try { if (this.resourceLoader != null) { scanner.setResourceLoader(this.resourceLoader); } List<String> packages = AutoConfigurationPackages.get(this.beanFactory); if (logger.isDebugEnabled()) { for (String pkg : packages) { logger.debug("Using auto-configuration base package '{}'", pkg); } } scanner.setAnnotationClass(Mapper.class); scanner.registerFilters(); scanner.doScan(StringUtils.toStringArray(packages)); } catch (IllegalStateException ex) { logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.", ex); } }
In this method, ClassPathMapperScanner is used to scan the Mapper interface under the specified package and register it to BeanFactory Next, take a look at the doScan method of ClassPathMapperScanner
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 { processBeanDefinitions(beanDefinitions); } return beanDefinitions; }
In this method, the doScan method of the parent class is called. doScan method of parent class
protected Set<BeanDefinitionHolder> doScan(String... basePackages) { Assert.notEmpty(basePackages, "At least one base package must be specified"); Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>(); for (String basePackage : basePackages) { 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; }
In this method, according to the package path, find the interface decorated by Mapper annotation, generate BeanDefinition, and register to BeanFactory
Next, let's look at the processBeanDefinitions method of ClassPathMapperScanner
private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) { GenericBeanDefinition definition; for (BeanDefinitionHolder holder : beanDefinitions) { definition = (GenericBeanDefinition) holder.getBeanDefinition(); if (logger.isDebugEnabled()) { logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + definition.getBeanClassName() + "' mapperInterface"); } // the mapper interface is the original class of the bean // but, the actual class of the bean is MapperFactoryBean definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59 definition.setBeanClass(this.mapperFactoryBean.getClass()); definition.getPropertyValues().add("addToConfig", this.addToConfig); boolean explicitFactoryUsed = false; if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) { definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionFactory != null) { definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory); explicitFactoryUsed = true; } if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionTemplate != null) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate); explicitFactoryUsed = true; } if (!explicitFactoryUsed) { if (logger.isDebugEnabled()) { logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'."); } definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE); } } }
In this method, the BeanDefinition generated by the doScan method of the parent class is transformed into MapperFactoryBean, and the original beanClass is saved in BeanDefinition as a parameter. MapperFactoryBean is a FactoryBean, and spring will use this FactoryBean to return the proxy of the interface annotated by Mapper. Next, take a look at the getObject method of MapperFactoryBean, which will return the proxy class of the interface
@Override public T getObject() throws Exception { return getSqlSession().getMapper(this.mapperInterface); }
The code in this is called deeply. You can debug the code yourself, but in the end, you use the dynamic proxy of JDK to generate the proxy class, and then the InvocationHandler implementation class to generate the proxy class is MapperProxy