src/main/java/org/apache/commons/configuration2/event/ConfigurationErrorEvent.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.event;

/**
 * <p>
 * An event class that is used for reporting errors that occurred while processing configuration properties.
 * </p>
 * <p>
 * Some configuration implementations (e.g. {@link org.apache.commons.configuration2.DatabaseConfiguration} or
 * {@link org.apache.commons.configuration2.JNDIConfiguration} use an underlying storage that can throw an exception on
 * each property access. In earlier versions of this library such exceptions were logged and then silently ignored. This
 * makes it impossible for a client to find out that something went wrong.
 * </p>
 * <p>
 * To give clients better control over the handling of errors that might occur while interacting with a configuration
 * object, a specialized error event type is introduced. Clients can register as listeners of this event type at a
 * configuration object and are then notified about all internal errors related to the source configuration object.
 * </p>
 * <p>
 * This class defines similar properties to the {@link ConfigurationEvent} class. This makes it possible to find out
 * which operation was performed on a configuration causing this error event. In addition, a {@code Throwable} object is
 * available representing the occurred error. Note that depending on the event type and the occurred exception not all
 * of the other properties (e.g. name of the affected property or its value) may be available.
 * </p>
 *
 * @since 1.4
 * @see ConfigurationEvent
 */
public class ConfigurationErrorEvent extends Event {
    /**
     * Constant for the common event type for all error events. Specific types for error events use this type as super type.
     *
     * @since 2.0
     */
    public static final EventType<ConfigurationErrorEvent> ANY = new EventType<>(Event.ANY, "ERROR");

    /**
     * Constant for the event type indicating a read error. Errors of this type are generated if the underlying data store
     * throws an exception when reading a property.
     *
     * @since 2.0
     */
    public static final EventType<ConfigurationErrorEvent> READ = new EventType<>(ANY, "READ_ERROR");

    /**
     * Constant for the event type indicating a write error. Errors of this type are generate if the underlying data store
     * throws an exception when updating data.
     *
     * @since 2.0
     */
    public static final EventType<ConfigurationErrorEvent> WRITE = new EventType<>(ANY, "WRITE_ERROR");

    /**
     * The serial version UID.
     */
    private static final long serialVersionUID = 20140712L;

    /** The event type of the operation which caused this error. */
    private final EventType<?> errorOperationType;

    /** Stores the property name. */
    private final String propertyName;

    /** Stores the property value. */
    private final Object propertyValue;

    /** Stores the exception that caused this event. */
    private final Throwable cause;

    /**
     * Creates a new instance of {@code ConfigurationErrorEvent} and sets all its properties.
     *
     * @param source the event source
     * @param eventType the type of this event
     * @param operationType the event type of the operation causing this error
     * @param propName the name of the affected property
     * @param propValue the value of the affected property
     * @param cause the exception object that caused this event
     */
    public ConfigurationErrorEvent(final Object source, final EventType<? extends ConfigurationErrorEvent> eventType, final EventType<?> operationType,
        final String propName, final Object propValue, final Throwable cause) {
        super(source, eventType);
        errorOperationType = operationType;
        propertyName = propName;
        propertyValue = propValue;
        this.cause = cause;
    }

    /**
     * Gets the cause of this error event. This is the {@code Throwable} object that caused this event to be fired.
     *
     * @return the cause of this error event
     */
    public Throwable getCause() {
        return cause;
    }

    /**
     * Gets the {@code EventType} of the operation which caused this error.
     *
     * @return the event type of the operation causing this error
     */
    public EventType<?> getErrorOperationType() {
        return errorOperationType;
    }

    /**
     * Gets the name of the property that was accessed when this error occurred.
     *
     * @return the property name related to this error (may be <b>null</b>)
     */
    public String getPropertyName() {
        return propertyName;
    }

    /**
     * Gets the value of the property that was accessed when this error occurred.
     *
     * @return the property value related this error (may be <b>null</b>)
     */
    public Object getPropertyValue() {
        return propertyValue;
    }
}