用Tomcat做一个简单的服务器，可以是非Web服务器

使用Tomcat做一个简单的Web服务器很简单，使用Tomcat做一个大型的网站也是Tomcat能够胜任的。前几天我就一直在想，如果我想做一款App，实现同组的驴友在活动时自动共享自己lat和lon信息以供其他人查看，位于热爱户外运动的人来说是一个挺不错的想法。我打算采用json个数的数据进行简单的数据交换，那么，服务器该怎么选择呢？使用php？不不不，那是我想做的还有一件事，就是在一个服务器内不仅仅是做请求->相应的动作，我想新开启一个全局的线程用来维护一些信息，那么以往的Tomcat能胜任吗？

答案是肯定的，下面献上我的代码：

package servlet;

import java.io.IOException;
import java.util.List;

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

import org.json.JSONException;
import org.json.JSONObject;

import core.RoomControllerMessageProcessor;
import core.SubServer;
import core.TcpServer;

/**
 * Servlet implementation class CoreService
 */
// @WebServlet("/CoreService")
@WebServlet(name = "/CoreService", urlPatterns = "/CoreService", loadOnStartup = 1)
public class CoreService extends HttpServlet {
  private static final long serialVersionUID = 1L;

  private static TcpServer tcps = null;
  // private static TaskPusher taskPusherThread = null;

  @Override
  public void init() throws ServletException {
    System.out.println("Starting..");
    // main service
    tcps = new TcpServer(RoomControllerMessageProcessor.class);
    tcps.start(7564);

    // task pusher
    // taskPusherThread = new TaskPusher(tcps.procList);
    // taskPusherThread.start();
    super.init();
  }

  /**
   * @see HttpServlet#HttpServlet()
   */
  public CoreService() {
    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());
  }

  /**
   * @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);
  }

  public static int changeStatus(int serverId, int controllerId, int deviceType, int deviceId, String value) {
    // step 1 : find tcp target by server id & controller id
    if (null == tcps)
      return -1; // service is not running
    SubServer s = null; // tag if find this client or not
    for (SubServer sub : tcps.procList) {
      RoomControllerMessageProcessor rcmp = (RoomControllerMessageProcessor) sub;
      if (rcmp.controllerId == controllerId) {
        s = rcmp;
        break;
      }
    }
    if (null != s) {
      JSONObject jo = new JSONObject();
      try {
        jo.put("code", 7);
        jo.put("deviceid", deviceId);
        jo.put("devicetype", deviceType);
        jo.put("value", value);
      } catch (JSONException e) {
        e.printStackTrace();
      }
      System.out.println("[Send Command] : " + jo.toString());
      s.send(jo.toString());
      return 1;
    } else {
      return -2; // do not find this client cause by offline
    }
  }

  public static List<SubServer> getClients() {
    return null == tcps ? null : tcps.procList;
  }

}

重点在这一句：

@WebServlet(name = "/CoreService", urlPatterns = "/CoreService", loadOnStartup = 1)

他告诉Tomcat容器在初始化的时候自动加载这个Servlet并且执行Servlet中的init（）方法，其中就会执行我自己编写的那一部分逻辑。这样就实现了当我们部署war的时候，这个小模块就会随着Tomcat容器加载工程进而加载起来。