尽管使用了servletContext（），getResourceAsStream仍然返回null

Question

This is a servlet that reads a .pdf and sends it as response. I don't understand why is it not working.

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("application/pdf");
        ServletContext sc = this.getServletContext();
        String path = sc.getRealPath("/WEB-INF/pdf/order.pdf");
        System.out.print(path);// this prints correct path
        InputStream is = null;
        try{
            is = sc.getResourceAsStream(path); // this is not working
        }catch(Exception e){
            e.printStackTrace();
        }
        System.out.print(is);// it is null
        int read = 0;
        byte[] bytes = new byte[2048];
        OutputStream os = response.getOutputStream();

        try{
        while((read = is.read(bytes))!= -1){  //exception is thrown here
            os.write(bytes,0,read);
        }
        }catch(Exception e){
            e.printStackTrace();
        }
        os.flush();
        os.close();
      }

Can anyone explain why is it not working, ispite of using this.getServletContext().getRealPath("/WEB-INF/pdf/demo.pdf");

here is the stack trace:

2/21/13 14:24:21:322 IST] 00000033 SystemErr     R java.lang.NullPointerException
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.tgmc.servlets.DisplayOrder_PDF_Servlet.doGet(DisplayOrder_PDF_Servlet.java:42)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at javax.servlet.http.HttpServlet.service(HttpServlet.java:718)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1449)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:790)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:443)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:175)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3610)
[2/21/13 14:24:21:323 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:274)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:926)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1557)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:173)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:455)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:384)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:288)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.ssl.channel.impl.SSLConnectionLink.determineNextChannel(SSLConnectionLink.java:1016)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.ssl.channel.impl.SSLConnectionLink$MyReadCompletedCallback.complete(SSLConnectionLink.java:639)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.ssl.channel.impl.SSLReadServiceContext$SSLReadCompletedCallback.complete(SSLReadServiceContext.java:1772)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
[2/21/13 14:24:21:324 IST] 00000033 SystemErr     R     at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:202)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:766)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:896)
[2/21/13 14:24:21:325 IST] 00000033 SystemErr     R     at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1527)

Answer 1

Did you try sc.getResourceAsStream("/WEB-INF/pdf/order.pdf")

and is it located under src/main/resources/WEB-INF/pdf ? file named .pdf and not .PDF?

edit: I tried this at home and it works for me.

    try{
        is = sc.getResourceAsStream("/WEB-INF/pdf/order.pdf"); // this works!
    }catch(Exception e){
        e.printStackTrace();
    }

Note: give you have a standard build, order.pdf should be in src/main/ webapp /WEB-INF/pdf folder

(rather than src/main/resources...).

Vishal, can you give this another try using my code above and checking the folder structure?

Answer 2

I had the NullPointerException when calling GetResourceAsStream() on ServletContext too and have fixed so I post here for those who encounter the same issue. According to the document at http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContext.html , the method getRealPath() will return the real path on the server filesystem, so calling sc.getRealPath("/WEB-INF/pdf/order.pdf") as the code above will probably return /opt/apache-tomcat/wtpwebap‌​ps/itext/WEB-INF/pdf/order.pdf assuming /opt/apache-tomcat/ is the location of your tomcat on the server. The document also mentions that for the method getResourceAsStream(), we should pass in the relative path to the servlet context root starting with /. So for the code above, you should pass /WEB-INF/pdf/order.pdf insead of the real path to getResourceAsStream() method.

sc.getResourceAsStream("/WEB-INF/pdf/order.pdf")