SpringBoot复习：（24）DeferredImportSelector

功能： 定一一个字符串数组，每个元素都是一个类的全限定名（包名+类名），把这些类的实例注册到Spring 容器。
一、定义要注册的类：

package cn.edu.tju.service;

import java.util.Arrays;
import java.util.List;

public class MusicService {
    public List getComposerList(){
        return Arrays.asList("Mozart", "Chopin");
    }
}

二、定义类实现DeferredImportSelector

package cn.edu.tju.config;

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

import java.util.ArrayList;
import java.util.List;


public class MyDeferredImportSelector implements DeferredImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        //return new String[]{"cn.edu.tju.service.MusicService"};
        return new String[0];
    }

    @Override
    public Class getImportGroup() {
        return MyGroup.class;
    }

    private static class MyGroup implements DeferredImportSelector.Group{
        AnnotationMetadata metadata;

        @Override
        public void process(AnnotationMetadata metadata, DeferredImportSelector selector) {
            this.metadata = metadata;
        }

        @Override
        public Iterable selectImports() {
            List list = new ArrayList<>();
            list.add(new Entry(this.metadata, "cn.edu.tju.service.MusicService"));
            return list;
        }
    }
}

三、在配置类中配置自定义的DeferredImportSelector

package cn.edu.tju.config;


import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

import java.io.IOException;
import java.io.Reader;

import static org.apache.ibatis.io.Resources.getResourceAsReader;

@Configuration
@Import({MyDeferredImportSelector.class})

public class MyConfig {

}

四、从容器中获取通过DeferredImportSelector注册的bean

package cn.edu.tju;

import cn.edu.tju.mapper.StudentMapper;
import cn.edu.tju.service.DemoService;
import cn.edu.tju.service.MusicService;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

@SpringBootApplication
public class Start {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Start.class, args);
        MusicService musicService = context.getBean(MusicService.class);

        System.out.println(musicService.getComposerList());


    }
}