Groovy - Groovy Templates

Groovy - Groovy Templates

Groovy Templates


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    Introduction

    Groovy supports multiple ways to generate text dynamically including GStrings, printf if you are using Java 5, and MarkupBuilder just to name a few. In addition to these, there is a dedicated template framework which is well-suited to applications where the text to be generated follows the form of a static template.
    Template framework

    The template framework in Groovy consists of a TemplateEngine abstract base class that engines must implement and a Template interface that the resulting templates they generate must implement.

    Included with Groovy are several template engines:

        SimpleTemplateEngine - for basic templates
        GStringTemplateEngine - stores the template as writable closures (useful for streaming scenarios)
        XmlTemplateEngine - works well when the template and output are valid XML

    SimpleTemplateEngine

    Shown here is the SimpleTemplateEngine that allows you to use JSP-like scriptlets (see example below), script, and EL expressions in your template in order to generate parameterized text. Here is an example of using the system:

    import groovy.text.SimpleTemplateEngine

    def text = 'Dear "$firstname $lastname",\nSo nice to meet you in <% print city %>.\nSee you in ${month},\n${signed}'

    def binding = ["firstname":"Sam", "lastname":"Pullara", "city":"San Francisco", "month":"December", "signed":"Groovy-Dev"]

    def engine = new SimpleTemplateEngine()
    template = engine.createTemplate(text).make(binding)

    def result = 'Dear "Sam Pullara",\nSo nice to meet you in San Francisco.\nSee you in December,\nGroovy-Dev'

    assert result == template.toString()

    While it is generally not deemed good practice to mix processing logic in your template (or view), sometimes very simple logic can be useful. E.g. in the example above, we could change this:

    $firstname

    to this (assuming we have set up a static import for capitalize inside the template):

    ${capitalize(firstname