实现步骤：
（1）创建servlet BrowserServer
（2）调用HttpServletRequest对象的getServerName()方法获取服务器名称
（3）调用HttpServletRequest对象的getServerPort()方法获取服务器端口
（4）首先调用getServletContext()方法获取ServletContext对象，然后调用ServletContext对象的getServerInfo()方法获取服务器环境信息名称、版本信息
（5）利用HttpServletResponse对象的PrintWriter将信息显示到页面
package example.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
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 BrowserServer
*/
@WebServlet("/BrowserServer")
public class BrowserServer extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out=response.getWriter();
ServletContext context=getServletContext();
out.println("<html>");
out.println("<head>");
out.println("<title>服务器信息</title>");
out.println("</head>");
out.println("<body>");
out.println("<h3>服务器名称："+request.getServerName()+"</h3>");
out.println("<h3>服务器端口："+request.getServerPort()+"</h3>");
out.println("<h3>"+context.getServerInfo()+"</h3>");
out.println("</body>");
out.println("<html>");
out.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
}
}