package com.demo.service;

public interface IDemoService {
  String demo();
}

package com.demo.service.impl;

import com.demo.service.IDemoService;
import org.springframework.stereotype.Service;

@Service
public class DemoServiceImpl implements IDemoService {
  @Override
  public String demo() {
    return "Hello World";
  }
}

package com.demo.test;

import com.demo.service.IDemoService;
import com.demo.utils.BeanUtil;

public class Test {
  public void test(){
    //獲取已經(jīng)實例化的接口bean
    IDemoService bean = BeanUtil.getBean(IDemoService.class);
    //執(zhí)行bean中方法
    String demo = bean.demo();
    //輸出結果
    System.out.println(demo);
  }
}

package com.demo.utils;
import org.springframework.context.ConfigurableApplicationContext;

public class BeanUtil {
  //將管理上下文的applicationContext設置成靜態(tài)變量，供全局調(diào)用
  public static ConfigurableApplicationContext applicationContext;
  //定義一個獲取已經(jīng)實例化bean的方法
  public static <T> T getBean(Class<T> c){
    return applicationContext.getBean(c);
  }
}

package com.demo;

import com.demo.test.Test;
import com.demo.utils.BeanUtil;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication()
public class DemoApplication {
  public static void main(String[] args) {
    //run方法的返回值ConfigurableApplicationContext繼承了ApplicationContext上下文接口
    ConfigurableApplicationContext applicationContext = SpringApplication.run(DemoApplication.class, args);
    //將run方法的返回值賦值給工具類中的靜態(tài)變量
    BeanUtil.applicationContext = applicationContext;
    //測試獲取已經(jīng)實例化的接口bean，執(zhí)行bean中方法
    new Test().test();
  }
}

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

@Component
public class SpringContextUtil implements ApplicationContextAware {

  private static ApplicationContext applicationContext;

  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    SpringContextUtil.applicationContext = applicationContext;
  }

  //獲取applicationContext
  public static ApplicationContext getApplicationContext() {
    return applicationContext;
  }

  //通過name獲取 Bean.
  public static Object getBean(String name) {
    return getApplicationContext().getBean(name);
  }

  //通過class獲取Bean.
  public static <T> T getBean(Class<T> clazz) {
    return getApplicationContext().getBean(clazz);
  }

  //通過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);
  }
}

import org.springframework.stereotype.Service;

/**
 * 這是一個單例的bean
 */
@Service
public class BeanSingletonService {
}

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

/**
 * 這是一個多例的bean
 */
@Service
@Scope("prototype")
public class BeanPrototypeService {
}

import com.xqnode.learning.common.config.SpringContextUtil;
import com.xqnode.learning.service.BeanPrototypeService;
import com.xqnode.learning.service.BeanSingletonService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class LearningApplicationTests {
  
  @Test
  public void contextLoads() {
    BeanSingletonService s1 = SpringContextUtil.getBean(BeanSingletonService.class);
    BeanSingletonService s2 = SpringContextUtil.getBean(BeanSingletonService.class);
    BeanPrototypeService p1 = SpringContextUtil.getBean(BeanPrototypeService.class);
    BeanPrototypeService p2 = SpringContextUtil.getBean(BeanPrototypeService.class);
    System.out.println("s1==s2: " + s1.equals(s2));
    System.out.println("p1==p2: " + p1.equals(p2));
  }
}