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Proper way for Javascript to read MySQL data through Java

I am now learning while developing my Java web app using JSF, and I was asked to study on using Javascript to create datatable/report dynamically and present it via .html/.xhtml. I am required to use Datatables.net to produce the table. The backend process is using Java instead of Php. Since it is so rare to use this method, I got no idea on this. My thought so far is:
MySQL data --convert to (processed by Java code)--> Json --read by-> Javascript
How do I process the SQL data? Can I directly run the query inside Java like:
SELECT
CONCAT("[",
GROUP_CONCAT(
CONCAT("{name:'",NAME,"'"),
CONCAT("email:'",email,"'"),
CONCAT(",address:'",address,"'}")
)
,"]") AS JSON FROM customer
If so, how do I parse the data out and make sure Javascript will read it?
The another way I found is to use some library like Gson or something similar.
Explanations or examples about this issue is much appreciated.

Dart wrapper over js library and use it in flutter app

Put it simple I want to make small currency exchange app (pet project- I want free API( 1000 requests per month including more currency is a perfect option)). I dont like the free APIs I have found so far but I have found this website https://bg.coinmill.com/ and I wanna use it for my purpose. Reading an answer to similar question:
The only way to make use of JS in Flutter is using WebView.
Dart compiles to JS only for browser applications, for Flutter it compiles >to native machine code.
convert js code direcly to dart, using package js
package JS doesn't convert JS, it just creates proxies for JS functions to >be able to call them from Dart, but that is also only supported in Dart web >applications.
Put it simple it isn't possible without hitting some compilation errors and some workarounds. However https://github.com/pichillilorenzo/flutter_inappbrowser looks promissing. Embedding the webpage that will look ugly and I won't have any control over ui/settings. My options now are looking for another free currency API or trying to find a workaround. I incline for another API, but not sure which one. Any suggestions ?

So basically what you actually want to do is use that website to do the currency conversion in the background (enter value, press "Convert"), then display the result in your Flutter app? You don't need javascript for that.
After entering pressing the submit button, the site simply redirects you to a different page (GET request) with an URL like this:
https://bg.coinmill.com/CAD_USD.html?CAD=22
Use dart's http library to perform the same request with the right currency/value parameters. The result of the request contains the source code of the web page.
Instead of displaying the web page, you just need to read the value you need from the source code of the web page:
<div id="currencyBox1">
<input class="currencyField" ... value="16.46" ...>
САЩ долар (USD)
</div>

So, how I understand your question, you have some js library, and you want to use it from Dart?
If question so, yes, you can do it using Dart JS Intertop. The more information in the link.
Edit
Yes, you are right, you can call js from Flutter only using evalJavascript function from flutter_webview_plugin.

You can use Firebase Cloud Functions and wrap your function in a callable function. You'll have all node js environment and Dart code will only call a function.

SQLite with JavaScript

I'm working on a small project where I'm going to read some parameters from a SQLite database. The data is generated from a Linux server running a C code. I then want to create a script using JavaScript to fetch the data from the database. I've tried with alasql.js but it takes very long time (~1 minute) before I get the list with the parameters from two tables.
SELECT sensors.id, sensors.sensorname, sensors.sensornumber, information.sensorvalue, information.timestamp FROM sensors INNER JOIN information ON sensors.id=information.sensorid
I've been reading about IndexedDB but seems like it only works with JavaScript but not with C-code. Please, correct me if I'm wrong. The clue here is that I want a database that supports writing to database from C-code and reading from database from JavaScript. The database can be read either from file:// schema or an IP address.
Would appreciate any help regarding this problem. Thanks!

Unfortunately, SQLite internal file format is complicated to fast parsing with JavaScript. One of the reasons, that the only browser side library which can read it is SQL.js and it is relatively slow, because it can not read data by selected pages from the database file, but only the whole file.
One of the options: you can switch from SQLite format to CSV or TSV plain tet formats, which can be eaily and quickly send to the browser and be parsed with jQuery.CSV, PapaParse, AlaSQL or any other CSV parsing libraries, like:
alasql('SELECT * FROM TSV("mydata.txt",{headers:true})',[],function(data){
// data
});
Another alternative: you can write simple server on node.js with native support of SQLite and then provide requested records in JSON format with ajax to your application (like in this article)

Saving / Retriving all the fields value's of an HTML form into / from a local file using JavaScript

I have a typical HTML form, with some fields of various types on it.
What I'm trying to achieve is the following:
Once the form's input fields are filled out with values, a button to be able to save all the filled-out field/value pairs into a local file of some sort that allows me in a future ocassion to...
Automatically fill the very same HTML form by retriving the field/values pairs from said file instead of typing them manually.
Ideally this would have to be achived thru JavaScript, because the webpage that contains the HTML form is served by an embedded system where PHP or other server side scripting is not available.
Is it possible to achive this thru JavaScript (or any other browser-side effort method)? If so, how?
Many thanks.
EDIT: The target environment is a regular user in a regular PC/laptop using any one of the 4 major browsers. It's acceptable to have "Cookies enabled" and "latest browser version installed" as requisites, but external plugins/addins are not.
Later: NullUserException has achived something in this direction. He's been able to read from a local file using JavaScript:
Using a local file as a data source in JavaScript

I think, for your particular site you can store data in local storage. Only your application will be able to access to that data. Also you can encrypt it before storing.
You can refer
diveintohtml5.info/storage to start with.
Happy coding.

Pretty sure you won't be able to save a file locally and then pick it up again.
However there are obviously cookies but there, and this is only in a modern browser, is also LocalStorage that can hold quite a bit of data that can be retrieved by Javascript and jQuery.
This is probably the way I would go but it does depend on your browser version.

question is some what ambiguous please specify what you are trying to do.
i can't tell if you want to do something just for you if so:
https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/

How Can I Read A Web Browser Hidden Document Value Using IWebBrowser2 In LabVIEW?

I've searched around the internet for a couple of hours and could not find anything related to what I'm trying to do. I wrote a HTML document that collects data from a user and stores it in a javascript array. This array is then joined together and stored as a string in a document which is hidden. Originally, I was going to transfer this string to a program I wrote in C#, but now I am using LabVIEW.
In C#, I used two simple lines of code to do what I wanted:
System.Windows.Forms.HtmlElement hidden = webBrowser1.Document.GetElementById("hiddenfield1");
List<latlng> data = formharvest.extract(hidden.GetAttribute("value"));
But now I cannot find a way to access the data that is in this hidden document. I'm using the IWebBrowser2 block to embed my HTML code in my VI. Any help would be greatly appreciated. Thank you for your time!

A solution would be to start a Web server in your LabVIEW program, and serve your HTML form from it. I suppose it wouldn't be too hard to retrieve form data then, but I haven't done such thing myself.
Here's an interesting discussion on this with sample code.

I'm not sure I really understand what you are doing above: in the C#, it looks like you are embedding an HTML-rendering engine in a Windows form (i.e. window).
You can embed .NET in your labview code and therefore you should be able to embed the same HTML rendering engine in a LabView VI, but you might consider changing your approach, as CharlesB suggests, to something more traditional where a server serves some HTML to a web browser, which then sends some data back to the server via HTTP GET or POST.