JSL Tech: Servlet Connection pool eaxmple

Connection pooling:

Create context.xml

Create employee class

package com.jsl.servlet.demo;

public class Employee {
        private int empno;
        private String ename;
        private String job;
        private double sal;
        public int getEmpno() {
            return empno;
        }
        public void setEmpno(int empno) {
            this.empno = empno;
        }
        public String getEname() {
            return ename;
        }
        public void setEname(String ename) {
            this.ename = ename;
        }
        public String getJob() {
            return job;
        }
        public void setJob(String job) {
            this.job = job;
        }
        public double getSal() {
            return sal;
        }
        public void setSal(double sal) {
            this.sal = sal;
        }
}

Creating a EmployeeServlet Class

package com.jsl.servlet.demo;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
 
@WebServlet("/getEmployee")
public class EmployeeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    Connection con=null;
    Statement st=null;
    ResultSet rs=null;
    DataSource ds=null;
    Context cx=null;
    @Override
    public void init() throws ServletException {
            try {
                cx=new InitialContext();
                Context envContext = (Context) cx.lookup("java:/comp/env");
                ds = (DataSource) envContext.lookup("jdbc/employee");
 
            } catch (NamingException e) {
                e.printStackTrace();
            }
            
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            PrintWriter out=response.getWriter();
            response.setContentType("text/html");
            out.print("Employee List");
            out.print("");
            List list=getEmployeeList();
            out.print("");
            out.print("");
            for(Employee emp:list){
                out.print("");
                out.print("");
                out.print("");
                out.print("");
                
            }
            out.print("
EmpNo Empname Job Sal
"+emp.getEmpno()+" "+emp.getEname()+" "+emp.getJob()+" "+emp.getSal()+"

");
            
        out.print("");
        out.print("");
    }
    private List getEmployeeList() {
        List emplist=new ArrayList();
        try{
            con=ds.getConnection();
            st=con.createStatement();
            rs=st.executeQuery("select empno,ename,job,sal from emp");
            while(rs.next()){
                Employee emp=new Employee();
                emp.setEmpno(rs.getInt("empno"));
                emp.setEname(rs.getString("ename"));
                emp.setJob(rs.getString("job"));
                emp.setSal(rs.getDouble("sal"));
                emplist.add(emp);
            }
            
        }catch(Exception e){
            e.printStackTrace();
        }
        
        return emplist;
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
    }
}