Javaweb实现简易的留言板项目- 校招VIP

转载声明：文章来源https://blog.csdn.net/yang_study_first/article/details/86383092

一、JavaBean层的设计

数据表参数的获取
主要是生成数据表字段的get，set方法，对数据进行设置和获取。

数据库连接和操作

/**数据库连接*/
public class DBConn {
 
 public static Connection conn;
  // Connection对象（链接）
  // 连接数据库
  public static Connection getConn() {
     try {
       // 加载注册SQLSever的JDBC驱动
       Class.forName("com.mysql.jdbc.Driver");
       // 编写链接字符串，创建并且获取链接
       conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/MessageBoard","root","root");
     } catch (Exception e) {
       e.printStackTrace();
     }
     return conn;
  }
 
  public static void CloseConn() {
     try {
       conn.close();
     } catch (Exception e) {
       e.printStackTrace();
     }
  }
 
  public static void main(String[] args) {
     Connection conn=DBConn.getConn();
     if(conn!=null) {
       System.out.println("数据库连接正常");
     }else {
       System.out.println("数据库连接失败");
     }
  }
}

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/**数据库操作*/
public class LoginDao {
 
  Connection conn = DBConn.getConn();
  // 数据库连接对象
  PreparedStatement pstmt;
   
  public Login checkLogin(String name, String password) {
     // 验证用户名密码
     try {
       pstmt = conn.prepareStatement("select*from logins where name=?and password=?");
       pstmt.setString(1, name);
       // 设置SQL语句参数
       pstmt.setString(2, password);
       // 设置SQL语句参数
       ResultSet rs = pstmt.executeQuery();
       // 执行查询，返回结果集
       if (rs.next()) {
         // 通过JavaBean保存值
         Login login = new Login();
         login.setId(rs.getInt(1));
         login.setName(rs.getString(2));
         login.setPassword(rs.getString(3));
         login.setRole(rs.getInt(4));
         return login;
         // 返回JavaBean对象
       }
       return null;
       // 验证失败返回null
     } catch (Exception e) {
       e.printStackTrace();
       return null;
     }
  }
 
  //留言查询
  public ArrayList<MessBor> findMbInfo() {
     try {
       ArrayList<MessBor> al = new ArrayList<MessBor>();
       pstmt = conn.prepareStatement("select *from messages");
       ResultSet rs = pstmt.executeQuery();
       while (rs.next()) {
         MessBor mb = new MessBor();
         mb.setId(rs.getInt(1));
         mb.setName(rs.getString(2));
         mb.setTime(rs.getDate(3));
         mb.setTitle(rs.getString(4));
         mb.setMessage(rs.getString(5));
         al.add(mb);
       }
       return al;
     } catch (Exception e) {
       e.printStackTrace();
       return null;
     }
  }
   
  public String getName(int id) {
     String name = null;
     try {
       pstmt = conn.prepareStatement("select namefrom logins where id=?");
       pstmt.setInt(1, id);
       ResultSet rs = pstmt.executeQuery();
       while (rs.next()) {
         name = rs.getString(1);
       }
       return name;
     } catch (Exception e) {
       e.printStackTrace();
       return null;
     }
  }
  
 //添加留言
  public boolean addInfo(MessBor mb) {
     try {
       pstmt = conn.prepareStatement("insert intomessages values(?,?,?,?,?)");
       pstmt.setInt(1, mb.getId());
       pstmt.setString(2, mb.getName());
       pstmt.setDate(3, mb.getTime());
       pstmt.setString(4, mb.getTitle());
       pstmt.setString(5, mb.getMessage());
       pstmt.executeUpdate();
       return true;
     } catch (Exception e) {
       e.printStackTrace();
       return false;
     }
  }
   
  //用户注册
  public boolean insertUser(int id, String name, String password) {
     try {
       pstmt = conn.prepareStatement("insert into
logins(id,name,password,role) values(?,?,?,?)");
       pstmt.setInt(1, id);
       pstmt.setString(2, name);
       pstmt.setString(3, password);
       pstmt.setInt(4, 0);
       pstmt.executeUpdate();
       return true;
     } catch (Exception e) {
       e.printStackTrace();
       return false;
     }
  }
}

二、jsp页面设计

jsp页面主要包括登陆和注册页面，留言主页面，留言界面。

<!-- 登陆界面 -->
<body>
  <div style="margin-left: 35%; margin-top: 100px; font-family: Microsoft YaHei">
     <h1>登录界面</h1>
     <form action="LoginServlet" method="post">
       <table>
         <tr>
            <td>账号:</td>
            <td><input name="name" type="text"></td>
         </tr>
         <tr>
            <td>密码:</td>
            <td ><input name="password" type="password"></td>
         </tr>
       </table>
       <input type="submit"  value="登录" style="font-size: 16px"> 
         <a href="register.jsp">注册</a>
     </form>
  </div>
</body>

<!-- 注册界面 -->
<body>
  <div>
     <h1>注册界面</h1>
     <form action="RegisterServlet" method="post">
       <table>
         <tr>
            <td>ID:</td>
            <td><input name="id" type="text" size="20"></td>
         </tr>
         <tr>
            <td>登录名：</td>
            <td><input name="name"type="text" size="20"></td>
         </tr>
         <tr>
            <td>密码:</td>
            <td><input name="password"type="password" size="21"></td>
         </tr>
       </table>
       <input type="submit"value="注册">
       <input type="reset" value="重置">
     </form>
     <br> <a href="login.jsp">登录</a>
  </div>
</body>

