Options.java

/**
 * Copyright 2005-2016 hdiv.org
 *
 * 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.
 */
/*
 * Copyright (c) 2014. Escalon System-Entwicklung, Dietrich Schulten
 *
 * 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.hdiv.services;

import java.util.List;

/**
 * Allows to determine possible values for an argument annotated with {@link TrustAssertion}.
 *
 * @author Dietrich Schulten
 */
public interface Options<T> {

	/**
	 * Gets possible values for an argument annotated with {@link TrustAssertion}. The default implementation {@link StringOptions} just
	 * passes on a given String array as possible values. Sometimes the possible values are more dynamic and depend on the context.
	 * Therefore, an Options implementation can also determine possible values based on another argument to the same call. The example below
	 * shows how to get possible options from a custom DetailOptions implementation which needs a personId for that:
	 * 
	 * <pre>
	 * @RequestMapping("/customer/{personId}/details")
	 * public HttpEntity<Resource<List<String>> showDetails(
	 *     @PathVariable Long personId,
	 *     @RequestParam("detail")
	 *     @TrustAssertion(options = DetailOptions.class, args = "personId")
	 *     List<String> details) {
	 *    ...
	 * }
	 * </pre>
	 * <p>
	 * The <code>@TrustAssertion</code> annotation above says that the possible detail values come from a DetailOptions class which
	 * determines those values based on the personId. Note how the <code>personId</code> is passed to showDetails as argument to the same
	 * call, alongside the <code>details</code> argument. This allows us to resolve the <code>"personId"</code> arg defined for
	 * DetailOptions to an actual value.
	 * </p>
	 * <p>
	 * Within the call to {@link Options#get} the args array contains the values specified by the args annotation attribute in the given
	 * order. In the example above, DetailOptions receives the personId and can read possible options for that particular person.
	 * </p>
	 *
	 * @param value parameters to be used by the implementation. Could be literal values as used by {@link StringOptions} or some argument
	 * to a custom implementation of Options, such as an SQL string.
	 * @param args from the same method call, as defined by {@link TrustAssertion#args()}. The possible values for a parameter might depend
	 * on the context. In that case, you can use {@link TrustAssertion#args()} to pass other argument values received in the same method
	 * call to an implementation of {@link Options}. See above for an example.
	 * @return possible values
	 * @see StringOptions
	 */
	List<Suggest<T>> get(String[] value, Object... args);
}