Wednesday, January 13, 2021

Adding packaging and refactoring known sample of Java CRUD Application for Tomcat 9.0.41 ( Mysql 8.0.22)

Why packaging is important ? Original code was pretty straight  forward Java coding which looks and works quite smoothly . However , all compiled classes appear to be placed in one folder WEB-INF/classes/ and in some way this minor design issue hides a business logic of apps see https://www.javatpoint.com/crud-in-servlet . Once again Connection to mariadb-Server on F33 is encapsulated in separate class and matches the most recent requirements (8.0.22) . Code below is just a tutorial for Java Servlets code writing rather then competitor for JSF && JPA

Orinal code may be found at https://www.javatpoint.com/crud-in-servlet . 

Application is starting from HTML form 

[tomcat@server33fedora ServletCRUD0121]$ cat index.html

<!DOCTYPE html>  

<html>  

<head>  

<meta charset="ISO-8859-1">  

<title>Insert title here</title>  

</head>  

<body bgcolor='C0C0C0'>  

<h1>Add New Employee</h1>  

<form action="SaveServlet" method="post">  

<table>  

<tr><td>Name:</td><td><input type="text" name="name"/></td></tr>  

<tr><td>Password:</td><td><input type="password" name="password"/></td></tr>  

<tr><td>Email:</td><td><input type="email" name="email"/></td></tr>  

<tr><td>Country:</td><td>  

<select name="country" style="width:150px">  

<option>India</option>  

<option>USA</option>  

<option>UK</option>  

<option>Other</option>  

</select>  

</td></tr>  

<tr><td colspan="2"><input type="submit" value="Save Employee"/></td></tr>  

</table>  

</form>  

<br/>  

<a href="ViewServlet">view employees</a>  

</body>  

</html>  

[tomcat@server33fedora src]$ cat DBConnection.java

package mypackage.dao ;

import java.util.*;

import java.sql.*;

public class DBConnection {

 public static Connection getConnection(){

 String url = "jdbc:mysql://localhost/data_demo?allowPublicKeyRetrieval=true&useSSL=false&serverTimezone=UTC";

    String username = "root";

    String password = "*******";

    System.out.println("In DBConnection.java class ");

    Connection con = null;

 try

  {

   try

   {

Class.forName("com.mysql.cj.jdbc.Driver").getDeclaredConstructor().newInstance();

    }

      catch (ClassNotFoundException e)

   {

            e.printStackTrace();

   }

   con = DriverManager.getConnection(url, username, password);

   }

     catch (Exception e)

  {

        e.printStackTrace();

  }

  return con ;

 }

}

[tomcat@server33fedora classes]$ cat  ../src/EmpDao.java

package mypackage.dao ;

import java.util.*;  

import java.sql.*;  

import mypackage.been.Emp;

import mypackage.dao.DBConnection ;

public class EmpDao {  

 public static int save(Emp e) {  

    int status=0; 

    String INSERT_EMP_SQL = "INSERT INTO emp2021(name,password,email,country) values (?,?,?,?)";  

    try(Connection con=DBConnection.getConnection(); PreparedStatement ps=con.prepareStatement(INSERT_EMP_SQL))

       {  

            ps.setString(1,e.getName());  

            ps.setString(2,e.getPassword());  

            ps.setString(3,e.getEmail());  

            ps.setString(4,e.getCountry());  

           status=ps.executeUpdate();  

           con.close();  

        } catch(Exception ex) { ex.printStackTrace(); }  

         return status;  

    }  

 public static int update(Emp e){  

   int status=0; 

   String UPDATE_EMP_SQL="update emp2021 set name=?,password=?,email=?,country=? where id=?" ; 

    try(Connection con=DBConnection.getConnection(); PreparedStatement ps=con.prepareStatement(UPDATE_EMP_SQL))

       { 

            ps.setString(1,e.getName());  

            ps.setString(2,e.getPassword());  

            ps.setString(3,e.getEmail());  

            ps.setString(4,e.getCountry());  

            ps.setInt(5,e.getId());  

            status=ps.executeUpdate();  

           con.close();  

