// 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.apache.tapestry5.ioc.services;
import java.util.List;
/**
* A service which can assemble an implementation based on a command interface, and an ordered list of objects
* implementing that interface (the "commands"). This is an implementation of the Gang of Four Chain Of Command
* pattern.
*
* For each method in the interface, the chain implementation will call the corresponding method on each command object
* in turn (with the order defined by the list). If any of the command objects return true, then the chain of command
* stops and the initial method invocation returns true. Otherwise, the chain of command continues to the next command
* (and will return false if none of the commands returns true).
*
* For methods whose return type is not boolean, the chain stops with the first non-null (for object types), or non-zero
* (for numeric types). The chain returns the value that was returned by the command. If the method return type is void,
* all commands will be invoked.
*
* Method invocations will also be terminated if an exception is thrown.
*/
public interface ChainBuilder
{
/**
* Creates a chain instance from a command interface and a list of commands (implementing the interface).
*/
<T> T build(Class<T> commandInterface, List<T> commands);
}