How to pass java string variable to the javascript function by jsp expression tag?

Question

I want to passing a java String variable to the javascript function parameter using jsp expression tag.Below is my jsp page.

First.jsp

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>Insert title here</title>
        <script>
            function stringGenerate(str){
                var x = document.getElementsByTagName("input");
                x[0].value = str;
            }
            function numberGenerate(num){
                var x = document.getElementsByTagName("input");
                x[1].value = num;
            }
        </script>
    </head>
    <body>
        <%
            String num ="1234567890";
            String str = "abcdefghij";
        %>

        <input type="text" name="string" readonly="readonly"/> &nbsp;&nbsp;
        <input type="text" name="number" readonly="readonly"/><br/><br/>

        <input type="button" value="String Generate" onclick= "stringGenerate(<%=str %>)" /> &nbsp;&nbsp;
        <input type="button" value="Number Generate" onclick= "numberGenerate(<%=num %>)" />
    </body>
</html>

When I click on the button with value "Number Generate",then the num variable value(1234567890) will display on the textbox(name="number") but when I click on the button with value "String Generate",then there is nothing display on the corresponding text box(name="string").Here both num and str are string type varible but why only num variable value is displayed on textbox and why not str variable value is displayed?

check what the html generated it worked for me.

singhakash
– singhakash

2015-03-22 17:52:01 +00:00
Commented Mar 22, 2015 at 17:52 — singhakash
– singhakash, Commented Mar 22, 2015 at 17:52

Manwal · Accepted Answer · 2015-03-22 17:57:51Z

2

Try using single quote ' when using string in HTML:

onclick= "stringGenerate('<%=str %>')"
                         ^        ^

Full Code:

<input type="button" value="String Generate" onclick= "stringGenerate('<%=str %>')" />

answered Mar 22, 2015 at 17:57

Manwal

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1 Comment

Aditya Over a year ago

Thanks a lot...it's run properly.

GabLeRoux · Accepted Answer · 2015-03-22 17:59:31Z

2

The reason is that when the page is rendered by the browser, it puts the str and num values directly in the code, so it looks like:

<input type="button" value="String Generate" onclick="stringGenerate(abcdefghij)"/>

The browser basically thinks you're trying to reference a Javascript variable called 'abcdefghij'.

You should add the ' chars before and after your string text to let javascript know it should use the value of that text and not search for a variable with that name.

The declaration of str should look like this to make it work:

String str = "\'abcdefghij\'";

Please note, you can't use \" to escape as this would break your code.

edited Mar 22, 2015 at 17:59

GabLeRoux

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answered Mar 22, 2015 at 17:54

Dimitri Grishin

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