        } catch(Exception ex) { ex.printStackTrace(); }  

      return status;  

    }  

 public static int delete(int id){  

   int status=0; 

   String DELETE_EMP_SQL="delete from emp2021 where id=?" ; 

   try(Connection con=DBConnection.getConnection(); PreparedStatement ps=con.prepareStatement(DELETE_EMP_SQL))

        {  

           ps.setInt(1,id);  

           status=ps.executeUpdate();  

           con.close();  

        } catch(Exception e) { e.printStackTrace(); }  

       return status;  

    }  

 public static Emp getEmployeeById(int id){  

  Emp e=new Emp();  

  String SELECT_EMP_SQL="select * from emp2021 where id=?" ;    try(Connection con=DBConnection.getConnection(); PreparedStatement ps=con.prepareStatement(SELECT_EMP_SQL))

       {  

         ps.setInt(1,id);  

         ResultSet rs=ps.executeQuery();  

         if(rs.next()){  

            e.setId(rs.getInt(1));  

            e.setName(rs.getString(2));  

            e.setPassword(rs.getString(3));  

            e.setEmail(rs.getString(4));  

            e.setCountry(rs.getString(5));  

        }  

            con.close();  

        } catch(Exception ex) {ex.printStackTrace();}  

      return e;  

    }  

 public static List<Emp> getAllEmployees() {  

   List<Emp> list=new ArrayList<Emp>();  

   String SELECT_ALL_SQL="select * from emp2021" ;        

  try(Connection con=DBConnection.getConnection();             PreparedStatement ps=con.prepareStatement(SELECT_ALL_SQL))

     {  

       ResultSet rs=ps.executeQuery();  

       while(rs.next()){  

        Emp e=new Emp();  

        e.setId(rs.getInt(1));  

        e.setName(rs.getString(2));  

        e.setPassword(rs.getString(3));  

        e.setEmail(rs.getString(4));  

        e.setCountry(rs.getString(5));  

        list.add(e);  

     }  

       con.close();  

     } catch(Exception e) { e.printStackTrace(); }  

   return list;  

 }  

}  

[tomcat@server33fedora src]$ cat ViewServlet.java

package mypackage.code ;

import java.io.IOException;  

import java.io.PrintWriter;  

import java.util.List;  

mport javax.servlet.ServletException;  

import javax.servlet.annotation.WebServlet;  

import javax.servlet.http.HttpServlet;  

import javax.servlet.http.HttpServletRequest;  

import javax.servlet.http.HttpServletResponse;  

import mypackage.dao.EmpDao ;

import mypackage.bean.Emp ;

@WebServlet("/ViewServlet")  

public class ViewServlet extends HttpServlet {  

    protected void doGet(HttpServletRequest request, HttpServletResponse response)   

       throws ServletException, IOException {  

        response.setContentType("text/html");  

        PrintWriter out=response.getWriter(); 

      out.println("<a href='index.html'>Add New Employee</a>");  

      out.println("<h1>Employees List</h1>");  

      List<Emp> list=EmpDao.getAllEmployees();  

      out.print("<body bgcolor='C0C0C0'><table border='1' width='100%'");  

        out.print("<tr><th>Id</th><th>Name</th><th>Password</th><th>Email</th><th>Country</th><th>Edit</th><th>Delete</th></tr>"); 

 for(Emp e:list)  {  

         out.print("<tr><td>"+e.getId()+"</td><td>"+e.getName()+"</td><td>"+e.getPassword()+"</td><td>"+e.getEmail()+"</td><td>"+e.getCountry()+"</td><td><a href='EditServlet?id="+e.getId()+"'>edit</a></td><td><a href='DeleteServlet?id="+e.getId()+"'>delete</a></td></tr>");  

        }  

        out.print("</table></body>");  

        out.close();  

