HttpServlet

来源：互联网发布：结构体中的数组赋值编辑：程序博客网时间：2024/04/28 22:59

什么是HttpServlet

sun公司为Servlet定义了一个抽象类HttpServlet

HttpServlet指能够处理HTTP请求的servlet，它在原有Servlet接口上添加了一些与HTTP协议处理方法，它比Servlet接口的功能更为强大。因此开发人员在编写Servlet时，通常应继承这个类，而避免直接去实现Servlet接口。

HttpServlet在实现Servlet接口时，覆写了service方法，该方法体内的代码会自动判断用户的请求方式，如为GET请求，则调用HttpServlet的doGet方法，如为Post请求，则调用doPost方法。因此，开发人员在编写Servlet时，通常只需要覆写doGet或doPost方法，而不要去覆写service方法

封装的service方法可以看下，不需要记

protected void service(HttpServletRequest req, HttpServletResponse resp)    throws ServletException, IOException  {    String method = req.getMethod();    if (method.equals("GET")) {      long lastModified = getLastModified(req);      if (lastModified == -1L)      {        doGet(req, resp);      } else {        long ifModifiedSince = req.getDateHeader("If-Modified-Since");        if (ifModifiedSince < lastModified)        {          maybeSetLastModified(resp, lastModified);          doGet(req, resp);        } else {          resp.setStatus(304);        }      }    }    else if (method.equals("HEAD")) {      long lastModified = getLastModified(req);      maybeSetLastModified(resp, lastModified);      doHead(req, resp);    }    else if (method.equals("POST")) {      doPost(req, resp);    }    else if (method.equals("PUT")) {      doPut(req, resp);    }    else if (method.equals("DELETE")) {      doDelete(req, resp);    }    else if (method.equals("OPTIONS")) {      doOptions(req, resp);    }    else if (method.equals("TRACE")) {      doTrace(req, resp);    }    else    {      String errMsg = lStrings.getString("http.method_not_implemented");      Object[] errArgs = new Object[1];      errArgs[0] = method;      errMsg = MessageFormat.format(errMsg, errArgs);      resp.sendError(501, errMsg);    }  }

HttpServlet的实现

package com.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class Servlet2 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {    }}

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