概述
通过Spring管理的类,默认是单例模式,但是如果有的类需要使用独立的属性,则需要配置为多例模式的.
但是多例模式不仅仅只是加一个声明,使用@Autowired进行注入,可能并不会是你想要的结果.因为多例模式的类是需要单独调用的.
不搞清楚原理直接撸
需要多例的类上加上注解@Scope("prototype")
@Component
@Scope("prototype")
public class ExampleService{
public void test(){
System.out.println("test,current bean is" + this);
}
}
引用直接使用@Autowired
@Controller
public class ExampleService{
@Autowired
private ExampleService exampleService;
@RequestMapping("test")
public void test(){
exampleService.test();
}
}
结果:
每个request过来的时候,exampleService实例均为同一个实例.
解决办法
不使用@Autowired
@Controller
public class ExampleService{
@Autowired
private org.springframework.beans.factory.BeanFactory beanFactory;
@RequestMapping("test")
public void test(){
ExampleService exampleService = beanFactory.getBean(ExampleService.class);
exampleService.test();
}
}
官方文档说明
4.5.3 Singleton beans with prototype-bean dependencies When you use singleton-scoped beans with dependencies on prototype beans, be aware that dependencies are resolved at instantiation time. Thus if you dependency-inject a prototype-scoped bean into a singleton-scoped bean, a new prototype bean is instantiated and then dependency-injected into the singleton bean. The prototype instance is the sole instance that is ever supplied to the singleton-scoped bean. However, suppose you want the singleton-scoped bean to acquire a new instance of the prototype-scoped bean repeatedly at runtime. You cannot dependency-inject a prototype-scoped bean into your singleton bean, because that injection occurs only once, when the Spring container is instantiating the singleton bean and resolving and injecting its dependencies. If you need a new instance of a prototype bean at runtime more than once, see Section 4.4.6, “Method injection”
