struts2 Action生命周期
Struts2.0中的对象既然都是线程安全的,都不是单例模式,那么它究竟何时创建,何时销毁呢?
这个和struts2.0中的配置有关,我们来看struts.properties
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如果我们使用的是com.opensymphony.xwork2.ObjectFactory ,老实说,我也没有研究过,xwork有一套像spring一样的IOC机制,小巧而简洁,有兴趣的朋友可以去研究下。struts2.0中的Action默认就是使用这种工厂模式的,我们来看
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class属性必须写类的全名,通过这种方式配置后,action对象的生命周期到底怎么样,你就认命吧,反正你就记住xwork有一个对象池,它会自己分配的,应对每次客户端的请求,它都会创建一个新的实例,至于这个实例何时销毁,由XWORK来控制。
接下来,我们用spring来控制action的生命周期,关于action和spring的集成,我这里就不累述了。
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这里的class是spring配置文件中bean的id
我们来看看spring文档中关于生命周期这个章节
Table 3.4. Bean scopes
Scope | Description |
---|---|
Scopes a single bean definition to a single object instance per spring IoC Container. |
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Scopes a single bean definition to any number of object instances. |
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Scopes a single bean definition to the lifecycle of a single HTTP request; that is each and every HTTP request will have its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring |
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Scopes a single bean definition to the lifecycle of a HTTP |
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Scopes a single bean definition to the lifecycle of a global HTTP |
是不是一目了然?
当然我们要使用request、session等,必须在web.xml中配置
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准备好这些之后,我们来对request这个scope进行下测试
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配置好后,发现每次刷新页面,都会建立一个新的实例,运行完后就销毁这个实例,这个效果和默认的是一样的,只是我们这个运行完后会立即销毁,而默认的不是立即销毁,由xwork优化销毁
如果设置为session,其实相当于ejb中的状态bean,对于每个session来说用的都是同一个实例,当然,一旦把浏览器关闭,或者超时,对象就会销亡。