org.springframework.webflow.execution.Event Maven / Gradle / Ivy
/*
* Copyright 2002-2006 the original author or authors.
*
* Licensed 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.springframework.webflow.execution;
import java.util.EventObject;
import org.springframework.util.Assert;
import org.springframework.webflow.core.collection.AttributeMap;
import org.springframework.webflow.core.collection.CollectionUtils;
/**
* Signals the occurrence of something an active flow execution should respond
* to. Each event has a string id that provides a key for identifying what
* happened: e.g "coinInserted", or "pinDropped". Events may have attributes
* that provide arbitrary payload data, e.g. "coin.amount=25", or
* "pinDropSpeed=25ms".
*
* As an example, a "submit" event might signal that a Submit button was pressed
* in a web browser. A "success" event might signal an action executed
* successfully. A "finish" event might signal a subflow ended normally.
*
* Why is this not an interface? A specific design choice. An event is not a
* strategy that defines a generic type or role--it is essentially an immutable
* value object. It is expected that specializations of this base class be
* "Events" and not part of some other inheritence hierarchy.
*
* @author Keith Donald
* @author Erwin Vervaet
* @author Colin Sampaleanu
*/
public final class Event extends EventObject {
/**
* The event identifier.
*/
private final String id;
/**
* The time the event occured.
*/
private final long timestamp = System.currentTimeMillis();
/**
* Additional event attributes that form this event's payload.
*/
private final AttributeMap attributes;
/**
* Create a new event with the specified id and no payload.
* @param source the source of the event (required)
* @param id the event identifier (required)
*/
public Event(Object source, String id) {
this(source, id, null);
}
/**
* Create a new event with the specified id and payload
* attributes.
* @param source the source of the event (required)
* @param id the event identifier (required)
* @param attributes additional event attributes
*/
public Event(Object source, String id, AttributeMap attributes) {
super(source);
Assert.hasText(id, "The event id is required: please set this event's id to a non-blank string identifier");
this.id = id;
this.attributes = (attributes != null ? attributes : CollectionUtils.EMPTY_ATTRIBUTE_MAP);
}
/**
* Returns the event identifier.
* @return the event id
*/
public String getId() {
return id;
}
/**
* Returns the time at which the event occured, represented as the number of
* milliseconds since January 1, 1970, 00:00:00 GMT.
* @return the timestamp
*/
public long getTimestamp() {
return timestamp;
}
/**
* Returns an unmodifiable map storing the attributes of this event. Never
* returns null.
* @return the event attributes (payload)
*/
public AttributeMap getAttributes() {
return attributes;
}
public String toString() {
return getId();
}
}