Java Servlet(四)：Servlet接口service工作（ServletRequest,ServletResponse对象）(jdk7+tomcat7+eclipse)

时间：2022-01-12 04:51:29

本篇将会记录，Servlet接收客户端传递来的参数信息，并返回信息使用的对象，及这些对象的函数相关用法。

还是在java ee工程中进行操作,在WebContent目录下创建一个login.jsp文件，并修改文件内容为：

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

    <form id="form1" method="POST" action="LoginServlet">

        用户名称：<input id="username" name="username" type="text" />

        用户 密码：<input id="password" name="password" type="password" />

        <br/>

        <input name="checkBox" type="checkbox" value="000"/>000

        <br/>

        <input name="checkBox" type="checkbox" value="001"/>001

        <br/>

        <input name="checkBox" type="checkbox" value="002"/>002

        <br/>

        <input name="checkBox" type="checkbox" value="003"/>003

        <br/>

        <input type="submit" name="submit" value="submit"/>

    </form>

</body>

</html>

在src目录下创建一个LoginServlet类，并实现Servlet接口及实现其接口函数：

 package com.dx.hello;

 import java.io.IOException;

 import java.util.*;

 import javax.servlet.Servlet;

 import javax.servlet.ServletConfig;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 import javax.servlet.http.HttpServletRequest;

 public class LoginServlet implements Servlet {

     public LoginServlet() {

         // TODO Auto-generated constructor stub

     }

     @Override

     public void destroy() {

         // TODO Auto-generated method stub

     }

     @Override

     public ServletConfig getServletConfig() {

         // TODO Auto-generated method stub

         return null;

     }

     @Override

     public String getServletInfo() {

         // TODO Auto-generated method stub

         return null;

     }

     @Override

     public void init(ServletConfig arg0) throws ServletException {

         // TODO Auto-generated method stub

     }

     @Override

     public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {

         System.out.println("LoginService's service ... ");

         // ServletRequest的getParameter(String argo)

         String username = request.getParameter("username");

         String password = request.getParameter("password");

         System.out.println("username:" + username);

         System.out.println("password:" + password);

         // ServletRequest的getParameterNames()

         Enumeration<String> names = request.getParameterNames();

         while (names.hasMoreElements()) {

             String name = names.nextElement();

             System.out.println("--->" + name);

             String value = request.getParameter(name);

             System.out.println("--->" + value);

         }

         // ServletRequest的getParameterValues(String argo)

         String[] checkboxs = request.getParameterValues("checkBox");

         for (String value : checkboxs) {

             System.out.println("key:checkBox,value:" + value);

         }

         // ServletRequest的getParameterMap()

         Map<String, String[]> map = request.getParameterMap();

         for (Map.Entry<String, String[]> item : map.entrySet()) {

             System.out

                     .println("getParameterMap()---->key:" + item.getKey() + ",value:" + Arrays.asList(item.getValue()));

         }

         // 强制转化为 HttpServletRequest

         HttpServletRequest httpRequest = (HttpServletRequest) request;

         // 获取request URI

         String requestURI = httpRequest.getRequestURI();

         System.out.println("HttpServletRequest的getRequestURI():"+requestURI);

         // 获取request Method

         String method = httpRequest.getMethod();

         System.out.println("HttpServletRequest的getMethod():"+method);

         // 获取资源文件在服务器上的物理路径

         String relaPath = httpRequest.getRealPath("/WEB-INF/classes/jdbc.properties");

         System.out.println("HttpServletRequest的getRealPath():"+relaPath);

         // 获取请求过程中，通过uri传递的参数

         String queryString = httpRequest.getQueryString();

         System.out.println("HttpServletRequest的getQueryString():"+queryString);

         // 获取servlet配置路径

         String servletPath = httpRequest.getServletPath();

         System.out.println("HttpServletRequest的getServletPath():"+servletPath);

         // 获取servlet服務名稱。

         String servletName = httpRequest.getServerName();

         System.out.println("HttpServletRequest的getServerName():"+servletName);

     }

 }

修改web.xml注册LoginServlet servlet:

     <servlet>

         <servlet-name>LoginServlet</servlet-name>

         <servlet-class>com.dx.hello.LoginServlet</servlet-class>

     </servlet>

     <servlet-mapping>

         <servlet-name>LoginServlet</servlet-name>

         <url-pattern>/LoginServlet</url-pattern>

     </servlet-mapping>

运行tomcat服务，在浏览器中输入http://localhost:8080/MyServlet001/login.jsp,填写表单信息提交，查看到console输出信息：

LoginService's service ...

