OAF(File Download from application server)

steps
1)create item as link or button or whatever u want which will fire after clicking or selecting
(here i have created button and event name is actionInMainSearchScreen )
2)make changes only at highlighted places

 import com.sun.java.util.collections.ArrayList;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import oracle.apps.fnd.common.VersionInfo;
import oracle.apps.fnd.framework.OAApplicationModule;
import oracle.apps.fnd.framework.webui.OAControllerImpl;
import oracle.apps.fnd.framework.webui.OAPageContext;
import oracle.apps.fnd.framework.webui.beans.OAWebBean;
import oracle.apps.fnd.framework.webui.beans.message.OAMessageTextInputBean;
import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;
import oracle.apps.fnd.framework.OAApplicationModule;
import oracle.sql.NUMBER;
import oracle.apps.fnd.framework.OAException;
import oracle.apps.fnd.framework.OARow;
import oracle.apps.fnd.framework.OAViewObject;
import oracle.apps.fnd.framework.server.OAApplicationModuleImpl;
import oracle.apps.fnd.framework.server.OADBTransaction;
import oracle.jbo.domain.Number;
import java.io.Serializable;
import oracle.apps.fnd.framework.OAApplicationModule;
import oracle.apps.fnd.common.VersionInfo;
import oracle.apps.fnd.framework.webui.OAControllerImpl;
import oracle.apps.fnd.framework.webui.OAPageContext;
import oracle.apps.fnd.framework.webui.beans.OAWebBean;
import oracle.apps.fnd.framework.OAException;
import oracle.cabo.ui.data.DataObject;
import java.io.FileOutputStream;
import java.io.InputStream;
import oracle.jbo.domain.BlobDomain;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import oracle.apps.fnd.common.URLTools;
import oracle.apps.fnd.common.WebAppsContext;
import oracle.apps.fnd.framework.server.OADBTransactionImpl;
import oracle.apps.fnd.framework.server.OAViewRowImpl;
import oracle.apps.fnd.framework.webui.beans.OABodyBean;
import oracle.jbo.AttributeDef;

 write the logic under the process form request  as actionInMainSearchScreen is the event name  and i have called the method    downloadFileFromServer(pageContext,"D:/c sharp development guide.pdf","c sharp development guide.pdf"); here  D:/c sharp development guide.pdf is the whole path of file to which u have to give access to download (u have to specify the path of server ) c sharp development guide.pdf is also the same name of file
if (actionInMainSearchScreen.equals("download"))
      {
          downloadFileFromServer(pageContext,"D:/c sharp development guide.pdf","c sharp development guide.pdf");
      }







public void downloadFileFromServer(OAPageContext pageContext,
    String file_name_with_path,
    String file_name_with_ext)
    {
    HttpServletResponse response =
    (HttpServletResponse) pageContext.getRenderingContext().getServletResponse();
    if (((file_name_with_path == null) ||
    ("".equals(file_name_with_path))))
    {
    throw new OAException("File path is invalid.");
    }

    File fileToDownload = null;
    try
    {
    fileToDownload = new File(file_name_with_path);
    }
    catch (Exception e)
    {
    throw new OAException("Invalid File Path or file does not exist.");
    }

    if (!fileToDownload.exists())
    {
    throw new OAException("File does not exist.");
    }

    if (!fileToDownload.canRead())
    {
    throw new OAException("Not Able to read the file.");
    }

    String fileType = getMimeType(file_name_with_ext);
    response.setContentType(fileType);
    response.setContentLength((int)fileToDownload.length());
    response.setHeader("Content-Disposition",
    "attachment; filename=\"" + file_name_with_ext +
    "\"");

    InputStream in = null;
    ServletOutputStream outs = null;

    try
    {
    outs = response.getOutputStream();
    in = new BufferedInputStream(new FileInputStream(fileToDownload));
    int ch;
    while ((ch = in.read()) != -1)
    {
    outs.write(ch);
    }

    }
    catch (IOException e)
    {
    // TODO
    e.printStackTrace();
    }
    finally
    {
    try
    {
    outs.flush();
    outs.close();
    if (in != null)
    {
    in.close();
    }
    }
    catch (Exception e)
    {
    e.printStackTrace();
    }
    }
    }

