ratpack.config.EnvironmentParser Maven / Gradle / Ivy
/*
* Copyright 2015 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 ratpack.config;
import ratpack.func.Pair;
import java.util.List;
import java.util.stream.Stream;
/**
* Strategy for parsing a set of environment variables into a form appropriate for use in a {@link ConfigSource}.
* The methods are called in order:
*
*
* - {@link #filter(ratpack.func.Pair)}
* - {@link #tokenize(String)}
* - {@link #map(String)}
*
*/
public interface EnvironmentParser {
/**
* Provides an opportunity to remove environment variables from parsing by the remainder of the pipeline.
* The pair can be modified if desired as well, such as to remove prefixes.
*
* @param entry an environment variable, encoded with the name on the left and the value on the right
* @return a stream containing the desired entries (if any) for this entry
* @throws Exception any
*
* @see Pair#mapLeft(ratpack.func.Function)
*/
Stream> filter(Pair entry) throws Exception;
/**
* Splits the name of an environment variable into per-object segments.
* For example, if you want name {@code SERVER__URL} to mean an object "SERVER" and a field "URL", you would return a two element list {@code ["SERVER", "URL"]}.
*
* @param name the name of the environment variable
* @return the per-object segments for the environment variable, starting with the segments closest to the root
* @throws Exception any
*/
List tokenize(String name) throws Exception;
/**
* Transforms a segment. Most commonly, this is used to convert between case formats.
*
* @param segment a segment of the object path
* @return the transformed segment
* @throws Exception any
*
* @see com.google.common.base.CaseFormat
*/
String map(String segment) throws Exception;
}