Filter integer list in Thymeleaf

Question

I am learning about Thymeleaf in Spring, and I am struggling with list fitlering.

The official Tutorial: Using Thymeleaf does not talk about collection filtering and projection, but I found out that Thymeleaf on Spring uses the Spring Expression Language.

This guide states the following:

• The syntax of the selection (filtering) operator is : ${collection.?[property == value]}
• The syntax of the projection (mapping) operator is : ${collection.![property]}

This is fine if I have a list of objects, for example a list of persons. Then I can perform things like that:

• Selection (filtering): e.g., ${persons.?[age >= 18]} selects all persons of at least 18 years
• Projection (mapping): e.g., ${persons.![name]} selects the name of every person

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Question:

What if I do not have a list of objects (such as a list of persons) but a list of numbers or list of Strings? How can I perform selection (filtering) then? Things like numbers.?[>10] does not work.

Answer 1

After some more search, I found the answer in the Spring Expression Language documentation.

In 10.5.11 Variables the documentation states the #this and #root variables.

The variable #this is always defined and refers to the current evaluation object (against which unqualified references are resolved).

So, assuming I have a list numbers filled with integers, ${numbers.?[#this >= 10]} creates a new list that contains all numbers that are at least 10.