QueryResult.java
- /*
- * 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.configuration2.tree;
- import org.apache.commons.lang3.StringUtils;
- import org.apache.commons.lang3.builder.EqualsBuilder;
- import org.apache.commons.lang3.builder.HashCodeBuilder;
- import org.apache.commons.lang3.builder.ToStringBuilder;
- /**
- * <p>
- * A data class representing a single query result produced by an {@link ExpressionEngine}.
- * </p>
- * <p>
- * When passing a key to the {@code query()} method of {@code ExpressionEngine} the result can be a set of nodes or
- * attributes - depending on the key. This class can represent both types of results. The aim is to give a user of
- * {@code ExpressionEngine} all information needed for evaluating the results returned.
- * </p>
- * <p>
- * Implementation note: Instances are immutable. They are created using the static factory methods.
- * </p>
- *
- * @param <T> the type of the result nodes
- * @since 2.0
- */
- public final class QueryResult<T> {
- /**
- * Creates a {@code QueryResult} instance representing an attribute result. An attribute result consists of the node the
- * attribute belongs to and the attribute name. (The value can be obtained based on this information.)
- *
- * @param parentNode the node which owns the attribute
- * @param attrName the attribute name
- * @param <T> the type of the parent node
- * @return the newly created instance
- */
- public static <T> QueryResult<T> createAttributeResult(final T parentNode, final String attrName) {
- return new QueryResult<>(parentNode, attrName);
- }
- /**
- * Creates a {@code QueryResult} instance representing the specified result node.
- *
- * @param <T> the type of the result node
- * @param resultNode the result node
- * @return the newly created instance
- */
- public static <T> QueryResult<T> createNodeResult(final T resultNode) {
- return new QueryResult<>(resultNode, null);
- }
- /** The node result. */
- private final T node;
- /** The name of the result attribute. */
- private final String attributeName;
- /**
- * Creates a new instance of {@code QueryResult}.
- *
- * @param nd the node
- * @param attr the attribute name
- */
- private QueryResult(final T nd, final String attr) {
- node = nd;
- attributeName = attr;
- }
- /**
- * Compares this object with another one. Two instances of {@code QueryResult} are considered equal if they are of the
- * same result type and have the same properties.
- *
- * @param obj the object to compare to
- * @return a flag whether these objects are equal
- */
- @Override
- public boolean equals(final Object obj) {
- if (this == obj) {
- return true;
- }
- if (!(obj instanceof QueryResult)) {
- return false;
- }
- final QueryResult<?> c = (QueryResult<?>) obj;
- return new EqualsBuilder().append(getNode(), c.getNode()).append(getAttributeName(), c.getAttributeName()).isEquals();
- }
- /**
- * Gets the name of the attribute. This method is defined only for results of type attribute.
- *
- * @return the attribute name
- */
- public String getAttributeName() {
- return attributeName;
- }
- /**
- * Gets the attribute value if this is an attribute result. If this is not an attribute result, an exception is
- * thrown.
- *
- * @param handler the {@code NodeHandler}
- * @return the attribute value
- * @throws IllegalStateException if this is not an attribute result
- */
- public Object getAttributeValue(final NodeHandler<T> handler) {
- if (!isAttributeResult()) {
- throw new IllegalStateException("This is not an attribute result! " + "Attribute value cannot be fetched.");
- }
- return handler.getAttributeValue(getNode(), getAttributeName());
- }
- /**
- * Gets the node referenced by this object. Depending on the result type, this is either the result node or the
- * parent node of the represented attribute.
- *
- * @return the referenced node
- */
- public T getNode() {
- return node;
- }
- @Override
- public int hashCode() {
- return new HashCodeBuilder().append(getNode()).append(getAttributeName()).toHashCode();
- }
- /**
- * Returns a flag whether this is a result of type attribute. If result is <strong>true</strong>, the attribute name and value can
- * be queried. Otherwise, only the result node is available.
- *
- * @return <strong>true</strong> for an attribute result, <strong>false</strong> otherwise
- */
- public boolean isAttributeResult() {
- return StringUtils.isNotEmpty(getAttributeName());
- }
- /**
- * Returns a string representation of this object. Depending on the result type either the result node or the parent
- * node and the attribute name are contained in this string.
- *
- * @return a string for this object
- */
- @Override
- public String toString() {
- final ToStringBuilder sb = new ToStringBuilder(this);
- if (isAttributeResult()) {
- sb.append("parentNode", getNode()).append("attribute", getAttributeName());
- } else {
- sb.append("resultNode", getNode());
- }
- return sb.toString();
- }
- }