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## org.apache.commons.jexl3
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
>      $$   } else if (x > 42) {
>      The value $(x} is over fourty-two
>      $$   } 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 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
`String` | `asString()` Recreate the template source from its inner components.
`void` | `evaluate(JexlContext context, Writer writer)` Evaluates this template.
`void` | `evaluate(JexlContext context, Writer writer, Object... args)` Evaluates this template.
`String[]` | `getParameters()` Gets the list of parameters expected by this template.
`Map<String,Object>` | `getPragmas()` Gets this script pragmas.
`Set<List<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

    String asString()

  Recreate the template source from its inner components.

  Returns:
    the template source rewritten

### evaluate

    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

    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

### 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

### getVariables

    Set<List<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

### getParameters

    String[] getParameters()

  Gets the list of parameters expected by this template.

  Returns:
    the parameter names array

### getPragmas

    Map<String,Object> getPragmas()

  Gets this script pragmas.

  Returns:
    the (non null, may be empty) pragmas map
  Since:
    3.1

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