JSP-一個理解MVC架構的簡單的登陸、註冊例子

最後更新：2018-12-07 來源：互聯網

上載者：User

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首先我們看看這個目錄結構


--+login
----------+WEB-INF
-----------------------+classes
                          -beans
                          -tags
-----------+tlds

login 是主目錄放jsp檔案，在例子login.jsp,loginFailed.jsp,login_form.jsp,newAccount.jsp,welcome.jsp,accountCreated.jsp

Web-inf下面有web.xml設定檔，classes檔案夾放類，tlds檔案夾放自訂標籤
由於我沒有用到資料庫，所以沒有用LIB檔案夾，是來放置*.jar檔案的。

classes目錄下，有beans,tags檔案夾，分別放置User,LoginDB類，和自訂標籤類GetRequestParameterTag,classes目錄下還直接放了LoginServlet,NewAccountServlet控制器類

我們先看beans下的兩個業務對象類
User.java

package beans;

public class User implements java.io.Serializable {
private final String userName,password,hint;
//final強調此屬性初始化後，不能修改hint是口令提示
public User(String userName,String password,String hint) {
this.userName = userName;
this.password = password;
this.hint = hint;
}
public String getUserName(){
return userName;
}
public String getPassword(){
return password;
}
public String getHint(){
return hint;
}
//判斷當前對象使用者名稱和密碼是否相等
public boolean equals(String uname,String upwd) {
return getUserName().equals(uname) &&
getPassword().equals(upwd);
}
}

LoginDB.java



package beans;

import java.util.Iterator;
import java.util.Vector;

public class LoginDB implements java.io.Serializable {
     private Vector users = new Vector();
    //Vector類是同步的，所以addUser就不需要同步了
    public void addUser(String name,String pwd,String hint) {
        users.add(new User(name,pwd,hint));
    }
          //下面方法判斷是否存在正確的user
    public User getUser(String name,String pwd) {
        Iterator it = users.iterator();
        User user;
         //迭代需要同步
        synchronized(users) {
while(it.hasNext()){
user = (User)it.next();
if(user.equals(name,pwd))
               return user;  //如果返回真，就返回當前user
                }
        }
     return null;
}
     public String getHint(String name) {
         Iterator it = users.iterator();
         User user;
         synchronized(users) {
while(it.hasNext()){
     user = (User)it.next();
     if(user.getUserName().equals(name))
     return user.getHint();
}
         }
   return null;
   }
}

login.jsp

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>Login Page</title>
</head>
<body>
<@ include file="login_form.jsp">
</body>
</html>
被包含的login_form.jsp

<%@ taglib uri="utilities" prefix="util" %>
 <!--調用自訂標籤，引用為util，uri的utilities在web.xml映射了-->
<p><font color="#6666CC">請登陸</font></p>
<hr>
<form name="form1" method="post" action="<%=response.encodeURL("login")%>"><!--login是LoginSevlet通過在web.xml映射了-->
  <table width="68%" border="0" cellpadding="2" cellspacing="2">
    <tr> 
      <td width="33%" align="right">使用者名稱：</td>
      <td width="67%">
  <input type="text" name="userName" value="<util:requestParameter property='userName'/>"></td><!--注意這裡用了自訂標籤，如果有值就顯示-->
    </tr>
    <tr> 
      <td align="right">密碼：</td>
      <td><input type="text" name="userPwd" ></td>
    </tr>
    <tr align="center"> 
      <td colspan="2"> 
        <input type="submit" name="Submit" value="登陸">
      </td>
    </tr>
  </table>
</form>
LoginServlet.java

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

import beans.User;
import beans.LoginDB;

public class LoginServlet extends HttpServlet {
         private LoginDB loginDB;

         public void init(ServletConfig config) throws ServletException {
super.init(config);
loginDB = new LoginDB();
config.getServletContext().setAttribute("loginDB",loginDB);
        }
        public void doGet(HttpServletRequest request,HttpServletResponse response)
                   throws ServletException,IOException{
           String name = request.getParameter("userName");
           //從login_form表單得到值
           String pwd = request.getParameter("userPwd");
           User user = loginDB.getUser(name,pwd);
           if(user != null){　//說明存在使用者
   request.getSession().setAttribute("user",user);
                   //放到session裡面
   request.getRequestDispatcher(response.encodeURL("/welcome.jsp"))
.forward(request,response);
　　　　　　//成功轉寄到welcome.jsp
          }else{
request.getRequestDispatcher(response.encodeURL("/loginFailed.jsp"))
.forward(request,response);
        }
}
        public void doPost(HttpServletRequest request,HttpServletResponse response)
                  throws ServletException,IOException{
doGet(request,response);
        }
}
web.xml添加

