SpringBoot @Bean注解

末蓝、 2023-02-28 05:27 21阅读 0赞

SpringBoot中，我们可以使用@Bean将自定义的一个类注入到spring容器中，让spring容器去管理bean,其相当于之前的配置文件中的<bean id="" class=""/>

直接贴代码，我们先建立一个配置类，类似之前的配置xml,然后在其中将自己的bean交给spring去管理。

package com.mayun.study.config;
    
    import com.mayun.study.bean.Monster;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.Scope;
    
    @Configuration
    public class BeanConfig {
        @Bean
        public Monster monster(){
            return new Monster();
        }
    }

当然，Monster类是我们自定义的

package com.mayun.study.bean;
    
    public class Monster {
    
        private Integer id = 10 ;
        private String nickname = "牛魔王";
        private String skill = "芭蕉扇";
        public Monster() {
    
            System.out.println("monster 创建..");
        }
        public Monster(Integer id, String nickname, String skill) {
            //System.out.println("Integer id, String nickname, String skill被调用");
            this.id = id;
            this.nickname = nickname;
            this.skill = skill;
        }
    
        public Monster( String nickname, String skill,Integer id) {
    
            this.id = id;
            this.nickname = nickname;
            this.skill = skill;
        }
        public Integer getId() {
            return id;
        }
        public void setId(Integer id) {
            this.id = id;
        }
        public String getNickname() {
            return nickname;
        }
        public void setNickname(String nickname) {
            this.nickname = nickname;
        }
        public String getSkill() {
            return skill;
        }
        public void setSkill(String skill) {
            this.skill = skill;
        }
        @Override
        public String toString() {
            return "Monster [id=" + id + ", nickname=" + nickname + ", skill="
                    + skill + "]";
        }
    
    
    }

这样Monster这个类就交给spring容器去管理了，那么怎么取呢

第一种：直接在其他需要的类中使用注解@Autowired注入

第二种：比较原始的，手动从spring容器中获取：

这里编写一个获取的工具类（网上直接拿过来的）

package com.mayun.study.common;
    
    import org.springframework.beans.BeansException;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    import org.springframework.stereotype.Component;
    
    @Component
    public class SpringUtil implements ApplicationContextAware {
        private static ApplicationContext applicationContext;
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            if (null == SpringUtil.applicationContext) {
                SpringUtil.applicationContext = applicationContext;
            }
            System.out.println("========ApplicationContext配置成功,在普通类可以通过调用SpringUtils.getAppContext()获取applicationContext对象,applicationContext="+SpringUtil.applicationContext+"========");
        }
    
        //获取applicationContext
        public static ApplicationContext getApplicationContext() {
            return applicationContext;
        }
    
        //通过name获取 Bean.
        public static Object getBean(String name){
            return getApplicationContext().getBean(name);
        }
    
        //通过class获取Bean.
        public static <T> T getBean(Class<T> clazz){
            return getApplicationContext().getBean(clazz);
        }
    
        //通过name,以及Clazz返回指定的Bean
        public static <T> T getBean(String name,Class<T> clazz){
            return getApplicationContext().getBean(name, clazz);
        }
    
    
    }

然后直接在测试类中使用工具类获得这个bean

package com.mayun.study.controller;
    
    import com.mayun.study.bean.Monster;
    import com.mayun.study.common.SpringUtil;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class TestController {
    
    
    
    //    @Autowired
    //    Monster monster;
    
        @GetMapping("/application")
        public String application(){
            Monster monster = (Monster) SpringUtil.getBean("monster");
            monster.setNickname("sssssss");
    
            Monster monster1 = (Monster) SpringUtil.getBean("monster");
            System.out.println(monster + "hascode==" + monster.hashCode());
            System.out.println(monster1 + "hascode==" + monster1.hashCode());
            return "hello world";
        }
    }