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Spring Boot Bean Spring Boot中Bean定义方调用方式解析

BarryW 人气:0

我们知道如果我们要在一个类使用spring提供的bean对象,我们需要把这个类注入到spring容器中,交给spring容器进行管理,但是在实际当中,我们往往会碰到在一个普通的Java类中,想直接使用spring提供的其他对象或者说有一些不需要交给spring管理,但是需要用到spring里的一些对象。如果这是spring框架的独立应用程序,我们通过

ApplicationContextac=newFileSystemXmlApplicationContext("applicationContext.xml");
ac.getBean("beanId");

这样的方式就可以很轻易的获取我们所需要的对象。

但是往往我们所做的都是WebApplication,这时我们启动spring容器是通过在web.xml文件中配置,这样就不适合使用上面的方式在普通类去获取对象了,因为这样做就相当于加载了两次spring容器,而我们想是否可以通过在启动web服务器的时候,就把Application放在某一个类中,我们通过这个类在获取,这样就可以在普通类获取springbean对象了,让我们接着往下看

下面介绍在SpringBoot中是如何使用的

1.在Spring Boot可以扫描的包下

写的工具类为SpringUtil,实现ApplicationContextAware接口,并加入Component注解,让spring扫描到该bean

springutil:

package me.shijunjie.util;

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(SpringUtil.applicationContext == null) {
      SpringUtil.applicationContext = applicationContext;
    }
    System.out.println("---------------------------------------------------------------------");

    System.out.println("---------------------------------------------------------------------");

    System.out.println("---------------me.shijunjie.util.SpringUtil------------------------------------------------------");

    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+"========");

    System.out.println("---------------------------------------------------------------------");
  }

  //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);
  }
}

为了测试,我们再启动的时候先通过代码方式给spring容器中注入一个bean,入下所示

package me.shijunjie.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import me.shijunjie.entity.Demo2;

@Configuration
public class BeanConfig {
  @Bean(name="testDemo")
  public Demo2 generateDemo() {
    Demo2 demo = new Demo2();
    demo.setId(12345);
    demo.setName("test");
    return demo;
  }
}

然后我们编写测试controller,并从刚才写的springutil中获取这个bean

package me.shijunjie.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import me.shijunjie.util.SpringUtil;

@RestController
@RequestMapping("/application")
public class TestApplicationController {
  
  @RequestMapping("/test1")
  public Object testSpringUtil1() {
    return SpringUtil.getBean("testDemo");
  }
  
}

测试

启动web应用,打开浏览器输入http://localhost:8080/application/test1,测试成功

2不在Spring Boot的扫描包下

这种情况处理起来也很简单,先编写SpringUtil类,同样需要实现接口:ApplicationContextAware,具体编码如下:

package me.shijunjie.util;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class SpringUtil2 implements ApplicationContextAware {

  private static ApplicationContext applicationContext;

  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    if(SpringUtil2.applicationContext == null) {
      SpringUtil2.applicationContext = applicationContext;
    }
    System.out.println("---------------------------------------------------------------------");

    System.out.println("---------------------------------------------------------------------");

    System.out.println("---------------me.shijunjie.util.SpringUtil------------------------------------------------------");

    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="+SpringUtil2.applicationContext+"========");

    System.out.println("---------------------------------------------------------------------");
  }

  //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);
  }

}

使用@Bean注解,在App.java类中将SpringUtil注解进

package me.shijunjie.controller;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.scheduling.annotation.EnableScheduling;

import me.shijunjie.util.SpringUtil2;

@ComponentScan(basePackages={"me.shijunjie"}) // 扫描该包路径下的所有spring组件
/*@EnableJpaRepositories("me.shijunjie.dao") // JPA扫描该包路径下的Repositorie
*//*@EntityScan("me.shijunjie.entity") // 扫描实体类
*/@SpringBootApplication
@EnableScheduling
public class App extends SpringBootServletInitializer{
  @Bean
  public SpringUtil2 getSpringUtil2() {
    return new SpringUtil2();
  }
  
  public static void main(String[] args) {
    SpringApplication.run(App.class, args);
  }
}

测试(使用热部署的需要重启服务器)

启动web应用,打开浏览器输入http://localhost:8080/application/test2,测试成功

除此以外,也可以在App.java中使用@Import进行导入。

package me.shijunjie.controller;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import org.springframework.scheduling.annotation.EnableScheduling;

import me.shijunjie.util.SpringUtil2;

@ComponentScan(basePackages={"me.shijunjie"}) // 扫描该包路径下的所有spring组件
/*@EnableJpaRepositories("me.shijunjie.dao") // JPA扫描该包路径下的Repositorie
*//*@EntityScan("me.shijunjie.entity") // 扫描实体类
*/@SpringBootApplication
@EnableScheduling
@Import(SpringUtil2.class)
public class App extends SpringBootServletInitializer{
  /*@Bean
  public SpringUtil2 getSpringUtil2() {
    return new SpringUtil2();
  }*/
  
  public static void main(String[] args) {
    SpringApplication.run(App.class, args);
  }
}

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