Using Scoped Beans

Bean的Scope

Spring支持的Scope有： * singleton: 默认scope
* prototype
* thread
* request
* session
* globalSession
* application

在定义Bean的地方添加org.springframework.context.annotation.Scopeannotation，为定义的Bean指定不同的Scope。该annotation可以用在type-level和method-level上。
* type-level: 该类型的所有的Bean都是指定的Scope
* method-level： 当前方法所定义的Bean是指定的Scope

Scope Annotation的属性：
* value： 指定Bean的scope类型
* proxyModel： 指定是否需要proxy以及proxy的机制。ScopedProxyModel.TARGET_CLASS用于指定该Bean所对应的类型没有接口，需要默认值是NO

Example of session scope

配置session scope的Bean 
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 package com.apress.prospringmvc.bookstore.web.config;
  //Other imports omitted
  import org.springframework.context.annotation.Scope;
  import org.springframework.context.annotation.ScopedProxyMode;
  import com.apress.prospringmvc.bookstore.domain.Cart;
  @Configuration
  @EnableWebMvc
  @ComponentScan(basePackages =      { "com.apress.prospringmvc.bookstore.web" })
public class WebMvcContextConfiguration extends WebMvcConfigurerAdapter {
//Other methods omitted
@Bean
@Scope(value = "session", proxyMode = ScopedProxyMode.TARGET_CLASS)
  
public Cart cart() {
        return new Cart();
    }
}

使用SessionStatus管理session scope bean的状态

SessionStatus实例 
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 @RequestMapping(method = RequestMethod.POST, params = "order")      
 public String checkout(SessionStatus status,@Validated @ModelAttribute Order order,
                           BindingResult errors) {
        if (errors.hasErrors()) {
            return "cart/checkout";
        } else {
            this.bookstoreService.store(order);
            status.setComplete(); //remove order from session
            this.cart.clear(); // clear the cart
            return "redirect:/index.htm";
      }
}
Java, Spring @MVC
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