    /**
    * @param s
    * @return file mime type from its name
    */
    public String getMimeType(String s)
    {
    int i = s.lastIndexOf(".");
    if (i > 0 && i < s.length() - 1)
    {
    String s1 = s.substring(i + 1);
    if (s1.equalsIgnoreCase("amr"))
    {
    return "audio/amr";
    }
    if (s1.equalsIgnoreCase("mid"))
    {
    return "audio/midi";
    }
    if (s1.equalsIgnoreCase("mmf"))
    {
    return "application/vnd.smaf";
    }
    if (s1.equalsIgnoreCase("qcp"))
    {
    return "audio/vnd.qcelp";
    }
    if (s1.equalsIgnoreCase("hqx"))
    {
    return "application/mac-binhex40";
    }
    if (s1.equalsIgnoreCase("cpt"))
    {
    return "application/mac-compactpro";
    }
    if (s1.equalsIgnoreCase("doc"))
    {
    return "application/msword";
    }
    if (s1.equalsIgnoreCase("jsp"))
    {
    return "application/jsp";
    }
    if (s1.equalsIgnoreCase("oda"))
    {
    return "application/oda";
    }
    if (s1.equalsIgnoreCase("pdf"))
    {
    return "application/pdf";
    }
    if (s1.equalsIgnoreCase("ai"))
    {
    return "application/postscript";
    }
    if (s1.equalsIgnoreCase("eps"))
    {
    return "application/postscript";
    }
    if (s1.equalsIgnoreCase("ps"))
    {
    return "application/postscript";
    }
    if (s1.equalsIgnoreCase("ppt"))
    {
    return "application/powerpoint";
    }
    if (s1.equalsIgnoreCase("rtf"))
    {
    return "application/rtf";
    }
    if (s1.equalsIgnoreCase("bcpio"))
    {
    return "application/x-bcpio";
    }
    if (s1.equalsIgnoreCase("vcd"))
    {
    return "application/x-cdlink";
    }
    if (s1.equalsIgnoreCase("Z"))
    {
    return "application/x-compress";
    }
    if (s1.equalsIgnoreCase("cpio"))
    {
    return "application/x-cpio";
    }
    if (s1.equalsIgnoreCase("csh"))
    {
    return "application/x-csh";
    }
    if (s1.equalsIgnoreCase("dcr"))
    {
    return "application/x-director";
    }
    if (s1.equalsIgnoreCase("dir"))
    {
    return "application/x-director";
    }
    if (s1.equalsIgnoreCase("dxr"))
    {
    return "application/x-director";
    }
    if (s1.equalsIgnoreCase("dvi"))
    {
    return "application/x-dvi";
    }
    if (s1.equalsIgnoreCase("gtar"))
    {
    return "application/x-gtar";
    }
    if (s1.equalsIgnoreCase("gz"))
    {
    return "application/x-gzip";
    }
    if (s1.equalsIgnoreCase("hdf"))
    {
    return "application/x-hdf";
    }
    if (s1.equalsIgnoreCase("cgi"))
    {
    return "application/x-httpd-cgi";
    }
    if (s1.equalsIgnoreCase("jnlp"))
    {
    return "application/x-java-jnlp-file";
    }
    if (s1.equalsIgnoreCase("skp"))
    {
    return "application/x-koan";
    }
    if (s1.equalsIgnoreCase("skd"))
    {
    return "application/x-koan";
    }
    if (s1.equalsIgnoreCase("skt"))
    {
    return "application/x-koan";
    }
    if (s1.equalsIgnoreCase("skm"))
    {
    return "application/x-koan";
    }
    if (s1.equalsIgnoreCase("latex"))
    {
    return "application/x-latex";
    }
    if (s1.equalsIgnoreCase("mif"))
    {
    return "application/x-mif";
    }
    if (s1.equalsIgnoreCase("nc"))
    {
    return "application/x-netcdf";
    }
    if (s1.equalsIgnoreCase("cdf"))
    {
    return "application/x-netcdf";
    }
    if (s1.equalsIgnoreCase("sh"))
    {
    return "application/x-sh";
