org.springframework.webflow.engine.FlowExecutionExceptionHandler Maven / Gradle / Ivy
/*
* 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.engine;
import org.springframework.webflow.execution.FlowExecutionException;
/**
* A strategy for handling an exception that occurs at runtime during an active flow execution.
*
* Note: special care should be taken when implementing custom flow execution exception handlers. Exception handlers are
* like Transitions in that they direct flow control when exceptions occur. They are more complex than Actions, which
* can only execute behaviors and return results that drive flow control. For this reason, if implemented incorrectly, a
* FlowExecutionHandler can leave a flow execution in an invalid state, which can render the flow execution unusable or
* its future use undefined. For example, if an exception thrown at flow session startup gets routed to an exception
* handler, the handler must take responsibility for ensuring the flow execution returns control to the caller in a
* consistent state. Concretely, this means the exception handler must transition the flow to its start state. The
* handler should not simply return leaving the flow with no current state set.
*
* Note: Because flow execution handlers are more difficult to implement correctly, consider catching exceptions in your
* web flow action code and returning result events that drive standard transitions. Alternatively, consider use of the
* existing {@code TransitionExecutingFlowExecutionExceptionHandler} which illustrates the proper way to implement an
* exception handler.
*
* @author Keith Donald
*/
public interface FlowExecutionExceptionHandler {
/**
* Can this handler handle the given exception?
* @param exception the exception that occurred
* @return true if yes, false if no
*/
boolean canHandle(FlowExecutionException exception);
/**
* Handle the exception in the context of the current request. An implementation is expected to transition the flow
* to a state using {@link RequestControlContext#execute(Transition)}.
* @param exception the exception that occurred
* @param context the execution control context for this request
*/
void handle(FlowExecutionException exception, RequestControlContext context);
}