Question

我正在尝试将HashMap放到ServletContext对象上，以便我可以从位于不同上下文的war文件中访问它。我还没有尝试从mutliple上下文访问它。我只是试图从同一个servlet访问，我似乎无法获得价值。以下两种方法都返回nullpointerexceptions。

public class TestServlet extends HttpServlet{

private static final long serialVersionUID = -8002515227440283546L;

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException{
    PrintWriter out = response.getWriter();

    HashMap<String ,String> hm = new HashMap<String, String>();
    hm.put("1", "1");

    this.getServletContext().setAttribute("usernamanager", hm);
    this.getServletConfig().getServletContext().setAttribute("usernamanager", hm);  

    HashMap newMap2 = (HashMap) this.getServletConfig().getServletContext().getAttribute("usermanager"); 
    HashMap newMap3 = (HashMap) this.getServletContext().getAttribute("usermanager"); 

    out.println("App1 - " + newMap2.get("1"));
    out.println("App1 - " + newMap3.get("1"));
}
}

servlet部署在Tomcat容器上。

Answer 1

属性名称应匹配：usernamanager vs usermanager

ServletContext - 返回null的应用程序作用域会话对象

1 个答案: