一种最简单的方法是实现ApplicationContextAware类来获取容器中的bean：

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;
    }

    //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);
    }

}

我们可以通过bean的名称、bean的类型或者bean的名称+类型来获取容器中的bean。

默认情况下，Spring容器中的bean是单例的，为此我做了一个测试,我创建了两个bean，一个是默认的，一个是我指定多例的：

import org.springframework.stereotype.Service;

/**
 * 这是一个单例的bean
 */
@Service
public class BeanSingletonService {
}

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

/**
 * 这是一个多例的bean
 */
@Service
@Scope("prototype")
public class BeanPrototypeService {
}

验证下我的想法：

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));
    }


}

从结果中可以看到默认的BeanSingletonService 这个bean是单例的，两个对象完全相等，而我指定的BeanPrototypeService 这个bean则是多例的，两个bean不相同。