为什么我在这个循环中收到 java.io.IOException？答案

【问题标题】：Why am I receiving a java.io.IOException in this loop?为什么我在这个循环中收到 java.io.IOException？
【发布时间】：2014-09-11 10:23:07
【问题描述】：

我已经编写了以下代码块，它获取一个纯文本文件，如果文件的当前修改日期大于循环的最后一次迭代，则将文件解析为 HTML 版本并将其上传到 ftp服务器。我相信这个问题与作家有关，但我不明白这里发生了什么。循环的第一次迭代似乎执行得很好，然后它休眠了 5 分钟并抛出以下错误：

java.io.IOException: Stream closed
at java.io.BufferedWriter.ensureOpen(BufferedWriter.java:116)
at java.io.BufferedWriter.write(BufferedWriter.java:221)
at java.io.Writer.write(Writer.java:157)
at java.io.Writer.append(Writer.java:227)
at PrintOutConvosFtp3.main(PrintOutConvosFtp3.java:130)

这是引发错误的代码：

import java.io.*;
import java.util.*;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import java.sql.Timestamp;

public class PrintOutConvosFtp3
{
public static void main(String[] args) throws IOException, InterruptedException
    {
    boolean infiniteLoop = true;
    long currentLoopModified = 0;
    long lastLoopModified = 0;

    while (infiniteLoop)
    {
    currentLoopModified = new File("C:/Documents and Settings/Cuckoo/Desktop/Syss-convos.LOG").lastModified();
    if (currentLoopModified > lastLoopModified)
    {

    //Read in the conversation log
BufferedReader reader = new BufferedReader(new FileReader("C:/Documents and Settings/Cuckoo/Desktop/Syss-convos.LOG"));
FileWriter output = new FileWriter("C:/Documents and Settings/Cuckoo/Desktop/Conversations.html");
List<String> lines = new ArrayList<String>();
String line = null;
while ((line = reader.readLine()) != null)
    //Remove some unnecessary clutter from the log
 {
 if (!(line.contains("just hung up!!!") || line.contains("just left the Realm.")
        || line.contains("Hurry, I've many esoteric secrets to divulge, and welcome to BaDbOy's realm.")
        || line.contains("For custom MegaMud paths and additional information, check out the website:")
        || line.contains("Syss gossips: Discuss new ideas/issues & see the most up to date information on Facebook!")
        || line.contains("Syss gossips: http://www.facebook.com/groups/EsotericEdits/")
        || line.contains("Syss gossips: MME Dats, Megamud path files and quest walkthroughs are available at my site")
        || line.contains("Syss gossips: www.esoteric-edits.fhero.net")
        || line.contains("telepaths: @")
        || line.contains("I'm a bot.  Try telepathing me with @commands.")
        || line.contains("Syss gossips: Remember, you can telepath me @commands for useful things like adding lives.")
        || line.contains("Syss gossips: Bring a friend, help keep mud alive!")
        || line.contains("You say \"http://esoteric-edits.fhero.net/\"")
        || line.contains("For a list of available commands, you can telepath me with @commands.")))
 {
 //Make the dates american style
     String day = line.substring(0,2);
     String month = line.substring(3,5);
lines.add(month + "/" + day + line.substring(5));
}


 }
//initialize the output file with HTML header
output.write("<html>");
output.write(System.getProperty("line.separator") + "\t<head>");
output.write(System.getProperty("line.separator") + "\t\t<link type=\"text/css\" rel=\"stylesheet\" href=\"stylesheet.css\"/>");
output.write(System.getProperty("line.separator") + "\t\t<title>Esoteric Edits BBS - Conversation Log</title>");
output.write(System.getProperty("line.separator") + "\t</head>");
output.write(System.getProperty("line.separator") + "\t<body>"+ System.getProperty("line.separator") + System.getProperty("line.separator"));
output.write(System.getProperty("line.separator") + "<div id='cssmenu'>");
output.write(System.getProperty("line.separator") + "\t\t<center><img src=\"logo_10_2.png\">");
output.write(System.getProperty("line.separator") + "<ul>");
output.write(System.getProperty("line.separator") + "\t<li> <a href='index.html'><span>Home</span></a></li>");
output.write(System.getProperty("line.separator") + "\t<li> <a href='downloads.html'><span>Downloads</span></a></li>");
output.write(System.getProperty("line.separator") + "\t<li> <a href='Quests.html'><span>Quest Walkthroughs</span></a></li>");
output.write(System.getProperty("line.separator") + "\t<li> <a href='https://www.facebook.com/groups/EsotericEdits/'><span>Facebook</span></a></li>");
output.write(System.getProperty("line.separator") + "\t<li> <a href='captures.html'><span>Captures</span></a></li>");
output.write(System.getProperty("line.separator") + "\t<li class='last'> <a href='FAQs.html'><span>FAQs</span></a></li>");
output.write(System.getProperty("line.separator") + "</ul></center>");
output.write(System.getProperty("line.separator") + "</div><div id='mainpage'>");
output.write(System.getProperty("line.separator") + "<center><img src=\"divider.png\"></center>");