<!-- 留言主界面 -->
<body>
  <div
     style="margin-left: 35%; margin-top: 100px; font-family: Microsoft YaHei">
     <h1 style="margin-left: 5%">这里是留言板主界面</h1>
     <form action="leavemessage.jsp" method="post">
       <table border="1">
         <caption>所有留言信息</caption>
         <tr>
            <th>留言人姓名</th>
            <th>留言时间</th>
            <th>留言标题</th>
            <th>留言内容</th>
         </tr>
         <%
            ArrayList<MessBor> al = new ArrayList<MessBor>();
            al = (ArrayList) session.getAttribute("al");
            if (al != null) {
              Iterator iter = al.iterator();
              while (iter.hasNext()) {
                MessBor mb = (MessBor) iter.next();
         %>
         <tr>
            <td><%=new LoginDao().getName(mb.getId())%></td>
            <td><%=mb.getTime().toString()%></td>
            <td><%=mb.getTitle()%></td>
            <td><%=mb.getMessage()%></td>
         </tr>
         <%
             }
          }
         %>
       </table>
     </form>
     <a style="margin-left: 22%" href="leavemessage.jsp">留言</a>
  </div>
</body>

<!-- 留言界面 -->
<body>
  <div style="text-align: center; margin-top: 140px">
     <h1>请留言</h1>
     <form action="LeaveMessage" method="post">
       <table style="margin-left: 37%" border="1">
         <caption>填写留言信息</caption>
         <tr>
            <td>留言标题</td>
            <td><input type="text"name="title" /></td>
         </tr>
         <tr>
            <td>留言内容</td>
            <td><textarea name="message" rows="5" cols="35"></textarea></td>
         </tr>
       </table>
       <input type="submit"value="提交" />
       <input type="reset"value="重置" />
     </form>
     <a href="main.jsp">返回留言板界面</a>
  </div>
</body>

三、servlet设计

servlet主要实现登录，注册，留言等功能。

/**登录操作*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;
 
  public LoginServlet() {
     super();
  }
 
  public void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     // 设置请求编码
     request.setCharacterEncoding("utf-8");
     // 设置响应编码
     response.setContentType("utf-8");
     LoginDao loginDao = new LoginDao();
     HttpSession session = request.getSession();
     // 先获得user对象，如果是第一次访问该Servlet，用户对象肯定为空，
     //但如果是第二次甚至是第三次，就不应该再判断该用户的信息
     Login l = (Login) session.getAttribute("login");
     if (l == null)
       l = loginDao.checkLogin(request.getParameter("name"), request.getParameter("password"));
     if (l != null) {
       // 如果登陆成功
       session.setAttribute("login", l);
       // 将获取的对象保存在session中
       ArrayList al = loginDao.findMbInfo();
       // 获取留言板的内容，返回一个数组
       session.setAttribute("al", al);
       // 把数组保存起来
       response.sendRedirect("main.jsp");
       // 验证成功跳转到 main.jsp
     } else {
       // 验证失败跳转到 error.jsp
       response.sendRedirect("error.jsp");
     }
     if(session!=null) {
       response.sendRedirect("login.jsp");
     }
  }
 
  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
     doGet(request, response);
  }
}

/**注册操作*/
@WebServlet("/RegisterServlet")
public class RegisterServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;
 
  public RegisterServlet() {
     super();
      }
 
  public void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
       //设置请求编码
     request.setCharacterEncoding("utf-8");
     //获取字段
     int id = Integer.valueOf(request.getParameter("id"));
     String name = request.getParameter("name");
     String password = request.getParameter("password");
     if (new LoginDao().insertUser(id, name, password)) {
       //注册成功，跳转到登录界面
       response.sendRedirect("login.jsp");
     }
  }
 
  public void doPost(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     doGet(request, response);
  }
}

/**留言操作*/
@WebServlet("/LeaveMessage")
public class LeaveMessage extends HttpServlet {
  private static final long serialVersionUID = 1L;
  public LeaveMessage() {
     super();
  }
 
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     // 设置请求编码        
     request.setCharacterEncoding("utf-8");         
     // 设置响应编码        
     response.setContentType("utf-8");         
     // 获取title内容         
     String title=request.getParameter("title");        
     // 获取message内容         
     String message=request.getParameter("message");         
     // 从session中取出当前用户对象         
     Login leaveMessageBoard=(Login) request.getSession().getAttribute("login");        
     // 建立留言表对应JavaBean对象，把数据封装进去        
     MessBor mb=new MessBor();        
     mb.setId(leaveMessageBoard.getId());        
     // 参数为获取的当前时间         
     mb.setName(leaveMessageBoard.getName());         
     mb.setTime(new Date(System.currentTimeMillis()));          
     mb.setTitle(title);         
     mb.setMessage(message);       
     // 调DB类中的方法判断是否插入成功         
     if(new LoginDao().addInfo(mb)){           
       response.sendRedirect("success.jsp") ;         
       }
  }
 
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     doGet(request, response);
  }
}

四、数据库设计

/*注册表和留言表*/
 
CREATE TABLE `logins` (
  `id` int(11) NOT NULL,
  `name` varchar(20) NOT NULL,
  `password` varchar(20) NOT NULL,
  `role` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-------------------------------------------------------------------
CREATE TABLE `messages` (
  `id` int(11) NOT NULL,
  `name` varchar(20) NOT NULL,
  `time` varchar(20) NOT NULL,
  `title` varchar(20) NOT NULL,
  `message` varchar(60) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

小结：

本项目采用MVC设计模式（所谓MVC：模型(model)－视图(view)－控制器(controller)，它是用一种业务逻辑、数据与界面显示分离的方法来组织代码，将众多的业务逻辑聚集到一个部件里面，在需要改进和个性化定制界面及用户交互的同时，不需要重新编写业务逻辑，达到减少编码的时间。是一种软件设计典范。），主要学习数据库与jsp和servlet的综合使用，也是本项目的难点。本项目已上传到GitHub，供大家下载使用。