why am I receiving NullPointerException on my jsp file?

Question

Once I click on a anchor tag on my jsp page, it perfectly works but the following exception will be thrown in console, based on this answer, I removed the jap-api*.jar files from my dependencies folder but the application still throws the exception.

   WARNING:   Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
    at org.apache.jsp.products.ProductShow_jsp._jspx_meth_c_if_1(ProductShow_jsp.java:211)
    at org.apache.jsp.products.ProductShow_jsp._jspService(ProductShow_jsp.java:119)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:875)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:739)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:695)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:626)
    at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:977)
    at org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:701)
    at org.apache.tiles.request.jsp.JspRequest.doInclude(JspRequest.java:123)
    at org.apache.tiles.request.AbstractViewRequest.dispatch(AbstractViewRequest.java:47)
    at org.apache.tiles.request.render.DispatchRenderer.render(DispatchRenderer.java:45)
    at org.apache.tiles.request.render.ChainedDelegateRenderer.render(ChainedDelegateRenderer.java:68)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:259)
    at org.apache.tiles.TilesContainerWrapper.render(TilesContainerWrapper.java:108)
    at org.apache.tiles.template.InsertAttributeModel.renderAttribute(InsertAttributeModel.java:188)
    at org.apache.tiles.template.InsertAttributeModel.execute(InsertAttributeModel.java:132)
    at org.apache.tiles.jsp.taglib.InsertAttributeTag.doTag(InsertAttributeTag.java:299)
    at org.apache.jsp.baseLayout_jsp._jspx_meth_tiles_insertAttribute_3(baseLayout_jsp.java:166)
    at org.apache.jsp.baseLayout_jsp._jspService(baseLayout_jsp.java:93)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:875)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:739)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:575)
    at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:546)
    at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:428)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:378)
    at org.apache.tiles.request.servlet.ServletRequest.forward(ServletRequest.java:265)
    at org.apache.tiles.request.servlet.ServletRequest.doForward(ServletRequest.java:228)
    at org.apache.tiles.request.AbstractClientRequest.dispatch(AbstractClientRequest.java:57)
    at org.apache.tiles.request.render.DispatchRenderer.render(DispatchRenderer.java:45)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:259)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:397)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:238)
    at org.apache.tiles.TilesContainerWrapper.render(TilesContainerWrapper.java:103)
    at org.apache.tiles.impl.mgmt.CachingTilesContainer.render(CachingTilesContainer.java:126)
    .....
WARNING:   Servlet.service() for servlet jsp threw exception
java.io.IOException: JSPException including path '/products/Product.jsp'.
    at org.apache.tiles.request.servlet.ServletUtil.wrapServletException(ServletUtil.java:61)
    at org.apache.tiles.request.jsp.JspRequest.doInclude(JspRequest.java:125)
    at org.apache.tiles.request.AbstractViewRequest.dispatch(AbstractViewRequest.java:47)
    at org.apache.tiles.request.render.DispatchRenderer.render(DispatchRenderer.java:45)

Code

<div id="product">
    <table>
        <tbody>
            <tr><td>ID:${product.id}</td></tr>
            .....
        </tbody>
    </table>


    <sec:authorize access="hasAnyRole('ROLE_ADMIN')">
        <c:if test="${product.available}">
            <s:if test="%{availability > 1}">
                <a href="" onclick="remove(${product.ID})">Remove</a>
            </s:if>
            <s:else>
                <c:if test="${cookie.containsKey('id')}">
                    <a href="" onclick="add(${product.ID})">Add</a>
                </c:if>
                <c:if test="${!cookie.containsKey('id')}">
                    <a href="index.jsp">index</a>
                </c:if>

            </s:else>
       </c:if>


    </sec:authorize>

</div>

Remove and Add are associated to their own javascript functions, both functions perfectly work but the exceptions will be thrown and after returning from javascript functions the page shows correct results.

@gumenimeda sure, question is updated. – AlexCartio1 Feb 28 '14 at 04:50 — AlexCartio1, Feb 28 '14 at 04:50

score 4 · Answer 1 · answered Feb 28 '14 at 05:27

4

You can actually figure this out yourself with a little work. JSPs are compiled into servlets and the source code can be found under your web server's works folder. Generally, find the 'work' folder and then drill down thru the packages, which for Tomcat is usually org.apache.... (sorry can't remember the exact and this machine doesn't have Tomcat installed). Just drill down and you should find ProductShow_jsp.java source code. Goto the line number specified and you can generally figure out the reason for the exception.

answered Feb 28 '14 at 05:27

mikemil

1,213
10
21

thanks, it seems the problem is caused by but even after removing this condition from my jsp, cleaning and re-running the application, it throws the same exception on the same line of java file. – AlexCartio1 Feb 28 '14 at 05:46
Did you delete the work and temp folders before restarting. Sometimes that helps - to ensure the jsp gets recompiled. – mikemil Feb 28 '14 at 05:48
I removed the folder, and rebuild the application but same exception is thrown! – AlexCartio1 Feb 28 '14 at 05:51

score 1 · Answer 2 · answered Feb 28 '14 at 05:14

1

Please check if the below suggestions gets rid of the error:

a) Check if product.id or product.ID is defined

b) Check if the attribute name is correct for product.available

c) Add the closing tag for <c:if test="${product.available}">

answered Feb 28 '14 at 05:14

raVan

296
2
15

product.id and all other variables are available, I've added the closing tag thanks. – AlexCartio1 Feb 28 '14 at 05:27

why am I receiving NullPointerException on my jsp file?

2 Answers2

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