Custom format functions for StringTemplate4

Question

Custom format functions for StringTemplate4

3.1k views Asked by Julio At 12 November 2014 at 16:06

I would like to know how to create a custom format function for string template. Let say I have the following code:

render(attributes) :: <<
<html>
    $atributes: {
        <div> $customformat(atribute.name)$</div>
    }


</html>
>>

customformat(name) ::= <<
    $name; format="upper"$
>>

Currently the behaviour of the function customformat is:

Input: "hello world" -> Output: "HELLO WORLD"

And I would like to modify the customformat function so the output is something like the following:

Input: "hello world" -> Output: "HELLO_WORLD"

Original Q&A

There are 2 answers

Lasitha Konara On 09 May 2017 at 05:16

Try this one

Object rendering using AttributeRenderer

public class BasicFormatRenderer implements AttributeRenderer {
public String toString(Object o) {
    return o.toString();
}
public String toString(Object o, String formatName) {
    if (formatName.equals("toUpper")) {
        return o.toString().toUpperCase();
    } else if (formatName.equals("toLower")) {
        return o.toString().toLowerCase();
    } else {
        throw new IllegalArgumentException("Unsupported format name");
    }
}}

**Andy Stabler** · Accepted Answer · 2014-11-24 11:53:05

~~As far as I'm aware this isn't possible, since StringTemplate is all about strict model-view separation.~~

~~Instead, I think you'd be better off having a getter in the controller that returned the formatted string.~~

~~You might find this question useful: embed java code inside a template~~

Actually, I found a simple way of doing this which avoids the need for the formatted string getters:

You need to create a new StringRenderer which can format the string in the way you want.

public class MyStringRenderer extends StringRenderer
{
    @Override
    public String toString(Object o, String formatString, Locale locale) {
        if (!("upperAndUnder".equals(formatString)))
            return super.toString(o, formatString, locale);
       // we want upper case words with underscores instead of spaces
        return ((String) o).replaceAll(" ", "_").toUpperCase(locale);
    }
}

Then you'll need to let the template group know about the new renderer:

public static void main(String[] args) {
    STGroup templates = new STGroupFile("test.stg");
    templates.registerRenderer(String.class, new MyStringRenderer());
    ST renderTemplate = templates.getInstanceOf("render");
    renderTemplate.add("attributes", new String[]{"blahh blahh I'm a string", "I'm another string"});
    System.out.println(renderTemplate.render());
}

Then you can call the format function like you did before, but pass "upperAndUnder" as the parameter:

group test;

delimiters "$","$"

render(attributes) ::= <<
<html>
    $attributes:{ attribute | <div> $customFormat(attribute)$</div>}; separator="\n"$


</html>
>>

customFormat(name) ::= <<
    $name; format="upperAndUnder"$
>>

which prints:

<html>
    <div> BLAHH_BLAHH_I'M_A_STRING</div>
    <div> I'M_ANOTHER_STRING</div>


</html>

FYI:

Here's the original StringRenderer code

More info on Renderers

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Custom format functions for StringTemplate4

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