Attribute.cs

Go to the documentation of this file.

/* 
 * 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.
 */

using System;

namespace Lucene.Net.Util
{
    
    /// <summary> Base class for Attributes that can be added to a 
    /// <see cref="Lucene.Net.Util.AttributeSource" />.
    /// <p/>
    /// Attributes are used to add data in a dynamic, yet type-safe way to a source
    /// of usually streamed objects, e. g. a <see cref="Lucene.Net.Analysis.TokenStream" />.
    /// </summary>
    [Serializable]
    public abstract class Attribute : System.ICloneable, IAttribute
    {
        /// <summary> Clears the values in this AttributeImpl and resets it to its 
        /// default value. If this implementation implements more than one Attribute interface
        /// it clears all.
        /// </summary>
        public abstract void  Clear();
        
        /// <summary> The default implementation of this method accesses all declared
        /// fields of this object and prints the values in the following syntax:
        /// 
        /// <code>
        /// public String toString() {
        /// return "start=" + startOffset + ",end=" + endOffset;
        /// }
        /// </code>
        /// 
        /// This method may be overridden by subclasses.
        /// </summary>
        public override System.String ToString()
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            System.Type clazz = this.GetType();
            System.Reflection.FieldInfo[] fields = clazz.GetFields(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.DeclaredOnly | System.Reflection.BindingFlags.Static);
            try
            {
                for (int i = 0; i < fields.Length; i++)
                {
                    System.Reflection.FieldInfo f = fields[i];
                    if (f.IsStatic)
                        continue;
                    //f.setAccessible(true);   // {{Aroush-2.9}} java.lang.reflect.AccessibleObject.setAccessible
                    System.Object value_Renamed = f.GetValue(this);
                    if (buffer.Length > 0)
                    {
                        buffer.Append(',');
                    }
                    if (value_Renamed == null)
                    {
                        buffer.Append(f.Name + "=null");
                    }
                    else
                    {
                        buffer.Append(f.Name + "=" + value_Renamed);
                    }
                }
            }
            catch (System.UnauthorizedAccessException e)
            {
                // this should never happen, because we're just accessing fields
                // from 'this'
                throw new System.SystemException(e.Message, e);
            }
            
            return buffer.ToString();
        }
        
        /// <summary> Subclasses must implement this method and should compute
        /// a hashCode similar to this:
        /// <code>
        /// public int hashCode() {
        /// int code = startOffset;
        /// code = code * 31 + endOffset;
        /// return code;
        /// }
        /// </code> 
        /// 
        /// see also <see cref="Equals(Object)" />
        /// </summary>
        abstract public override int GetHashCode();
        
        /// <summary> All values used for computation of <see cref="GetHashCode()" /> 
        /// should be checked here for equality.
        /// 
        /// see also <see cref="Object.Equals(Object)" />
        /// </summary>
        abstract public override bool Equals(System.Object other);
        
        /// <summary> Copies the values from this Attribute into the passed-in
        /// target attribute. The target implementation must support all the
        /// Attributes this implementation supports.
        /// </summary>
        public abstract void  CopyTo(Attribute target);
        
        /// <summary> Shallow clone. Subclasses must override this if they 
        /// need to clone any members deeply,
        /// </summary>
        public virtual System.Object Clone()
        {
            System.Object clone = null;
            try
            {
                clone = base.MemberwiseClone();
            }
            catch (System.Exception e)
            {
                throw new System.SystemException(e.Message, e); // shouldn't happen
            }
            return clone;
        }
    }
}