1.Connecting to JSON using Flexmonster Data Server

In the previous article, we described how to connect the pivot table to the JSON data source. To gain even better performance while working with JSON datasets, use Flexmonster Data Server – a special server developed by Flexmonster. This server communicates with the client using the custom data source API – our custom communication protocol allowing you to retrieve already aggregated data from a server to Flexmonster Pivot.

Flexmonster Data Server has the following advantages:

Reduced browser’s memory usage. Since loading, processing, filtering, and aggregating of the data is made on the server side, Flexmonster Pivot gets the data in a ready-to-show format. Thus, the data is visualized up to 10 times faster, and the browser’s resources are used more efficiently.
Larger datasets. Despite Flexmonster Pivot can connect to a JSON file directly, the size of a file is limited by the browser’s capability (on average, up to 100 MB). With Flexmonster Data Server, it is possible to visualize much larger datasets.
Built-in security configurations. Flexmonster Data Server is provided with convenient tools for data access security management.
Cross-platform solution. The Data Server is available for popular operating systems: Windows, Ubuntu/Linux, and macOS.

Get Flexmonster Data Server on a special download page. You can also find a detailed step-by-step guide on how to install the Data Server there.

Flexmonster Data Server supports only a specific JSON format – an array of objects, where each object is an unordered set of "key": "value" pairs. Here is an example:

[
   {
       "Color" : "green",
       "Country" : "Canada",
       "State" : "Ontario",
       "City" : "Toronto",
       "Price" : 174,
       "Quantity" : 22
   },
   ...
]

Flexmonster Data Server can be configured in the flexmonster-config.json file. To learn more about all the available configurations, see the configurations reference. To set configurations needed for the JSON data source, follow these steps:

Set up an empty component in your HTML page. If Flexmonster is not yet embedded – return to Quick start. Your code should look similar to the following example:

<div id="pivotContainer">The component will appear here</div>
<script src="flexmonster/flexmonster.js"></script>
<script>
    var pivot = new Flexmonster({
        container: "pivotContainer",
        toolbar: true,
        licenseKey: "XXXX-XXXX-XXXX-XXXX-XXXX"
    });
</script>

The previous step demonstrated how to set up Flexmonster Pivot. Now it’s time to configure Flexmonster Data Server. Set the "Type" property in flexmonster-config.json to "json". It should be done as follows:
```
"DataSources": [
    {
        "Type": "json"
    }
], 
```

Create an index for the file with your data. "Path" is the path to the file. For example:

"DataSources": [
    {
        "Type": "json",
        "Indexes": {
            "index_json": {
                "Path": "./data/data.json"
            }
        }
    }
],

In a similar way, more indexes can be specified:

"Indexes": {
    "index_json": {
        "Path": "./data/data.json"
    },
    "another_index_json": {
        "Path": "./data/another_data.json"
    }
}

Note: "index_json" and "another_index_json" are dataset identifiers. They will be used to configure the data source on the client side.

On the client side, the report should be configured as follows:

<div id="pivotContainer">The component will appear here</div>
<script src="flexmonster/flexmonster.js"></script>
<script>
    var pivot = new Flexmonster({
        container: "pivotContainer",
        toolbar: true,
        report: {
            dataSource: {
                type: "api",
                url: "http://localhost:9500",
                index: "index-json"
            }
        },
        licenseKey: "XXXX-XXXX-XXXX-XXXX-XXXX"
    });
</script>

Note 1: index must match the name of the index defined in step 2 (e.g., "index_json").
Note 2: when Flexmonster Pivot requests the data, Flexmonster Data Server server sends the response and then caches it. In case the component sends the same request once again, the server responds with the data from its cache. The cache is cleared only when the server is restarted, though the cache has a memory limit: when the limit is reached, and the new response can’t be cached, Flexmonster Data Server server deletes one of the previously cached responses from the cache.

Start Flexmonster Data Server by running the following command in the console:
```
flexmonster-data-server.exe
```

As soon as you start Flexmonster Data Server, it automatically preloads the data specified in the "Indexes" property. Thus, when Flexmonster Pivot requests the data, the server responds with already preloaded data.

Note that the preloaded data is kept in the server’s RAM, so the number of indexes you can specify is limited by the amount of RAM available to the server.

What’s next?

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