Ajax JavaWeb JS 三级联动

package net.laokboke.servlet; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.HashMap; import java.util.Map; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.google.gson.Gson; public class GetDropdownDataServlet extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response)throws IOException,ServletException{ doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{ String parentId = request.getParameter("parentId"); if(parentId == null || parentId==""){ parentId = "0";//如果传的父结点为空，则默认赋值为中国的父结点，也就是每一级查询所有省份。 } Connection conn = null; String json = ""; try{ Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection("jdbc:mysql://localhost/demo" , "demo" , "demo"); Statement stat = conn.createStatement(); ResultSet rs = stat.executeQuery("select region_id,region_name from region where parent_id = "+parentId); ArrayList rsList = new ArrayList(); Map map = null; while(rs.next()){ map = new HashMap(); map.put("id", rs.getInt(1)); map.put("name", rs.getString(2)); rsList.add(map); } rs=null; Gson gson = new Gson(); json = gson.toJson(rsList); System.out.println("json="+json); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally{ if(conn != null){ try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } response.setCharacterEncoding("UTF-8");//防止出现中文乱码现象 response.getWriter().print(json); } }