一后处理机制实现方式

代码

package com.qing.config;

import com.qing.sevice.impl.BookServiceImpl2;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;

public class MyPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        //注册一个bean
        BeanDefinition beanDefinition= BeanDefinitionBuilder.
                rootBeanDefinition(BookServiceImpl2.class).
                getBeanDefinition();
        //beanDefinition可以设置单例啥的
        registry.registerBeanDefinition("bookService",beanDefinition);
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {

    }
}

import

package com.qing.config;


import org.springframework.context.annotation.Import;


@Import({MyPostProcessor.class})
public class SpringConfig8 {

}

测试

package com.qing.app;

import com.qing.config.SpringConfig8;
import com.qing.sevice.BookService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App8 {
    public static void main(String[] args) {

        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig8.class);
        
        BookService bookService= ctx.getBean("bookService", BookService.class);
        bookService.check();

    }
}

结果

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二 import导入加载顺序比较

MyDefinitionRegistrar加载BookServiceImpl1

package com.qing.config;


import com.qing.sevice.impl.BookServiceImpl1;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

public class MyDefinitionRegistrar implements ImportBeanDefinitionRegistrar {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
        //metadata 元数据的用法同动态加载bean
        BeanDefinition beanDefinition= BeanDefinitionBuilder.
                rootBeanDefinition(BookServiceImpl1.class).
                getBeanDefinition();
        //beanDefinition可以设置单例啥的
        registry.registerBeanDefinition("bookService",beanDefinition);
    }
}

后处理机制MyPostProcessor加载BookServiceImpl2

package com.qing.config;

import com.qing.sevice.impl.BookServiceImpl2;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;

public class MyPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        //注册一个bean
        BeanDefinition beanDefinition= BeanDefinitionBuilder.
                rootBeanDefinition(BookServiceImpl2.class).
                getBeanDefinition();
        //beanDefinition可以设置单例啥的
        registry.registerBeanDefinition("bookService",beanDefinition);
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {

    }
}

ImportSelector加载BookServiceImpl3

package com.qing.config;

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata metadata) {
  

        return new String[]{"com.qing.sevice.impl.bookServiceImpl3"};
    }
}

package com.qing.sevice.impl;

import com.qing.sevice.BookService;
import org.springframework.stereotype.Service;

@Service("bookService")
public class BookServiceImpl3 implements BookService {

    @Override
    public void check() {
        System.out.println("book service 3..");
    }
}

import

package com.qing.config;


import org.springframework.context.annotation.Import;


@Import({MyImportSelector.class,MyPostProcessor.class,MyDefinitionRegistrar.class,})
public class SpringConfig8 {

}

测试

package com.qing.app;

import com.qing.config.SpringConfig8;
import com.qing.sevice.BookService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App8 {
    public static void main(String[] args) {

        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig8.class);
        BookService bookService= ctx.getBean("bookService", BookService.class);
        bookService.check();

    }
}

因为bean的名字都是bookService,所以会覆盖,猜猜最后会是哪一个实现类?

会是写在最后面MyDefinitionRegistrar加载的BookServiceImpl1 吗?