org.apache.velocity.app.FieldMethodizer Maven / Gradle / Ivy
package org.apache.velocity.app;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import org.apache.velocity.util.ClassUtils;
/**
*
* 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.COUNTER_NAME
*
*
*
* 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 652755 2008-05-02 04:00:58Z nbubna $
*/
public class FieldMethodizer
{
/** Hold the field objects by field name */
private HashMap fieldHash = 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.err.println("Could not add " + s
+ " for field methodizing: "
+ e.getMessage());
}
}
/**
* 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 o Name of class to methodize.
*/
public FieldMethodizer( Object o )
{
try
{
addObject(o);
}
catch( Exception e )
{
System.err.println("Could not add " + o
+ " for field methodizing: "
+ e.getMessage());
}
}
/**
* Add the Name of the class to methodize
* @param s
* @throws Exception
*/
public void addObject ( String s )
throws Exception
{
inspect(ClassUtils.getClass(s));
}
/**
* Add an Object to methodize
* @param o
* @throws Exception
*/
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 )
{
Object value = null;
try
{
Field f = (Field) fieldHash.get( fieldName );
if (f != null)
{
value = f.get(null);
}
}
catch( IllegalAccessException e )
{
System.err.println("IllegalAccessException while trying to access " + fieldName
+ ": " + e.getMessage());
}
return value;
}
/**
* 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]);
}
}
}
}