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Merge pull request helidon-io#509 from batsatt/se-map-env-vars_446
Make SE and MP share config env var mapping
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143
config/config/src/main/java/io/helidon/config/EnvironmentVariables.java
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| /* | ||
| * Copyright (c) 2019 Oracle and/or its affiliates. All rights reserved. | ||
| * | ||
| * 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. | ||
| */ | ||
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| package io.helidon.config; | ||
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| import java.util.HashMap; | ||
| import java.util.Map; | ||
| import java.util.regex.Pattern; | ||
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| /** | ||
| * Provides environment variables that include mapped variants enabling setting or overriding configuration with keys that are | ||
| * unlikely to be legal as environment variables. | ||
| * <p> | ||
| * The <a href="https://github.com/eclipse/microprofile-config/blob/master/spec/src/main/asciidoc/configsources.asciidoc"> | ||
| * MP config specification</a> describes the environment variables {@code ConfigSource} as follows: | ||
| * <pre> | ||
| * Some operating systems allow only alphabetic characters or an underscore, _, in environment variables. Other | ||
| * characters such as ., /, etc may be disallowed. In order to set a value for a config property that has a name | ||
| * containing such disallowed characters from an environment variable, the following rules are used. | ||
| * | ||
| * This ConfigSource searches 3 environment variables for a given property name (e.g. com.ACME.size): | ||
| * | ||
| * 1. Exact match (i.e. com.ACME.size) | ||
| * 2. Replace the character that is neither alphanumeric nor _ with _ (i.e. com_ACME_size) | ||
| * 3. Replace the character that is neither alphanumeric nor _ with _ and convert to upper case (i.e. COM_ACME_SIZE) | ||
| * | ||
| * The first environment variable that is found is returned by this ConfigSource. | ||
| * </pre> | ||
| * <p> | ||
| * The spec assumes the mapping takes place during search, where the desired key is known, but Helidon merges | ||
| * {@code ConfigSource}s instead; therefore this implementation produces <em>additional</em> KV pairs with variant keys | ||
| * for any variable that can meaningfully be mapped. See {@link #shouldMap(String)} for the mapping criteria. | ||
| * <p> | ||
| * Since Helidon supports many configuration keys that contain {@code '-'} (e.g. {@code "server.executor-service.max-pool-size"}), | ||
| * an additional mapping is required to produce a matching variant. Given that it must map from legal environment variable names | ||
| * and reduce the chances of inadvertent mappings, a verbose mapping is used: {@code "_dash_"} substrings (lowercase only) are | ||
| * first replaced by {@code '-'}. See {@link #expand()} for the variants produced. | ||
| * <p> | ||
| */ | ||
| public class EnvironmentVariables { | ||
| private static final Pattern DASH_PATTERN = Pattern.compile("_dash_", Pattern.LITERAL); | ||
| private static final String UNDERSCORE = "_"; | ||
| private static final String DOUBLE_UNDERSCORE = "__"; | ||
| private static final String DASH = "-"; | ||
| private static final char UNDERSCORE_CHAR = '_'; | ||
| private static final char DOT_CHAR = '.'; | ||
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| /** | ||
| * Tests whether mappings should be created for the given environment variable name. | ||
| * <p> | ||
| * To provide a meaningful mapping, the name must meet <em>all</em> of the following criteria: | ||
| * <ol> | ||
| * <li>does not begin or end with a {@code '_'} character</li> | ||
| * <li>does not contain {@code "__"}</li> | ||
