spring ioc 泛型保留，

spring ioc 泛型保留

在上一篇中,说到spring中并不能自动注入泛型，如何生成泛型类型已经讲的很清楚了，在本篇着重讲在spring中如何自动注入。

环境

这里所有代码基于如下环境，如有出入请参考当前环境。

java version "1.8.0_201"
Java(TM) SE Runtime Environment (build 1.8.0_201-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)

 implementation 'org.aspectj:aspectjweaver:1.9.2' 
 implementation "org.springframework:spring-context:5.1.9.RELEASE" 
 implementation 'org.javassist:javassist:3.25.0-GA' 

方法一

通过实现org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor和org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor 自定义bean泛型的注入

MainConfig.java

 @Configuration
public class MainConfig
{

     @Bean
    public static MyBeanFactoryPostProcessor newMyBeanFactoryPostProcessor()
    {
        return new MyBeanFactoryPostProcessor();
    }
....

MyBeanFactoryPostProcessor.java

public class MyBeanFactoryPostProcessor implements BeanDefinitionRegistryPostProcessor
{

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException
    {
        System.out.println("beanFactory=" + beanFactory);
         beanFactory.addBeanPostProcessor(new MyBeanPostProcessor(beanFactory));

    }
...

MyBeanPostProcessor.java

public class MyBeanPostProcessor implements InstantiationAwareBeanPostProcessor
{
    public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException
    {
        // System.out.println("创建类:" + beanClass);
        List<Field> fields = new ArrayList<>();
        for (Field field : beanClass.getDeclaredFields())
        {
            if (field.getAnnotation(Autowired.class) != null && MyProvider.class.isAssignableFrom(field.getType()))
            {
                Type type = field.getGenericType();
                if (type != null && type instanceof ParameterizedType)
                {
                    fields.add(field);
                }
            }
        }
        if (!fields.isEmpty())
        {
            //创建bean，请参考上一篇文章
            ....
        }
        return null;
    }
...

输出结果如下:

beanFactory=org.springframework.beans.factory.support.DefaultListableBeanFactory@51081592: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,main,mainConfig,baseProvider,myAspect,testService,testService2,newMyBeanFactoryPostProcessor,newBeanConfig,org.springframework.aop.config.internalAutoProxyCreator]; root of factory hierarchy
service=test.spring.service.TestService2@1817d444
superclass=test.spring.provider.MyProvider<test.spring.model.User>
userProviderFieldType=[]
ResolvableType=test.spring.service.TestService2