Is it possible to use jsp variable value to initialize JQUERY variable?

Question

I have some questions which are as follows:

1. How can I use the JSP variable/array in JQUERY code? Here what ever the JQUERY code we have is stored in separate .js file and that file is included in the JSP file.

2. Actually I want to initialize the JQUERY array with the JSP variable. So please guide me to achieve this task.

Answer 1

Try to convert them to JS constants. There is no constants in JS but let it be so called constant. Just do not change it anywhere else.

<script>
  var const = yourJSPvariable;

And use CONST in your js file

Answer 2

Not directly. You'd have to set it into the page somewhere.

<script>
   var fromJsp = '${theVar}';
</script>

Note that this could get tricky for complex objects. Maybe JSON serialization can be your friend here.

Also note that this is one-way only. It is impossible to set the value of JSP variables from JavaScript (since the JavaScript runs client-side after the JSP has finished its work).

Answer 3

You can use this -

<input type="hidden" id="var1" value="<%=jspVar%>" />

and then use var1 in jQuery.

Answer 4

In Plain Old JSP

<script>
  var someText = "<%= myBean.getText() %>";
</script>

Using EL (Expression Language)

<script>
  var someText = "${myBean.text}";
</script>

Using Struts

<script>
  var someText = "<bean:write name="myBean" property="text" />";
</script>

Using JSTL

<script>
  var someText = "<c:out value="${myBean.text}" />";
</script>

In essence, it's possible to populate Javascript objects from JSP. Don't forget that scriptlets and tags are just rendered back as HTML/XHTML, so JS cannot talk to tags and vice-versa.

Answer 5

Java/JSP runs in webserver at the server machine and produces HTML/CSS/JS code. Server machine sends HTML/CSS/JS code to client machine. HTML/CSS/JS runs in webbrowser at client machine. Rightclick page and view source, you don't see any Java/JSP code.

JSP is a view technology which provides a template to write HTML/CSS/JS in and the ability to interact with backend Java data using taglibs/EL to control page flow and access data.

Whenever you want to let JavaScript access Java/JSP variables, all you need to do is to just write a Java variable as if it is a JavaScript variable.

<script>var foo = '${bean.foo}';</script>

Is an excellent example. Note that those quotes are required for JavaScript itself, not for JSP/EL. Imagine that ${bean.foo} returns bar, then the generated HTML/CSS/JS page which arrived at the client side would end up looking like:

<script>var foo = 'bar';</script>

Whenever you want to let Java/JSP access JavaScript variables, all you need to do is to let JavaScript fire a (XML)HTTP request. More background info and examples can be found in this article.