[Java / Eclipse / Servlet / JSP / PostgreSQL] Framework d'application WEB avec fonctions de publication / sauvegarde / édition / mise à jour / suppression de données

Contenu de cet article

Développement d'une application avec des fonctions de publication / sauvegarde / édition / mise à jour / suppression de données en Java, et un mémorandum

Caractéristiques de la personne qui a écrit cet article

・ J'ai l'expérience du téléchargement d'une application WEB qui a des fonctions de publication / sauvegarde / édition / mise à jour / suppression de données dans l'environnement de production avec Rails. ・ Aucune expérience dans le développement d'applications WEB en Java

Environnement de développement

article
PC	MacBook Air
OS	MacOS Mojave
Langue	Java
IDE	Eclipse
DB	PostgreSQL
Gestion de la base de données	pgAdmin
contrôle de version	GitHub
navigateur	Chrome

Conditions préalables

DB (1) Les fonctions à implémenter et le servlet / JSP correspondant sont les suivants.

process	method	Servlet	JSP
/list	GET	ListServlet.java	list.jsp
/show	GET	ShowServlet.java	list.jsp
/new	GET	NewServlet.java	new.jsp
/create	POST	CreateServlet.java	-
/edit	GET	EditServlet.java	edit.jsp
/update	POST	UpdateServlet.java	-
/delete	POST	DeleteServlet.java	-

② Préparez une table POSTS sur la base de données MEMO et connectez la table à l'application.

article	valeur
Adresse DB	http://localhost:5432/
DB	memo
Nom d'utilisateur	SAMPLEUSER
mot de passe	SAMPLEPASSWORD

`SQL`


CREATE TABLE posts (
id SERIAL PRIMARY KEY,
title varchar,
content varchar
);

`SQL`


SELECT * FROM posts;

`Résultat de l'exécution SQL`


id |     title     |             content              
----+---------------+----------------------------------
 14 | 2019/05/15    | memo app by Java Servlet and JSP
 15 | sample title  | sample content
 16 | memoapp       | made of Java Servlet and JSP
 17 | sample_edited | sample_edited
 21 | sample_edited | sample_edited
 22 | sample        | sample
(6 rows)

Eclipse ① L'application WEB est créée par "Dynamic WEB Project"

Autre

① Ne considérez pas la communauté du code en double cette fois (2) La conception frontale avec CSS / JavaScript n'est pas prise en compte cette fois.

Exemple de code

Servlet ListServlet.java

`ListServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/list")
public class ListServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ListServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
		//DB connection
		String url = "jdbc:postgresql://localhost:5432/memo";
		String user = "SAMPLEUSER";
		String password = "SAMPLEPASSWORD";
		
	    try{
            Class.forName("org.postgresql.Driver");
        } catch(Exception e) {
            e.printStackTrace();
        }
		
		try { 
			Connection connection = DriverManager.getConnection(url, user, password);
			connection.setAutoCommit(false);
			String sql = "SELECT * FROM posts;";
			PreparedStatement statement = connection.prepareStatement(sql);

			
			ResultSet results = statement.executeQuery();
			
			ArrayList<HashMap<String,String>> rows = new ArrayList<HashMap<String,String>>();
			
			while(results.next()) {
				HashMap<String,String> columns = new HashMap<String,String>();
				
				String id = results.getString("id");
				columns.put("id",id);
				
				String title = results.getString("title");
				columns.put("title", title);
				
				String content = results.getString("content");
				columns.put("content",content);
				
				rows.add(columns);
			}
			request.setAttribute("rows", rows);
			results.close();
			statement.close();
		
			
		} catch(Exception e) {
			e.printStackTrace();
		}
		
		RequestDispatcher dispatcher = request.getRequestDispatcher("WEB-INF/views/list.jsp");
		dispatcher.forward(request,response);
		System.out.println("-----Écran affiché-----");
		System.out.println("/list");
		System.out.println("");
	}

}

ShowServlet.java

`ShowServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/show")
public class ShowServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ShowServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
		//DB connection
		String url = "jdbc:postgresql://localhost:5432/memo";
		String user = "SAMPLEUSER";
		String password = "SAMPLEPASSWORD";
		
	    try{
            Class.forName("org.postgresql.Driver");
        } catch(Exception e) {
            e.printStackTrace();
        }
		
		try { 
			Connection connection = DriverManager.getConnection(url, user, password);
			connection.setAutoCommit(false);
			String sql = "SELECT * FROM posts WHERE id = ?;";
			PreparedStatement statement = connection.prepareStatement(sql);
			statement.setInt(1, Integer.parseInt(request.getParameter("id")));
			
			ResultSet results = statement.executeQuery();
			
