在URL重寫中，我們將令牌或標(biāo)識符附加到下一個(gè)Servlet或下一個(gè)資源的URL。可以使用以下格式發(fā)送參數(shù)名稱/值對：
http://localhost/myappurl?key1=value1&key2=value2&??...
使用=符號分隔名稱和值，使用&符號將參數(shù)名/值對與其他參數(shù)分開。當(dāng)用戶單擊超鏈接時(shí)，參數(shù)名稱/值對將被傳遞到服務(wù)器。 從Servlet中可以使用getParameter()方法獲取指定參數(shù)的值。
網(wǎng)址重寫的優(yōu)點(diǎn)
URL重寫的缺點(diǎn)
在這個(gè)例子中，我們使用鏈接來維護(hù)用戶的狀態(tài)。為此，在查詢字符串中附加用戶的名稱，并從另一頁面的查詢字符串中獲取該值。
打開Eclipse，創(chuàng)建一個(gè)動(dòng)態(tài)Web項(xiàng)目：UrlRewriting，其完整的結(jié)構(gòu)如下所示 -
下面是此項(xiàng)目中幾個(gè)重要的文件代碼。
文件：index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>URL重寫</title>
</head>
<body>
<div style="text-algin: center; padding-top: 12px;">
<form action="servlet1" method="get">
名字：<input type="text" name="username" value="maxsu"/><input type="submit"
value="提交" />
</form>
</div>
</body>
</html>
文件：FirstServlet.java
package com.yiibai;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class FirstServlet
*/
public class FirstServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String n = request.getParameter("username");
out.print("您好， " + n + "<br/><hr/>");
// appending the username in the query string
out.print("<a href='servlet2?uname=" + n + "'>使用URL參數(shù)訪問用戶名</a>");
out.close();
}
}
文件：SecondServlet.java
package com.yiibai;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class FirstServlet
*/
@WebServlet("/FirstServlet")
public class SecondServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//getting value from the query string
String n=request.getParameter("uname");
out.print("Hello "+n);
out.close();
}
}
文件：web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
<display-name>UrlRewriting</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>s1</servlet-name>
<servlet-class>com.yiibai.FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>s1</servlet-name>
<url-pattern>/servlet1</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>s2</servlet-name>
<servlet-class>com.yiibai.SecondServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>s2</servlet-name>
<url-pattern>/servlet2</url-pattern>
</servlet-mapping>
</web-app>
在編寫上面代碼后，部署此Web應(yīng)用程序，打開瀏覽器訪問URL： http://localhost:8080/UrlRewriting ，如果沒有錯(cuò)誤，應(yīng)該會(huì)看到以下結(jié)果 -
填寫用戶名后點(diǎn)擊提交表單，應(yīng)該會(huì)看到以下結(jié)果 -
注意： 在URL中，附加了參數(shù)”username=maxsu” 來區(qū)別用戶。
再次點(diǎn)擊“使用URL參數(shù)訪問用戶名”鏈接，看到顯示的用戶名:maxsu -
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