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Karrtik Iyer
3,738 PointsThymeLeaf Template, when to use | vs + operator
In this video we learnt to read the color code and adding to the th:style variable the category.colorCode, we could have done this using + operator like below, which also works, th:style="'background-color:'+ ${cat.colorCode}" instead in video we were taught the | operator which is something like below: th:style="|background-color:${cat.colorCode}|" What's the difference between both and when to use what? Please advise.
2 Answers
Chris Ramacciotti
Treehouse Guest TeacherGreat question! Thymeleaf offers string concatenation with the '+' operator, and literal substitution with the '|' character. Whatever you can do with literal substitution, you can do with concatenation. But, substitution with the '|' tends to be simpler syntax, so that is the preferred approach.
However, the one case in which you'd need to use concatenation is if you wanted something like a conditional expression as a concatenated value. When using substitution, only variables can be used inside the ${...}. For example, in Giflib, you couldn't do the equivalent of the following, using a literal substitution instead:
th:class="(${gif.favorite}? 'un' : '') + 'mark favorite'"
This is because it involves a conditional (ternary) expression that is invalid in a literal substitution. Now, if you computed this value in the controller, and made it available as a model attribute, you could get around this. Essentially you'd be moving this logic to the controller. But, if it's for the sole purpose of presentation (like a CSS class), you want to keep that in the view, not the controller.
Karrtik Iyer
3,738 PointsThanks Chris Ramacciotti for the great explanation with example, one more question, like thymeleaf do we have other template engines available as alternatives, which are the ones widely used in industry as of today?
Chris Ramacciotti
Treehouse Guest TeacherYes, there are definitely others. Template engines like Velocity, Freemarker, and Handlebars are popular. If you're interested in using those, do a quick web search with Spring and [template engine of choice]. You should see a bunch of guidance offered. You'd be well-served to play with some other template engines!
As a starting point, you can check out how Craig Dennis uses Handlebars in his course, Intro to Java Web Development with Spark.
Karrtik Iyer
3,738 PointsKarrtik Iyer
3,738 PointsChris Ramacciotti , can you please help answer this question?