			ArrayList<HashMap<String,String>> rows = new ArrayList<HashMap<String,String>>();
			
			while(results.next()) {
				
				String id = results.getString("id");
				request.setAttribute("id", id);
				
				String title = results.getString("title");
				request.setAttribute("title", title);

				
				String content = results.getString("content");
				request.setAttribute("content", content);
				

			}
			request.setAttribute("rows", rows);
			System.out.println("-----Les données stockées-----");
			System.out.println(rows);
			System.out.println("");
			results.close();
			statement.close();
		
			
		} catch(Exception e) {
			e.printStackTrace();
		}
		
		RequestDispatcher dispatcher = request.getRequestDispatcher("WEB-INF/views/show.jsp");
		dispatcher.forward(request,response);
		System.out.println("-----Écran affiché-----");
		System.out.println("/show?id=" + request.getParameter("id"));
		System.out.println("");
	}

}

NewServlet.java

`NewServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/new")
public class NewServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public NewServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
		RequestDispatcher dispatcher = request.getRequestDispatcher("WEB-INF/views/new.jsp");
		dispatcher.forward(request,response);
		System.out.println("-----Écran affiché-----");
		System.out.println("/new");
		System.out.println("");
	}

}

CreateServlet.java

`CreateServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/create")
public class CreateServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public CreateServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
				String title = request.getParameter("title");
				String content = request.getParameter("content");
		
		//DB connection
				String url = "jdbc:postgresql://localhost:5432/memo";
				String user = "SAMPLEUSER";
				String password = "SAMPLEPASSWORD";
				
			    try{
		            Class.forName("org.postgresql.Driver");
		        } catch(Exception e) {
		            e.printStackTrace();
		        }
				
				try { 
					Connection connection = DriverManager.getConnection(url, user, password);
					connection.setAutoCommit(false);
					String sql = "INSERT INTO posts (title,content) VALUES (?,?)" ;
					PreparedStatement statement = connection.prepareStatement(sql);
					statement.setString(1, title);
					statement.setString(2, content);
					int number = statement.executeUpdate();			
					connection.commit();
				} catch(Exception e) {
					e.printStackTrace();
				}
		
		
		
		String forward = "/memo/list";
		response.sendRedirect(forward);
		System.out.println("-----J'ai posté une note.-----");
		System.out.println("ID: " + request.getParameter("title") + " TITLE: " + request.getParameter("content"));
		System.out.println("");
	}
}

EditServlet.java

`EditServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/edit")
public class EditServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public EditServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
		//DB connection
		String url = "jdbc:postgresql://localhost:5432/memo";
		String user = "SAMPLEUSER";
		String password = "SAMPLEPASSWORD";
		
	    try{
            Class.forName("org.postgresql.Driver");
        } catch(Exception e) {
            e.printStackTrace();
        }
		
		try { 
			Connection connection = DriverManager.getConnection(url, user, password);
			connection.setAutoCommit(false);
			String sql = "SELECT * FROM posts WHERE id = ?;";
			PreparedStatement statement = connection.prepareStatement(sql);
			statement.setInt(1, Integer.parseInt(request.getParameter("id")));
			
			ResultSet results = statement.executeQuery();
			
			ArrayList<HashMap<String,String>> rows = new ArrayList<HashMap<String,String>>();
			
			while(results.next()) {
				
				String id = results.getString("id");
				request.setAttribute("id", id);
				
				String title = results.getString("title");
				request.setAttribute("title", title);

				
				String content = results.getString("content");
				request.setAttribute("content", content);
				

			}
			request.setAttribute("rows", rows);
			System.out.println(rows);
			System.out.println("");
			results.close();
			statement.close();
		
			
		} catch(Exception e) {
			e.printStackTrace();
		}
		
		RequestDispatcher dispatcher = request.getRequestDispatcher("WEB-INF/views/edit.jsp");
		dispatcher.forward(request,response);
		System.out.println("-----Écran affiché-----");
		System.out.println("/edit?id=" + request.getParameter("id"));
		System.out.println("");
	}

}

UpdateServlet.java

`UpdateServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/update")
public class UpdateServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UpdateServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
				String title = request.getParameter("title");
				String content = request.getParameter("content");
				int id = Integer.parseInt(request.getParameter("id"));
		
		//DB connection
				String url = "jdbc:postgresql://localhost:5432/memo";
				String user = "SAMPLEUSER";
				String password = "SAMPLEPASSWORD";
				
			    try{
		            Class.forName("org.postgresql.Driver");
		        } catch(Exception e) {
		            e.printStackTrace();
		        }
				
				try { 
					Connection connection = DriverManager.getConnection(url, user, password);
					connection.setAutoCommit(false);
					String sql = "UPDATE posts SET title = ?, content = ? WHERE id = ?";
					PreparedStatement statement = connection.prepareStatement(sql);
					statement.setString(1, title);
					statement.setString(2, content);
					statement.setInt(3, id);
					int number = statement.executeUpdate();			
					connection.commit();
				} catch(Exception e) {
					e.printStackTrace();
				}
		
