Set file permission in java 5

问题

I am using the below code to upload image. The problem is that after uploading the image i cant change the file permission. my file permission set by default is rw-r--r-- (0644). Is it possible to change the file permission or set it as 0777 by default? It works fine in my local system. But not able to change the permission in my linux server.

    <%
    try

    {

        int filesize=0;
        String fieldname="",fieldvalue="",filename="",content="",bookid="",bkdescription="";        

        try {
            List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
            for (FileItem item : items) {
                if (item.isFormField()) {
                    fieldname = item.getFieldName();
                    fieldvalue = item.getString();                 
                    if(fieldname.equals("homeid")){
                        bookid=fieldvalue;
                    }

                    if(fieldname.equals("bkdescription")){
                        bkdescription=fieldvalue;
                    }             

                } else {
                    try{
                    fieldname = item.getFieldName();
                    filename = FilenameUtils.getName(item.getName());
                    InputStream filecontent = item.getInputStream();
                    filesize=(int)item.getSize();
                    filename="literal_"+bookid+".jpg";
                    if(filesize>0){                     
                    byte[] b=new byte[filesize];                  
                    int c=0;                                   

                    File f=new File(getServletConfig().getServletContext().getRealPath("/")+"/imagesX");
    String filePah=getServletConfig().getServletContext().getRealPath("/")+"/imagesX";

                    if(f.isDirectory())
                    {
                        String fl[]=f.list();
                        for(int i=0;i<fl.length;i++)

                            {

              File fd=new File(getServletConfig().getServletContext().getRealPath("/")+"/imagesX/"+fl[i]);
                             if(fd.getName().equals(filename))
                             fd.delete();

                        }

                    }

                    if(!f.exists())
    {
            new File(filePah).mkdir();      
f.mkdir()
    }                

   java.io.FileOutputStream fout=new java.io.FileOutputStream(getServletConfig().getServletContext().getRealPath("/")+"/imagesX/"+filename);    

                    while((c = filecontent.read(b)) != -1 )
                    {
                        fout.write(b, 0, c);

                    }

                    fout.close();
                    filecontent.close();
                    }

                    }catch (Exception e) {
                System.out.println("Exception in creation of file      :"+e);

                    }

                }

            }

        } catch (FileUploadException e) {
            throw new ServletException("Cannot parse multipart request.", e);
        }

    }

    catch(Exception exp)

    {
        out.println(exp);
    }

    %>

回答1:

You cannot change the file permission from inside java code.

Your system's default umask is set to 0644 for new file. It wouldn't be good idea to change the default umask.

What you need is to do is set the permission of your directory to 0777 and then redefine your directory's ACL to recursive, so all new file created inside will inherit the same permission.

Heres a link which shows how to go about - https://superuser.com/questions/151911/how-to-make-new-file-permission-inherit-from-the-parent-directory

回答2:

An alternative solution is to change the permissions externally with a system command, chmod.

Example:

public static void runCmd (String[] cmd) {

    try {
        Process p = Runtime.getRuntime().exec(cmd);
        BufferedReader r = new BufferedReader(
            new InputStreamReader (
                p.getInputStream()
            )
        );
    } catch(Exception e) {
    }
}

    runCmd(new String[] {
        "/bin/chmod",
        "755",
        "/path/to/your/script"
    });

P.S. were you also trying to call Java from a stored proc in an Oracle database?

来源：https://stackoverflow.com/questions/11095728/set-file-permission-in-java-5