servlet+jsp+MySQL實現簡單的頁面登陸
阿新 • • 發佈：2019-02-19
由於對於前端的程式碼不熟悉，頁面登陸介面會比較簡陋，請見諒。
本部落格為本人自學後自行嘗試的實戰，若有錯誤，望指出，不勝感激。
在eclipse中，整個專案結構如下：
login.jsp用於登陸，register.jsp用於註冊，welcome.jsp為登陸後的介面
linkdb.java主要用來連線資料庫，程式碼如下：
package secondsfj;
import java.sql.DriverManager;
import java.sql.SQLException;
import com.mysql.jdbc.Connection;
public class linkdb {
public static final String db="com.mysql.jdbc.Driver";
public static final String url="jdbc:mysql://localhost:3306";
public static final String user="root";
public static final String password="9999999";
private Connection conn;
public void linkdatabase()
{
try {
Class.forName(db);
conn=(Connection) DriverManager.getConnection(url,user,password);
} catch (ClassNotFoundException e) {
System.out.println("載入資料庫類失敗");
} catch (SQLException e) {
System.out.println("連線資料庫失敗");
}
}
public Connection getconn()
{
return conn;
}
public void close()
{
try {
if(!conn.isClosed())conn.close();
} catch (SQLException e) {
System.out.println("關閉資料庫連線失敗");
}
}
}
controldb.java主要用於資料庫的操作，程式碼如下：
package secondsfj; import java.sql.ResultSet; import java.sql.SQLException; import com.mysql.jdbc.Statement; import secondsfj.linkdb; public class controldb { private Statement state=null; private ResultSet res = null; linkdb deal=new linkdb(); public void dealcontroldb()//連線資料庫，建立SQL語句物件 { try { deal.linkdatabase(); state=(Statement) (deal.getconn()).createStatement(); } catch (SQLException e) { System.out.println("建立SQL語句失敗"); } hasdb(); } void hasdb()//判斷資料庫是否存在，不存在，進行建立 { String temp; boolean x=false; try { res=state.executeQuery("show databases;"); while(res.next()) { temp=res.getString(1); if(temp.equals("login")) { x=true; break; } } if(x==false) { state.execute("create database login;"); state.execute("use login;"); state.execute("create table user (username char(20),password char(20));"); } } catch (SQLException e) { System.out.println("controldb中的SQL語句執行失敗"); } } public boolean verify(String username,String password)//用於驗證登陸 { String usertemp; String passtemp; if(username==null||password=="null"||"".equals(username)||"".equals(password)) return false; try { state.execute("use login;"); res=state.executeQuery("select * from user"); while(res.next()) { usertemp=res.getString(1); if(usertemp.equals(username)) { passtemp=res.getString(2); if(passtemp.equals(password)) return true; } } } catch (SQLException e) { System.out.println("verify中的SQL語句執行失敗"); } return false; } public boolean register(String user,String passwd)//用於註冊 { if(user==null||passwd==null||"".equals(user)||"".equals(passwd)) return false; try { state.execute("use login;"); state.execute("insert into user(username,password) values("+user+","+passwd+");"); } catch (SQLException e) { System.out.println("register中的SQL語句執行失敗"); return false; } return true; } public void close()//關閉連線 { try { if(!state.isClosed())state.close(); if(!res.isClosed())res.close(); deal.close(); } catch (SQLException e) { System.out.println("controldb關閉失敗"); } } }
servletforlogin用於處理登陸介面的post請求，程式碼如下：
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 secondsfj.controldb; import secondsfj.linkdb; @WebServlet(displayName="servletforlogin", urlPatterns={"/servletforlogin"}) public class servletforlogin extends HttpServlet { private static final long serialVersionUID = 1L; public servletforlogin() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub response.getWriter().append("Served at: ").append(request.getContextPath()); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username=request.getParameter("user"); String password=request.getParameter("password"); controldb temp=new controldb(); temp.dealcontroldb(); boolean x=temp.verify(username, password); String error=null; if(x==false) { error="使用者名稱或是密碼錯誤"; request.setAttribute("error", error); request.getRequestDispatcher("login.jsp").forward(request, response); } else { response.sendRedirect("welcome.jsp"); } temp.close(); } }
servletforregister負責註冊，程式碼如下：
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 secondsfj.controldb;
import secondsfj.linkdb;
@WebServlet(displayName="servletforregister",urlPatterns={"/servletforregister"})
public class servletforregister extends HttpServlet {
private static final long serialVersionUID = 1L;
public servletforregister() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username=request.getParameter("user");
String password=request.getParameter("password");
controldb deal=new controldb();
deal.dealcontroldb();
String error=null;
boolean x=deal.register(username, password);
if(x==false)
{
error="密碼或是使用者名稱為空";
request.setAttribute("error", error);
request.getRequestDispatcher("register.jsp").forward(request, response);
}
else response.sendRedirect("login.jsp");
deal.close();
}
}login.jsp為登陸介面，程式碼如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陸</title>
</head>
<body>
<%
String deal=(String)request.getAttribute("error");
if(deal!=null)
out.println(deal);
%>
<form action="servletforlogin" method="post">
使用者:<input type="text" name="user"/>
<br>
<br>
密碼:<input type="password" name="password"/>
<br>
<br>
<input type="submit" value="提交">
</form>
<br>
<br>
<button onclick="{location.href='/secondsfj/register.jsp'}">註冊</button>
</body>
</html>register.jsp用於註冊，程式碼如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>註冊</title>
</head>
<body>
<%
String error=(String)request.getAttribute("error");
if(error!=null)
out.println(error);
%>
<form action="/secondsfj/servletforregister" method="post">
使用者:<input type="text" name="user"/>
<br/>
<br/>
密碼:<input type="password" name="password"/>
<br/>
<br/>
<input type="submit" value="提交"/>
</form>
</body>
</html>welcome.jsp為登陸後的介面，程式碼如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
歡迎!!!!!
</body>
</html>執行過程如下，先註冊後登陸：
若我們登陸時輸入錯誤的使用者或密碼，會出現錯誤提示：
注意到url處不為login.jsp，因為我們呼叫的是forward，此時位址列的url不會發生改變。
若我們註冊時只輸入空格或不輸入就按提交，會出現如下錯誤資訊
url欄不變原因同上。