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DolphinDB整合前端chart组件展示数据

1. 概述

数据图表前端组件在物联网和实时监控的场景有非常广的应用,当前比较流行的有Echarts、HighCharts等组件。本文主要讲解如何利用DolphinDB的Web数据接口,结合JavaScript使用前端组件来展示DolphinDB中的数据。

2. 接口数据格式分析

DolphinDB提供了基于HTTP协议的接口,可以通过HTTP post方式提交查询语句并返回JSON格式的结果。具体信息可以参考DolphinDB WebApi

从文档中可以了解,DolphinDB的返回数据格式是列式的JSON字符串,一个单表返回JSON如下:

{
	"sessionID": "3691974869",
	"userId": "admin",
	"resultCode": "0",
	"msg": "",
	"object": [{
		"name": "",
		"form": "table",
		"size": "11",
		"value": [{
			"name": "second_time",
			"form": "vector",
			"type": "second",
			"size": "11",
			"value": ["13:03:50", "13:03:51", "13:03:52", "13:03:53", "13:03:54", "13:03:55", "13:03:56", "13:03:57", "13:03:58", "13:03:59", "13:04:00"]
		}, {
			"name": "ec",
			"form": "vector",
			"type": "double",
			"size": "11",
			"value": [1.019094, 0.971753, 0.962792, 1.014048, 0.991746, 1.016851, 0.98674, 1.00463, 0.991642, 1.018987, 1.008604]
		}]
	}]
}

Echarts 前端组件所需的数据格式:

option = {
	xAxis: {
		data: ["13:03:50", "13:03:51", "13:03:52", "13:03:53", "13:03:54", "13:03:55", "13:03:56", "13:03:57", "13:03:58", "13:03:59", "13:04:00"]
	},
	yAxis: {
		type: 'value'
	},
	series: [{
		data: [1.019094, 0.971753, 0.962792, 1.014048, 0.991746, 1.016851, 0.98674, 1.00463, 0.991642, 1.018987, 1.008604],
		type: 'line'
	}]
};

从两者的结构来看,只需要将DolphinDB的返回结果稍作转换即可满足Echarts的数据格式规范。而且使用DolphinDB的WebApi开发包可以让这个过程变得更加简单。

3. Echarts代码示例

本例通过在DolphinDB结合Echarts展示如下场景:工厂有10台设备,每一毫秒采集温度值数据并写入DolphinDB分布式数据表中,然后在网页中展示出每秒钟平均温度线状图。示例中的样本数据为持续采集10秒钟的数据,通过模拟脚本生成。

  • 使用DolphinDB脚本模拟生成样本数据
data = table(100000:0, `devId`time`ec,[INT,TIMESTAMP,DOUBLE]);
data.tableInsert(take(1..10,10000),add((1..10000),now()) , norm(1,0.5,10000))
share data as iotTable

JavaScript 脚本做的主要工作是从DolphinDB获取数据,并转换为Echarts所需的格式。这里使用了DolphinDB JavaScript的接口开发包,从GitHub下载,并引入DolphinDBConnection.jsDolphinDBEntity.js两个js文件。

var conn = new DolphinDBConnection('http://localhost:8848');
//向DolphinDB发送查询脚本,并获取返回的数据
conn.run("select avg(ec) as ec from iotTable group by second(time)", function(re){
	if(re.resultCode&&re.resultCode=="1"){
		alert(re.msg);
	} else {
		jobj = new DolphinDBEntity(re).toVector();//将返回结果转换成列数据
		var time = jobj[0].value;
		var ecdata = jobj[1].value;
		var option = {
			title: {
				text: '设备温度'
			},
			xAxis: {
				data: time
			},
			yAxis: {},
			series: [{
				name: '温度',
				type: 'line',
				data: ecdata
			}]
		};
		myChart.setOption(option);
	}
});

代码运行的结果如图所示:

image

  • 完整的Echarts实现脚本如下,本例中需要引入jQuery库
<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<script src="jquery-1.9.1.min.js"></script>
	<script src="DBConnection.js"></script>
	<script src="DolphinDBEntity.js"></script>
	<script src="http://echarts.baidu.com/gallery/vendors/echarts/echarts-all-3.js"></script>
</head>
<body>
	<div id="main" style="width: 600px;height:400px;"></div>

	<script type="text/javascript">
		var myChart = echarts.init(document.getElementById('main'));
		var conn = new DolphinDBConnection('http://localhost:8848');
		//向DolphinDB发送查询脚本,并获取返回的数据
		conn.run("select avg(ec) as ec from iotTable group by second(time)", function(re){
		if(re.resultCode&&re.resultCode=="1"){
			alert(re.msg);
		} else {
			jobj = new DolphinDBEntity(re).toVector();//将返回结果转换成列数据
			var time = jobj[0].value;
			var ecdata = jobj[1].value;
			var option = {
				title: {
					text: '设备温度'
				},
				xAxis: {
					data: time
				},
				yAxis: {},
				series: [{
					name: '温度',
					type: 'line',
					data: ecdata
				}]
			};
			myChart.setOption(option);
		}
	});
		
	</script>
</body>
</html>

4. HighCharts 代码示例

使用HighCharts展示DolphinDB数据的方式与Echarts类似,下面直接给出完整的脚本示例供参考:

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<script src="http://code.jquery.com/jquery-1.12.4.min.js" integrity="sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ+Xp8a4MxAQ=" crossorigin="anonymous"></script>
	<script src="DolphinDBConnection.js"></script>
	<script src="DolphinDBEntity.js"></script>
    <script src="http://cdn.highcharts.com.cn/highcharts/highcharts.js"></script>
    <script src="https://code.highcharts.com.cn/highcharts-plugins/highcharts-zh_CN.js"></script>
</head>
<body>
	<div id="main" style="width: 600px;height:400px;"></div>

    <script type="text/javascript">
    	var conn = new DolphinDBConnection('http://localhost:8848');
		//向DolphinDB发送查询脚本,并获取返回的数据
		conn.run("select avg(ec) as ec from iotTable group by second(time)", function(re){
		if(re.resultCode&&re.resultCode=="1"){
			alert(re.msg);
		} else {
			jobj = new DolphinDBEntity(re).toVector();//将返回结果转换成列数据
			var time = jobj[0].value;
			var ecdata = jobj[1].value;
			var option = {
                    chart: {
                    type: 'line'
                    },
                    title: {
                        text: '温度'
                    },
                    xAxis: {
                        categories: time
                    },
                yAxis: {
                    title: {
                        text: '温度'
                    }
                },
                 series: [{
                    name: '平均温度',
                    data: ecdata
                }]
            };
			var chart = Highcharts.chart('main', option);

		}
	});
    
	</script>
</body>
</html>

代码运行的结果:

image

5. 总结

从上述示例可以了解,通过DolphinDB的WebApi开发包,Echarts、HighCharts等组件与DolphinDB集成展示数据是非常方便的,其他前端chart组件与DolphinDB的集成,均可以参考本文方式实现。

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