servlet入门介绍

servlet的三种方式

1.实现servlet的接口

2.继承GenericServlet

3.继承HttpServlet

 

对于第一次实现servlet的开发

<pre class="java" name="code">package com.sgp;import javax.servlet.*;import javax.servlet.http.*;/** * Servlet implementation class ServletImp */public class ServletImp implements Servlet {    public ServletImp() {        super();    }    public void destroy() {        }//该函数用于初始化servlet，就是把servlet加载到内存中//该函数只会被调用一次public void init(ServletConfig config) throws ServletException {}//得到ServletConfig对象public ServletConfig getServletConfig() {return null;}/** * service方面里面来处理业务的逻辑，可以调用多次*/@Overridepublic void service(ServletRequest req, ServletResponse res)throws ServletException, IOException {//得到配置信息public String getServletInfo() {// TODO Auto-generated method stubreturn null;}}

 

servllet的开发，java文件保存在class中

如果使用javac去编译一个打包的java文件 则需要带命令参数

javac -d  .java文件

经过编译后，生成包，为class文件。也就可以删除写的java文件

 

编译后不能访问，因为还没有部署servlet，在web-inf的web.xml中部署。

<servlet>         <description></description>

    <display-name>HelloServlet</display-name>    <!--名字任意，不过建议和类名一样-->    <servlet-name>HelloServlet</servlet-name>    <!--类名+包路径-->    <servlet-class>com.kiritor.servlet.HelloServlet</servlet-class>      <!--初始化是的参数，必须在这里进行配置-->      <init-param>      <description></description>      <param-name>info</param-name>      <param-value>this is a init message</param-value>    </init-param>  <!--映射配置-->  </servlet>  <servlet-mapping>  <!--和上述的Servlet名一样-->  <servlet-name>HelloServlet</servlet-name>  <!--浏览器的访问路径-->  <url-pattern>/HelloServlet</url-pattern>  </servlet-mapping>

 

 

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HttpServlet一般使用比较多

package com.kiritor.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;/** * Servlet implementation class ExHttpServlet */public class ExHttpServlet extends HttpServlet {private static final long serialVersionUID = 1L;           /**     * @see HttpServlet#HttpServlet()     */    public ExHttpServlet() {        super();        // TODO Auto-generated constructor stub    }    /**     * 继承HttpServlet一般在doPost、doGet方法     * 里面处理业务逻辑     * 之后由service回调。*//** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request, response);}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {PrintWriter writer = response.getWriter();writer.write("Imp Servlet!");                writer.flush();                writer.close();       }}