Package edu.internet2.middleware.grouperClientExt.org.apache.commons.jexl2

Class UnifiedJEXL.Template

java.lang.Object
edu.internet2.middleware.grouperClientExt.org.apache.commons.jexl2.UnifiedJEXL.Template
Enclosing class:
UnifiedJEXL
public final class UnifiedJEXL.Template extends Object
A Template is a script that evaluates by writing its content through a Writer. This is a simplified replacement for Velocity that uses JEXL (instead of OGNL/VTL) as the scripting language.

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
 $$   } else if (x > 42) {
 The value $(x} is over fourty-two
 $$   } else {
 The value ${x} is under fourty-two
 $$   }
 $$ }
Will evaluate as: 

 The value 1 is under fourty-two
 The value 3 is under fourty-two
 The value 5 is under fourty-two
 Life, the universe, and everything
 The value 169 is over fourty-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 UnifiedJEXL expressions; each UnifiedJEXL expression being replace 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 expression array and the writer (java.io.Writer) that the 'jexl:print(...)' delegates the output generation to.

Since:
2.1

  • Constructor Details

    • Template

      public Template(String directive, Reader reader, String... parms)
      Creates a new template from an input.
      Parameters:
      directive - the prefix for lines of code; can not be "$", "${", "#" or "#{" since this would preclude being able to differentiate directives and UnifiedJEXL expressions
      reader - the input reader
      parms - the parameter names
      Throws:
      NullPointerException - if either the directive prefix or input is null
      IllegalArgumentException - if the directive prefix is invalid

  • Method Details

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • asString

      public String asString()
      Recreate the template source from its inner components.
      Returns:
      the template source rewritten

    • prepare

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

    • evaluate

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

    • evaluate

      public void evaluate(JexlContext context, Writer writer, Object... args)
      Evaluates this template.
      Parameters:
      context - the context to use during evaluation
      writer - the writer to use for output
      args - the arguments