getmaxid.java

重点不是信息管理系统

package com.yijia_ctgu.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.Enumeration;

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

import org.json.simple.JSONObject;
import org.json.simple.JSONArray;

import com.yijia_ctgu.DB.DB;
import com.yijia_ctgu.exception.NotQueryException;
/**
 * 
 * @author yijia
 *
 */
public class GetMaxId extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public GetMaxId() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

	    doPost(request,response);
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest req, HttpServletResponse res)
			throws ServletException, IOException {
		res.setCharacterEncoding("utf-8");
		res.setContentType("text/html");
		PrintWriter out = res.getWriter();
		
		JSONObject obj=new JSONObject();
		try {
			Enumeration enu=req.getParameterNames();
			JSONArray array=new JSONArray();
			while(enu.hasMoreElements()){
			  String s=(String)enu.nextElement();
			  int maxId;
			  if(DB.getTable(s).count()==0)  maxId=0;
			  else maxId=DB.getTable(s).getMax("id");
			  //System.out.println(s+" "+maxId);
			  obj.put(s, maxId);
			}
			obj.put("success",true);
		} catch (SQLException e) {
			obj.put("errors", "抱歉初始化参数出错");
		} catch (NotQueryException e) {
			System.out.println("呵呵，天上掉馅饼了");
		}catch(Exception e){
			obj.put("errors", "见鬼了，未知异常");
			System.out.println("数据库里没数据，可能在这里异常");
		}
		out.println(obj);
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occure
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}