I would like to write an article for those who are writing applications for the first time using Java. We would appreciate it if you could use it as a reference for creating training assignments for your portfolio and company. This time, we will create a task manager. By applying this, you can also use it to create Twitter clones.
I will post articles for each function of the application.
eclipse4.16.0 Tomcat9 Java11
This is a common input form.
task-insert.jsp
<body>
<!-- header.jsp will be created last-->
<jsp:include page="header.jsp"/>
<div class="contain">
<h3>Task registration</h3>
<!-- task-insert-Pass each input parameter to servlet-->
<form action="task-insert-servlet" method="post">
<table class="form-table" border="1">
<tbody>
<tr>
<th>Task name</th>
<td>
<div class="input-key">
<input type="text" class="form-control" name="task_name" size="60" placeholder="Please enter">
</div>
</td>
</tr>
<tr>
<th>Category</th>
<td>
<div class="input-key">
<select class="form-control" name="category_id">
<option selected>Choose...</option>
<option value="1">New product A: Development project</option>
<option value="2">Existing product B:Improvement project</option>
</select>
</div>
</td>
</tr>
<tr>
<th>Deadline</th>
<td>
<div class="input-key">
<input type="date" name="limit_date" class="form-control" size="60">
</div>
</td>
</tr>
<tr>
<th>status</th>
<td>
<div class="input-key">
<select class="form-control" name="status_code" >
<option selected>Choose...</option>
<option value="00">not started yet</option>
<option value="50">Start</option>
<option value="99">Done</option>
</select>
</div>
</td>
</tr>
<tr>
<th>Note</th>
<td>
<div class="input-key">
<input type="text" class="form-control" name="memo" size="60">
</div>
</td>
</tr>
<tr>
<th><input type="submit" value="Registration" class="input-submit"></th>
<td></td>
</tr>
</tbody>
</table>
</form>
</div>
</body>
This is the confirmation screen when the posting is completed. Here you can see what you are posting.
task-insert-comp.jsp
<body>
<%
String task_name = (String)request.getAttribute("task_name");
int category_id = (int)request.getAttribute("category_id");
String category_name = (String)request.getAttribute("category_name");
Date limit_date = (Date)request.getAttribute("limit_date");
String status_code = (String)request.getAttribute("status_code");
String status_name = (String)request.getAttribute("status_name");
String memo = (String)request.getAttribute("memo");
%>
<jsp:include page="header.jsp"/>
<div class="contain">
<div class="box">
<h3>Task registration is complete</h3>
<p>I registered with the following contents</p>
<hr>
<p>
Task name:<%=task_name %><br>
Category:<%=category_id %>：<%=category_name %><br>
Deadline:<%=limit_date %><br>
status:<%=status_code %>：<%=status_name %><br>
Note:<%=memo %><br>
</p>
<a href="menu.jsp">Return to menu</a>
</div>
</div>
</body>
This is the display when posting fails. In particular, in the case of an input error, the location where the error occurred is displayed.
task-insert-failure.jsp
<body>
<!--The request scope error lists the reasons why the input was incorrect, so receive this.-->
<%
List<String> error = (List<String>)request.getAttribute("error");
%>
<jsp:include page="header.jsp"/>
<div class="contain">
<div class="box">
<h3>Failed to register the task</h3>
<hr>
<p>*The following causes are possible</p>
<ul>
<!--Display error-->
<%for(String er : error){ %>
<li><%=er %></li>
<%} %>
</ul>
<a href="task-insert.jsp">Return to registration screen</a>
</div>
</div>
</body>
First, create a method for task registration.
