public class ConstantLookup
extends org.apache.commons.lang.text.StrLookup
A specialized lookup implementation that allows access to constant fields of classes.
Sometimes it is necessary in a configuration file to refer to a constant
defined in a class. This can be done with this lookup implementation.
Variable names passed in must be of the form
mypackage.MyClass.FIELD. The lookup() method
will split the passed in string at the last dot, separating the fully
qualified class name and the name of the constant (i.e. static final)
member field. Then the class is loaded and the field's value is obtained
using reflection.
Once retrieved values are cached for fast access. This class is thread-safe. It can be used as a standard (i.e. global) lookup object and serve multiple clients concurrently.
| Constructor and Description |
|---|
ConstantLookup() |
| Modifier and Type | Method and Description |
|---|---|
static void |
clear()
Clears the shared cache with the so far resolved constants.
|
protected Class<?> |
fetchClass(String className)
Loads the class with the specified name.
|
String |
lookup(String var)
Tries to resolve the specified variable.
|
protected Object |
resolveField(String className,
String fieldName)
Determines the value of the specified constant member field of a class.
|
public String lookup(String var)
resolveField() method and pass in the name of the class
and the field.lookup in class org.apache.commons.lang.text.StrLookupvar - the name of the variable to be resolvedpublic static void clear()
protected Object resolveField(String className, String fieldName) throws Exception
fetchClass() to obtain the
java.lang.Class object for the target class. Then it will
use reflection to obtain the field's value. For this to work the field
must be accessable.className - the name of the classfieldName - the name of the member field of that class to readException - if an error occursprotected Class<?> fetchClass(String className) throws ClassNotFoundException
getClass() method of
Commons Lang's
ClassUtils.className - the name of the class to be loadedClassNotFoundException - if the class cannot be loadedCopyright © 2001–2013 The Apache Software Foundation. All rights reserved.