How to Use a JavaScript Reporting Tool in a GoLang Web App

ActiveReportsJS is a 100% client-side reporting tool with zero server dependencies. It means that you can use ActiveReportsJS and any web server, including a Golang application. This article contains a simple yet thorough tutorial on integrating ActiveReportsJS with a GoLang application. By the end, you will be able to do the following:

• Create a GoLang application serving a JSON API
• Initialize the data from a CSV file
• Configure JSON API endpoints
• Create an ActiveReportsJS report to visualize the data from the JSON API
• Create a static HTML page to display the report in the report viewer

Prerequisites 

The following content assumes that you have GoLang installed on your machine. If you don't have it, you can obtain it from the GoLang website. It would be best if you also had ActiveReportsJS installed on your machine. If you don't have it, you can obtain it from the ActiveReportsJS website.

Create a GoLang Application

For this tutorial, we will use the Echo Go web framework. 
To create a new GoLang application that uses the Echo web framework, run the following commands from a terminal or command prompt.

mkdir ReportingOnTheGo && cd ReportingOnTheGo
go mod init ReportingOnTheGo
go get github.com/labstack/echo/v4

Then open the newly created ReportingOnTheGo directory in your favorite code editor, such as Visual Studio Code, create a new file called “server.go,” and add the following code at the beginning:

package main
 
import (
    "log"
    "net/http"
    "encoding/csv"
    "strconv"
    "os"   
    "github.com/labstack/echo/v4"
)

Create a data model for the JSON API

We will use the Sales dataset that you can download from the E for Excel website. It offers datasets of various sizes, starting from 100 records to 5M records. For simplicity, we will use the first dataset, which has 100 records.
There are many fields in the dataset, but we will only use several of them in this tutorial. Insert the following code fragment into the server.go file:

type Sale struct {
    Region  string `json:"region"`
    ItemType string `json:"itemType"`
    UnitsSold int `json:"unitsSold"`
  }

Initialize the data from a CSV file

Download and unzip the data from the 100-Sales-Records.zip  archive into the "data" directory of the application. Add the following code into the server.go file:

func ReadCsv(filename string) ([][]string, error) {
   f, err := os.Open(filename)
    if err != nil {
        return [][]string{}, err
    }
    defer f.Close()
    lines, err := csv.NewReader(f).ReadAll()
    if err != nil {
        return [][]string{}, err
    }
    return lines, nil
}
 
func main() {   
    lines, err := ReadCsv("data\\100 Sales Records.csv")
    if err != nil {
        log.Fatal(err)
    }
    var sales []Sale
    for _, line := range lines[1:] {
        unitsSold, err := strconv.Atoi(line[8])
        if err != nil {
            log.Fatal(err)
        }
        sale := Sale{
            Region: line[0],
            ItemType: line[2],
            UnitsSold: unitsSold,
        }
        sales = append(sales, sale)        
    }
}

Configure JSON API endpoints

At the end of the main() function, add the following code that initializes the web-server, adds the JSON endpoint that returns the sales data, and serves the static files from the assets folder:

    e := echo.New()    
    e.Static("/", "assets")
    e.GET("api/sales", func(c echo.Context) error {
        return c.JSON(http.StatusOK, sales)
    }   )
    e.Logger.Fatal(e.Start(":3000"))

In the command prompt or terminal, run the go run server.go command from the application's root folder and open the browser to http://localhost:3000/api/sales to see the data the JSON API returns.

Create an ActiveReportsJS report

Let's now create a report that visualizes the data from the JSON API.

In the Standalone Report Designer Application, click the File menu and select the Continuous Page Layout template for a newly created report.

Open the Data panel of the property inspector and click the Add button.

In the Data Source editor dialog, type http://localhost:3000/api/sales in the ENDPOINT field and click the Save Changes button.

Click the + icon near DataSource in the Data panel.

In the Data Set Editor dialog, type Sales in the NAME field and $.* in the JSON Path field.

Click the Validate button, ensure that the DataBase Fields section displays [3 items] text, and click the Save Changes button.

Expand the toolbox using the Hamburger menu located on the toolbar’s left side.

Drag and drop the Chart item from the toolbox to the report page area's top-left corner. The Chart Wizard dialog appears. Select the Bar type and click the Next button on the first screen.

On the second screen of the dialog, configure the data as shown in the following image and click the Next button.

On the third screen, click the Finish button.

Resize the chart report item to fill the entire width of the report page. Click the chart legend to load its properties into the properties panel and set the Orientation property to Horizontal and Position property to Bottom.

Click the File menu and save the newly created report in the assets folder of the application under the name SalesReport.rdlx-json.

Create a static HTML page to display the report

In the application's assets folder, create an index.html file and replace its content with the following code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Sales Report</title>
    <link
    rel="stylesheet"
    href="https://cdn.grapecity.com/activereportsjs/3.latest/styles/ar-js-ui.css"
    type="text/css"
  />
  <link
    rel="stylesheet"
    href="https://cdn.grapecity.com/activereportsjs/3.latest/styles/ar-js-viewer.css"
    type="text/css"
  />
  <script src="https://cdn.grapecity.com/activereportsjs/3.latest/dist/ar-js-core.js"></script>
  <script src="https://cdn.grapecity.com/activereportsjs/3.latest/dist/ar-js-viewer.js"></script>
  <script src="https://cdn.grapecity.com/activereportsjs/3.latest/dist/ar-js-pdf.js"></script>
  <style>
    #viewer-host {
      width: 100%;
      height: 100vh;
    }
  </style>      
</head>
  
<body>
    <div id="viewer-host"></div>
    <script>
        var viewer = new ActiveReports.Viewer("#viewer-host");
        viewer.open('SalesReport.rdlx-json');
      </script>  
</body>
</html>

Restart the application using the go run server.go command and visit the browser to http://localhost:3000/index.html to see the report. If you followed the steps correctly, you should see a report that displays the data from the JSON API.