コード判定結果
#11:具体例：特定のプレイヤーを表示する
この動画を見るにはpaiza会員登録のうえ
有料会員登録が必要です
ここでは、ServletとJSP・データベースを使って、簡単なWebアプリケーションを作ります。RPGのプレイヤー一覧から、各プレイヤーの詳細情報を表示するアプリケーションを作ってみましょう。
(tomcat/webapps/mydatabase/PlayerListServlet.java)// RPG Playerリスト
// Servlet-JSP間をArryaListで渡す
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
public class PlayerListServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
request.setAttribute("message", "Playerリスト");
String url = "jdbc:mysql://localhost/mydb";
String user = "root";
String password = "";
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (Exception e) {
e.printStackTrace();
}
try (Connection connection = DriverManager.getConnection(url, user, password);
PreparedStatement statment = connection.prepareStatement("SELECT * FROM players LEFT JOIN jobs ON jobs.id = players.jobId");
ResultSet results = statment.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 name = results.getString("name");
columns.put("name", name);
String level = results.getString("level");
columns.put("level", level);
String jobId = results.getString("jobId");
columns.put("jobId", jobId);
String jobName = results.getString("jobName");
columns.put("jobName", jobName);
rows.add(columns);
}
request.setAttribute("rows", rows);
} catch (Exception e) {
request.setAttribute("message", "Exception:" + e.getMessage());
}
String view = "/WEB-INF/views/playerList.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(view);
dispatcher.forward(request, response);
}
}
(tomcat/webapps/mydatabase/WEB-INF/views/playerList.jsp)<!-- ServletからArryaListでデータ渡し -->
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html" charset="UTF-8">
<title>Java - paiza</title>
<style>body {padding: 30px;}</style>
</head>
<body>
<h1><%= request.getAttribute("message") %></h1>
<%
ArrayList<HashMap<String,String>> rows = (ArrayList<HashMap<String,String>>)request.getAttribute("rows");
%>
<table>
<%
for (HashMap<String,String> columns : rows) {
%>
<tr>
<td><%= columns.get("id") %></td>
<td><%= columns.get("name") %></td>
<td><%= columns.get("level") %></td>
<td><%= columns.get("jobName") %></td>
</tr>
<% } %>
</table>
</body>
</html>
(tomcat/webapps/mydatabase/PlayerProfileServlet.java)// RPG Playerリスト
// Servlet-JSP間をArryaListで渡す
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
public class PlayerProfileServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
int playerId = Integer.parseInt(request.getParameter("id"));
request.setAttribute("message", "Hello player " + playerId);
String url = "jdbc:mysql://localhost/mydb";
String user = "root";
String password = "";
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (Exception e) {
e.printStackTrace();
}
try (Connection connection = DriverManager.getConnection(url, user, password);
PreparedStatement statment = connection.prepareStatement("SELECT * FROM players LEFT JOIN jobs ON jobs.id = players.jobId WHERE players.id = ?")) {
statment.setInt(1, playerId);
ResultSet results = statment.executeQuery();
while (results.next()) {
String id = results.getString("id");
request.setAttribute("id", id);
String name = results.getString("name");
request.setAttribute("name", name);
String level = results.getString("level");
request.setAttribute("level", level);
String jobId = results.getString("jobId");
request.setAttribute("jobId", jobId);
String jobName = results.getString("jobName");
request.setAttribute("jobName", jobName);
}
} catch (Exception e) {
request.setAttribute("message", "Exception:" + e.getMessage());
}
String view = "/WEB-INF/views/playerProfile.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(view);
dispatcher.forward(request, response);
}
}