Spring scans the class corresponding to the custom annotation and loads it into the IOC container

Deng Bencheng 2020-11-09 22:19:35
spring scans class corresponding custom


This article follows the author's study mybatis After the source , Modelled on the mybatis utilize spring The expansion point of will be Mapper Interface proxy class loading IOC Methods , Implement custom annotations , Give Way spring Assemble the class with this annotation in the specified package into IOC Containers to manage , It ends up in a singleton pool of containers .


1. Custom annotation

public @interface XxgComponent {

2. XxgComponentScannerConfigurer

2.1 Realization BeanDefinitionRegistryPostProcessor

BeanDefinitionRegistryPostProcessor, yes spring Give us an expansion point , It inherits itself from BeanFactoryPostProcessor Interface .
The class that implements this interface ,spring After initialization , It will call the following two methods :

void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry var1) throws BeansException;
void postProcessBeanFactory(ConfigurableListableBeanFactory var1) throws BeansException;

So we can use the corresponding method of its implementation class , Execute our business logic -- That is to let spring Scan the class corresponding to our custom annotation .

2.2 Code

public class XxgComponentScannerConfigurer implements BeanDefinitionRegistryPostProcessor {
private String basePackages;
public void setBasePackages(String basePackages) {
this.basePackages = basePackages;
public void postProcessBeanFactory(ConfigurableListableBeanFactory factory) throws BeansException {
// left intentionally blank
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
XxgComponentScanner scanner = new XxgComponentScanner(registry);

3. Scanning class XxgComponentScanner

3.1 ClassPathBeanDefinitionScanner

This is spring For scanning bean Class ,

  1. Its doScan() Method according to the interceptor rules configured , To assemble the required classes into BeanDefinitionHolder Object and return .
  2. Call its scan() Method , It calls first doScan() Method , And then it will scan BeanDefinitionHolder Objects in the IOC Containers

so , We can inherit its class , then :

  1. Do not use its default interception rules , It's based on our custom annotations to intercept
  2. Rewrite it doScan() Method , First call the parent class's doScan() Get the... With our custom annotation BeanDefinitionHolder The objects , Then you can traverse the operation , Change some of the parameters we need , Setting up scope For single example, etc .

3.2 Code

public class XxgComponentScanner extends ClassPathBeanDefinitionScanner {
public XxgComponentScanner(BeanDefinitionRegistry registry) {
// The second parameter :useDefaultFilters
// Set to false, Do not use default interceptors
super(registry, false);
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
// utilize spring Scanning method of , scanning mapper The package where the interface is located , Get all BeanDefinitionHolder
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
return beanDefinitions;
private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitionHolders) {
for (BeanDefinitionHolder holder : beanDefinitionHolders) {
GenericBeanDefinition beanDefinition = (GenericBeanDefinition)holder.getBeanDefinition();
// Define interceptors , Give Way spring Assemble the objects we need to IOC Containers
public void registerFilters() {
// Set up Only scanning has @XxgComponent Annotated classes
addIncludeFilter(new AnnotationTypeFilter(XxgComponent.class));
// Set up Ignore package-info.java addExcludeFilter((metadataReader, metadataReaderFactory) -> {
String className = metadataReader.getClassMetadata().getClassName();
return className.endsWith("package-info");

4. Give Way spring Managing our XxgComponentScannerConfigurer

<!-- Test custom assembly bean annotation -->
<bean class="com.dbc.springMybatis.util.XxgComponentScannerConfigurer">
<property name="basePackages" value="com.dbc.springMybatis.myBean"/>
本文为[Deng Bencheng]所创,转载请带上原文链接,感谢

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