		
		
		String forward = "/memo/show?id=" + id;
		response.sendRedirect(forward);
		System.out.println("-----Le mémo a été mis à jour.-----");
		System.out.println("ID: " + request.getParameter("id") + " TITLE: " + request.getParameter("title")  + " CONTENT: " + request.getParameter("content"));
		System.out.println("");
	}
}

DeleteServlet.java

`DeleteServlet.java`


package sample;

import java.io.IOException;
import javax.servlet.*;
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 java.util.*;
import java.sql.*;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/delete")
public class DeleteServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DeleteServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
				int id = Integer.parseInt(request.getParameter("id"));
		
		//DB connection
				String url = "jdbc:postgresql://localhost:5432/memo";
				String user = "SAMPLEUSER";
				String password = "SAMPLEPASSWORD";
				
			    try{
		            Class.forName("org.postgresql.Driver");
		        } catch(Exception e) {
		            e.printStackTrace();
		        }
				
				try { 
					Connection connection = DriverManager.getConnection(url, user, password);
					String sql = "DELETE FROM posts WHERE id = ?";
					PreparedStatement statement = connection.prepareStatement(sql);
					statement.setInt(1, id);
					int number = statement.executeUpdate();			
				} catch(Exception e) {
					e.printStackTrace();
				}
		
		
		
		String forward = "/memo/list";
		response.sendRedirect(forward);
		System.out.println("-----J'ai supprimé le mémo.-----");
		System.out.println("ID: " + request.getParameter("id"));
		System.out.println("");
	}
}

JSP list.jsp

`list.jsp`


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import = "java.util.*" %>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
 <h2>MEMO LIST</h2>
 <p>This app is made by Java Servlet and JSP.</p>



<table>
<tr><th>ID</th><th>TITLE</th></tr>
<% ArrayList<HashMap<String,String>> rows = (ArrayList<HashMap<String,String>>)request.getAttribute("rows"); %>

<% for(HashMap<String,String> columns: rows){ %>
<tr><td><%= columns.get("id") %></td><td><a href="show?id=<%= columns.get("id") %>"><%= columns.get("title") %></a></td></tr>
<% } %>
</table>
 
 <p></p>
 <a href="new">Create new memo</a>
</body>
</html>

show.jsp

`show.jsp`


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import = "java.util.*" %>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
 <h2>MEMO DETAIL</h2>
 <p>This app is made by Java Servlet and JSP.</p>


<br>
<form action="delete?id=<%= request.getAttribute("id") %>" method="POST">
<p>ID: <%= request.getAttribute("id") %></p>
<p>TITLE: <%= request.getAttribute("title") %></p>
<p>CONTENT:</p>
<p><%= request.getAttribute("content") %></p>
<br>
 <a href="edit?id=<%= request.getAttribute("id") %>">Edit</a><br>
 <button>Delete</button><br>
 </form>
<br>
 <a href="list">Return list</a>
</body>
</html>

new.jsp

`new.jsp`


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import = "java.util.*" %>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
 <h2>CREATE NEW MEMO</h2>
 <p>This app is made by Java Servlet and JSP.</p>
<p></p>

<form action="create" method="POST">
<p>TITLE:</p>
<input type=text name="title">
<p>CONTENT:</p>
<input type=text name="content">
<p></p>
 <button>Create</button><br>
 </form>
 
<p></p>
 <a href="list">Cancel</a>
</body>
</html>

edit.jsp

`edit.jsp`


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import = "java.util.*" %>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
 <h2>EDIT MEMO</h2>
 <p>This app is made by Java Servlet and JSP.</p>
<p></p>

<form action="update" method="POST">
<p>ID: <%= request.getAttribute("id") %></p>
<input type='hidden' name='id' value='<%= request.getAttribute("id") %>'>
<p>TITLE:</p>
<input type="text" name="title" value="<%= request.getAttribute("title") %>">
<p>CONTENT:</p>
<input type="text" name="content" value="<%= request.getAttribute("content") %>">
<p></p>
 <button>Update</button><br>
 </form>
 
<p></p>
 <a href="list">Cancel</a>
</body>
</html>

Ce que je veux faire dans le futur

(1) Mise en œuvre de la fonction de connexion / déconnexion ② Cryptage du mot de passe ③ Ajout de validation (contrainte) ④ Modèle de pièce ⑤ Améliorer la capacité de conception grâce au développement d'applications WEB (application de livre de comptes des ménages attachée par la comptabilité composée) avec Java