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NullPointerException与JSP / Servlet

[英]NullPointerException with JSP/Servlet

I have my doGet as: 我的doGet为:

protected void doGet(HttpServletRequest request, 
        HttpServletResponse response)
        throws IOException, ServletException{


    String resourceIDstr = request.getParameter("ResourceID");
    int resourceID = Integer.valueOf(resourceIDstr);

    Resource resourceToLend  =  ResourceModule.getInstance()
                                .getResourceByID(Integer.valueOf(resourceID));



    request.setAttribute("resourceToLent", resourceToLend);

    request.setAttribute("innerTab", "LendResource.jsp");
    getServletConfig().getServletContext()
                    .getRequestDispatcher("/WEB-INF/jsp/admin/resourcelend.jsp")
                    .forward(request, response);
}

Whenever I forward any GET request to this servlet, it does not forward request to JSP and instead throws exception as: 每当我将任何GET请求转发到此servlet时,它都不会将请求转发到JSP,而是将异常抛出为:

HTTP Status 500 - org.apache.jasper.JasperException: 
java.lang.NullPointerException

The strange thing is this particular JSP is being used by other servlet without any problem and this particular servlet throws exception. 奇怪的是,这个特定的JSP被其他servlet使用而没有任何问题,并且该特定的servlet引发异常。 I am trying to find the possible causes for the exception. 我正在尝试查找导致异常的可能原因。

Thanks in advance. 提前致谢。

UPDATE: 更新:

org.apache.jasper.JasperException: org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
servlet.TempResourceLendServlet.doGet(TempResourceLendServlet.java:37)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

root cause

org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:954)
org.apache.jsp.WEB_002dINF.jsp.admin.resourcelend_jsp._jspService(resourcelend_jsp.java:114)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
servlet.TempResourceLendServlet.doGet(TempResourceLendServlet.java:37)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

root cause

java.lang.NullPointerException
org.apache.jsp.WEB_002dINF.jsp.admin.LendResource_jsp._jspService(LendResource_jsp.java:84)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:954)
org.apache.jsp.WEB_002dINF.jsp.admin.resourcelend_jsp._jspService(resourcelend_jsp.java:114)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
servlet.TempResourceLendServlet.doGet(TempResourceLendServlet.java:37)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

As asgoth says, you should provide your jsp in the question, rather than the servlet. 正如asgoth所说,您应该在问题中提供jsp,而不是servlet。

Also, your root cause stacktrace contains a line saying 另外,您的根本原因stacktrace包含一行

org.apache.jsp.WEB_002dINF.jsp.admin.resourcelend_jsp._jspService(resourcelend_jsp.java:114)

This refers to the automatially created servlet that your jsp has turned into. 这是指您的jsp变成自动创建的servlet。 You will find this in tomcat's work folder - as it's autogenerate java code, you'll have to do some mapping work, but it should be more or less self-explaining what line 114 refers to in your jsp. 您将在tomcat的工作文件夹中找到它-因为它是自动生成的Java代码,因此您必须做一些映射工作,但是它应该或多或少地自我解释jsp中第114行所指的内容。 With this you can find out the root cause for yourself. 这样您就可以找到自己的根本原因。 (last time I've seen those files, they had some comments that referred to the equivalent jsp code) (上次我看到这些文件时,它们有一些注释引用了等效的jsp代码)

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