servlet的工作流程

来源：互联网发布：基调网络编辑：程序博客网时间：2024/05/01 13:13

首先我们看一下servlet的一个例子：

<span style="font-family: Helvetica, Tahoma, Arial, sans-serif; font-size: 13.75px; line-height: 25.1953125px;">首先servlet继承于HttpServlet </span>

package com.test.action;    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 继承与 HttpServlet 重写 doGet() doPost()方法  * servlet可以直接返回 ，即获取PrintWriter输出流，在PrintWriter中输出字符串  * servlet也可以返回jsp，即response.sendRedirect(jspPath)  *   * @author  姓名 工号  * @version  [版本号, 2012-10-14]  * @see  [相关类/方法]  * @since  [产品/模块版本]  */  public class TestServlet extends HttpServlet  {        @Override      protected void doGet(HttpServletRequest req, HttpServletResponse resp)              throws ServletException, IOException      {          //直接返回  //      resp.setContentType("text/html;charset=utf-8");  //      PrintWriter pw = resp.getWriter();  //      pw.println("<html><head>");  //      pw.println("<title>testServlet</title>");  //      pw.println("</head><body>this is a testServlet example!");  //      pw.println("</body></html>");  //      pw.close();                    //返回jsp          resp.sendRedirect("servlet.jsp");      }        @Override      protected void doPost(HttpServletRequest req, HttpServletResponse resp)              throws ServletException, IOException      {          // TODO Auto-generated method stub          doGet(req, resp);      }        }

web.xml的配置：

<servlet>          <servlet-name>TestServlet</servlet-name>          <servlet-class>com.test.action.TestServlet</servlet-class>      </servlet>            <servlet-mapping>          <servlet-name>TestServlet</servlet-name>          <url-pattern>/testServlet</url-pattern>      </servlet-mapping>

首先从servlet-mappig中可以看出如果用户请求一个含有testServlet后缀的url时会调用名字为TestServlet的servlet，显然此servlet对应

com.test.action.TestServlet类，所以就会调用这个类中的doGet或doPost方法，那么到底调用那个方法呢，就取决于客户端的method是get还是post（比如form表单中会选择method）这两种方法可以互相调用，上面的例子演示了servlet即可直接返回html也可以返回jsp。

我们可以从<span style="font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', Consolas, 'Courier New', monospace; font-size: 11.875px; line-height: 17.998046875px; background-color: rgb(250, 250, 250);">HttpServletRequest 的实例req</span>中获取用户提交的参数，实例如下：（拿到用户输入的username）

<span style="font-family: Arial; font-size: 13.75px; line-height: 25.99609375px; background-color: silver;">String</span><span style="font-family: Arial; font-size: 13.75px; line-height: 25.99609375px;">username = req.getParameter(</span><span style="font-family: Arial; font-size: 13.75px; line-height: 25.99609375px; color: rgb(42, 0, 255);">"username"</span><span style="font-family: Arial; font-size: 13.75px; line-height: 25.99609375px;">); </span>

<span style="font-family: Arial;font-size:14px; line-height: 25.993303298950195px;">显然</span><span style="font-size:14px; line-height: 17.991071701049805px;"><span style="font-family:Monaco, DejaVu Sans Mono, Bitstream Vera Sans Mono, Consolas, Courier New, monospace;">我们同过resp返回客户端需要的信息。</span></span>

<span style="font-size:14px; line-height: 17.991071701049805px;"><span style="font-family:Monaco, DejaVu Sans Mono, Bitstream Vera Sans Mono, Consolas, Courier New, monospace;"></span></span>

<span style="font-family:Monaco, DejaVu Sans Mono, Bitstream Vera Sans Mono, Consolas, Courier New, monospace;font-size:14px;"><span style="line-height: 17.991071701049805px;">所以总结一下流程：客户端请求特定url----->根据mappering配置找到处理这个请求的类(请求和处理之后的结果封装在<span style="font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', Consolas, 'Courier New', monospace; font-size: 11.875px; line-height: 17.998046875px; background-color: rgb(250, 250, 250);">req和<span style="font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', Consolas, 'Courier New', monospace; font-size: 11.875px; line-height: 17.998046875px; background-color: rgb(250, 250, 250);">resp中</span></span>)-------->返回给客户信息</span></span>

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