java获取请求url的域名 java获取http请求的响应

Java Web程序设计——请求和响应（二）

思维导图：

实现重定向

实现重定向的相关方法

• 302和Location配合使用，实现重定向
  比如：response.setStatus(302); response.setHeader("Location", "/chapter/login.html");
• sendRediect("/chapter/login.html"); 例：
  重定向通过登录案例完成，在登录页面输入用户名和密码，在LoginServlet里面，判断用户名和密码是否正确。如果输入错误，或重新定向到登录页面，如果正确，跳转到欢迎页面。获取登录页面提交的用户名和密码：request.getParmeter()方法。

package chapter.response;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 1.获取登录的用户名和密码
		String name = request.getParameter("username");
		String password = request.getParameter("psw");
		// 2. 判断用户名和密码是否正确
		if (name.equals("admin") && password.equals("123")) {// 表明输入的数据是正确的
			response.sendRedirect("/chapter/welcome.html");
		} else {// 登录失败
			response.sendRedirect("/chapter/login.html");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

welcom.html

login.html

输入正确：

输入错误：

重新跳转至原页面，重新输入

重定向的特点

• 浏览器地址栏发生变化
• 发送了两次请求，都是浏览器发送的请求

重定向的路径

• 由于是浏览器发送得到的请求，所以路径必须要带项目名称，比如：/chapter/welcome.html

HttpServletRequest对象

• HttpServletRequest它是一个接口，父接口ServletRequest，在开发中，常用的是带协议的请求对象

获取请求行信息的相关方法

• 获取请求提交的方式：getMethod();
• 获取请求的协议：getProtocol();
• 获取项目名称：getContextPath();
• 获取servlet路径：getServletPath();
• 获取请求路径：getRequestURI()，getRequestURL();

ps:此处只是例举了一些常用的，还有很多。

例：

package chapter.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestLineServlet
 */
public class RequestLineServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 获取请求提交的方式：getMethod();
		String method = request.getMethod();
		System.out.println("请求方式："+method);
		// 获取请求的协议：getProtocol();
		String proto = request.getProtocol();
		System.out.println("请求协议："+proto);
		// 获取项目名称：getContextPath();
		String contextPath = request.getContextPath();
		System.out.println("项目路径："+contextPath);
		// 获取servlet路径：getServletPath();
		String servletPath = request.getServletPath();
		System.out.println("servlet路径："+servletPath);
		// 获取请求路径：getRequestURI()，getRequestURL();
		String pathURI = request.getRequestURI();
		String pathURL = request.getRequestURL().toString();
		System.out.println("URI对应的值："+pathURI);
		System.out.println("URL对应的值："+pathURL);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

控制台可看到：

注：URI对应的值：/项目名称/servlet路径
URL对应的值：http://localhost:8080/uri

获取请求消息头的相关方法

• 根据消息头，获取值：String value = getHeader(消息头的名称);
• 获取所有的消息头：Enumeration er = getHeaderNames();
  例：

package chapter.request;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestHeaderServlet
 */
public class RequestHeaderServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 处理响应中文的乱码问题
		response.setContentType("text/html;charset=utf-8");
		// 1. 获取所有的消息头名称
		Enumeration<String> er = request.getHeaderNames();
		// 2.遍历
		while (er.hasMoreElements()) {
			// 3.获取消息头
			String name = er.nextElement();
			// 4.获取消息头对应的值
			String value = request.getHeader(name);
			response.getWriter().print("消息头：" + name + " " + value + "<br/>");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

打开浏览器可看到：

根据Referer请求消息头，做一个防盗链的案例：

package chapter.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class DownLoadServlet
 */
public class DownLoadServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 1.获取Referer请求头：referer=http://localhost:8080/chapter/download
		String referer = request.getHeader("Referer");
		// 2.获取服务器名称
		String serverName = request.getServerName();
		// 3.判断是否是从本网站发起的下载请求
		if (referer != null && referer.contains(serverName)) {
			// refer请求头对于的值包含了服务器名称，说明是从本网站发起的请求，允许下载
			response.getWriter().print("download-------------");
		} else {
			// 说明不是从本站发起的请求，不允许下载，可以定向到本网站的下载页面，从而让用户从本网站的页面开始下载
			response.sendRedirect("/chapter/download.html");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

download.html

打开浏览器，可看到：