通过ajax异步向后端发送请求，响应请求向前端传送json格式数据的

一、前端异步请求代码：

<span style="font-size:14px;">$.ajax
        ({   
            type: "POST",//请求的方式
            url: "outputservlet3",//请求url
            data: {},//前端向后端传送的数据
            dataType: "json",//数据格式json
            error: function ()      //请求错误的回调函数
            {
                
            },success: function ()   //请求成功的回调函数
            {
               
                                  
            }
        })</span>

<span style="font-size:14px;"><servlet>
    <servlet-name>outputservlet3</servlet-name>            
    <servlet-class>output.outputservlet3</servlet-class>   //对应的Java类
  </servlet>
  <servlet-mapping>
    <servlet-name>outputservlet3</servlet-name>
    <url-pattern>/outputservlet3</url-pattern>          //注意这里开始的地方有“/”
  </servlet-mapping></span>

//响应的是post请求

<span style="font-size:14px;">protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
		// TODO Auto-generated method stub
		//doGet(request,response);
		OracleConnection myoracle=new OracleConnection ();
		Connection conn=null;
		PreparedStatement pre=null;
		ResultSet result = null; 
		String sql="select RANK,POINT from MAPGIS.FIRERANK,MAPGIS.WUHAN where FIRERANK.WUHAN_ID=WUHAN.ID ";
		JSONObject jsonObject = new JSONObject();
		PrintWriter out = response.getWriter();
		try
		{
			conn = myoracle.getConnection1();
			pre = conn.prepareStatement(sql);
			result = pre.executeQuery();
			while(result.next())
			{
				out o1=new out();
				o1.setRank(result.getInt("rank"));
				JGeometry geom = JGeometry.load(result.getBytes(2));
				point= geom.getLabelPointXYZ();
				o1.setX(point[0]);
				o1.setY(point[1]);
				out1.add(o1);
			}
			JSONArray ja3=JSONArray.fromObject(out1);
			jsonObject.put("point",ja3);
		}
		catch (ClassNotFoundException e)
		{
			e.printStackTrace();
		} 
		catch (SQLException e) 
		{
			e.printStackTrace();
		} 
		catch (Exception e) {
			
			e.printStackTrace();
		} 
		finally
		{
			myoracle.close(result,pre,conn);
		}
		out.print(jsonObject.toString());
   }</span>

（编辑：李大同）

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