springboot定义bean的几种实现方式

1.@bean

@bean
public demoservice demoservice() {
  return new demoservice();
}

2.@component

@component
public class demoservice {
}

3.@controller、@restcontroller、@service、@repository

@restcontroller
public class democontroller{
  @getmapping("/test")
  public string test() {
      return "succeed";
  }
}

4.@controlleradvice、@restcontrolleradvice

import org.springframework.core.methodparameter;
import org.springframework.http.mediatype;
import org.springframework.http.server.serverhttprequest;
import org.springframework.http.server.serverhttpresponse;
import org.springframework.web.bind.annotation.controlleradvice;
import org.springframework.web.servlet.mvc.method.annotation.responsebodyadvice;
/**
 * 
 @title democontrolleradvice
 * 
 @description controller增强
 *
 * @author acgkaka
 * @date 2023/4/25 21:07
 */
@controlleradvice
public class democontrolleradvice implements responsebodyadvice {
    @override
    public boolean supports(methodparameter methodparameter, class aclass) {
        return true;
    }
    @override
    public object beforebodywrite(object body, methodparameter methodparameter, mediatype mediatype, class aclass, serverhttprequest serverhttprequest, serverhttpresponse serverhttpresponse) {
        system.out.println("body is: " + body);
        return body;
    }
}

注意：@controlleradvice相当于对于controller的切面，可以绑定propertyeditor。

（类似于aop，但是底层不是aop实现。）

5.@configuration

@configuration
public class democonfig {
}

注意：@configuration 主要标识一个bean是一个配置bean，利用这个bean可以对spring进行配置，比如扫描路径、定义其他的bean。

6.@import

@springbootappilcation
@import(demo.class)
public class myapplication {
  public static void main(string[] args) {
      springapplication.run(myapplication.class);
  }
}

7.beandefinition

这是我们其他所有方法的底层实现。

myapplication.java

@springbootapplication
@import(demoimportbeandefinitionregistrar.class)
public class myapplication {
  public static void main(string[] args) {
      springapplication.run(myapplication.class);
  }
}

demoimportbeandefinitionregistrar.java

import com.demo.service.demoservice;
import org.springframework.beans.factory.support.abstractbeandefinition;
import org.springframework.beans.factory.support.beandefinitionbuilder;
import org.springframework.beans.factory.support.beandefinitionregistry;
import org.springframework.beans.factory.support.beannamegenerator;
import org.springframework.context.annotation.importbeandefinitionregistrar;
import org.springframework.core.type.annotationmetadata;
/**
 * 
 @title demoimportbeandefinationregistar
 * 
 @description @import注解的实现类
 *
 * @author acgkaka
 * @date 2023/4/25 21:18
 */
public class demoimportbeandefinitionregistrar implements importbeandefinitionregistrar {
    @override
    public void registerbeandefinitions(annotationmetadata importingclassmetadata, beandefinitionregistry registry, beannamegenerator importbeannamegenerator) {
        abstractbeandefinition beandefinition = beandefinitionbuilder.genericbeandefinition().getbeandefinition();
        // 定义bean
        beandefinition.setbeanclass(demoservice.class);
        // 注册bean
        registry.registerbeandefinition("demoservice", beandefinition);
    }
}

8.

最古老的方式

@springbootapplication
@importresource("classpath:spring.xml")
public class myapplication {
  public static void main(string[] args) {
      springapplication.run(myapplication.class);
  }
}

spring.xml

<!--?xml version="1.0" encoding="utf-7"