/*
    * 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.
   */
  package org.apache.commons.beanutils;
  
  import java.beans.IntrospectionException;
  import java.beans.Introspector;
  import java.beans.PropertyDescriptor;
  import java.lang.reflect.Method;
  import java.util.Locale;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * <p>
   * An implementation of the <code>BeanIntrospector</code> interface which can
   * detect write methods for properties used in fluent API scenario.
   * </p>
   * <p>
   * A <em>fluent API</em> allows setting multiple properties using a single
   * statement by supporting so-called <em>method chaining</em>: Methods for
   * setting a property value do not return <b>void</b>, but an object which can
   * be called for setting another property. An example of such a fluent API could
   * look as follows:
   *
   * <pre>
   * public class FooBuilder {
   *     public FooBuilder setFooProperty1(String value) {
   *        ...
   *        return this;
   *    }
   *
   *     public FooBuilder setFooProperty2(int value) {
   *        ...
   *        return this;
   *    }
   * }
   * </pre>
   *
   * Per default, <code>PropertyUtils</code> does not detect methods like this
   * because, having a non-<b>void</b> return type, they violate the Java Beans
   * specification.
   * </p>
   * <p>
   * This class is more tolerant with regards to the return type of a set method.
   * It basically iterates over all methods of a class and filters them for a
   * configurable prefix (the default prefix is <code>set</code>). It then
   * generates corresponding <code>PropertyDescriptor</code> objects for the
   * methods found which use these methods as write methods.
   * </p>
   * <p>
   * An instance of this class is intended to collaborate with a
   * {@link DefaultBeanIntrospector} object. So best results are achieved by
   * adding this instance as custom {@code BeanIntrospector} after the
   * <code>DefaultBeanIntrospector</code> object. Then default introspection finds
   * read-only properties because it does not detect the write methods with a
   * non-<b>void</b> return type. {@code FluentPropertyBeanIntrospector}
   * completes the descriptors for these properties by setting the correct write
   * method.
   * </p>
   *
   * @version $Id$
   * @since 1.9
   */
  public class FluentPropertyBeanIntrospector implements BeanIntrospector {
      /** The default prefix for write methods. */
      public static final String DEFAULT_WRITE_METHOD_PREFIX = "set";
  
      /** The logger. */
      private final Log log = LogFactory.getLog(getClass());
  
      /** The prefix of write methods to search for. */
      private final String writeMethodPrefix;
  
      /**
       *
       * Creates a new instance of <code>FluentPropertyBeanIntrospector</code> and
       * initializes it with the prefix for write methods used by the classes to
       * be inspected.
       *
       * @param writePrefix the prefix for write methods (must not be <b>null</b>)
       * @throws IllegalArgumentException if the prefix is <b>null</b>
       */
      public FluentPropertyBeanIntrospector(final String writePrefix) {
          if (writePrefix == null) {
             throw new IllegalArgumentException(
                     "Prefix for write methods must not be null!");
         }
         writeMethodPrefix = writePrefix;
     }
 
     /**
      *
      * Creates a new instance of <code>FluentPropertyBeanIntrospector</code> and
      * sets the default prefix for write methods.
      */
     public FluentPropertyBeanIntrospector() {
         this(DEFAULT_WRITE_METHOD_PREFIX);
     }
 
     /**
      * Returns the prefix for write methods this instance scans for.
      *
      * @return the prefix for write methods
      */
     public String getWriteMethodPrefix() {
         return writeMethodPrefix;
     }
 
     /**
      * Performs introspection. This method scans the current class's methods for
      * property write methods which have not been discovered by default
      * introspection.
      *
      * @param icontext the introspection context
      * @throws IntrospectionException if an error occurs
      */
     public void introspect(final IntrospectionContext icontext)
             throws IntrospectionException {
         for (final Method m : icontext.getTargetClass().getMethods()) {
             if (m.getName().startsWith(getWriteMethodPrefix())) {
                 final String propertyName = propertyName(m);
                 final PropertyDescriptor pd = icontext
                         .getPropertyDescriptor(propertyName);
                 try {
                     if (pd == null) {
                         icontext.addPropertyDescriptor(createFluentPropertyDescritor(
                                 m, propertyName));
                     } else if (pd.getWriteMethod() == null) {
                         pd.setWriteMethod(m);
                     }
                 } catch (final IntrospectionException e) {
                     log.info("Error when creating PropertyDescriptor for " + m
                             + "! Ignoring this property.");
                     log.debug("Exception is:", e);
                 }
             }
         }
     }
 
     /**
      * Derives the name of a property from the given set method.
      *
      * @param m the method
      * @return the corresponding property name
      */
     private String propertyName(final Method m) {
         final String methodName = m.getName().substring(
                 getWriteMethodPrefix().length());
         return (methodName.length() > 1) ? Introspector.decapitalize(methodName) : methodName
                 .toLowerCase(Locale.ENGLISH);
     }
 
     /**
      * Creates a property descriptor for a fluent API property.
      *
      * @param m the set method for the fluent API property
      * @param propertyName the name of the corresponding property
      * @return the descriptor
      * @throws IntrospectionException if an error occurs
      */
     private PropertyDescriptor createFluentPropertyDescritor(final Method m,
             final String propertyName) throws IntrospectionException {
         return new PropertyDescriptor(propertyName(m), null, m);
     }
 }