FlowDefinitionHolder.java :  » Workflow-Engines » spring-webflow-2.0.8 » org » springframework » webflow » definition » registry » Java Open Source

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spring webflow 2.0.8 » org » springframework » webflow » definition » registry » FlowDefinitionHolder.java
/*
 * Copyright 2004-2008 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.definition.registry;

import org.springframework.webflow.definition.FlowDefinition;

/**
 * A holder holding a reference to a Flow definition. Provides a layer of indirection, enabling things like
 * "hot-reloadable" flow definitions.
 * 
 * @see FlowDefinitionRegistry#registerFlowDefinition(FlowDefinitionHolder)
 * 
 * @author Keith Donald
 */
public interface FlowDefinitionHolder {

  /**
   * Returns the <code>id</code> of the flow definition held by this holder. This is a <i>lightweight</i> method
   * callers may call to obtain the id of the flow without triggering full flow definition assembly (which may be an
   * expensive operation).
   */
  public String getFlowDefinitionId();

  /**
   * Returns a descriptive string that identifies the source of this FlowDefinition. This is also a lightweight method
   * callers may call to obtain the logical resource where the flow definition resides without triggering flow
   * definition assembly. Used for informational purposes.
   * @return the flow definition resource string
   */
  public String getFlowDefinitionResourceString();

  /**
   * Returns the flow definition held by this holder. Calling this method the first time may trigger flow assembly
   * (which may be expensive).
   * @throws FlowDefinitionConstructionException if there is a problem constructing the target flow definition
   */
  public FlowDefinition getFlowDefinition() throws FlowDefinitionConstructionException;

  /**
   * Refresh the flow definition held by this holder. Calling this method typically triggers flow re-assembly, which
   * may include a refresh from an externalized resource such as a file.
   * @throws FlowDefinitionConstructionException if there is a problem constructing the target flow definition
   */
  public void refresh() throws FlowDefinitionConstructionException;

  /**
   * Indicates that the system is being shutdown and any resources flow resources should be released. After this
   * method is called, calls to {@link #getFlowDefinition()} are undefined. Should only be called once. May be a no-op
   * if the held flow was never constructed to begin with.
   */
  public void destroy();

}
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