    }  

}  

tomcat@server33fedora src]$ cat EditServlet.java

package mypackage.code ;

import java.io.IOException;  

import java.io.PrintWriter;  

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 mypackage.dao.EmpDao ;

import mypackage.bean.Emp ;

 @WebServlet("/EditServlet")  

public class EditServlet extends HttpServlet {  

    protected void doGet(HttpServletRequest request, HttpServletResponse response)   

           throws ServletException, IOException {  

        response.setContentType("text/html");  

        PrintWriter out=response.getWriter();  

        // out.print("<html><body='C0C0C0'>");

        out.println("<h1>Update Employee</h1>");  

        String sid=request.getParameter("id");  

        int id=Integer.parseInt(sid);  

        Emp e=EmpDao.getEmployeeById(id);  

         out.print("<form action='EditServlet2' method='post'>");  

        out.print("<table>");  

        out.print("<tr><td></td><td><input type='hidden' name='id' value='"+e.getId()+"'/></td></tr>");  

        out.print("<tr><td>Name:</td><td><input type='text' name='name' value='"+e.getName()+"'/></td></tr>");  

        out.print("<tr><td>Password:</td><td><input type='password' name='password' value='"+e.getPassword()+"'/></td></tr>");  

        out.print("<tr><td>Email:</td><td><input type='email' name='email' value='"+e.getEmail()+"'/></td></tr>");  

        out.print("<tr><td>Country:</td><td>");  

        out.print("<select name='country' style='width:150px'>");  

        out.print("<option>India</option>");  

        out.print("<option>USA</option>");  

        out.print("<option>UK</option>");  

        out.print("<option>Other</option>");  

        out.print("</select>");  

        out.print("</td></tr>");  

        out.print("<tr><td colspan='2'><input type='submit' value='Edit & Save '/></td></tr>");  

        out.print("</table>");  

        out.print("</form>");  

        out.print("</html>");          

        out.close();  

    }  

}  

[tomcat@server33fedora src]$ cat EditServlet2.java

package mypackage.code ;

import java.io.IOException;  

import java.io.PrintWriter;  

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 mypackage.dao.EmpDao ;

import mypackage.bean.Emp ;

@WebServlet("/EditServlet2")  

public class EditServlet2 extends HttpServlet {  

    protected void doPost(HttpServletRequest request, HttpServletResponse response)   

          throws ServletException, IOException {  

        response.setContentType("text/html");  

        PrintWriter out=response.getWriter();  

       String sid=request.getParameter("id");  

        int id=Integer.parseInt(sid);  

        String name=request.getParameter("name");  

        String password=request.getParameter("password");  

        String email=request.getParameter("email");  

        String country=request.getParameter("country");  

       Emp e=new Emp();  

        e.setId(id);  

        e.setName(name);  

        e.setPassword(password);  

        e.setEmail(email);  

        e.setCountry(country);  

       int status=EmpDao.update(e);  

        if(status>0){  

            response.sendRedirect("ViewServlet");  

        } else  {  

            out.println("Sorry! unable to update record");  

        }  

       out.close();  

    }  

}  

[tomcat@server33fedora src]$ cat DeleteServlet.java

package mypackage.code ;

import java.io.IOException;  

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 mypackage.dao.EmpDao ;

@WebServlet("/DeleteServlet")  

public class DeleteServlet extends HttpServlet {  

    protected void doGet(HttpServletRequest request, HttpServletResponse response)   

             throws ServletException, IOException {  

        String sid=request.getParameter("id");  

        int id=Integer.parseInt(sid);  

        EmpDao.delete(id);  

        response.sendRedirect("ViewServlet");  

    }  

}  

[tomcat@server33fedora src]$ cat SaveServlet.java

package mypackage.code ;

import java.io.IOException;  

import java.io.PrintWriter;  

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 mypackage.dao.EmpDao ;

import mypackage.bean.Emp ;

@WebServlet("/SaveServlet")  

public class SaveServlet extends HttpServlet {  

    protected void doPost(HttpServletRequest request, HttpServletResponse response)   

         throws ServletException, IOException {  

        response.setContentType("text/html");  

