Using JDBC with servlets
This page gives brief details how to access your database via a servlet using JDBC.
Note that connection details do not need to be supplied as your datasource as been preconfigured.
Datasources are available by using the JNDI name of "java:comp/env/jdbc/db_username" where username should
be replaced with your account name. Please note that Postgres users should use the JNDI name of "java:comp/env/jdbc/pgdb_username" instead.
Next is example servlet code showing the connecting to a database and submition of a simple query.
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
public class ExampleServlet extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
//Get the client's output stream
PrintWriter out;
response.setContentType("text/html");
out = response.getWriter();
DataSource ds = null;
Connection c = null;
Statement Stmt = null;
ResultSet RS = null;
try{
Context initCtx = new InitialContext();
ds = (DataSource) initCtx.lookup("java:comp/env/jdbc/db_user");
c = ds.getConnection();
//Create a new session with the database
Stmt = c.createStatement();
//Query the database
RS = Stmt.executeQuery("SELECT field1 FROM atable WHERE (field2 ='foo')");
while (RS.next()) {
//Print out results
out.println(RS.getString("field1"));
}
}
//Catch Errors
catch(Exception e){
out.println("ERROR:"+e.getMessage());
}
finally{
try{
if(RS != null){
RS.close();
}
if(Stmt != null){
Stmt.close();
}
if(c != null){
c.close();
}
}
catch(Exception e2){
out.println("Unable to close connection: "+e2.getMessage());
}
}
//Close output stream to client
out.close();
}
}
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