【SpringBoot3】Bean管理

1.Bean扫描

1.1传统Spring

标签：<context:component-scan base-package="com. example "/>
注解：@ComponentScan(basePackages = "com.example")

1.2SpringBoot

SpringBoot默认扫描启动类所在的包及其子包

2.Bean注册

如果要注册的bean对象来自于第三方（不是自定义的,可能无法修改，则不能为添加注解），是无法用 @Component 及衍生注解声明bean的

解决

2.1@Bean

2.1.1下载jar包

2.1.2导入依赖

2.1.3配置类

如果要注册第三方bean，建议在配置类中集中注册

2.2@Import

2.2.1导入配置类

2.2.2导入 ImportSelector 接口实现类

package com.aaa.config;

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

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class CommonImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        //读取配置文件的内容
        List<String> imports = new ArrayList<>();
        InputStream is = CommonImportSelector.class.getClassLoader().getResourceAsStream("common.imports");
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String line = null;
        try {
            while((line = br.readLine())!=null){
                imports.add(line);
            }

        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            if (br!=null){
                try {
                    br.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
        return imports.toArray(new String[0]);
    }
}