Spring底层原理(四)
本章内容
模拟实现Spring中的几个常见BeanFactory后置处理器
常见的BeanFactory后置处理器
java
GenericApplicationContext context = new GenericApplicationContext();
context.registerBean("config",Config.class);
context.registerBean(ConfigurationClassPostProcessor.class);//解析@ComponentScan @Bean @Import @ImportResource
ontext.registerBean(MapperScannerConfigurer.class,bd->{
bd.getPropertyValues().add("basePackage","com.vmware.mapper");
});
//初始化容器
context.refresh();
for (String name : context.getBeanDefinitionNames()) {
System.out.println(name);
}
context.close();ConfigurationClassPostProcessor:解析@ComponentScan@Bean@Import@ImportResourceMapperScannerConfigurer:解析@Mapper
模拟实现组件扫描
- 创建一个
BeanFactoryPostProcessor的实现类
java
public class ComponentScanPostProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
ComponentScan componentScan = AnnotationUtils.findAnnotation(Config.class, ComponentScan.class);
try {
if (componentScan != null) {
for (String basePackage : componentScan.basePackages()) {
System.out.println(basePackage);
String path = "classpath*:" + basePackage.replace(".", "/") + "/**/*.class";
System.out.println(path);
//用于获取元数据的工具类
CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
//用于生成bean名称的工具
AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();
Resource[] resources = new PathMatchingResourcePatternResolver().getResources(path);
for (Resource resource : resources) {
MetadataReader metadataReader = factory.getMetadataReader(resource);//根据resource获取元数据读取器
AnnotationMetadata annotationMetadata = metadataReader.getAnnotationMetadata();
// ClassMetadata classMetadata = metadataReader.getClassMetadata();
// System.out.println("类名:" + classMetadata.getClassName());
// //判读是否有注解@Component
// boolean hasComponent = metadataReader.getAnnotationMetadata().hasAnnotation(Component.class.getName());
// System.out.println("包含注解Component:" + hasComponent);
// boolean hasMetaAnnotation = metadataReader.getAnnotationMetadata().hasMetaAnnotation(Component.class.getName());
// System.out.println("元注解中包含Component:"+hasMetaAnnotation);
if (annotationMetadata.hasAnnotation(Component.class.getName()) || annotationMetadata.hasMetaAnnotation(Component.class.getName())) {
//构建beanDefinition对象
AbstractBeanDefinition bd = BeanDefinitionBuilder.genericBeanDefinition(metadataReader.getClassMetadata().getClassName()).getBeanDefinition();
if (configurableListableBeanFactory instanceof DefaultListableBeanFactory) {
//获取容器
DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) configurableListableBeanFactory;
//生成bean name
String name = generator.generateBeanName(bd, beanFactory);
//注册bean
beanFactory.registerBeanDefinition(name, bd);
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}-
注册该后置处理器
javacontext.registerBean(ComponentScanPostProcessor.class);
模拟实现@Bean
java
public class AtBeanPostProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
try {
CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
MetadataReader reader = factory.getMetadataReader(new ClassPathResource("com/vmware/a5/Config.class"));
Set<MethodMetadata> methods = reader.getAnnotationMetadata().getAnnotatedMethods(Bean.class.getName());
for (MethodMetadata method : methods) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition();
//Bean的名称由方法名生成，除此之外还需要一个工厂Bean对象
builder.setFactoryMethodOnBean(method.getMethodName(), "config");
builder.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
AbstractBeanDefinition bd = builder.getBeanDefinition();
if (configurableListableBeanFactory instanceof DefaultListableBeanFactory) {
DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) configurableListableBeanFactory;
beanFactory.registerBeanDefinition(method.getMethodName(), bd);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}模拟实现Mapper扫描
java
public class MapperPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanFactory) throws BeansException {
try {
PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
Resource[] resources = resolver.getResources("classpath:com/vmware/a5/mapper/**/*.class");
AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();
CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
for (Resource resource : resources) {
MetadataReader reader = factory.getMetadataReader(resource);
//获取类元数据
ClassMetadata classMetadata = reader.getClassMetadata();
//过滤接口类型
if (classMetadata.isInterface()){
AbstractBeanDefinition bd = BeanDefinitionBuilder.genericBeanDefinition(MapperFactoryBean.class)
.addConstructorArgValue(classMetadata.getClassName())//构造方法需要对应的接口字节码
.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE)//需要对MapperFactory进行注入
.getBeanDefinition();
//根据接口名称重新生成一个bean，仅用于生成mapper的名称，否则所有名称都是MapperFactoryBean
AbstractBeanDefinition bd2 = BeanDefinitionBuilder.genericBeanDefinition(classMetadata.getClassName()).getBeanDefinition();
String name = generator.generateBeanName(bd2, beanFactory);
beanFactory.registerBeanDefinition(name,bd);
}
}
}catch (Exception e){
e.printStackTrace();
}
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
}
}- 将Mapper封装成
MapperFactoryBean类型，然后注册到容器中