質問編集履歴

DB接続共通処理のクラスを作成し、ご指摘頂いたforName()を使いJDBCドライバをつなげました。

2020/06/16 12:40

投稿

yyuukkii

スコア7

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@@ -24,6 +24,24 @@
+↓
+forName()をConnectionUtilクラスに追加したところ別のエラーが発生しました。
+java.lang.IllegalStateException: レスポンスをコミットした後でフォワードできません
+	servlet.LoginServlet.doPost(LoginServlet.java:55)
+	javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
+	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
+	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
 試したこと
@@ -32,11 +50,13 @@
 - jarファイルをWEB-INF/libフォルダに入れると解決するという記事を見て試しましたが解決されませんでした。
+- ConnectionUtilというクラスに接続共通処理をつくりそこにForName()を入れました。
+-デバッガで確認しLoginInfoDaoのResultSet rsの変数の値がnullになってしまいます。
-Daoクラス
+ConnectionUtil　DB接続共通処理
@@ -46,10 +66,100 @@
+import java.lang.reflect.InvocationTargetException;
 import java.sql.Connection;
 import java.sql.DriverManager;
+import java.sql.SQLException;
+public class ConnectionUtil {
+	//JDBCドライバーと接続先データベース名を代入
+	private static String driverName = "com.mysql.cj.jdbc.Driver";
+	private static String url = "jdbc:mysql://localhost:3306/company?characterEncoding=UTF8&serverTimezone=JST";
+	//userアカウントを代入
+	private static final String user = "root";
+	private static final String pass = "Sy";
+	//DB接続のメソッド
+	public Connection getConnection() throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException, SecurityException {
+		Connection conn = null;
+    try {
+    	Class.forName(driverName).getDeclaredConstructor().newInstance();　//newInstance()の書き方が正しいのか不安なところです。
+    } catch (ClassNotFoundException e1) {
+    	e1.printStackTrace();
+    }
+    try {
+        conn = DriverManager.getConnection(url, user, pass);
+    } catch (SQLException e) {
+        e.printStackTrace();
+    }
+        return conn;
+    }
+}
+```
+LoginInfoDao
+```
+package dao;
+import java.lang.reflect.InvocationTargetException;
+import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
@@ -62,216 +172,236 @@
 public class LoginInfoDao {
-	private static final String URL = "jdbc:mysql://localhost:3306/company?characterEncoding=UTF-8&serverTimezone=JST";
-	private static final String USER = "root";
-	private static final String PASS = "Sy";
-	public LoginModel findAccount(LoginModel lm) {
-		LoginModel returnLm = new LoginModel();
-		try (Connection conn = DriverManager.getConnection(URL, USER, PASS)) {
-			PreparedStatement ps;
-			ps = conn.prepareStatement("select * from login_info where = login_id = ? and password = ?");
-			ps.setString(1, lm.getLogin_id());
-			ps.setString(2, lm.getPassword());
-			ResultSet rs = ps.executeQuery();
-			if (rs.next()) {
-				returnLm.setLogin_id(rs.getString("login_id"));
-				returnLm.setPassword(rs.getString("password"));
-			} else {
-				return null;
+    public LoginModel findAccount (String login_id, String password) throws SQLException {
+    	LoginModel model = new LoginModel();
+    	ConnectionUtil db = new ConnectionUtil();
+    	Connection conn = null;
+		try {
+			conn = db.getConnection();
+		} catch (InstantiationException e1) {
+			e1.printStackTrace();
+		} catch (IllegalAccessException e1) {
+			e1.printStackTrace();
+		} catch (IllegalArgumentException e1) {
+			e1.printStackTrace();
+		} catch (InvocationTargetException e1) {
+			e1.printStackTrace();
+		} catch (NoSuchMethodException e1) {
+			e1.printStackTrace();
+		} catch (SecurityException e1) {
+			e1.printStackTrace();
+		}
+    	String sql = "select * from login_info where login_id = ? and password = ?";
+    	try {
+    		PreparedStatement ps = conn.prepareStatement(sql);
+    		ps.setString(1,  login_id);
+    		ps.setString(2, password);
+    		ResultSet rs = ps.executeQuery();
+    		while (rs.next()) {
+    			model.setLogin_id(rs.getString("login_id"));
+    			model.setPassword(rs.getString("password"));
+    		}
+    	} catch (SQLException e) {
+			e.printStackTrace();
+		} catch (Exception e) {
+			e.printStackTrace();
+		} finally {
+            conn.close();
+		}
+    	return model;
+    }
+```
+LoginServlet
+```
+package servlet;
+import java.io.IOException;
+import java.sql.SQLException;
+import javax.servlet.RequestDispatcher;
+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 dao.LoginInfoDao;
+import model.LoginModel;
+/**
+ * Servlet implementation class LoginServlet
+ */
+@WebServlet("/Login")
+public class LoginServlet extends HttpServlet {
+	private static final long serialVersionUID = 1L;
+	public LoginServlet() {
+		super();
+	}
+	protected void doGet(HttpServletRequest request, HttpServletResponse response)
+			throws ServletException, IOException {
+		RequestDispatcher dispacher = request.getRequestDispatcher("/WEB-INF/jsp/Login.jsp");
+		dispacher.forward(request, response);
+	}
+	protected void doPost(HttpServletRequest request, HttpServletResponse response)
+			throws ServletException, IOException {
+		//login-id,password取得
+		String login_id = request.getParameter("login-id");
+		String password = request.getParameter("login-password");
+		LoginInfoDao dao = new LoginInfoDao();
+		LoginModel model = new LoginModel();
+		try {
+			model = dao.findAccount(login_id, password);
+			//ユーザーの有無検索
+			if (model != null) {
+				response.sendRedirect("/Manager/List");
 			}
+			request.setAttribute("error", "入力内容が間違っています。");
+			request.getRequestDispatcher("/WEB-INF/jsp/Login.jsp").forward(request, response);
 		} catch (SQLException e) {
 			e.printStackTrace();
-			return null;
-		} finally {
 		}
-		return returnLm;
 	}
 }
-```
-Servlet　クラス
-```
-package servlet;
-import java.io.IOException;
-import javax.servlet.RequestDispatcher;
-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.servlet.http.HttpSession;
-import dao.LoginInfoDao;
-import model.LoginModel;
-/**
- * Servlet implementation class LoginServlet
- */
-@WebServlet("/Login")
-public class LoginServlet extends HttpServlet {
-	private static final long serialVersionUID = 1L;
-    public LoginServlet() {
-        super();
-    }
-	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
-		RequestDispatcher dispacher = request.getRequestDispatcher("/WEB-INF/jsp/Login.jsp");
-        dispacher.forward(request, response);
-	}
-	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
-        //login-id,password取得
-		String login_id = request.getParameter("login-id");
-		String password = request.getParameter("login-password");
-		LoginModel lm = new LoginModel();
-		lm.setLogin_id(login_id);
-		lm.setPassword(password);
-		//dao情報取得
-		LoginInfoDao dao = new LoginInfoDao();
-		LoginModel returnLm  = dao.findAccount(lm);
-		//ユーザーの有無検索
-		if (returnLm != null ) {
-			HttpSession session = request.getSession();
-		    response.sendRedirect("/Manager/List");
-		}
-		request.setAttribute("error", "入力内容が間違っています。");
-		request.getRequestDispatcher("/WEB-INF/jsp/Login.jsp").forward(request, response);
-	}
-}
 ```