一.Eclipse集成Tomcat

二.创建Javaweb项目

File--New--Dynamic Web Project

next-next

Finish!

三.部署web项目到Tomcat上

项目右击New--Servlet

Finish以后，会自动生成以下代码

修改doGet()方法

String ua = request.getHeader("User-Agent");
System.out.println("User-Agent: " + ua);

　　完整代码如下：

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

/**
 * Servlet implementation class GetHttpHeader
 */
@WebServlet("/GetHttpHeader")
public class GetHttpHeader extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public GetHttpHeader() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		String ua = request.getHeader("User-Agent");
        System.out.println("User-Agent: " + ua);
	}

	/**
	 * @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);
	}

}

在左侧Java文件上右击，Run As-->Run on server

Add添加至右边后，点击Finish后，直接运行

运行结果，控制台显示如下（同时浏览器会自动打开网址http://localhost:8081/test/GetHttpHeader）

-------------------------------------------------------------

获取HTTP所有请求头信息（同样修改doGet()方法即可）

完整代码如下：

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

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

/**
 * Servlet implementation class GetHttpHeader
 */
@WebServlet("/GetHttpHeader")
public class GetHttpHeader extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public GetHttpHeader() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		System.out.println("-----------获取单个请求头信息-----");
		String ua = request.getHeader("User-Agent");
		System.out.println("User-Agent: " + ua);
		System.out.println("-----------获取所有请求头信息-----");
		Enumeration<String> headers = request.getHeaderNames();
		while (headers.hasMoreElements()) {
		    String headerName = headers.nextElement();
		    String headerValue = request.getHeader(headerName);
		    System.out.println(headerName + ": " + headerValue);
	    }
	}

	/**
	 * @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);
	}

}

　　运行结果