org.apache.logging.log4j.plugins.Node Maven / Gradle / Ivy

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/*
 * 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.logging.log4j.plugins;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;

import org.apache.logging.log4j.plugins.model.PluginType;
import org.apache.logging.log4j.util.Cast;

/**
 * Configurations are represented as a tree of Node instances. Each Node may have
 * {@linkplain #getAttributes() attributes}, {@linkplain #getChildren() children nodes},
 * an {@linkplain #getValue() optional value} (which is a special kind of attribute for certain configuration file
 * formats which support the concept), and a {@linkplain #getName() name} which corresponds to a
 * {@link Plugin} class in the {@linkplain Configurable Core namespace}. Configuration factories parse a configuration
 * resource into a tree of Nodes with a single root Node.
 */
public class Node {

    /**
     * Main plugin namespace for plugins which are represented as a configuration node. Such plugins tend to be
     * available as XML elements in a configuration file.
     *
     * @since 2.1
     * @see Configurable
     */
    public static final String CORE_NAMESPACE = "Core";

    private Node parent;
    private final String name;
    private String value;
    private final PluginType type;
    private final Map attributes = new HashMap<>();
    private final List children = new ArrayList<>();
    private Object object;


    /**
     * Creates a new instance of {@code Node} and initializes it
     * with a name and the corresponding XML element.
     *
     * @param parent the node's parent.
     * @param name the node's name.
     * @param type The Plugin Type associated with the node.
     */
    public Node(final Node parent, final String name, final PluginType type) {
        this.parent = parent;
        this.name = name;
        this.type = type;
    }

    /**
     * Constructs a root node. Root nodes have no defined type, name, or parent node.
     */
    public Node() {
        this.parent = null;
        this.name = null;
        this.type = null;
    }

    /**
     * Constructs a fresh copy of the provided Node.
     *
     * @param node original node to copy
     */
    public Node(final Node node) {
        this.parent = node.parent;
        this.name = node.name;
        this.type = node.type;
        this.attributes.putAll(node.getAttributes());
        this.value = node.getValue();
        for (final Node child : node.getChildren()) {
            this.children.add(new Node(child));
        }
        this.object = node.object;
    }

    public void setParent(final Node parent) {
        this.parent = parent;
    }

    public Map getAttributes() {
        return attributes;
    }

    public List getChildren() {
        return children;
    }

    public boolean hasChildren() {
        return !children.isEmpty();
    }

    public String getValue() {
        return value;
    }

    public void setValue(final String value) {
        this.value = value;
    }

    public Node getParent() {
        return parent;
    }

    public String getName() {
        return name;
    }

    public boolean isRoot() {
        return parent == null;
    }

    public void setObject(final Object obj) {
        object = obj;
    }

    @SuppressWarnings("unchecked")
    public  T getObject() {
        return Cast.cast(object);
    }

    /**
     * Returns this node's object cast to the given class.
     *
     * @param clazz the class to cast this node's object to.
     * @param    the type to cast to.
     * @return this node's object.
     * @since 2.1
     */
    public  T getObject(final Class clazz) {
        return clazz.cast(object);
    }

    /**
     * Determines if this node's object is an instance of the given class.
     *
     * @param clazz the class to check.
     * @return {@code true} if this node's object is an instance of the given class.
     * @since 2.1
     */
    public boolean isInstanceOf(final Class clazz) {
        return clazz.isInstance(object);
    }

    public PluginType getType() {
        return type;
    }

    /**
     * Finds and removes the attribute with a name equaling ignoring case either the provided name or one of the provided
     * aliases.
     *
     * @param name    name of attribute to find
     * @param aliases aliases of attribute to find
     * @return the removed attribute value if found or empty if no attributes match
     */
    public Optional removeMatchingAttribute(final String name, final Collection aliases) {
        final var iterator = attributes.entrySet().iterator();
        while (iterator.hasNext()) {
            final var entry = iterator.next();
            final String key = entry.getKey();
            if (key.equalsIgnoreCase(name) || aliases.stream().anyMatch(key::equalsIgnoreCase)) {
                iterator.remove();
                return Optional.ofNullable(entry.getValue());
            }
        }
        return Optional.empty();
    }

    @Override
    public String toString() {
        if (object == null) {
            return "null";
        }
        return type.isObjectPrintable() ? object.toString() :
            type.getPluginClass().getName() + " with name " + name;
    }
}