--- /dev/null
+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;
+import java.lang.ref.WeakReference;
+import java.util.LinkedList;
+
+import org.apache.lucene.analysis.tokenattributes.CharTermAttributeImpl; // deprecated
+
+/**
+ * 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();
+
+ /**
+ * Returns a string representation of the object. In general, the {@code toString} method
+ * returns a string that "textually represents" this object.
+ *
+ * <p><b>WARNING:</b> For backwards compatibility this method is implemented as
+ * {@code return reflectAsString(false)}. In Lucene 4.0 this default implementation
+ * will be removed. The reason for this is the problem of
+ * {@link CharTermAttributeImpl#toString} that must return a string representation
+ * of the term's char sequence.
+ *
+ * <p>It is recommeneded to use {@link #reflectAsString} or {@link #reflectWith}
+ * to get a well-defined output of AttributeImpl's internals.
+ */
+ // TODO: @deprecated remove this method in 4.0
+ @Override
+ public String toString() {
+ return reflectAsString(false);
+ }
+
+ /**
+ * This method returns the current attribute values as a string in the following format
+ * by calling the {@link #reflectWith(AttributeReflector)} method:
+ *
+ * <ul>
+ * <li><em>iff {@code prependAttClass=true}:</em> {@code "AttributeClass#key=value,AttributeClass#key=value"}
+ * <li><em>iff {@code prependAttClass=false}:</em> {@code "key=value,key=value"}
+ * </ul>
+ *
+ * @see #reflectWith(AttributeReflector)
+ * @see #toString()
+ */
+ public final String reflectAsString(final boolean prependAttClass) {
+ final StringBuilder buffer = new StringBuilder();
+ reflectWith(new AttributeReflector() {
+ public void reflect(Class<? extends Attribute> attClass, String key, Object value) {
+ if (buffer.length() > 0) {
+ buffer.append(',');
+ }
+ if (prependAttClass) {
+ buffer.append(attClass.getName()).append('#');
+ }
+ buffer.append(key).append('=').append((value == null) ? "null" : value);
+ }
+ });
+ return buffer.toString();
+ }
+
+ /**
+ * @deprecated this will be removed in Lucene 4.0
+ */
+ @Deprecated
+ private static final VirtualMethod<AttributeImpl> toStringMethod =
+ new VirtualMethod<AttributeImpl>(AttributeImpl.class, "toString");
+
+ /**
+ * When {@code true} (default), if a subclass overrides {@link #toString()},
+ * its output is parsed by {@link #reflectWith} and used for attribute reflection.
+ * This is added to enable attribute implementations from Lucene 2.9 or 3.0 to
+ * work correctly with reflection.
+ * @deprecated this will be removed in Lucene 4.0.
+ */
+ @Deprecated
+ protected boolean enableBackwards = true;
+
+ /**
+ * @deprecated this will be removed in Lucene 4.0
+ */
+ @Deprecated
+ private boolean assertExternalClass(Class<? extends AttributeImpl> clazz) {
+ final String name = clazz.getName();
+ return (!name.startsWith("org.apache.lucene.") && !name.startsWith("org.apache.solr."))
+ || name.equals("org.apache.lucene.util.TestAttributeSource$TestAttributeImpl");
+ }
+
+ /**
+ * This method is for introspection of attributes, it should simply
+ * add the key/values this attribute holds to the given {@link AttributeReflector}.
+ *
+ * <p>The default implementation calls {@link AttributeReflector#reflect} for all
+ * non-static fields from the implementing class, using the field name as key
+ * and the field value as value. The Attribute class is also determined by reflection.
+ * Please note that the default implementation can only handle single-Attribute
+ * implementations.
+ *
+ * <p>Custom implementations look like this (e.g. for a combined attribute implementation):
+ * <pre>
+ * public void reflectWith(AttributeReflector reflector) {
+ * reflector.reflect(CharTermAttribute.class, "term", term());
+ * reflector.reflect(PositionIncrementAttribute.class, "positionIncrement", getPositionIncrement());
+ * }
+ * </pre>
+ *
+ * <p>If you implement this method, make sure that for each invocation, the same set of {@link Attribute}
+ * interfaces and keys are passed to {@link AttributeReflector#reflect} in the same order, but possibly
+ * different values. So don't automatically exclude e.g. {@code null} properties!
+ *
+ * @see #reflectAsString(boolean)
+ */
+ public void reflectWith(AttributeReflector reflector) {
+ final Class<? extends AttributeImpl> clazz = this.getClass();
+ final LinkedList<WeakReference<Class<? extends Attribute>>> interfaces = AttributeSource.getAttributeInterfaces(clazz);
+ if (interfaces.size() != 1) {
+ throw new UnsupportedOperationException(clazz.getName() +
+ " implements more than one Attribute interface, the default reflectWith() implementation cannot handle this.");
+ }
+ final Class<? extends Attribute> interf = interfaces.getFirst().get();
+
+ // TODO: @deprecated sophisticated(TM) backwards
+ if (enableBackwards && toStringMethod.isOverriddenAsOf(clazz)) {
+ assert assertExternalClass(clazz) : "no Lucene/Solr classes should fallback to toString() parsing";
+ // this class overrides toString and for backwards compatibility we try to parse the string returned by this method:
+ for (String part : toString().split(",")) {
+ final int pos = part.indexOf('=');
+ if (pos < 0) {
+ throw new UnsupportedOperationException("The backwards compatibility layer to support reflectWith() " +
+ "on old AtributeImpls expects the toString() implementation to return a correct format as specified for method reflectAsString(false)");
+ }
+ reflector.reflect(interf, part.substring(0, pos).trim(), part.substring(pos + 1));
+ }
+ return;
+ }
+ // end sophisticated(TM) backwards
+
+ final Field[] fields = clazz.getDeclaredFields();
+ try {
+ for (int i = 0; i < fields.length; i++) {
+ final Field f = fields[i];
+ if (Modifier.isStatic(f.getModifiers())) continue;
+ f.setAccessible(true);
+ reflector.reflect(interf, f.getName(), f.get(this));
+ }
+ } catch (IllegalAccessException e) {
+ // this should never happen, because we're just accessing fields
+ // from 'this'
+ throw new RuntimeException(e);
+ }
+ }
+
+ /**
+ * 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;
+ }
+}
fnp / pylucene.git / blobdiff