一個servlet例子-統計網站訪問量
1.建立JavaWeb專案，名WebCount
2.修改web.xml，如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>WebCount1</display-name>
<servlet>
<servlet-name>CounterServlet</servlet-name>
<servlet-class>com.CounterServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CounterServlet</servlet-name>
<url-pattern>/counter</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>counter</welcome-file>
</welcome-file-list>
</web-app>、
3.新建名稱為CounterServlet的servlet類，在該類dopost（）方法中實現統計訪問數目。
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
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 CounterServlet
*/
@WebServlet("/CounterServlet")
public class CounterServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public CounterServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see Servlet#destroy()
*/
public void destroy() {
super.destroy();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//獲得ServletContext物件
ServletContext context=getServletContext();
//從ServletContext中獲取計數器物件
Integer count=(Integer) context.getAttribute("counter");
if(count==null){//如果為空，則在ServletContext中設定一個計數器的屬性
count=1;
context.setAttribute("counter", count);
}else{
context.setAttribute("counter", count+1);
}
response.setContentType("text/html");//響應正文的MIME型別
response.setCharacterEncoding("UTF-8");//響應的編碼格式
PrintWriter out=response.getWriter();
// out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
// out.println("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
// out.println("<HTML>");
out.println("<HEAD><TITLE>統計網站訪問次數</TITLE></HEAD>");
out.println("<BODY>");
// out.println("<h2><font color='gray'");
out.println("您是第"+context.getAttribute("counter")+"位訪客！");
// out.println("</font>");
// out.println("</h2>");
out.println("</BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
4.將專案部署到伺服器，啟動伺服器。結果如下。
