How to convert string into integer in the Velocity template?

I have a Veloci开发者_运维知识库ty template file which has the data from XML. I want to convert the string into integer type.

How can I do that?

Aha! Been there.

#set($intString = "9")
#set($Integer = 0)
$Integer.parseInt($intString)

Doing this uses the java underlying velocity. The $Integer variable is nothing more that a java Integer object which you can then use to access .parseInt

Edit: The above code is for demonstration. Of course there are ways to optimize it.

If you have some control over the velocity context, here's an alternative that alleviates the need to set a variable in the Velocity template.

Context velocityContext = new Context();
velocityContext.put(Integer.class.getSimpleName(), Integer.class);

This allows you to call the static methods of java.lang.Integer in your template using $Integer.parseInt($value) and doesn't rely upon the #set having been called prior to performing the type conversion in the template.

The problem with parseInt is that it throws an exception in case the string is not parseable. In case you have the NumberTool loaded into your context a better solution than parseInt is the following:

#set($intString = "009")
#set($Integer=$numberTool.toNumber($intString).intValue())

#if($Integer)
 ## ok
#else
 ## nok
#end

Sometimes the NumberTool is also loaded as $number.

However, a little drawback is, that the NumberTool simply parses the first number it finds and ignores the rest, so "123a" => 123.

Nice and easy:

#set( $stringToCast = "0" )
$number.toNumber($stringToCast)

$number is the default key name for the NumberTool, but it can be override by specifying a different name in the configuration (for example $numberTool). You have to check what name for NumberTool is used in your Velocity environment.

toNumber method returns:

the object as a Number or null if no conversion is possible

If you want to have explicite an int variable, not a Number object, you can use the intValue method on the result. So the above code will looks like this:

#set( $stringToCast = "0" )
$number.toNumber($stringToCast).intValue()

Of course, you can assign the result to another variable (for example $intVal).

So the full code can look like this:

#set( $stringToCast = "0" )
#set( $intVal = $number.toNumber($stringToCast).intValue() )