//write out a new file with HTML coloration
for (ListIterator<String> iter = lines.listIterator(); iter.hasNext(); ) 
{
    String currentline = iter.next();
    output.write("<b>"); //make everything bold
    if (currentline.contains("gangpaths: "))
{
output.write(System.getProperty("line.separator") + "<font color=\"#808000\">" + currentline + "<br></font>");
}
    else if (currentline.contains("gossips: ") || currentline.contains("auctions: "))
{
output.write(System.getProperty("line.separator") + "<font color=\"#FF00FF\">" + currentline + "<br></font>");
}
else if (currentline.contains("Broadcast from "))
{
output.write(System.getProperty("line.separator") + "<font color=\"yellow\">" + currentline + "<br></font>");
}
else if (currentline.contains("says \"") || currentline.contains("greets you.") || currentline.contains("bows deeply.")
             || currentline.contains("breaks into a wide grin.") || currentline.contains("You say \"") 
             || currentline.contains("nods affirmatively.") || currentline.contains("grin slyly"))
{
output.write(System.getProperty("line.separator") + "<font color=\"green\">" + currentline + "<br></font>");
}
else
{
output.write(System.getProperty("line.separator") + currentline + "<br>");
}
}
//finalize the HTML footer
output.write(System.getProperty("line.separator") + "</b>");
output.write(System.getProperty("line.separator") + "</div>");
output.write(System.getProperty("line.separator") + "</body>");
output.write(System.getProperty("line.separator") + "\t</html>");
output.close(); //file is finalized locally



//define variables for FTP process
String server = "servername";
int port = 21;
String user = "fake";
String pass = "password";

//begin FTP process to web server
FTPClient ftpClient = new FTPClient();
FileInputStream fis = null;
try {

    File localFile = new File("C:/Documents and Settings/Cuckoo/Desktop/Conversations.html");
    ftpClient.connect(server, port);
    ftpClient.login(user, pass);
    ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
    fis = new FileInputStream(localFile);
    String remoteFile = "/public_html/Conversations.html";
    ftpClient.storeFile(remoteFile, fis);
    java.util.Date currentDate = new java.util.Date();
    Timestamp ftpTimestamp = new Timestamp(currentDate.getTime());
    //Create writer file to log iterations of the loop as successful or skipped.
    Writer writer = new BufferedWriter(new FileWriter("C:/Documents and Settings/Cuckoo/Desktop/Convo-Upload.log", true));
    writer.append("Successfully uploaded file as of " + ftpTimestamp.toString() + System.getProperty("line.separator"));
    writer.close(); //close the iteration logger
    ftpClient.logout();
} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        if (fis != null) {
            fis.close();
        }
        ftpClient.disconnect();
    } catch (IOException e) {
        e.printStackTrace();
        }
    }


lastLoopModified = currentLoopModified; //set the timestamp for the lastmodified on the file being read in
Thread.sleep(300000); //5 minutes
}
    else
    {
        java.util.Date currDate = new java.util.Date();
        Timestamp currTimestamp = new Timestamp(currDate.getTime());
        //Create writer file to log iterations of the loop as successful or skipped.
        Writer writer = new BufferedWriter(new FileWriter("C:/Documents and Settings/Cuckoo/Desktop/Convo-Upload.log", true));
        writer.append("Did not detect any new content in file.  Did not upload as of " + currTimestamp.toString() + System.getProperty("line.separator"));
        writer.close(); //close the iteration logger
    }
}

}
}

我认为这与作者被关闭有关，但我尝试过移动它，让它保持打开状态，直到无限循环完成（这永远不会），等等，我仍然有奇怪的行为。我是不是做错了什么？

【问题讨论】：

因为流被关闭了，因为你关闭了它...
要查明这一点，请在您的代码中放置一个断点，然后逐行查看您的 Stream 的状态。这应该会给你一个关于关闭你的 Stream 的线索
@immibis -- 我对 java 有点陌生，所以请原谅我的不理解。我需要让 Writer 永远打开吗？如果我尝试将 writer.close() 放在巨大的 where(infiniteLoop) 之外，它在技术上永远不会关闭，我相信我这样做会遇到问题。你能更清楚你的意思吗？
什么 IOException？堆栈跟踪？
@cuckoo 当您确定不会再次使用任何 IO 对象时，您应该关闭它。所以最好在 finally 块中关闭它。

标签： java stream ioexception writer

【解决方案1】：

我在我的机器上运行了代码并且运行良好 - 我只注释掉了与 FTP 传输相关的代码，因为我无法在此处执行此操作。我的机器相当新而且速度很快，所以我怀疑可能存在时间问题。

堆栈跟踪指向的代码行可能与 Thread.Sleep(nnn) 有问题。如果在 Writer 完成任务之前 Sleep 阻塞了线程，那么这可能会导致您的问题。

如果这是问题所在，与其在主线程上完成所有这些工作，不如生成一个新线程来执行执行并放置所有代码（除了我认为将 Thread.sleep 保留在主线程中）仅线程）在此处。通过使用单独的线程来执行写入任务，它将给 Writers 足够的时间来完成他们的任务，而不会被 Sleep 拖住。

此外，在您当前的实现中，如果没有更改，则不会调用 Sleep，因为它仅嵌入在循环的“更改”部分中，因此它直接返回检查时间又变了，一点也不耽误。

【讨论】：

【解决方案2】：

如果您仔细检查代码，您会注意到 Thread.sleep() 仅在文件自上次迭代后更新时才被执行。每当这不是真的时，我认为它会陷入“写入未更新的时间戳”等疯狂的无限循环......无休止。我将 Thread.sleep() 语句移到了 if 和 else 语句之外，就在 while } 括号结束之前，它现在似乎执行得很好。谢谢你们的帮助。

【讨论】：