org.apache.velocity.app.FieldMethodizer Maven / Gradle / Ivy
package org.apache.velocity.app;
/*
* Copyright 2001,2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.lang.Class;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
/**
*
* This is a small utility class allow easy access to static fields in a class,
* such as string constants. Velocity will not introspect for class
* fields (and won't in the future :), but writing setter/getter methods to do
* this really is a pain, so use this if you really have
* to access fields.
*
*
* The idea it so enable access to the fields just like you would in Java.
* For example, in Java, you would access a static field like
*
* MyClass.STRING_CONSTANT
*
* and that is the same thing we are trying to allow here.
*
*
* So to use in your Java code, do something like this :
*
* context.put("runtime", new FieldMethodizer( "org.apache.velocity.runtime.Runtime" ));
*
* and then in your template, you can access any of your static fields in this way :
*
* $runtime.RUNTIME_LOG_WARN_STACKTRACE
*
*
*
* Right now, this class only methodizes public static fields. It seems
* that anything else is too dangerous. This class is for convenience accessing
* 'constants'. If you have fields that aren't static it may be better
* to handle them by explicitly placing them into the context.
*
* @author Geir Magnusson Jr.
* @version $Id: FieldMethodizer.java,v 1.3.14.1 2004/03/03 23:22:53 geirm Exp $
*/
public class FieldMethodizer
{
/** Hold the field objects by field name */
private HashMap fieldHash = new HashMap();
/** Hold the class objects by field name */
private HashMap classHash = new HashMap();
/**
* Allow object to be initialized without any data. You would use
* addObject() to add data later.
*/
public FieldMethodizer()
{
}
/**
* Constructor that takes as it's arg the name of the class
* to methodize.
*
* @param s Name of class to methodize.
*/
public FieldMethodizer( String s )
{
try
{
addObject(s);
}
catch( Exception e )
{
System.out.println( e );
}
}
/**
* Constructor that takes as it's arg a living
* object to methodize. Note that it will still
* only methodized the public static fields of
* the class.
*
* @param s Name of class to methodize.
*/
public FieldMethodizer( Object o )
{
try
{
addObject(o);
}
catch( Exception e )
{
System.out.println( e );
}
}
/**
* Add the Name of the class to methodize
*/
public void addObject ( String s )
throws Exception
{
inspect(Class.forName(s));
}
/**
* Add an Object to methodize
*/
public void addObject ( Object o )
throws Exception
{
inspect(o.getClass());
}
/**
* Accessor method to get the fields by name.
*
* @param fieldName Name of static field to retrieve
*
* @return The value of the given field.
*/
public Object get( String fieldName )
{
try
{
Field f = (Field) fieldHash.get( fieldName );
if (f != null)
return f.get( (Class) classHash.get(fieldName) );
}
catch( Exception e )
{
}
return null;
}
/**
* Method that retrieves all public static fields
* in the class we are methodizing.
*/
private void inspect(Class clas)
{
Field[] fields = clas.getFields();
for( int i = 0; i < fields.length; i++)
{
/*
* only if public and static
*/
int mod = fields[i].getModifiers();
if ( Modifier.isStatic(mod) && Modifier.isPublic(mod) )
{
fieldHash.put(fields[i].getName(), fields[i]);
classHash.put(fields[i].getName(), clas);
}
}
}
}