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Jun 24, 2016 am 11:48 AM

The learning website is from www.imooc.com

Servlet Basics
1. What is Servelet?
Servelet is a small program running on the server. A Servlet is a Java class
, and the Servlet program that resides in the server memory
can be accessed through the "request-response" programming model. Servlet is the predecessor of jsp.

2. Tomcat container levels
Tomcat containers are divided into four levels. The Servlet container manages the Context container, and one
Context corresponds to a Web project. Engine is an engine container; Host is a host container.

3. Writing a Servlet
is divided into three steps.
1. Write a class that inherits HttpServlet
2. Override the doGet() or doPost() method; depending on the submission method.
3. Register Servlet in web.xml.
The procedure is as follows:

Code in index.jsp:

<body>    <h1 id="第一个Servlet小例子">第一个Servlet小例子</h1>    <hr>    <!-- 用get方式请求，写一个超链接就可以了;超链接访问就是get请求-->    <a href="servlet/HelloServlet">get方式请求HelloServlet</a><br>    <!-- 用post方式，做一个表单就可以实现 -->    <form action="servlet/HelloServlet" method="post">    <input type="submit" value="post方式请求HelloServlet"/>    </form>  </body>

HelloServlet.java Code in:

package Servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//继承于HttpServletpublic class HelloServlet extends HttpServlet {//重写方法	@Override	protected void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		// TODO Auto-generated method stub		System.out.println("处理Get()请求...");		//获得一个给浏览器输出的对象out,类型为 PrintWriter		PrintWriter out = response.getWriter();		//指定输出文件的类型		response.setContentType("text/html;charset=utf-8");		//用out对象给浏览器输出一个信息。可以在里面用html的代码		out.println("<strong>Hello Servelet!</strong><br>");		//3.注册；在WEB-INF里面的web.xml中注册	}	@Override	protected void doPost(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		// TODO Auto-generated method stub		System.out.println("处理post()请求...");		//获得一个给浏览器输出的对象out,类型为 PrintWriter		PrintWriter out = response.getWriter();		//指定输出文件的类型		response.setContentType("text/html;charset=utf-8");		//用out对象给浏览器输出一个信息。可以在里面用html的代码		out.println("<strong>Hello Servelet!post</strong><br>");		//3.注册；在WEB-INF里面的web.xml中注册；已经注册完 就不用重复	}}

Registration code in web.xml:

The registration process is to add two tags
< in web.xml ;servlet> and
and each tag must contain two sub-tags
in To include give the Servlet a name
and the class name of the Servlet to be accessed (package name and class name)
> ;
In , include Give
Servlet a name (note: it must be the same as the name above) and
The path visited by Servlet

<servlet>  <servlet-name>HelloServlet</servlet-name>  <servlet-class>Servlet.HelloServlet</servlet-class>  </servlet>  <servlet-mapping>  <servlet-name>HelloServlet</servlet-name>  <url-pattern>/servlet/HelloServlet</url-pattern>  </servlet-mapping>

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