001// Copyright 2004, 2005 The Apache Software Foundation 002// 003// Licensed under the Apache License, Version 2.0 (the "License"); 004// you may not use this file except in compliance with the License. 005// You may obtain a copy of the License at 006// 007// http://www.apache.org/licenses/LICENSE-2.0 008// 009// Unless required by applicable law or agreed to in writing, software 010// distributed under the License is distributed on an "AS IS" BASIS, 011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012// See the License for the specific language governing permissions and 013// limitations under the License. 014 015package org.apache.hivemind.internal; 016 017import java.util.List; 018import java.util.Map; 019 020import org.apache.hivemind.ApplicationRuntimeException; 021import org.apache.hivemind.schema.Schema; 022 023/** 024 * An extension point that provides configuration data in the form of a list of elements. 025 * 026 * @author Howard Lewis Ship 027 */ 028public interface ConfigurationPoint extends ExtensionPoint 029{ 030 /** 031 * Returns the constructed extensions as a list of elements assembled from the various 032 * contributions. The List is unmodifiable. May return an empty list, but won't return null. May 033 * return a proxy to the actual data (which is constructed only as needed), but user code 034 * shouldn't care about that. 035 */ 036 public List getElements(); 037 038 /** 039 * Returns true if the elements contributed to this configuration point can be 040 * {@link #getElementsAsMap() retrieved as a Map}. The contributions in the map are keyed on 041 * an attribute as specified by the contributions schema. Thus, as a requirement, this 042 * configuration point must have a defined schema, which in turn must support 043 * {@link Schema#canInstancesBeKeyed() keying} of all valid instances. 044 * 045 * @since 1.1 046 */ 047 public boolean areElementsMappable(); 048 049 /** 050 * Returns the constructed extensions as a Map of elements assembled from the various 051 * contributions. The returned Map is unmodifiable and is keyed on the contribution elements' 052 * {@link org.apache.hivemind.schema.ElementModel#getKeyAttribute() key attribute}. Just as 053 * {@link #getElements()} this method may also return a proxy. 054 * <p> 055 * If there is no key attribute defined for this configuration's contribution elements an 056 * {@link org.apache.hivemind.ApplicationRuntimeException} is thrown. 057 * 058 * @since 1.1 059 */ 060 public Map getElementsAsMap() throws ApplicationRuntimeException; 061 062 /** 063 * Returns the Schema for contributions to the configuration point (which may be null if the 064 * point does not define a schema for contributions). 065 */ 066 public Schema getContributionsSchema(); 067}