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Diffstat (limited to 'velocity-engine-core/src/main/java/org/apache/velocity/app/FieldMethodizer.java')
-rw-r--r-- | velocity-engine-core/src/main/java/org/apache/velocity/app/FieldMethodizer.java | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/app/FieldMethodizer.java b/velocity-engine-core/src/main/java/org/apache/velocity/app/FieldMethodizer.java new file mode 100644 index 00000000..3428d1c6 --- /dev/null +++ b/velocity-engine-core/src/main/java/org/apache/velocity/app/FieldMethodizer.java @@ -0,0 +1,185 @@ +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 org.apache.velocity.util.ClassUtils; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.lang.reflect.Field; +import java.lang.reflect.Modifier; +import java.util.HashMap; +import java.util.Map; + +/** + * <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.COUNTER_NAME + * </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:geirm@optonline.net">Geir Magnusson Jr.</a> + * @version $Id$ + */ +public class FieldMethodizer +{ + /** Hold the field objects by field name */ + private Map<String, Field> fieldHash = new HashMap<>(); + private Logger logger = LoggerFactory.getLogger(FieldMethodizer.class); + + /** + * 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 ) + { + logger.error("[FieldMethodizer] Could not add {} for field methodizing", s, 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 o Name of class to methodize. + */ + public FieldMethodizer( Object o ) + { + try + { + addObject(o); + } + catch( Exception e ) + { + logger.error("[FieldMethodizer] Could not add {} for field methodizing", o, e); + } + } + + /** + * 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 = 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 (Field field : fields) + { + /* + * only if public and static + */ + int mod = field.getModifiers(); + if (Modifier.isStatic(mod) && Modifier.isPublic(mod)) + { + fieldHash.put(field.getName(), field); + } + } + } +} |