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

Class UnifiedJEXL

java.lang.Object
edu.internet2.middleware.grouperClientExt.org.apache.commons.jexl2.UnifiedJEXL
public final class UnifiedJEXL extends Object
An evaluator similar to the Unified EL evaluator used in JSP/JSF based on JEXL. It is intended to be used in configuration modules, XML based frameworks or JSP taglibs and facilitate the implementation of expression evaluation.

An expression can mix immediate, deferred and nested sub-expressions as well as string constants;

  • The "immediate" syntax is of the form "...${jexl-expr}..."
  • The "deferred" syntax is of the form "...#{jexl-expr}..."
  • The "nested" syntax is of the form "...#{...${jexl-expr0}...}..."
  • The "composite" syntax is of the form "...${jexl-expr0}... #{jexl-expr1}..."

Deferred & immediate expression carry different intentions:

  • An immediate expression indicate that evaluation is intended to be performed close to the definition/parsing point.
  • A deferred expression indicate that evaluation is intended to occur at a later stage.

For instance: "Hello ${name}, now is #{time}" is a composite "deferred" expression since one of its subexpressions is deferred. Furthermore, this (composite) expression intent is to perform two evaluations; one close to its definition and another one in a later phase.

The API reflects this feature in 2 methods, prepare and evaluate. The prepare method will evaluate the immediate subexpression and return an expression that contains only the deferred subexpressions (& constants), a prepared expression. Such a prepared expression is suitable for a later phase evaluation that may occur with a different JexlContext. Note that it is valid to call evaluate without prepare in which case the same JexlContext is used for the 2 evaluation phases.

In the most common use-case where deferred expressions are to be kept around as properties of objects, one should parse & prepare an expression before storing it and evaluate it each time the property storing it is accessed.

Note that nested expression use the JEXL syntax as in: "#{${bar}+'.charAt(2)'}" The most common mistake leading to an invalid expression being the following: "#{${bar}charAt(2)}"

Also note that methods that parse evaluate expressions may throw unchecked exceptions; The UnifiedJEXL.Exception are thrown when the engine instance is in "non-silent" mode but since these are RuntimeException, user-code should catch them where appropriate.

Since:
2.0

  • Constructor Details

    • UnifiedJEXL

      public UnifiedJEXL(JexlEngine aJexl)
      Creates a new instance of UnifiedJEXL with a default size cache.
      Parameters:
      aJexl - the JexlEngine to use.

    • UnifiedJEXL

      public UnifiedJEXL(JexlEngine aJexl, int cacheSize)
      Creates a new instance of UnifiedJEXL creating a local cache.
      Parameters:
      aJexl - the JexlEngine to use.
      cacheSize - the number of expressions in this cache

  • Method Details

    • getEngine

      public JexlEngine getEngine()
      Gets the JexlEngine underlying the UnifiedJEXL.
      Returns:
      the JexlEngine

    • clearCache

      public void clearCache()
      Clears the cache.
      Since:
      2.1

    • parse

      public UnifiedJEXL.Expression parse(String expression)
      Creates a a UnifiedJEXL.Expression from an expression string. Uses & 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 UnifiedJEXL string expression
      Returns:
      the UnifiedJEXL object expression, null if silent and an error occured
      Throws:
      UnifiedJEXL.Exception - if an error occurs and the JexlEngine is not silent

    • startsWith

      protected int startsWith(CharSequence sequence, CharSequence pattern)
      Whether a sequence starts with a given set of characters (following spaces).

      Space characters at beginning of line before the pattern are discarded.

      Parameters:
      sequence - the sequence
      pattern - the pattern to match at start of sequence
      Returns:
      the first position after end of pattern if it matches, -1 otherwise
      Since:
      2.1

    • readTemplate

      protected List<edu.internet2.middleware.grouperClientExt.org.apache.commons.jexl2.UnifiedJEXL.TemplateBlock> readTemplate(String prefix, Reader source)
      Reads lines of a template grouping them by typed blocks.
      Parameters:
      prefix - the directive prefix
      source - the source reader
      Returns:
      the list of blocks
      Since:
      2.1

    • createTemplate

      public UnifiedJEXL.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
      Since:
      2.1

    • createTemplate

      public UnifiedJEXL.Template createTemplate(String source, String... parms)
      Creates a new template.
      Parameters:
      source - the source
      parms - the parameter names
      Returns:
      the template
      Since:
      2.1

    • createTemplate

      public UnifiedJEXL.Template createTemplate(String source)
      Creates a new template.
      Parameters:
      source - the source
      Returns:
      the template
      Since:
      2.1