<servlet>
<servlet-name>Login</servlet-name><!--名字-->
<servlet-class>LoginServlet</servlet-class><!--指定類-->
  </servlet><servlet>
<servlet-name>new_account</servlet-name>
<servlet-class>NewAccountServlet</servlet-class>
  </servlet>
   <servlet-mapping>
<servlet-name>new_account</servlet-name>
<url-pattern>/new_account</url-pattern>
  </servlet-mapping>
   <servlet-mapping>
<servlet-name>Login</servlet-name><!--和上面的名字一致-->
<url-pattern>/login</url-pattern><!--映射路徑-->
  </servlet-mapping>
 <taglib>
<taglib-uri>utilities</taglib-uri>
<taglib-location>/WEB-INF/tlds/utilities.tld</taglib-location>
　　　　　　　　　　<!--自訂標籤的實際位置-->
  </taglib>
utilities.tld關鍵區段

<taglib>
<tag>
<name>requestParameter</name>
<tagclass>tags.GetRequestParameterTag</tagclass>
<!--類的位置，如果有包寫上-->
<info>Simplest example: inserts one line of output</info>
<bodycontent>Empty</bodycontent>
<attribute>
<name>property</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
自訂標籤類GetRequestParameterTag.java


package tags;

import javax.servlet.ServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

public class GetRequestParameterTag extends TagSupport {
       private String property;

      public void setProperty(String property) {
this.property = property;
     }
      public int doStartTag() throws JspException {
ServletRequest reg = pageContext.getRequest();
String value = reg.getParameter(property);

try{
pageContext.getOut().print(value == null ? "":value);
}catch(java.io.IOException e){
throw new JspException(e.getMessage());
}
return SKIP_BODY;
       }
}
 
登陸成功welcome.jsp

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>Welcome Page</title>
</head>
<body>
<jsp:userBean id="user" scope="session" class="beans.User"/>
<!--也可以
<%
User user = (User)session.getAttribute("user");
%>
-->
歡迎你：<font color=red><%=user.getUserName()%></font>
</body>
</html>
登陸失敗loginFailed.jsp

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>Login Failed</title>
</head>

<body>
<font color="#993366">請輸入使用者名稱和密碼，或者建立一個新使用者！</font> 
<%@ include file="/login_form.jsp"%>
<hr>
<a href="<%=response.encodeURL("newAccount.jsp")%>">建立一個新使用者 </a>
</body>
</html>
建立使用者newAccount.jsp

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>New Account</title>
</head>

<body>
<font color="#996633">建立新使用者 </font>
<form name="form1" method="post" action="<%=response.encodeURL("new_account")%>">
  <table width="75%" border="0" cellpadding="3">
    <tr> 
      <td width="42%" align="right">使用者名稱：</td>
      <td width="58%"><input type="text" name="userName"></td>
    </tr>
    <tr> 
      <td align="right">密碼：</td>
      <td><input type="text" name="userPwd"></td>
    </tr>
    <tr>
      <td align="right">密碼問題：</td>
      <td><input type="text" name="hint"></td>
    </tr>
    <tr align="center"> 
      <td colspan="2"> <input type="submit" name="Submit" value="提交"> </td>
    </tr>
  </table>
</form>
</body>
</html>
註冊的控制器NewAccountServlet

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

import beans.LoginDB;

public class NewAccountServlet extends HttpServlet {

       public void doPost(HttpServletRequest request,HttpServletResponse response)
                  throws ServletException,IOException{
LoginDB loginDB = (LoginDB)getServletContext().getAttribute("loginDB");
loginDB.addUser(request.getParameter("userName"),
request.getParameter("userPwd"),
request.getParameter("hint"));
request.getRequestDispatcher(response.encodeUrl("accountCreated.jsp")).forward(request,response);
     }
}
accountCreated.jsp

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>無標題文檔</title>
</head>

<body>
新使用者已經建立！ <font color="#0000FF"><%=request.getParameter("userName")%></font> 
<hr><%@ include file="login_form.jsp"%>
</body>
</html>

本文章原先以中文撰寫並發佈於 aliyun.com，亦設英文版本，僅作資訊用途。本網站不對文章的準確性，完整性或可靠性或其任何翻譯作出任何明示或暗示的陳述或保證。如對該文章有任何疑慮或投訴，請傳送電郵至 info-contact@alibabacloud.com 並提供相關疑慮或投訴的詳細說明。職員會於 5 個工作天內與您聯絡，一經驗證之後，即會刪除該侵權內容。

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