model.dao.TaskDAO.java
/**
*Method for task registration
* @param task_name
* @param category_id
* @param limit_date
* @param user_id
* @param status_code
* @param memo
* @return Number of executions
* @throws SQLException
* @throws ClassNotFoundException
*/
public int insertTask(String task_name, int category_id, Date limit_date, String user_id, String status_code, String memo) throws SQLException, ClassNotFoundException {
//SQL statement input parameters and user_Create record by specifying id
String sql = "insert into t_task (task_name, category_id, limit_date, user_id, status_code, memo) values(?, ?, ?, ?, ?, ?)";
int sum = 0;
//Connect to database
try(Connection con = ConnectionManager.getConnection();
PreparedStatement pstmt = con.prepareStatement(sql)){
pstmt.setString(1, task_name);
pstmt.setInt(2, category_id);
pstmt.setDate(3, limit_date);
pstmt.setString(4, user_id);
pstmt.setString(5, status_code);
pstmt.setString(6, memo);
//Execution of update SQL statement
sum = pstmt.executeUpdate();
}
return sum;
}
The detailed explanation is the same as in the second UserDAO.java. I want to display the status name because it is easy to understand just by the status id. So let's use a method to get status_name with status_id as an argument
model.dao.StatusDAO.java
public class StatusDAO {
/**
*Method to get the status name
* @param status_code
* @return
* @throws SQLException
* @throws ClassNotFoundException
*/
public String getStatusName(String status_code) throws SQLException, ClassNotFoundException {
String sql = "select status_name from m_status where status_code = ?";
String status_name ="unknown";
try(Connection con = ConnectionManager.getConnection();
PreparedStatement pstmt = con.prepareStatement(sql)){
pstmt.setString(1, status_code);
ResultSet res = pstmt.executeQuery();
while(res.next()) {
status_name = res.getNString("status_name");
}
}
return status_name;
}
}
The detailed explanation is the same as in the second UserDAO.java. I want to display the status name because it is easy to understand only by the category Code. So let's use a method to get category_name with category_code as an argument
model.dao.CategoryDAO.java
public class CategoryDAO {
/**
*Method to get the category name
* @param category_id
* @return
* @throws SQLException
* @throws ClassNotFoundException
*/
public String getCategoryName(int category_id) throws SQLException, ClassNotFoundException {
String sql = "select category_name from m_category where category_id = ?";
String category_name ="unknown";
try(Connection con = ConnectionManager.getConnection();
PreparedStatement pstmt = con.prepareStatement(sql)){
pstmt.setInt(1, category_id);
ResultSet res = pstmt.executeQuery();
while(res.next()) {
category_name = res.getNString("category_name");
}
}
return category_name;
}
servlet.TaskInsertServlet.java
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//DAO generation
TaskDAO taskdao = new TaskDAO();
CategoryDAO categorydao = new CategoryDAO();
StatusDAO statusdao = new StatusDAO();
//Get parameters
request.setCharacterEncoding("UTF-8");
String task_name = request.getParameter("task_name");
String category_id_str = request.getParameter("category_id");
String limit_date_check = request.getParameter("limit_date");
String status_code = request.getParameter("status_code");
String memo = request.getParameter("memo");
//Get the logged-in user information from the session scope and user_Get id
HttpSession session = request.getSession();
String user_id = (String)session.getAttribute("current_user_id");
//List generation to save error display
List<String> error = new ArrayList<String>();
//session check
boolean sessioncheck = (boolean)session.getAttribute("login");
if(!sessioncheck) {
error.add("Please log in before registering the task");
}
//Check for input omissions
if(task_name.equals("")) {
error.add("The task name is blank");
}
if(category_id_str.equals("Choose...")) {
error.add("No category selected");
}
if(status_code.equals("Choose...")) {
error.add( "No status selected");
}
//Deadline (limit)_date) is special because it is a Date type
boolean limit_check;
limit_date_check = limit_date_check.replace('-', '/');
DateFormat format = DateFormat.getDateInstance();
format.setLenient(false);
try {
format.parse(limit_date_check);
limit_check = true;
} catch(Exception e) {
limit_check = false;
}
if(!limit_check) {
error.add("Please enter the date for the deadline");
}
//Save error to request scope
request.setAttribute("error", error);
if(task_name != "") {
try {
//Convert categories and deadlines (non-String type) that cannot be received according to the parameters
int category_id = Integer.parseInt( category_id_str);
Date limit_date = Date.valueOf(request.getParameter("limit_date"));
//Database processing by insert method
taskdao.insertTask(task_name, category_id, limit_date, user_id, status_code, memo);
//Get category name / status name
String category_name = categorydao.getCategoryName(category_id);
String status_name = statusdao.getStatusName(status_code);
//Save registration information in request scope
request.setAttribute("task_name", task_name);
request.setAttribute("category_id", category_id);
request.setAttribute("category_name", category_name);
request.setAttribute("limit_date", limit_date);
request.setAttribute("status_code", status_code);
request.setAttribute("status_name", status_name);
request.setAttribute("memo", memo);
RequestDispatcher rd = request.getRequestDispatcher("task-insert-comp.jsp");
rd.forward(request, response);
} catch(SQLException | ClassNotFoundException | IllegalArgumentException e) {
RequestDispatcher rd = request.getRequestDispatcher("task-insert-failure.jsp");
rd.forward(request, response);
}
}else {
RequestDispatcher rd = request.getRequestDispatcher("task-insert-failure.jsp");
rd.forward(request, response);
}
}
This time I implemented the task registration function Next time, I will try to display a list of registered tasks, add a sort function, and add a search function.
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