Interface JxltEngine.Template

  • All Known Implementing Classes:
    TemplateScript
    Enclosing class:
    JxltEngine

    public static interface JxltEngine.Template
    A template is a JEXL script that evaluates by writing its content through a Writer.

    The source text is parsed considering each line beginning with '$$' (as default pattern) as JEXL script code and all others as Unified JEXL expressions; those expressions will be invoked from the script during evaluation and their output gathered through a writer. It is thus possible to use looping or conditional construct "around" expressions generating output.

    For instance:
     $$ for(var x : [1, 3, 5, 42, 169]) {
     $$   if (x == 42) {
     Life, the universe, and everything
     $$   } else if (x > 42) {
     The value $(x} is over forty-two
     $$   } else {
     The value ${x} is under forty-two
     $$   }
     $$ }
     

    Will evaluate as:

     The value 1 is under forty-two
     The value 3 is under forty-two
     The value 5 is under forty-two
     Life, the universe, and everything
     The value 169 is over forty-two
     

    During evaluation, the template context exposes its writer as '$jexl' which is safe to use in this case. This allows writing directly through the writer without adding new-lines as in:

     $$ for(var cell : cells) { $jexl.print(cell); $jexl.print(';') }
     

    A template is expanded as one JEXL script and a list of template expressions; each template expression is being replaced in the script by a call to jexl:print(expr) (the expr is in fact the expr number in the template). This integration uses a specialized JexlContext (TemplateContext) that serves as a namespace (for jexl:) and stores the template expression array and the writer (java.io.Writer) that the 'jexl:print(...)' delegates the output generation to.

    Since:
    3.0
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      java.lang.String asString()
      Recreate the template source from its inner components.
      void evaluate​(JexlContext context, java.io.Writer writer)
      Evaluates this template.
      void evaluate​(JexlContext context, java.io.Writer writer, java.lang.Object... args)
      Evaluates this template.
      java.lang.String[] getParameters()
      Gets the list of parameters expected by this template.
      java.util.Map<java.lang.String,​java.lang.Object> getPragmas()
      Gets this script pragmas.
      java.util.Set<java.util.List<java.lang.String>> getVariables()
      Gets the list of variables accessed by this template.
      JxltEngine.Template prepare​(JexlContext context)
      Prepares this template by expanding any contained deferred TemplateExpression.
    • Method Detail

      • asString

        java.lang.String asString()
        Recreate the template source from its inner components.
        Returns:
        the template source rewritten
      • evaluate

        void evaluate​(JexlContext context,
                      java.io.Writer writer)
        Evaluates this template.
        Parameters:
        context - the context to use during evaluation
        writer - the writer to use for output
      • evaluate

        void evaluate​(JexlContext context,
                      java.io.Writer writer,
                      java.lang.Object... args)
        Evaluates this template.
        Parameters:
        context - the context to use during evaluation
        writer - the writer to use for output
        args - the arguments
      • getParameters

        java.lang.String[] getParameters()
        Gets the list of parameters expected by this template.
        Returns:
        the parameter names array
      • getPragmas

        java.util.Map<java.lang.String,​java.lang.Object> getPragmas()
        Gets this script pragmas.
        Returns:
        the (non null, may be empty) pragmas map
        Since:
        3.1
      • getVariables

        java.util.Set<java.util.List<java.lang.String>> getVariables()
        Gets the list of variables accessed by this template.

        This method will visit all nodes of the sub-expressions and extract all variables whether they are written in 'dot' or 'bracketed' notation. (a.b is equivalent to a['b']).

        Returns:
        the set of variables, each as a list of strings (ant-ish variables use more than 1 string) or the empty set if no variables are used
      • prepare

        JxltEngine.Template prepare​(JexlContext context)
        Prepares this template by expanding any contained deferred TemplateExpression.
        Parameters:
        context - the context to prepare against
        Returns:
        the prepared version of the template