| * <li>contains one or more {@code '_'} characters</li> | ||
| * </ol> | ||
| * | ||
| * @param name The environment variable name. | ||
| * @return {@code true} if mappings should be created. | ||
| */ | ||
| public static boolean shouldMap(final String name) { | ||
| final int length = name.length(); | ||
| return length > 2 | ||
| && name.charAt(0) != UNDERSCORE_CHAR | ||
| && name.charAt(length - 1) != UNDERSCORE_CHAR | ||
| && name.contains(UNDERSCORE) | ||
| && !name.contains(DOUBLE_UNDERSCORE); | ||
| } | ||
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| /** | ||
| * Returns the environment variables and their mapped variants. | ||
| * <p> | ||
| * The following mappings are applied to any environment variable name for which {@link #shouldMap(String)} returns | ||
| * {@code true}: | ||
| * <ol> | ||
| * <li>Replace {@code "_dash_"} by {@code '-'}, e.g. {@code "SERVER_EXECUTOR_dash_SERVICE_MAX_dash_POOL_dash_SIZE"} becomes | ||
| * {@code "SERVER_EXECUTOR-SERVICE_MAX-POOL-SIZE"}.</li> | ||
| * <li>Replace {@code '_'} by {@code '.'} and add as a variant, e.g. {@code "com_ACME_size"} becomes {@code "com.ACME.size"} | ||
| * and {@code "SERVER_EXECUTOR-SERVICE_MAX-POOL-SIZE"} becomes {@code "SERVER.EXECUTOR-SERVICE.MAX-POOL-SIZE"}. This mapping | ||
| * is added primarily to support mixed case config keys such as {@code "app.someCamelCaseKey"}.</li> | ||
| * <li>Convert the result of step 2 to lowercase and add as a variant, e.g. {@code "com.ACME.size"} becomes | ||
| * {@code "com.acme.size"} and {@code "SERVER.EXECUTOR-SERVICE.MAX-POOL-SIZE"} becomes | ||
| * {@code "server.executor-service.max-pool-size"}. | ||
| * </li> | ||
| * </ol> | ||
| * | ||
| * @return The map. | ||
| */ | ||
| public static Map<String, String> expand() { | ||
| return expand(System.getenv()); | ||
| } | ||
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| /** | ||
| * Returns the environment variables and their mapped variants. | ||
| * <p> | ||
| * The following mappings are applied to any environment variable name for which {@link #shouldMap(String)} returns | ||
| * {@code true}: | ||
| * <ol> | ||
| * <li>Replace {@code "_dash_"} by {@code '-'}, e.g. {@code "SERVER_EXECUTOR_dash_SERVICE_MAX_dash_POOL_dash_SIZE"} becomes | ||
| * {@code "SERVER_EXECUTOR-SERVICE_MAX-POOL-SIZE"}.</li> | ||
| * <li>Replace {@code '_'} by {@code '.'} and add as a variant, e.g. {@code "com_ACME_size"} becomes {@code "com.ACME.size"} | ||
| * and {@code "SERVER_EXECUTOR-SERVICE_MAX-POOL-SIZE"} becomes {@code "SERVER.EXECUTOR-SERVICE.MAX-POOL-SIZE"}. This mapping | ||
| * is added primarily to support mixed case config keys such as {@code "app.someCamelCaseKey"}.</li> | ||
| * <li>Convert the result of step 2 to lowercase and add as a variant, e.g. {@code "com.ACME.size"} becomes | ||
| * {@code "com.acme.size"} and {@code "SERVER.EXECUTOR-SERVICE.MAX-POOL-SIZE"} becomes | ||
| * {@code "server.executor-service.max-pool-size"}. | ||
| * </li> | ||
| * </ol> | ||
| * | ||
| * @param env The environment variables. | ||
| * @return A copy of {@code env} with variants added. | ||
| */ | ||
| public static Map<String, String> expand(final Map<String, String> env) { | ||
| final Map<String, String> result = new HashMap<>(env.size()); | ||
| env.forEach((name, value) -> { | ||
| result.put(name, value); | ||
| if (shouldMap(name)) { | ||
| String alternateName = DASH_PATTERN.matcher(name).replaceAll(DASH); | ||
| alternateName = alternateName.replace(UNDERSCORE_CHAR, DOT_CHAR); | ||
| result.put(alternateName, value); | ||
| result.put(alternateName.toLowerCase(), value); | ||
| } | ||
| }); | ||
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| return result; | ||
| } | ||
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| private EnvironmentVariables() { | ||
| } | ||
| } |
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