Using velocity split() to split a string into an a

问题:

I HATE velocity and rarely ever use it but sometimes I am called upon at my job to do so. I can never really figure out just how to use it.

I have this

#foreach( $product in $browseSiteProducts )
    alert("$product.productId");
    #foreach( $stringList in $product.productId.split("|") )
        alert("inner loop");
    #end
#end

$browseSiteProducts is an Array. Or List. Or whatever. I don't even know. The first alert of the productId works fine. I get "|" which is what I expected when printed out. The inner loop then should split that on the "|" as the delimiter and give me to alerts of "inner loop". But instead I always get 24 alerts because there are 24 characters in the productId. so split() is not delimiting correctly for me. What the heck am I doing wrong??

Thanks Kyle

回答1:

Velocity has extremely few objects and methods of its own. Instead, it allows you to work with real Java objects and call real Java methods on those objects. Which Velocity documentation says that the delimiter is a string?

Moreover, since Velocity is Java-based, a string is just a data type that can hold many types of information: phone numbers, names, identifiers, regular expressions... In Java, many methods dealing with regular expressions pass those REs as String objects.

You can check the actual type that a value behind a variable has by printing its classname:

Product class is $product.class
Product ID class is $product.productId.class

If the product ID is indeed a java.lang.String, then you can check that the split method takes a String parameter, but that String is expected to be a valid regular expression.

And since | is a special character in regular expressions, you need to escape it somehow. This works:

#foreach( $stringList in $product.productId.split("[|]") )

回答2:

Without using StringUtils this can be done using the String split() method.

Unlike it's Java counterpart for special characters one doesn't need to escape the forward slash (.e.g "\\|") as @kamcknig correctly stated:

#set ($myString = “This|is|my|dummy|text”) 

#set ($myArray = $myString.split("\|")) or
#set ($myArray = $myString.split('\|')) or
#set ($myArray = $myString.split("[|]"))

Note 1: To get the size of the array use: $myArray.size()

Note 2: To get actual values use $myArray.get(0) or $myArray[0] … etc

Suggestion: one could use beforehand #if ($myString.indexOf(‘|’)) ... #end

回答3:

## Splitting by Pipes
#set($prodId = $product.productId)
#foreach($id in $prodId.split("[|]"))
$id
#end

回答4:

Apparently even though the velocity documentation says that the delimiter is a string it's really a regular expression. Thanks apache.

proper way is

$product.product.split("\|");