org.apache.commons.configuration2.interpol

Class ExprLookup

java.lang.Object

org.apache.commons.configuration2.interpol.ExprLookup

All Implemented Interfaces:

Lookup

public class ExprLookup
extends Object
implements Lookup

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and 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.

Constructor Summary

Constructors

Constructor and Description
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

Modifier and Type	Method and Description
ConfigurationInterpolator	getInterpolator() Returns the ConfigurationInterpolator used by this object.
ConfigurationLogger	getLogger() Returns the logger used by this object.
ExprLookup.Variables	getVariables() Returns the list of Variables that are accessible within expressions.
String	lookup(String var) Evaluates the expression.
void	setInterpolator(ConfigurationInterpolator interpolator) Sets the ConfigurationInterpolator to be used by this object.
void	setLogger(ConfigurationLogger logger) Sets the logger to be used by this object.
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 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. This method returns a copy of the variables managed by this lookup; so modifying this object has no impact on this lookup.

Returns:

the List of Variables that are accessible within expressions.

getLogger

public ConfigurationLogger getLogger()

Returns the logger used by this object.

Returns:

the Log

Since:

2.0

setLogger

public void setLogger(ConfigurationLogger logger)

Sets the logger to be used by this object. If no logger is passed in, no log output is generated.

Parameters:

logger - the Log

Since:

2.0

getInterpolator

public ConfigurationInterpolator getInterpolator()

Returns the ConfigurationInterpolator used by this object.

Returns:

the ConfigurationInterpolator

Since:

2.0

setInterpolator

public void setInterpolator(ConfigurationInterpolator interpolator)

Sets the ConfigurationInterpolator to be used by this object.

Parameters:

interpolator - the ConfigurationInterpolator (may be null)

Since:

2.0

lookup

public String lookup(String var)

Evaluates the expression.

Specified by:

lookup in interface Lookup

Parameters:

var - The expression.

Returns:

The String result of the expression.