Question

严重: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException

严重: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.jsp.index_jsp._jspService(index_jsp.java:306)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
跪求大神解决

Answer 1

出现此错误一般都是在jsp中使用了输出流（如输出图片验证码，文件下载等），没有妥善处理好的原因。具体的原因就是在tomcat中jsp编译成servlet之后在函数_jspService(HttpServletRequestrequest,HttpServletResponseresponse)的最后有一段这样的代码finally{if(_jspxFactory!=null)_jspxFactory.releasePageContext(_jspx_page_context);}这里是在释放在jsp中使用的对象，会调用response.getWriter(),因为这个方法是和response.getOutputStream()相冲突的！所以会出现以上这个异常。然后当然是要提出解决的法，其实挺简单的（并不是和某些朋友说的那样--将jsp内的所有空格和回车符号所有都删除掉），在使用完输出流以后调用以下两行代码即可：out.clear();out=pageContext.pushBody();最后这里是一个输出彩色验证码例子（这样的例子几乎随处可见）imag.jsp255)fc=255;if(bc>255)bc=255;intr=fc+random.nextInt(bc-fc);intg=fc+random.nextInt(bc-fc);intb=fc+random.nextInt(bc-fc);returnnewColor(r,g,b);}%>如有不足之处，欢迎斧正！2getOutputStream()hasalreadybeencalledforthisresponse问题的解决在jsp向页面输出图片的时候,使用response.getOutputStream()会有这样的提示：java.lang.IllegalStateException:getOutputStream()hasalreadybeencalledforthisresponse,会抛出Exception原因一:JSP默认的输出流为PrintWriter,即以外的东西所默认的输出方式,如果你尝试在JSP中使用ServletOutputStream就会引起错误.要嘛直接改用Servlet输出(复写service方法),要嘛删除除%>0){output.write(b,0,len);}output.flush();而不是把response.getOutputStream().write()放到循环体内在页面中直接写：将会出现错误消息如下：java.lang.IllegalStateException:getOutputStream()hasalreadybeencalledforthisresponseorg.apache.catalina.connector.Response.getWriter(Response.java:604)org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)

Answer 2

你的jsp文件有问题

追问

哪个jsp有问题？

Answer 3

看下jsp哪一行报错就行了。

追问

怎么找呢？