geirm 01/01/21 12:52:48
Added: src/java/org/apache/velocity/util FieldMethodizer.java
Log:
Small utility to automatically expose public static fields in a class for easy
access in a Velocity template. See the code or javadoc for better documentation,
but the upshot... in Java :
context.put( "runtime", new
FieldMethodizer("org.apache.velocity.runtime.Runtime");
and in your template access the public static fields like you would in java:
$runtime.RUNTIME_LOG_ERROR_STACKTRACE
Allows access to public static fields only for safety.
Revision Changes Path
1.1
jakarta-velocity/src/java/org/apache/velocity/util/FieldMethodizer.java
Index: FieldMethodizer.java
===================================================================
package org.apache.velocity.util;
/*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [EMAIL PROTECTED]
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
import java.lang.Class;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
/**
* <p>
* 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.
*
* <p>
* 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
* <blockquote><pre>
* MyClass.STRING_CONSTANT
* </pre></blockquote>
* and that is the same thing we are trying to allow here.
*
* <p>
* So to use in your Java code, do something like this :
* <blockquote><pre>
* context.put("runtime", new FieldMethodizer(
"org.apache.velocity.runtime.Runtime" ));
* </pre></blockquote>
* and then in your template, you can access any of your static fields in this way :
* <blockquote><pre>
* $runtime.RUNTIME_LOG_WARN_STACKTRACE
* </pre></blockquote>
*
* <p>
* Right now, this class only methodizes <code>public static</code> fields. It
seems
* that anything else is too dangerous. This class is for convenience accessing
* 'constants'. If you have fields that aren't <code>static</code> it may be better
* to handle them by explicitly placing them into the context.
*
* @author <a href="mailto:[EMAIL PROTECTED]">Geir Magnusson Jr.</a>
* @version $Id: FieldMethodizer.java,v 1.1 2001/01/21 20:52:48 geirm Exp $
*/
public class FieldMethodizer
{
/** Hold the field objects by field name */
private HashMap fieldhash = new HashMap();
/** The class we are 'methodizing' */
Class clas = null;
/**
* 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
{
clas = Class.forName( s );
inspect();
}
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
{
clas = o.getClass();
inspect();
}
catch( Exception e )
{
System.out.println( e );
}
}
/**
* 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( clas );
}
catch( Exception e )
{
}
return null;
}
/**
* Method that retrieves all public static fields
* in the class we are methodizing.
*/
private void inspect()
{
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]);
}
}
}
}
