[英]Java - Dynamic Web Project - Global Object
Im interesting in Creating a Global Object which will be shared by all my servlets and all my JSP files. 在创建将由我的所有servlet和我的所有JSP文件共享的全局对象中,我的工作很有趣。 But i dont understand how to do it.
但是我不知道该怎么做。 Please advice.
请指教。
for a senario this object would contain lots of information my servlets and jsp files would like to take information from. 对于senario,此对象将包含很多信息,我的servlet和jsp文件希望从中获取信息。 I know how to pass objects between servlets and jsp's.
我知道如何在servlet和jsp之间传递对象。 But i dont know how to initialize 1 global object for the whole "system" or" website"
但是我不知道如何为整个“系统”或“网站”初始化1个全局对象
<display-name>WebTest1</display-name>
<listener>
<listener-class>listeners.AppListener</listener-class>
</listener>
<welcome-file-list>
<welcome-file>MainPage.html</welcome-file>
<welcome-file>MainPage.htm</welcome-file>
<welcome-file>MainPage.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>SimpleServlet</servlet-name>
<servlet-class>servlets.SimpleServlet</servlet-class>
</servlet>
You should store the object inside application context. 您应该将对象存储在应用程序上下文中。 You can do this when the application starts using
ServletContextListener
. 当应用程序开始使用
ServletContextListener
时,您可以执行此操作。
public AppListener implements ServletContextListener {
public void contextInitialized(ServletContextEvent sce) {
//application is being deployed
//register the "global" object here
ServletContext sc = sce.getServletContext();
MyGlobalClass globalObject = ...
sc.setAttribute("globalObject", globalObject);
}
public void contextDestroyed(ServletContextEvent sce) {
//application is being undeployed
}
}
Register this class as a listener in web.xml: 在web.xml中将此类注册为侦听器:
<listener>
<listener-class>package.where.defined.AppListener</listenerclass>
</listener>
Then you can access to this object in both Servlet and JSPs: 然后,您可以在Servlet和JSP中访问此对象:
Servlet: Servlet:
public void doGet(...) throws ... {
ServletContext servletContext = request.getServletContext();
MyGlobalClass globalObject = (MyGlobalClass)servletContext.getAttribute("globalObject");
//use it...
}
JSP: JSP:
${globalObject.someField}
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