    }
    if (s1.equalsIgnoreCase("shar"))
    {
    return "application/x-shar";
    }
    if (s1.equalsIgnoreCase("sit"))
    {
    return "application/x-stuffit";
    }
    if (s1.equalsIgnoreCase("sv4cpio"))
    {
    return "application/x-sv4cpio";
    }
    if (s1.equalsIgnoreCase("sv4crc"))
    {
    return "application/x-sv4crc";
    }
    if (s1.equalsIgnoreCase("tar"))
    {
    return "application/x-tar";
    }
    if (s1.equalsIgnoreCase("tcl"))
    {
    return "application/x-tcl";
    }
    if (s1.equalsIgnoreCase("tex"))
    {
    return "application/x-tex";
    }
    if (s1.equalsIgnoreCase("textinfo"))
    {
    return "application/x-texinfo";
    }
    if (s1.equalsIgnoreCase("texi"))
    {
    return "application/x-texinfo";
    }
    if (s1.equalsIgnoreCase("t"))
    {
    return "application/x-troff";
    }
    if (s1.equalsIgnoreCase("tr"))
    {
    return "application/x-troff";
    }
    if (s1.equalsIgnoreCase("roff"))
    {
    return "application/x-troff";
    }
    if (s1.equalsIgnoreCase("man"))
    {
    return "application/x-troff-man";
    }
    if (s1.equalsIgnoreCase("me"))
    {
    return "application/x-troff-me";
    }
    if (s1.equalsIgnoreCase("ms"))
    {
    return "application/x-troff-ms";
    }
    if (s1.equalsIgnoreCase("ustar"))
    {
    return "application/x-ustar";
    }
    if (s1.equalsIgnoreCase("src"))
    {
    return "application/x-wais-source";
    }
    if (s1.equalsIgnoreCase("xml"))
    {
    return "text/xml";
    }
    if (s1.equalsIgnoreCase("ent"))
    {
    return "text/xml";
    }
    if (s1.equalsIgnoreCase("cat"))
    {
    return "text/xml";
    }
    if (s1.equalsIgnoreCase("sty"))
    {
    return "text/xml";
    }
    if (s1.equalsIgnoreCase("dtd"))
    {
    return "text/dtd";
    }
    if (s1.equalsIgnoreCase("xsl"))
    {
    return "text/xsl";
    }
    if (s1.equalsIgnoreCase("zip"))
    {
    return "application/zip";
    }
    if (s1.equalsIgnoreCase("au"))
    {
    return "audio/basic";
    }
    if (s1.equalsIgnoreCase("snd"))
    {
    return "audio/basic";
    }
    if (s1.equalsIgnoreCase("mpga"))
    {
    return "audio/mpeg";
    }
    if (s1.equalsIgnoreCase("mp2"))
    {
    return "audio/mpeg";
    }
    if (s1.equalsIgnoreCase("mp3"))
    {
    return "audio/mpeg";
    }
    if (s1.equalsIgnoreCase("aif"))
    {
    return "audio/x-aiff";
    }
    if (s1.equalsIgnoreCase("aiff"))
    {
    return "audio/x-aiff";
    }
    if (s1.equalsIgnoreCase("aifc"))
    {
    return "audio/x-aiff";
    }
    if (s1.equalsIgnoreCase("ram"))
    {
    return "audio/x-pn-realaudio";
    }
    if (s1.equalsIgnoreCase("rpm"))
    {
    return "audio/x-pn-realaudio-plugin";
    }
    if (s1.equalsIgnoreCase("ra"))
    {
    return "audio/x-realaudio";
    }
    if (s1.equalsIgnoreCase("wav"))
    {
    return "audio/x-wav";
    }
    if (s1.equalsIgnoreCase("pdb"))
    {
    return "chemical/x-pdb";
    }
    if (s1.equalsIgnoreCase("xyz"))
    {
    return "chemical/x-pdb";
    }
    if (s1.equalsIgnoreCase("gif"))
    {
    return "image/gif";
    }
    if (s1.equalsIgnoreCase("ief"))
    {
    return "image/ief";
    }
    if (s1.equalsIgnoreCase("jpeg"))
    {
    return "image/jpeg";
    }
    if (s1.equalsIgnoreCase("jpg"))
    {
    return "image/jpeg";
    }
    if (s1.equalsIgnoreCase("jpe"))
