# Class JxltEngine

java.lang.Object
org.apache.commons.jexl3.JxltEngine

public abstract class JxltEngine extends Object
A simple "JeXL Template" engine.

At the base is an evaluator similar to the Unified EL evaluator used in JSP/JSF based on JEXL. At the top is a template engine inspired by Velocity that uses JEXL (instead of OGNL/VTL) as the scripting language.

The evaluator is intended to be used in configuration modules, XML based frameworks or JSP taglibs and facilitate the implementation of expression evaluation.

The template engine is intended to output any form of text; html, XML, CSV...

Since:
  3.0

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `JxltEngine.Exception`
  The sole type of (runtime) exception the JxltEngine can throw.
  `static interface`
  `JxltEngine.Expression`
  A unified expression that can mix immediate, deferred and nested sub-expressions as well as string constants; The "immediate" syntax is of the form `"...`
  `static interface`
  `JxltEngine.Template`
  A template is a JEXL script that evaluates by writing its content through a Writer.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `JxltEngine()`
  Default constructor

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract void`
  `clearCache()`
  Clears the cache.
  `JxltEngine.Expression`
  `createExpression(String expression)`
  Creates a `JxltEngine.Expression` from an expression string.
  `abstract JxltEngine.Expression`
  `createExpression(JexlInfo info, String expression)`
  Creates a `JxltEngine.Expression` from an expression string.
  `JxltEngine.Template`
  `createTemplate(String source)`
  Creates a new template.
  `JxltEngine.Template`
  `createTemplate(String prefix, Reader source, String... parms)`
  Creates a new template.
  `JxltEngine.Template`
  `createTemplate(String source, String... parms)`
  Creates a new template.
  `JxltEngine.Template`
  `createTemplate(JexlInfo info, String source)`
  Creates a new template.
  `abstract JxltEngine.Template`
  `createTemplate(JexlInfo info, String prefix, Reader source, String... parms)`
  Creates a new template.
  `JxltEngine.Template`
  `createTemplate(JexlInfo info, String source, String... parms)`
  Creates a new template.
  `abstract JexlEngine`
  `getEngine()`
  Gets the `JexlEngine` underlying this template engine.

  ### Methods inherited from class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### JxltEngine

    public JxltEngine()
    Default constructor

- ## Method Details

  - ### clearCache

    public abstract void clearCache()
    Clears the cache.

  - ### createExpression

    public abstract JxltEngine.Expression createExpression(JexlInfo info, String expression)
    Creates a `JxltEngine.Expression` from an expression string. Uses and fills up the expression cache if any.

    If the underlying JEXL engine is silent, errors will be logged through its logger as warnings.

    Parameters:
      `info` - the `JexlInfo` source information
      `expression` - the `JxltEngine.Template` string expression
    Returns:
      the `JxltEngine.Expression`, null if silent and an error occurred
    Throws:
      `JxltEngine.Exception` - if an error occurs and the `JexlEngine` is not silent

  - ### createExpression

    public JxltEngine.Expression createExpression(String expression)
    Creates a `JxltEngine.Expression` from an expression string. Uses and fills up the expression cache if any.

    If the underlying JEXL engine is silent, errors will be logged through its logger as warnings.

    Parameters:
      `expression` - the `JxltEngine.Template` string expression
    Returns:
      the `JxltEngine.Expression`, null if silent and an error occurred
    Throws:
      `JxltEngine.Exception` - if an error occurs and the `JexlEngine` is not silent

  - ### createTemplate

    public JxltEngine.Template createTemplate(JexlInfo info, String source)
    Creates a new template.
    Parameters:
      `info` - the source info
      `source` - the source
    Returns:
      the template

  - ### createTemplate

    public abstract JxltEngine.Template createTemplate(JexlInfo info, String prefix, Reader source, String... parms)
    Creates a new template.
    Parameters:
      `info` - the jexl info (file, line, column)
      `prefix` - the directive prefix
      `source` - the source
      `parms` - the parameter names
    Returns:
      the template

  - ### createTemplate

    public JxltEngine.Template createTemplate(JexlInfo info, String source, String... parms)
    Creates a new template.
    Parameters:
      `info` - the source info
      `source` - the source
      `parms` - the parameter names
    Returns:
      the template

  - ### createTemplate

    public JxltEngine.Template createTemplate(String source)
    Creates a new template.
    Parameters:
      `source` - the source
    Returns:
      the template

  - ### createTemplate

    public JxltEngine.Template createTemplate(String prefix, Reader source, String... parms)
    Creates a new template.
    Parameters:
      `prefix` - the directive prefix
      `source` - the source
      `parms` - the parameter names
    Returns:
      the template

  - ### createTemplate

    public JxltEngine.Template createTemplate(String source, String... parms)
    Creates a new template.
    Parameters:
      `source` - the source
      `parms` - the parameter names
    Returns:
      the template

  - ### getEngine

    public abstract JexlEngine getEngine()
    Gets the `JexlEngine` underlying this template engine.
    Returns:
      the JexlEngine