org.apache.commons.configuration.interpol
Class ExprLookup

java.lang.Object
  org.apache.commons.lang.text.StrLookup
      org.apache.commons.configuration.interpol.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

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.

Constructor Summary

ExprLookup()
The default constructor.

ExprLookup(ExprLookup.Variables list)
Constructor for use by applications.

ExprLookup(ExprLookup.Variables list, String prefix, String suffix)
Constructor for use by applications.

Method Summary

ExprLookup.Variables	getVariables() Returns the list of Variables that are accessible within expressions.
String	lookup(String var) Evaluates the expression.
void	setConfiguration(AbstractConfiguration config) Set the configuration to be used to interpolate subordinate expressions.
void	setVariablePrefixMatcher(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(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,
                  String prefix,
                  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(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(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 String lookup(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.