錯誤500與NoSuchElementException

Question

我在虛擬機（ubuntu 14）上部署我的春天項目，當我使用執行ajax調用的按鈕時，它給出了錯誤500與堆棧NoSuchElementException指向一個迭代器。在Eclipse上

我的應用程序做工精細，並在我的虛擬機部署的時候，所以我導出的VM（所有做工精細）到客戶端計算機，但仍然給錯誤500

這裏是跟蹤：

HTTP Status 500 - An exception occurred processing JSP page /executeComparison.jsp at line 7 

type Exception report 

message An exception occurred processing JSP page /executeComparison.jsp at 
line 7 

description The server encountered an internal error that prevented it from 
fulfilling this request. 

exception 

org.apache.jasper.JasperException: An exception occurred processing JSP page 
/executeComparison.jsp at line 7 

4: 
5: <% 
6: System.out.println("I'm comparing"); 
7: ComputeDifference.printDiffs(ComputeDifference.getAllDiffs("P1", "P2")); 
8: String data = "active"; 
9: out.print(data); 
10: out.flush(); 


Stacktrace: 
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568) 
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:727) 
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
root cause 

java.util.NoSuchElementException 
java.util.ArrayList$Itr.next(ArrayList.java:834) 
comparator.ComputeDifference.compare(ComputeDifference.java:212) 
comparator.ComputeDifference.getAllDiffs(ComputeDifference.java:29) 
org.apache.jsp.executeComparison_jsp._jspService(executeComparison_jsp.java:70) 
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:727) 
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:727) 
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
note The full stack trace of the root cause is available in the Apache 
Tomcat/7.0.53 logs. 

Apache Tomcat/7.0.53 

我不認爲它與迭代器或看到它的做工精細的日食，並在我的VM在我的電腦中的Java代碼什麼的，錯誤是那裏當我使用相同的VM，但是，客戶端電腦，阿賈克斯調用失敗，並給出以下錯誤

jquery-1.11.0.min.js:4 GET 
https://193.169.100.12:8443/DMX.v.3.10/executeComparison.jsp? 
rand=0.9844812755765802 500 (Internal Server Error) 

這裏是Ajax調用：

 function evaluateDelta() { 
     var rand = Math.random(); 
     $.ajax({ 
      url: "executeComparison.jsp", 
      dataType: 'text', 
      data: { rand: rand }, 
      success: function (data) { 
       console.log("got the difference"); 
       displayDelta(); 
      } 
     }); 

    } 

這裏是jsp頁面：

<%@page import="java.util.*"%> 
<%@page import="comparator.ComputeDifference"%> 

<% 
    System.out.println("I'm comparing"); 
    ComputeDifference.printDiffs(ComputeDifference.getAllDiffs("P1", "P2")); 
    String data = "active"; 
    out.print(data); 
    out.flush(); 
%> 

當我檢查日誌，我發現「我比較印」，這意味着阿賈克斯去到jsp但jsp在下一行失敗，如堆棧跟蹤所示。

最後，這裏是迭代器指向堆棧的函數（syso中的一個「System.out.println（」\ r \ n \ r \ n ----------- - 命令 「+ it.next（）+」 \ r \ n \ r \ n 「）;」：

static public void compare (String fileName1,String fileName2) throws IOException{ 

    String filePath1="C:/Users/Mike/Desktop/"+fileName1+".txt"; 
    String filePath2="C:/Users/Mike/Desktop/"+fileName2+".txt"; 

    BufferedReader in = null; 
    BufferedReader inN=null; 
    BufferedReader in2=null; 
    BufferedReader in2N=null; 
    String line = "", line2= ""; 
    ArrayList<String> commands=ComputeDifference.getCommands(filePath1); 
    Iterator<String> it = commands.iterator(); 
    boolean command=true; 
    try { 

     in = new BufferedReader(new FileReader(filePath1)); 
     inN = new BufferedReader(new FileReader(filePath1)); inN.readLine(); 
     in2= new BufferedReader(new FileReader(filePath2));  
     in2N= new BufferedReader(new FileReader(filePath2)); in2N.readLine(); 

     File file = new File("C:/Users/Mike/Desktop/command1.txt"); 
     File file1 = new File("C:/Users/Mike/Desktop/command2.txt"); 
     File fileDiff = new File("C:/Users/Mike/Desktop/commandDiff.txt"); 

     PrintStream printStreamToFile = new PrintStream(file);   
     PrintStream printStreamToFile1 = new PrintStream(file1); 
     PrintStream printStreamToFileDiff = new PrintStream(fileDiff); 
     int i=0; 
     while ((line = in.readLine()) != null) { 
       String next=inN.readLine(); 

       System.setOut(printStreamToFile); 
       System.out.println(line); 

       if(next != null && next.contains("#")){ 

       command=true; 


        while (command == true && (line2 = in2.readLine()) != null) { 

         String next2=in2N.readLine(); 
         System.setOut(printStreamToFile1); 
         System.out.println(line2); 

         if(next2 != null && next2.contains("#")){ 
          System.setOut(printStreamToFileDiff); 
          if(i!=0){ 


          System.out.println("\r\n\r\n------------ Command "+it.next()+"\r\n\r\n"); 

          List<String> original = fileToLines("command1"); 
          List<String> revised = fileToLines("command2"); 

          System.setOut(printStreamToFileDiff); 
          Patch<String> patch = DiffUtils.diff(original, revised); 
          for (Delta<String> delta: patch.getDeltas()) { 

           System.setOut(printStreamToFileDiff); 
           System.out.println(delta); 


          } 
          } 
          else{ 
           i++; 
           it.next(); 
           } 
          printStreamToFile1.close(); 
          file1.delete(); 
          file1.createNewFile(); 
          printStreamToFile1=new PrintStream(file1); 
          command=false; 
         } 
               } 
          printStreamToFile.close(); 
          file.delete(); 
          file.createNewFile(); 
          printStreamToFile=new PrintStream(file); 
      } 

     } 

System.setOut(ApplicationConstant.console); 


} catch (IOException e) { 
    e.printStackTrace(); 
} finally { 

    if (in != null) { 
     try { 
      in.close(); 
     } catch (IOException e) { 
     } 
    } 
    if (in2 != null) { 
     try { 
      in2.close(); 
     } catch (IOException e) { 

     } 
    } 
} 
} 

任何想法是這個錯誤，但是來自我找遍了所有論壇和網站，我知道白白。

非常感謝。

Answer 1

您必須檢查是否Iterator.hasNext()調用Iterator.next()之前有NoSuchElementEx的可能性即使它在某些環境中工作，也可以在代碼中使用ception。

參見： https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html