Context.xml
<Resource
name="jdbc/TestDB" auth="Container"
type="javax.sql.DataSource"
maxActive="100"
maxIdle="30" maxWait="10000"
username="root"
password="" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/cdcol"/>
//This should be added in the servers context,xml file. For example if you are using apache server then the context.xml will be found in C:\apache-tomcat-6.0.26\conf\Context.xml
web.xml
<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/TestDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
//This should be added in the web.xml of the local project. (Not in server's web.xml).
Program:
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
public class UploadFile extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletOutputStream output = null;
ByteArrayInputStream fileToDownload = null;
StringBuffer data = new StringBuffer("First Name, Last Name, Mobile Number, Company Name");
data.append("\n");
Connection con = null;
Statement stmt;
try
{
Context ctx=new InitialContext();
Context envContext = (Context)ctx.lookup("java:comp/env");
DataSource ds=(DataSource)envContext.lookup("jdbc/TestDB");//TestDB is the Database Name
con=ds.getConnection();
stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from <table_name> where <condition>");
while(rs.next()) //This is for four columns
{
data.append(rs.getString(1));
data.append(',');
data.append(rs.getString(2));
data.append(',');
data.append(rs.getString(3));
data.append(',');
data.append(rs.getString(4));
data.append('\n');
}
}
catch(Exception e)
{ //Print the stack trace }
fileToDownload = new ByteArrayInputStream(data.toString().getBytes());
output = response.getOutputStream();
response.setContentType("application/csv");
response.setHeader("Content-Disposition", "attachment; filename=data.csv");//data.csv - Download file name
response.setContentLength(fileToDownload.available());
int c;
while ((c = fileToDownload.read()) != -1)
{
output.write(c);
}
output.flush();
output.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// The code can be done in post also
}
}
