package org.apache.lucene.util;
/**
* 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.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
/**
* Base class for Attributes that can be added to a
* {@link org.apache.lucene.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 {@link org.apache.lucene.analysis.TokenStream}.
*/
public abstract class AttributeImpl implements Cloneable, Serializable, Attribute {
/**
* 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.
*/
public abstract void clear();
/**
* The default implementation of this method accesses all declared
* fields of this object and prints the values in the following syntax:
*
* <pre>
* public String toString() {
* return "start=" + startOffset + ",end=" + endOffset;
* }
* </pre>
*
* This method may be overridden by subclasses.
*/
@Override
public String toString() {
StringBuilder buffer = new StringBuilder();
Class clazz = this.getClass();
Field[] fields = clazz.getDeclaredFields();
try {
for (int i = 0; i < fields.length; i++) {
Field f = fields[i];
if (Modifier.isStatic(f.getModifiers())) continue;
f.setAccessible(true);
Object value = f.get(this);
if (buffer.length()>0) {
buffer.append(',');
}
if (value == null) {
buffer.append(f.getName() + "=null");
} else {
buffer.append(f.getName() + "=" + value);
}
}
} catch (IllegalAccessException e) {
// this should never happen, because we're just accessing fields
// from 'this'
throw new RuntimeException(e);
}
return buffer.toString();
}
/**
* Subclasses must implement this method and should compute
* a hashCode similar to this:
* <pre>
* public int hashCode() {
* int code = startOffset;
* code = code * 31 + endOffset;
* return code;
* }
* </pre>
*
* see also {@link #equals(Object)}
*/
@Override
public abstract int hashCode();
/**
* All values used for computation of {@link #hashCode()}
* should be checked here for equality.
*
* see also {@link Object#equals(Object)}
*/
@Override
public abstract boolean equals(Object other);
/**
* Copies the values from this Attribute into the passed-in
* target attribute. The target implementation must support all the
* Attributes this implementation supports.
*/
public abstract void copyTo(AttributeImpl target);
/**
* Shallow clone. Subclasses must override this if they
* need to clone any members deeply,
*/
@Override
public Object clone() {
Object clone = null;
try {
clone = super.clone();
} catch (CloneNotSupportedException e) {
throw new RuntimeException(e); // shouldn't happen
}
return clone;
}
}