请求对象Request

1.概念

<1>请求：请求:获取资源。在BS架构中，就是客户端浏览器向服务器端发出询问。
<2>请求对象：就是在项目当中用于发送请求的对象。
<3>对象创建：需要实现ServletRequest和HttpservletRequest接口，不过在tomcat底层已经帮我们创建好了请求对象。

关系视图如下:

2.Request获取路径的相关方法

注：浏览器返回【本机地址】ipv6和ipv4的地址是本地host文件控制

//Request获取路径的相关方法
@WebServlet("/ServletDemo1")
public class ServletDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//1.获取虚拟目录名称getContextPath()String contextPath = req.getContextPath();System.out.println(contextPath);//2.获取Servlet映射路径getServletPath()String servletPath = req.getServletPath();System.out.println(servletPath);//3.获取访问者ip getRemoteAddr()String remoteAddr = req.getRemoteAddr();//http://127.0.0.1:8080    //127.0.0.1//http://localhost:8080[和host文件的配置有关] //0:0:0:0:0:0:0:1System.out.println(remoteAddr);//4.获取请求消息的数据getQueryString()//?username=zhangsan&password=123456String queryString = req.getQueryString();System.out.println(queryString);//5.获取统一资源标识符 getRequestURI()String requestURI = req.getRequestURI();System.out.println(requestURI);//URL更精确,表示范围比URI小//6.获取统一资源定位符 getRequestURL()StringBuffer requestURL = req.getRequestURL();System.out.println(requestURL);//浏览器访问http://127.0.0.1:8080/ServletRequest/ServletDemo1?username=zhangsan&password=123456}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}打印结果：
-----------------------------------------------------------------------
/ServletRequest
/ServletDemo1
127.0.0.1
null
/ServletRequest/ServletDemo1
http://127.0.0.1:8080/ServletRequest/ServletDemo1

3.Request获取请求头内信息的相关方法

//Request获取请求头内信息的相关方法
@WebServlet("/ServletDemo2")
public class ServletDemo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//请求头名称[可以有多个值]不区分大小写//1.getHeader("请求头名称")根据请求头名称获取值String connection = req.getHeader("Connection");System.out.println(connection);System.out.println("------------------------");//返回类型和前面不同,返回为集合//2.getHeader("请求头名称")根据请求头名称[有多个值]获取多个值String AcceptEncoding = req.getHeader("Accept-Encoding");System.out.println(AcceptEncoding);System.out.println("------------------------");//3.getHeaderNames获取所有的请求头名称Enumeration<String> headerNames = req.getHeaderNames();while (headerNames.hasMoreElements()) {String headerName = headerNames.nextElement();String value = req.getHeader("s");System.out.println(headerName + "..." + value);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}打印结果：
----------------------------------------------------------------------
keep-alive
------------------------
gzip, deflate
------------------------
host...null
user-agent...null
accept...null
accept-language...null
accept-encoding...null
connection...null
cookie...null
upgrade-insecure-requests...null
sec-fetch-dest...null
sec-fetch-mode...null
sec-fetch-site...null
sec-fetch-user...null

4.获取请求参数相关信息的方法

表单属性为【form action="/ServletRequest/ServletDemo3" method=“post” autocomplete=“off”】

@WebServlet("/ServletDemo3")
public class ServletDemo3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//1.getParameter()根据名称获取数据String value = req.getParameter("name");System.out.println(value);System.out.println("-------------------------");//2.getParameterValues()根据名称获取所有数据String[] hobbies = req.getParameterValues("hobby");System.out.println(Arrays.toString(hobbies));/*for (String hobby : hobbies) {System.out.println(hobby);}*/System.out.println("-------------------------");//3.getParameterNames()获取所有名称Enumeration<String> parameterNames = req.getParameterNames();while (parameterNames.hasMoreElements()){String s = parameterNames.nextElement();System.out.println(s);}System.out.println("-------------------------");//4.getParameterMap()获取所有参数的键值对,存入Map集合Map<String, String[]> parameterMap = req.getParameterMap();Set<String> keys = parameterMap.keySet();for (String key : keys) {String[] values = parameterMap.get(key);System.out.println(key + Arrays.toString(values));}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}打印结果：
----------------------------------------------------------------------
zhangsan
-------------------------
[study, game, book]
-------------------------
name
password
hobby
-------------------------
name[zhangsan]
password[123456]
hobby[study, game, book

5.通过流对象获取数据

【请求方法必须是post方式】
表单属性为【form action="/ServletRequest/ServletDemo7" method=“post” autocomplete=“off”】

//通过流对象获取数据[请求方法必须是post方式]
//不是自己new的都不需要释放资源
@WebServlet("/ServletDemo7")
public class ServletDemo7 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//字符流/*BufferedReader br = req.getReader();String line = br.readLine();while (line != null) {System.out.println(line);line = br.readLine();}*///字节流[应用场景,上传文件]ServletInputStream sis = req.getInputStream();byte[] bytes = new byte[1024];int len = sis.read(bytes);while (len!=-1){System.out.println(new String(bytes,0,len));len = sis.read(bytes);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}打印结果：
---------------------------------------------------------------------
name=%E6%9D%8E%E5%9B%9B&password=123&hobby=game

6.请求转发

表单属性为【form action="/ServletRequest/ServletDemo9" method=“post” autocomplete=“off”】

//ServletDemo9
@WebServlet("/ServletDemo9")
public class ServletDemo9 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//设置请求字符编码,防止乱码req.setCharacterEncoding("utf-8");//设置共享数据setAttribute(键,值)System.out.println("ServletDemo9设置共享数据");req.setAttribute("name","zhangsan");//getRequestDispatcher()获取请求调度对象[中介]RequestDispatcher rd = req.getRequestDispatcher("/ServletDemo10");//实现转发功能[参数为请求对象和相应对象]rd.forward(req,resp);//所以ServletDemo9中接收的请求参数也会传递到10中}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}//ServletDemo10
@WebServlet("/ServletDemo10")
public class ServletDemo10 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//设置请求字符编码,防止乱码req.setCharacterEncoding("utf-8");//获取共享数据System.out.println("ServletDemo10获取共享数据");Object name = req.getAttribute("name");System.out.println(name);System.out.println("获取ServletDemo7的请求参数");System.out.println(req.getParameter("name"));}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}打印结果：
----------------------------------------------------------------------
ServletDemo9设置共享数据
ServletDemo10获取共享数据
zhangsan
获取ServletDemo7的请求参数
王五

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