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

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：

  1 package com.dx.hello;
  2 
  3 import java.io.IOException;
  4 import java.util.*;
  5 
  6 import javax.servlet.Servlet;
  7 import javax.servlet.ServletConfig;
  8 import javax.servlet.ServletException;
  9 import javax.servlet.ServletRequest;
 10 import javax.servlet.ServletResponse;
 11 import javax.servlet.http.HttpServletRequest;
 12 
 13 public class LoginServlet implements Servlet {
 14 
 15     public LoginServlet() {
 16         // TODO Auto-generated constructor stub
 17     }
 18 
 19     @Override
 20     public void destroy() {
 21         // TODO Auto-generated method stub
 22 
 23     }
 24 
 25     @Override
 26     public ServletConfig getServletConfig() {
 27         // TODO Auto-generated method stub
 28         return null;
 29     }
 30 
 31     @Override
 32     public String getServletInfo() {
 33         // TODO Auto-generated method stub
 34         return null;
 35     }
 36 
 37     @Override
 38     public void init(ServletConfig arg0) throws ServletException {
 39         // TODO Auto-generated method stub
 40 
 41     }
 42 
 43     @Override
 44     public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {
 45         System.out.println("LoginService's service ... ");
 46         // ServletRequest的getParameter(String argo)
 47         String username = request.getParameter("username");
 48         String password = request.getParameter("password");
 49         System.out.println("username:" + username);
 50         System.out.println("password:" + password);
 51 
 52         // ServletRequest的getParameterNames()
 53         Enumeration<String> names = request.getParameterNames();
 54         while (names.hasMoreElements()) {
 55             String name = names.nextElement();
 56             System.out.println("--->" + name);
 57             String value = request.getParameter(name);
 58             System.out.println("--->" + value);
 59         }
 60 
 61         // ServletRequest的getParameterValues(String argo)
 62         String[] checkboxs = request.getParameterValues("checkBox");
 63         for (String value : checkboxs) {
 64             System.out.println("key:checkBox,value:" + value);
 65         }
 66 
 67         // ServletRequest的getParameterMap()
 68         Map<String, String[]> map = request.getParameterMap();
 69         for (Map.Entry<String, String[]> item : map.entrySet()) {
 70             System.out
 71                     .println("getParameterMap()---->key:" + item.getKey() + ",value:" + Arrays.asList(item.getValue()));
 72         }
 73 
 74         // 强制转化为 HttpServletRequest
 75         HttpServletRequest httpRequest = (HttpServletRequest) request;
 76         
 77         // 获取request URI
 78         String requestURI = httpRequest.getRequestURI();
 79         System.out.println("HttpServletRequest的getRequestURI():"+requestURI);
 80 
 81         // 获取request Method
 82         String method = httpRequest.getMethod();
 83         System.out.println("HttpServletRequest的getMethod():"+method);
 84         
 85         // 获取资源文件在服务器上的物理路径
 86         String relaPath = httpRequest.getRealPath("/WEB-INF/classes/jdbc.properties");
 87         System.out.println("HttpServletRequest的getRealPath():"+relaPath);
 88         
 89         // 获取请求过程中，通过uri传递的参数
 90         String queryString = httpRequest.getQueryString();
 91         System.out.println("HttpServletRequest的getQueryString():"+queryString);
 92         
 93         // 获取servlet配置路径
 94         String servletPath = httpRequest.getServletPath();
 95         System.out.println("HttpServletRequest的getServletPath():"+servletPath);
 96         
 97         // 获取servlet服務名稱。
 98         String servletName = httpRequest.getServerName();
 99         System.out.println("HttpServletRequest的getServerName():"+servletName);
100         
101     }
102 
103 }

修改web.xml注册LoginServlet servlet:

1     <servlet>
2         <servlet-name>LoginServlet</servlet-name>
3         <servlet-class>com.dx.hello.LoginServlet</servlet-class>
4     </servlet>
5     <servlet-mapping>
6         <servlet-name>LoginServlet</servlet-name>
7         <url-pattern>/LoginServlet</url-pattern>
8     </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:javaworkset.metadata.pluginsorg.eclipse.wst.server.core	mp0wtpwebappsMyServlet001WEB-INFclassesjdbc.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：

1 System.out.println(request);
2 //执行上边语句将会输出如下信息：
3 //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)

1 String username = request.getParameter("username");
2 String password = request.getParameter("password");
3 System.out.println("username:" + username);
4 System.out.println("password:" + password);

ServletRequest的getParameterNames()

1 Enumeration<String> names = request.getParameterNames();
2 while (names.hasMoreElements()) {
3 　　String name = names.nextElement();
4 　　System.out.println("--->" + name);
5 　　String value = request.getParameter(name);
6 　　System.out.println("--->" + value);
7 }

ServletRequest的getParameterValues(String argo)

1 String[] checkboxs = request.getParameterValues("checkBox");
2 for (String value : checkboxs) {
3     System.out.println("key:checkBox,value:" + value);
4 }

ServletRequest的getParameterMap()

1 Map<String, String[]> map = request.getParameterMap();
2 for (Map.Entry<String, String[]> item : map.entrySet()) {
3     System.out
4 .println("getParameterMap()---->key:" + item.getKey() + ",value:" + Arrays.asList(item.getValue()));
5 }

HttpServletRequest强制转化为 HttpServletRequest

1 HttpServletRequest httpRequest = (HttpServletRequest) request;

HttpServletRequest 获取request URI

1 String requestURI = httpRequest.getRequestURI();
2 System.out.println("HttpServletRequest的getRequestURI():"+requestURI);

HttpServletRequest获取request Method

1 String method = httpRequest.getMethod();
2 System.out.println("HttpServletRequest的getMethod():"+method);

HttpServletRequest获取资源文件在服务器上的物理路径

1 String relaPath = httpRequest.getRealPath("/WEB-INF/classes/jdbc.properties");
2 System.out.println("HttpServletRequest的getRealPath():"+relaPath);

HttpServletRequest获取请求过程中，通过uri传递的参数

1 String queryString = httpRequest.getQueryString();
2 System.out.println("HttpServletRequest的getQueryString():"+queryString);

HttpServletRequest获取servlet配置路径

1 String servletPath = httpRequest.getServletPath();
2 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。

1         // 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。
2         PrintWriter out = response.getWriter();
3         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。