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Sunday, 15 May 2011

Using servlet to download the file from Oracle Instance

As part of the project I am working on , I had to find a way to download the file from OA. I will demostrate here a way to do it on R12 instance

First of all we need to write a servlet.

Here is the code:

 

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

public class DownloadFile extends HttpServlet
{

//I assumed that OA is running on Unix under Korn shell and .profile file used to source the instance


private String doCommand(String cmd) throws IOException, InterruptedException
{
int exitCode = 0;
int c;
BufferedReader b;
String [] params
= new String[]{"/bin/ksh", "-c", ". profile 1> /dev/null;set -e;" + cmd};
Process subProc
= Runtime.getRuntime().exec(params);
StringBuffer sb
= new StringBuffer();

b
= new BufferedReader(new InputStreamReader(subProc.getInputStream()));

c
= b.read();

while (c != -1)
{
sb.append((
char)c);
c
= b.read();
}

b.close();

exitCode
= subProc.waitFor();
if (exitCode != 0)
{
sb
= new StringBuffer();
b
= new BufferedReader(new InputStreamReader(subProc.getErrorStream()));
c
= b.read();
while (c != -1)
{
sb.append((
char)c);
c
= b.read();
}
//end while
System.out.println("Output from 'doCommand' "+ sb.toString());
return sb.toString();
}
else
{

System.out.println(
"Output from 'doCommand' "+ sb.toString());
return sb.toString();
}
}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
{ PrintWriter requestOutput
= null;
String resolvedFile
=null;
try
{
String file
= request.getParameter("fileName");
resolvedFile
= doCommand("echo "+file).trim();
File documentFile
= new File(resolvedFile);
FileInputStream fin
= new FileInputStream(documentFile);
if (resolvedFile.indexOf('/')!=-1)
resolvedFile
= resolvedFile.substring(resolvedFile.lastIndexOf('/')+1) ;
response.setHeader(
"Content-disposition", "attachment; filename=" + resolvedFile);
response.setContentType(
"application/octet-stream");
response.setContentLength((
int)documentFile.length());
requestOutput
= response.getWriter();
int c;
c
= fin.read();
while (c != -1) {
requestOutput.write(c);
c
= fin.read();


}
fin.close();
}
catch (Exception e)
{
if (requestOutput == null)
{
response.setContentType(
"text/html");
requestOutput
= response.getWriter();
}
requestOutput.write(
"Error trying to get file : ");
requestOutput.write(e.toString());
requestOutput.write(
"");
}
requestOutput.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
{
doGet(request, response);
}
}


Compile the file. Put it under $OA_JAVA on Application Node

Now we need to add servlet definition to OA web service configuration file. It is usually located under  $ORA_CONFIG_HOME/10.1.3/j2ee/oacore/application-deployments/oacore/html/orion-web.xml

Add the following to the servlet section


<servlet>
<servlet-name>DownloadFile</servlet-name>
<display-name>DownloadFile</display-name>
<servlet-class>DownloadFile</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DownloadFile</servlet-name>
<url-pattern>/DownloadFile</url-pattern>
</servlet-mapping>

Save the file and restart OC4J service.

Now you can download any file located on the Application node simply by running http://<instance url>:<instance port>/OA_HTML/DownloadFile?fileName=/path_to_your_file. You can also use instance variables inside  the path, like http://<instance url>:<instance port>/OA_HTML/DownloadFile?fileName=$APPL_TOP/admin/myFile.txt

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