    {
    return "image/jpeg";
    }
    if (s1.equalsIgnoreCase("png"))
    {
    return "image/png";
    }
    if (s1.equalsIgnoreCase("tiff"))
    {
    return "image/tiff";
    }
    if (s1.equalsIgnoreCase("tif"))
    {
    return "image/tiff";
    }
    if (s1.equalsIgnoreCase("ras"))
    {
    return "image/x-cmu-raster";
    }
    if (s1.equalsIgnoreCase("pnm"))
    {
    return "image/x-portable-anymap";
    }
    if (s1.equalsIgnoreCase("pbm"))
    {
    return "image/x-portable-bitmap";
    }
    if (s1.equalsIgnoreCase("pgm"))
    {
    return "image/x-portable-graymap";
    }
    if (s1.equalsIgnoreCase("ppm"))
    {
    return "image/x-portable-pixmap";
    }
    if (s1.equalsIgnoreCase("rgb"))
    {
    return "image/x-rgb";
    }
    if (s1.equalsIgnoreCase("xbm"))
    {
    return "image/x-xbitmap";
    }
    if (s1.equalsIgnoreCase("xpm"))
    {
    return "image/x-xpixmap";
    }
    if (s1.equalsIgnoreCase("xwd"))
    {
    return "image/x-xwindowdump";
    }
    if (s1.equalsIgnoreCase("html"))
    {
    return "text/html";
    }
    if (s1.equalsIgnoreCase("htm"))
    {
    return "text/html";
    }
    if (s1.equalsIgnoreCase("txt"))
    {
    return "text/plain";
    }
    if (s1.equalsIgnoreCase("rtx"))
    {
    return "text/richtext";
    }
    if (s1.equalsIgnoreCase("tsv"))
    {
    return "text/tab-separated-values";
    }
    if (s1.equalsIgnoreCase("etx"))
    {
    return "text/x-setext";
    }
    if (s1.equalsIgnoreCase("sgml"))
    {
    return "text/x-sgml";
    }
    if (s1.equalsIgnoreCase("sgm"))
    {
    return "text/x-sgml";
    }
    if (s1.equalsIgnoreCase("mpeg"))
    {
    return "video/mpeg";
    }
    if (s1.equalsIgnoreCase("mpg"))
    {
    return "video/mpeg";
    }
    if (s1.equalsIgnoreCase("mpe"))
    {
    return "video/mpeg";
    }
    if (s1.equalsIgnoreCase("qt"))
    {
    return "video/quicktime";
    }
    if (s1.equalsIgnoreCase("mov"))
    {
    return "video/quicktime";
    }
    if (s1.equalsIgnoreCase("avi"))
    {
    return "video/x-msvideo";
    }
    if (s1.equalsIgnoreCase("movie"))
    {
    return "video/x-sgi-movie";
    }
    if (s1.equalsIgnoreCase("ice"))
    {
    return "x-conference/x-cooltalk";
    }
    if (s1.equalsIgnoreCase("wrl"))
    {
    return "x-world/x-vrml";
    }
    if (s1.equalsIgnoreCase("vrml"))
    {
    return "x-world/x-vrml";
    }
    if (s1.equalsIgnoreCase("wml"))
    {
    return "text/vnd.wap.wml";
    }
    if (s1.equalsIgnoreCase("wmlc"))
    {
    return "application/vnd.wap.wmlc";
    }
    if (s1.equalsIgnoreCase("wmls"))
    {
    return "text/vnd.wap.wmlscript";
    }
    if (s1.equalsIgnoreCase("wmlsc"))
    {
    return "application/vnd.wap.wmlscriptc";
    }
    if (s1.equalsIgnoreCase("wbmp"))
    {
    return "image/vnd.wap.wbmp";
    }
    if (s1.equalsIgnoreCase("css"))
    {
    return "text/css";
    }
    if (s1.equalsIgnoreCase("jad"))
    {
    return "text/vnd.sun.j2me.app-descriptor";
    }
    if (s1.equalsIgnoreCase("jar"))
    {
    return "application/java-archive";
    }
    if (s1.equalsIgnoreCase("3gp"))
    {
    return "video/3gp";
    }
    if (s1.equalsIgnoreCase("3g2"))
    {
    return "video/3gpp2";
    }
    if (s1.equalsIgnoreCase("mp4"))
    {
    return "video/3gpp";
    }
    }
    return "application/octet-stream";
    }