qq_23232225 2015-03-25 09:08 采纳率: 0%
浏览 2999

为什么我访问路径报出空指针异常(javaweb)

这是异常提示:

java.lang.NullPointerException
at java.io.FileOutputStream.<init>(FileOutputStream.java:206)
at java.io.FileOutputStream.<init>(FileOutputStream.java:104)

**at com.mifan.web.UpLoadServlet.doGet(UpLoadServlet.java:41)**
at com.mifan.web.UpLoadServlet.doPost(UpLoadServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:644)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1086)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:659)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:285)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2439)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2428)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:722)

这是源代码:
public class UpLoadServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    try{
        //创建工厂类  这是阿帕奇提供的那个第三包jar包
        DiskFileItemFactory factory = new DiskFileItemFactory();
        //生产文件上传核心类
        ServletFileUpload fileUpload = new ServletFileUpload(factory);
        List<FileItem> list = fileUpload.parseRequest(request);
        //遍历所有的FileItem
        for(FileItem item : list){
            if(item.isFormField()){
                //当前是一个普通的字段项
                String name = item.getFieldName();//普通字段的名字
                String value = item.getString();  //普通字段名字所对应的值
                System.out.println(name+":"+value);
            }else {//当前是一个文件上传项
                //获取文件上传项的文件名
                String filename = item.getName();
                InputStream in = item.getInputStream();
                OutputStream out = new FileOutputStream(
                        this.getServletContext().getRealPath("upload/"+filename));
                IOUtils.InAndOut(in, out);
                IOUtils.close(in, out);

            }
        }
        //利用文件上传核心类解析request
    }catch (Exception e) {
        e.printStackTrace();
    }
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    doGet(request, response);
}

}

  • 写回答

1条回答 默认 最新

  • wangweirong1205 2015-03-26 05:01
    关注

    Debug 跟一下你就知道哪个为空了。

    评论

报告相同问题?

悬赏问题

  • ¥15 vue3+express部署到nginx
  • ¥20 搭建pt1000三线制高精度测温电路
  • ¥15 使用Jdk8自带的算法,和Jdk11自带的加密结果会一样吗,不一样的话有什么解决方案,Jdk不能升级的情况
  • ¥15 画两个图 python或R
  • ¥15 在线请求openmv与pixhawk 实现实时目标跟踪的具体通讯方法
  • ¥15 八路抢答器设计出现故障
  • ¥15 opencv 无法读取视频
  • ¥15 按键修改电子时钟,C51单片机
  • ¥60 Java中实现如何实现张量类,并用于图像处理(不运用其他科学计算库和图像处理库))
  • ¥20 5037端口被adb自己占了