Class ExprLookup


  • public class ExprLookup
    extends org.apache.commons.lang.text.StrLookup
    Lookup that allows expressions to be evaluated.
         ExprLookup.Variables vars = new ExprLookup.Variables();
         vars.add(new ExprLookup.Variable("String", org.apache.commons.lang.StringUtils.class));
         vars.add(new ExprLookup.Variable("Util", new Utility("Hello")));
         vars.add(new ExprLookup.Variable("System", "Class:java.lang.System"));
         XMLConfiguration config = new XMLConfiguration(TEST_FILE);
         config.setLogger(log);
         ExprLookup lookup = new ExprLookup(vars);
         lookup.setConfiguration(config);
         String str = lookup.lookup("'$[element] ' + String.trimToEmpty('$[space.description]')");
     
    In the example above TEST_FILE contains xml that looks like:
     <configuration>
       <element>value</element>
       <space xml:space="preserve">
         <description xml:space="default">     Some text      </description>
       </space>
     </configuration>
     
    The result will be "value Some text". This lookup uses Apache Commons Jexl and requires that the dependency be added to any projects which use this.
    Since:
    1.7
    Version:
    $Id: ExprLookup.java 1234539 2012-01-22 16:19:15Z oheger $
    Author:
    Commons Configuration team
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  ExprLookup.Variable
      The key and corresponding object that will be made available to the JexlContext for use in expressions.
      static class  ExprLookup.Variables
      List wrapper used to allow the Variables list to be created as beans in DefaultConfigurationBuilder.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      ExprLookup.Variables getVariables()
      Returns the list of Variables that are accessible within expressions.
      java.lang.String lookup​(java.lang.String var)
      Evaluates the expression.
      void setConfiguration​(AbstractConfiguration config)
      Set the configuration to be used to interpolate subordinate expressions.
      void setVariablePrefixMatcher​(java.lang.String prefix)
      Set the prefix to use to identify subordinate expressions.
      void setVariables​(ExprLookup.Variables list)
      Add the Variables that will be accessible within expressions.
      void setVariableSuffixMatcher​(java.lang.String suffix)
      Set the suffix to use to identify subordinate expressions.
      • Methods inherited from class org.apache.commons.lang.text.StrLookup

        mapLookup, noneLookup, systemPropertiesLookup
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • ExprLookup

        public ExprLookup()
        The default constructor. Will get used when the Lookup is constructed via configuration.
      • ExprLookup

        public ExprLookup​(ExprLookup.Variables list)
        Constructor for use by applications.
        Parameters:
        list - The list of objects to be accessible in expressions.
      • ExprLookup

        public ExprLookup​(ExprLookup.Variables list,
                          java.lang.String prefix,
                          java.lang.String suffix)
        Constructor for use by applications.
        Parameters:
        list - The list of objects to be accessible in expressions.
        prefix - The prefix to use for subordinate lookups.
        suffix - The suffix to use for subordinate lookups.
    • Method Detail

      • setVariablePrefixMatcher

        public void setVariablePrefixMatcher​(java.lang.String prefix)
        Set the prefix to use to identify subordinate expressions. This cannot be the same as the prefix used for the primary expression.
        Parameters:
        prefix - The String identifying the beginning of the expression.
      • setVariableSuffixMatcher

        public void setVariableSuffixMatcher​(java.lang.String suffix)
        Set the suffix to use to identify subordinate expressions. This cannot be the same as the suffix used for the primary expression.
        Parameters:
        suffix - The String identifying the end of the expression.
      • setVariables

        public void setVariables​(ExprLookup.Variables list)
        Add the Variables that will be accessible within expressions.
        Parameters:
        list - The list of Variables.
      • getVariables

        public ExprLookup.Variables getVariables()
        Returns the list of Variables that are accessible within expressions.
        Returns:
        the List of Variables that are accessible within expressions.
      • setConfiguration

        public void setConfiguration​(AbstractConfiguration config)
        Set the configuration to be used to interpolate subordinate expressions.
        Parameters:
        config - The Configuration.
      • lookup

        public java.lang.String lookup​(java.lang.String var)
        Evaluates the expression.
        Specified by:
        lookup in class org.apache.commons.lang.text.StrLookup
        Parameters:
        var - The expression.
        Returns:
        The String result of the expression.