java之后台返回json格式字符串,前台接受并转为json文件
作为一个菜鸟，做项目真的好困难呀，这两天被一个问题困了两天，终于解决了，但是也不算太完美。首先，先说一下问题吧，根据后台返回的值，前台接受并作出一个折线图。
最初，在后台根据从数据库中的值，强制拼成了json格式的字符串，利用model返回给前台，前台Ajax success：function(data)data接收数据，这是应该接收的是字符串，由于折线图中series中的data为非字符串，(这个是后来百度才知道的)，就没有成功。然后就想后台直接将数据转换成json，然后返回前台，利用里JSONArray，JSONObject这两个包，将数据转换成了json格式，可是问题是不知道如何将json类型返回到前台，（百度了好多，还是不会，如果有会的教教我呗，）最后还是将json转换成了String类型返回到前台，最后利用eval()函数转换成了json格式。(这里的eval（”(“+data+”)”) 原因由于json是以”{}”的方式来开始以及结束的，在js中，它会被当成一个语句来处理，所以必须强制性的将它转换成一种表达式。JavaScript代码的时候强制将括号内的表达式。像字面量{}，如若不加外层的括号，那么eval会将大括号识别为结束标记，那么{}将会被认为是执行了一句空语句。所以下面两个执行结果是不同的：
alert(eavl(“{}”);//return undefined
alert(eval(“({})”);//return object[Object]
我的代码如下
java
public String statisticalKd(String ksId,Model model) throws IOException{ String s = "select c_kd_1,c_kd_2,c_kd_3,c_kd_4,c_kd_5,c_kd_6,c_kd_7,c_kd_8,c_kd_9 from c_ksxxb where c_ks_id=?"; List<Map<String, Object>> kd = jt.queryForList(s,ksId); String val = ""; Set<String> set = new HashSet<String>(); for (int i = 0; i < kd.size(); i++) { Map<String, Object> map = kd.get(i); for (int j = 0; j < map.size(); j++) { Object vala = map.get("c_kd_"+(j+1)); System.out.println("j============================"+vala); if (vala!= null) { String v= vala.toString(); set.add(v.substring(3, v.length())); } } } int i = 0; JSONArray series = new JSONArray(); for(String value : set){ JSONObject json = new JSONObject(); JSONArray data = new JSONArray(); //val = val + "\'" + value + "\',"; String sql = "select count(*) from c_ksxxb where c_ks_id = ? and (c_kd_1 like \'%"+value+"\' or c_kd_2 like \'%"+value+"\' or c_kd_3 like \'%"+value+"\' or c_kd_4 like \'%"+value+"\' or c_kd_5 like \'%"+value+"\' or c_kd_6 like \'%"+value+"\' or c_kd_7 like \'%"+value+"\' or c_kd_8 like \'%"+value+"\' or c_kd_9 like \'%"+value+"\')"; double sum = jt.queryForObject(sql,new Object[]{ksId},int.class); String sql2 = "select count(*) from c_wjxxb where c_ks_id = ? and (c_kd_1 like \'%"+value+"\' or c_kd_2 like \'%"+value+"\' or c_kd_3 like \'%"+value+"\' or c_kd_4 like \'%"+value+"\' or c_kd_5 like \'%"+value+"\' or c_kd_6 like \'%"+value+"\' or c_kd_7 like \'%"+value+"\' or c_kd_8 like \'%"+value+"\' or c_kd_9 like \'%"+value+"\')"; double wjnum =jt.queryForObject(sql2,new Object[]{ksId},int.class); double wjl = wjnum/sum*100; wjl=(double)Math.round(wjl*100)/100; String sql3 = "select count(*) from c_cwxxb where c_ks_id = ? and (c_kd_1 like \'%"+value+"\' or c_kd_2 like \'%"+value+"\' or c_kd_3 like \'%"+value+"\' or c_kd_4 like \'%"+value+"\' or c_kd_5 like \'%"+value+"\' or c_kd_6 like \'%"+value+"\' or c_kd_7 like \'%"+value+"\' or c_kd_8 like \'%"+value+"\' or c_kd_9 like \'%"+value+"\')"; double cwnum=jt.queryForObject(sql3,new Object[]{ksId},int.class); double cwl=cwnum/sum*100; cwl=(double)Math.round(cwl*100)/100; System.out.println("sum==================================="+sum); System.out.println("wjnum=================================="+wjnum); String sql4 = "select c_kd_name from c_kdb where c_kd_code=?"; String name=jt.queryForObject(sql4, new Object[]{value},String.class); System.out.println("name======================================"+name); data.put(0,wjl); data.put(1,cwl); data.put(2,1.2); data.put(3,2.1); json.put("name",name); json.put("data", data); series.put(i,json); System.out.println(i+"==============="+series); i++; } System.out.println("series======================================="+series); model.addAttribute("series",series.toString()); return "json"; }
jsp
<%-- Created by IntelliJ IDEA. User: Administrator Date: 2017/7/31 0031 Time: 19:20 To change this template use File | Settings | File Templates. --%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <% String cp = request.getContextPath(); String ksId = request.getParameter("ksId").toString(); %> <html> <head> <title>折线图</title> <script type="text/javascript" src="<%=cp%>/js/jquery-1.7.1.js"></script> <script src="<%=cp%>/js/code/highcharts.js"></script> <script src="<%=cp%>/js/code/modules/exporting.js"></script> </head> <body> <div id="kdtj" style="min-width: 400px;height:400px"></div> <script type="text/javascript"> var ksId=\'<%=ksId%>\'; $.ajax({ type:\'POST\', url:\'tjkdAjax?ksId=\'+ksId, success: function(data1){ var series=eval("("+data1.series+")");//转换成json $("#kdtj").highcharts({ chart: { type: \'spline\' }, title: { text: \'考点四率\' }, xAxis: { categories: [\'错误率\',\'违纪率\',\'雷同率\',\'合格率\'] }, yAxis: { title: { text: \'率(%)\' }, labels: { formatter: function () { return this.value + \'%\'; } } }, tooltip: { valueSuffix: \'%\' }, plotOptions: { spline: { marker: { radius: 4, lineColor: \'#666666\', lineWidth: 1 } } }, series:series }); } }); </script> </body> </html>
希望大佬指点，，，谢谢
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