Servlet——Request和Response详解编程语言

Request和Response分别用来处理客户端发送的数据和服务器应该作出的响应，使用较为简单，主要都是api。读者可使用以下代码自行练习

/** 
 * HttpServletRequest用来存放客户端请求的参数 
 * 请求行 
 * 请求头 
 * 请求数据 
 * 
 * @author Song X. 
 * @date 2020/02/11 
 */ 
public class RequestServlet extends HttpServlet {
    
 
    @Override 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        System.out.println("It is from POST Request/n"); 
        showRequestInfo(request); 
    } 
 
    @Override 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        System.out.println("It is from GET Request/n"); 
        showRequestInfo(request); 
 
    } 
 
    private void showRequestInfo(HttpServletRequest request) {
    
        /*以下都是请求行里的内容*/ 
        System.out.println("-----------Request Line-----------"); 
 
        //获取请求中的请求方式 
        String method = request.getMethod(); 
        System.out.println("Request Method: " + method); 
 
        //获取请求的完整地址 
        StringBuffer requestURL = request.getRequestURL(); 
        System.out.println("Entire Request Address: " + requestURL); 
 
        //获取请求中的资源路径 
        String requestURI = request.getRequestURI(); 
        System.out.println("Entire Request Path: " + requestURI); 
 
        //获取请求中的协议与版本号 
        String protocol = request.getProtocol(); 
        System.out.println("Protocol: " + protocol); 
 
        //获取请求中的协议 
        String scheme = request.getScheme(); 
        System.out.println("Schema: " + scheme); 
 
        System.out.println("----------------------------------/n"); 
 
        /*以下都是请求头里的内容*/ 
        //根据Key获取对应Value的值 
        System.out.println("-----------Request Header-----------"); 
 
        //比如获取User-Agent 
        String userAgent = request.getHeader("User-Agent"); 
        System.out.println("User-Agent" + userAgent); 
 
        //header中有很多的Key，可通过以下方式获取请求头信息中的所有key的枚举对象，并获取到所有的Value 
        Enumeration<String> headerNames = request.getHeaderNames(); 
        while (headerNames.hasMoreElements()) {
    
            //headerNames.nextElement()是所有的Key 
            String key = headerNames.nextElement(); 
            String value = request.getHeader(key); 
            System.out.println(key + " : " + value); 
        } 
 
        System.out.println("------------------------------------/n"); 
 
        /*以下都是请求数据里的内容*/ 
        System.out.println("-----------Request Data-----------"); 
 
        //这里的参数是method.jsp里配置的，如果不一致，这里只会获取到null 
        String name = request.getParameter("name"); 
        String pwd = request.getParameter("pwd"); 
        System.out.println(name + " : " + pwd); 
 
        //如果不知道都有什么配置参数，可以通过如下方式获得 
        Enumeration<String> parameterNames = request.getParameterNames(); 
        while(parameterNames.hasMoreElements()) {
    
            System.out.println(parameterNames.nextElement()); 
        } 
 
        System.out.println("----------------------------------/n"); 
    } 
 
} 

/** 
 * HttpServletResponse用来存放服务器端响应的参数 
 * 响应行 
 * 响应头 
 * 响应体 
 * 
 * @author frank 
 * @date 2020/02/11 
 */ 
public class ResponseServlet extends HttpServlet {
    
 
    @Override 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        System.out.println("It is from POST Request/n"); 
        showResponseInfo(response); 
    } 
 
    @Override 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        System.out.println("It is from GET Request/n"); 
        showResponseInfo(response); 
    } 
 
    private void showResponseInfo(HttpServletResponse response) throws IOException {
    
 
        /*以下都是响应行里的内容*/ 
        //设置响应码和响应状态 
        ///response.sendError(404,"The Page is lost"); 
 
        /*以下都是响应头里的内容*/ 
 
        /* 按照Key-Value键值对的方式设置响应头，下面两种方式都可以设置响应头 
           区别在于在key相同的情况下，set的方式，新的会覆盖旧的，add的方式则不会 */ 
        response.setHeader("beijing","gugong"); 
        response.setHeader("beijing", "yiheyuan"); 
        response.addHeader("shanghai","dongfangmingzhu"); 
        response.addHeader("shanghai","waitan"); 
 
        /*以下都是响应体里的内容*/ 
        //服务端给客户端回消息，并且会解析其中的html标签 
        //如果不想解析其中的html标签，或者想自定义解析方式，只要设置ContentType即可(text/xxx)，默认就是text/html 
        //可以有比如text/palin纯文本，text/json用json解析 
        response.getWriter().write("<b>Hello world</b>"); 
        response.setContentType("text/html"); 
 
    } 
} 
 

<%--method.jsp--%> 
<%@ page contentType="text/html;charset=UTF-8" language="java" %> 
 
<html> 
<head> 
    <title>Title</title> 
</head> 
<body> 
    <%--这里action的值配置的是对应跳转的Servlet的url-pattern--%> 
    <form action="response" method="post"> 
        用户名: <input type="text" name="name" value="" /><br> 
        密码: <input type="text" name="pwd" value="" /><br> 
        <input type="submit" value="登陆"> 
    </form> 
</body> 
</html> 
 

<!--web.xml--> 
    <servlet> 
        <servlet-name>RequestServlet</servlet-name> 
        <servlet-class>home.frank.RequestServlet</servlet-class> 
    </servlet> 
    <servlet-mapping> 
        <servlet-name>RequestServlet</servlet-name> 
        <url-pattern>/request</url-pattern> 
    </servlet-mapping> 
 
    <servlet> 
        <servlet-name>ResponseServlet</servlet-name> 
        <servlet-class>home.frank.ResponseServlet</servlet-class> 
    </servlet> 
    <servlet-mapping> 
        <servlet-name>ResponseServlet</servlet-name> 
        <url-pattern>/response</url-pattern> 
    </servlet-mapping> 

页面输入localhost:8080/method.jsp即可测试运行