        PrintWriter out=response.getWriter();  

       String name=request.getParameter("name");  

        String password=request.getParameter("password");  

        String email=request.getParameter("email");  

        String country=request.getParameter("country");  

       Emp e=new Emp();  

        e.setName(name);  

        e.setPassword(password);  

        e.setEmail(email);  

        e.setCountry(country);  

       int status=EmpDao.save(e);  

      if(status>0){  

      out.print("<p>Record saved successfully!</p>");  

      request.getRequestDispatcher("index.html").include(request, response);  

        } else  {  

            out.println("Sorry! unable to save record");  

        }  

        out.close();  

    }  

}  

[tomcat@server33fedora src]$ cat Emp.java

package mypackage.bean ;

public class Emp {  

private int id;  

private String name,password,email,country;  

public int getId() {  

    return id;  

}  

public void setId(int id) {  

    this.id = id;  

}  

public String getName() {  

    return name;  

}  

public void setName(String name) {  

    this.name = name;  

}  

public String getPassword() {  

    return password;  

}  

public void setPassword(String password) {  

    this.password = password;  

}  

public String getEmail() {  

    return email;  

}  

public void setEmail(String email) {  

    this.email = email;  

}  

public String getCountry() {  

    return country;  

}  

public void setCountry(String country) {  

    this.country = country;  

}  

  

}  

Building ( I have some issues with Eclipse installed via snap and will make attempt to follow recent post at Fedora Magazine at my earliest convenience )

 javac -cp .:$CLASSPATH ../src/DBConnection.java -d  .

  javac -cp .:$CLASSPATH ../src/EmpDao.java -d  .

  javac -cp .:$CLASSPATH ../src/DeleteServlet.java -d  .

  javac -cp .:$CLASSPATH ../src/EditServlet.java -d  .

  javac -cp .:$CLASSPATH ../src/EditServlet2.java -d  .

  javac -cp .:$CLASSPATH ../src/SaveServlet.java -d  .

  javac -cp .:$CLASSPATH ../src/DeleteServlet.java -d  .

  javac -cp .:$CLASSPATH ../src/ViewServlet.java -d  . 

*************************************

Files layout under WEB-INF/classes/

*************************************

$ cd /opt/tomcat/latest/webapps/ServletCRUD0121/WEB-INF/src

[tomcat@server33fedora src]$ ll

total 32

-rw-r--r--. 1 tomcat tomcat  764 Jan 13 14:56 DBConnection.java

-rw-r-----. 1 tomcat tomcat  713 Jan 13 15:18 DeleteServlet.java

-rw-r-----. 1 tomcat tomcat 1462 Jan 13 15:23 EditServlet2.java

-rw-r-----. 1 tomcat tomcat 2113 Jan 13 15:24 EditServlet.java

-rw-r-----. 1 tomcat tomcat 3478 Jan 13 15:05 EmpDao.java

-rw-r-----. 1 tomcat tomcat  727 Jan 13 14:42 Emp.java

-rw-r-----. 1 tomcat tomcat 1439 Jan 13 15:23 SaveServlet.java

-rw-r-----. 1 tomcat tomcat 1511 Jan 13 15:23 ViewServlet.java

tomcat@server33fedora classes]$ ls -CR

.:

mypackage

./mypackage:

bean  code  dao

./mypackage/bean:

Emp.class

./mypackage/code:

DeleteServlet.class  EditServlet2.class  EditServlet.class  SaveServlet.class  ViewServlet.class

./mypackage/dao:

DBConnection.class  EmpDao.class


Mysql 8.0.22 table creation script :-

create database data_demo ;

CREATE TABLE emp2021 (

     id  int NOT NULL AUTO_INCREMENT,

     name varchar(20) ,

     password varchar(20) ,

     email varchar(20) ,

     country varchar(20) ,

     PRIMARY KEY (id) );

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