username:111

password:2222

--->username

--->111

--->password

--->2222

--->checkBox

--->001

--->submit

--->submit

key:checkBox,value:001

key:checkBox,value:002

getParameterMap()---->key:username,value:[111]

getParameterMap()---->key:password,value:[2222]

getParameterMap()---->key:checkBox,value:[001, 002]

getParameterMap()---->key:submit,value:[submit]

HttpServletRequest的getRequestURI():/MyServlet001/LoginServlet

HttpServletRequest的getMethod():POST

HttpServletRequest的getRealPath():D:\java\workset\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\MyServlet001\WEB-INF\classes\jdbc.properties

HttpServletRequest的getQueryString():null

HttpServletRequest的getServletPath():/LoginServlet

HttpServletRequest的getServerName():localhost

代码示例已经完成，接下来进行分析service接收参数的原理及相关对象：

如何在Servlet中获取请求信息?

1、Servlet中的service()方法用于应答请求，每次请求都会调用service()方法。（service方法是服务器调用的）

@Override
public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {。。。}

ServletRequest ：封装了请求信息，可以从中获取到任何的请求信息；

ServletResponse :封装了响应信息，可以使用该接口的方法实现用户响应的信息。

这两个（ServletRequest 和ServletResponse ）接口的实现都是服务器实现的，并在服务器调用service（）方法时传入。

可以通过以下操作去查证下：

 System.out.println(request);

 //执行上边语句将会输出如下信息：

 //org.apache.catalina.connector.RequestFacade@d952d1

而这个服务器可能是tomcat,也可能是其他servlet容器。

2、ServletRequest相关函数：

  • ServletRequest的getParameter(String argo)
 String username = request.getParameter("username");

 String password = request.getParameter("password");

 System.out.println("username:" + username);

 System.out.println("password:" + password);
  • ServletRequest的getParameterNames()
 Enumeration<String> names = request.getParameterNames();

 while (names.hasMoreElements()) {

 　　String name = names.nextElement();

 　　System.out.println("--->" + name);

 　　String value = request.getParameter(name);

 　　System.out.println("--->" + value);

 }
  • ServletRequest的getParameterValues(String argo)
 String[] checkboxs = request.getParameterValues("checkBox");

 for (String value : checkboxs) {

     System.out.println("key:checkBox,value:" + value);

 }
  • ServletRequest的getParameterMap()
 Map<String, String[]> map = request.getParameterMap();

 for (Map.Entry<String, String[]> item : map.entrySet()) {

     System.out

 .println("getParameterMap()---->key:" + item.getKey() + ",value:" + Arrays.asList(item.getValue()));

 }
  • HttpServletRequest强制转化为 HttpServletRequest
 HttpServletRequest httpRequest = (HttpServletRequest) request;
  • HttpServletRequest 获取request URI
 String requestURI = httpRequest.getRequestURI();

 System.out.println("HttpServletRequest的getRequestURI():"+requestURI);
  • HttpServletRequest获取request Method
 String method = httpRequest.getMethod();

 System.out.println("HttpServletRequest的getMethod():"+method);
  • HttpServletRequest获取资源文件在服务器上的物理路径
 String relaPath = httpRequest.getRealPath("/WEB-INF/classes/jdbc.properties");

 System.out.println("HttpServletRequest的getRealPath():"+relaPath);
  • HttpServletRequest获取请求过程中，通过uri传递的参数
 String queryString = httpRequest.getQueryString();

 System.out.println("HttpServletRequest的getQueryString():"+queryString);
  • HttpServletRequest获取servlet配置路径
 String servletPath = httpRequest.getServletPath();

 System.out.println("HttpServletRequest的getServletPath():"+servletPath);
  • HttpServletRequest获取servlet服務名稱。
String servletName = httpRequest.getServerName();

System.out.println("HttpServletRequest的getServerName():"+servletName);

3.ServletResponse对象

封装了响应信息，如果需要给用户什么响应，具体可以使用该接口的方法实现。

  • getWriter()方法：

可以返回一个PrintWriter对象，调用该对象的print（）方法，将把print()中的参数直接打印到客户端浏览器上。

         // 返回PrintWriter对象，如果想给用户什么响应，具体可以使用该接口的方法实现。

         PrintWriter out = response.getWriter();

         out.println("hello");

setContentType(string arg0):

设置相应内容类型：

        // 设置相应的内容类型

        response.setContentType("miscrosoft/word");

内容类型可以参考：/tomcat/config/web.xml中设置信息。

可以通过response对象强制转化为：HttpServletResponse对象。

该对象比ServletResponse接口内容更多。

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