CODEWITHSUNDEEP
javafileservlets
Ankur Verma
Ankur Verma

Reputation: 5933

Writing to a file in a servlet

I am working in a servlet and has this code :

public void doPost(blah blah){

   response.setContentType("text/html");

    String datasent = request.getParameter("dataSent");
    System.out.println(datasent);

    try{

        FileWriter writer = new FileWriter("C:/xyz.txt");
        writer.write("hello");


        System.out.println("I wrote");
    }catch(Exception ex){
        ex.printStackTrace();
    }

    response.getWriter().write("I am from server");

}

But everytime it is throwing an error saying Access Denied.. Even when there is no lock on that file and there is no file whose name is C:/xyz.txt

what should I do? ;(

   java.io.FileNotFoundException: C:\xyz.txt (Access is denied)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:212)
at java.io.FileOutputStream.<init>(FileOutputStream.java:104)
at java.io.FileWriter.<init>(FileWriter.java:63)
at test.TestServlet.doPost(TestServlet.java:49)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:306)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:558)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:379)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:259)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:237)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:281)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)

Upvotes: 1

Views: 8211

Answers (4)

Alex Turbin
Alex Turbin

Reputation: 2702

Try close FileWriter:

writer.close();

I imagine what happens: One thread in Tomcat creates the file and terminates but not closes its handle, so from file system view file lock is not released. Another thread tries to open it for write but OS still cannot grant write access to the file, because it already has one pending.

This is called resource leak: Garbage Collector does not release resources allocated by programmer manually (here IO handle)

Upvotes: 5

Chris
Chris

Reputation: 85

try looking at this site seems like thats what your looking for (scroll down some ways)

Upvotes: 0

PVR
PVR

Reputation: 2524

The exception shows that it is of FileNotFound Exception. Please try to make new file first. Try with following code.

File file = File file("c:/xyz.txt");
if(!file.exists()){  // this will return boolean {true} if file exists.
   file.createNewFile(); // create new empty file.
}
FileWriter writer = new FileWriter("C:/xyz.txt", true);
BufferedWriter out = new BufferedWriter(writer);
out.write("your text");
out.close();

Ok no issues.. try to figure out it using different Readers and Writers. 

    String currentExecutablePath = System.getProperty("user.dir");
    String rootPath = currentExecutablePath + "xyz.txt";
    File file = new File(rootPath);
    ServletOutputStream op = res.getOutputStream(); 
    if(file.exists()){
        int length = 0;
        res.setContentType("application/octet-stream");
        res.setContentLength((int) file.length());

        byte[] bbuf = new byte[1000];
        DataInputStream in = new DataInputStream(new FileInputStream(file));            
        while ((in != null) && ((length = in.read(bbuf)) != -1)) {
            op.write(bbuf, 0, length);
        }
    }

Upvotes: -1

Zaw Than oo
Zaw Than oo

Reputation: 9935

During this process, don't open the file.Try as below : 

FileWriter writer = new FileWriter("C:/xyz.txt", true);
BufferedWriter out = new BufferedWriter(writer);
out.write("your text");
out.close();

Upvotes: -1

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