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https://issues.apache.org/jira/browse/MNG-7914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17863176#comment-17863176
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ASF GitHub Bot commented on MNG-7914:
-------------------------------------
gnodet commented on code in PR #1595:
URL: https://github.com/apache/maven/pull/1595#discussion_r1666555646
##########
maven-embedder/src/main/java/org/apache/maven/cli/props/InterpolationHelper.java:
##########
@@ -0,0 +1,364 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.maven.cli.props;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class InterpolationHelper {
+
+ private InterpolationHelper() {}
+
+ private static final char ESCAPE_CHAR = '\\';
+ private static final String DELIM_START = "${";
+ private static final String DELIM_STOP = "}";
+ private static final String MARKER = "$__";
+ private static final String ENV_PREFIX = "env:";
+
+ /**
+ * Callback for substitution
+ */
+ public interface SubstitutionCallback {
+
+ String getValue(String key);
+ }
+
+ /**
+ * Perform substitution on a property set
+ *
+ * @param properties the property set to perform substitution on
+ * @param callback Callback for substituion
+ */
+ public static void performSubstitution(Map<String, String> properties,
SubstitutionCallback callback) {
+ performSubstitution(properties, callback, true, true, true);
+ }
+
+ /**
+ * Perform substitution on a property set
+ *
+ * @param properties the property set to perform substitution on
+ * @param callback the callback to obtain substitution values
+ * @param substituteFromConfig If substitute from configuration
+ * @param substituteFromSystemProperties If substitute from system
properties
+ * @param defaultsToEmptyString sets an empty string if a replacement
value is not found, leaves intact otherwise
+ */
+ public static void performSubstitution(
+ Map<String, String> properties,
+ SubstitutionCallback callback,
+ boolean substituteFromConfig,
+ boolean substituteFromSystemProperties,
+ boolean defaultsToEmptyString) {
+ Map<String, String> org = new HashMap<>(properties);
+ for (String name : properties.keySet()) {
+ properties.compute(
+ name,
+ (k, value) -> substVars(
+ value,
+ name,
+ null,
+ org,
+ callback,
+ substituteFromConfig,
+ substituteFromSystemProperties,
+ defaultsToEmptyString));
+ }
+ }
+
+ /**
+ * <p>
+ * This method performs property variable substitution on the
+ * specified value. If the specified value contains the syntax
+ * {@code ${<prop-name>}}, where {@code <prop-name>}
+ * refers to either a configuration property or a system property,
+ * then the corresponding property value is substituted for the variable
+ * placeholder. Multiple variable placeholders may exist in the
+ * specified value as well as nested variable placeholders, which
+ * are substituted from inner most to outer most. Configuration
+ * properties override system properties.
+ * </p>
+ *
+ * @param val The string on which to perform property substitution.
+ * @param currentKey The key of the property being evaluated used to
+ * detect cycles.
+ * @param cycleMap Map of variable references used to detect nested cycles.
+ * @param configProps Set of configuration properties.
+ * @return The value of the specified string after system property
substitution.
+ * @throws IllegalArgumentException If there was a syntax error in the
+ * property placeholder syntax or a recursive variable reference.
+ **/
+ public static String substVars(
+ String val, String currentKey, Map<String, String> cycleMap,
Map<String, String> configProps)
+ throws IllegalArgumentException {
+ return substVars(val, currentKey, cycleMap, configProps,
(SubstitutionCallback) null);
+ }
+
+ /**
+ * <p>
+ * This method performs property variable substitution on the
+ * specified value. If the specified value contains the syntax
+ * {@code ${<prop-name>}}, where {@code <prop-name>}
+ * refers to either a configuration property or a system property,
+ * then the corresponding property value is substituted for the variable
+ * placeholder. Multiple variable placeholders may exist in the
+ * specified value as well as nested variable placeholders, which
+ * are substituted from inner most to outer most. Configuration
+ * properties override system properties.
+ * </p>
+ *
+ * @param val The string on which to perform property substitution.
+ * @param currentKey The key of the property being evaluated used to
+ * detect cycles.
+ * @param cycleMap Map of variable references used to detect nested cycles.
+ * @param configProps Set of configuration properties.
+ * @param callback the callback to obtain substitution values
+ * @return The value of the specified string after system property
substitution.
+ * @throws IllegalArgumentException If there was a syntax error in the
+ * property placeholder syntax or a recursive variable reference.
+ **/
+ public static String substVars(
+ String val,
+ String currentKey,
+ Map<String, String> cycleMap,
+ Map<String, String> configProps,
+ SubstitutionCallback callback)
+ throws IllegalArgumentException {
Review Comment:
I'll fix that. Fwiw, those three classes come from Karaf/Felix. They even
provide a bit more, as they can even be used to programmatically modify
properties file while keeping layout and comments (though I don't think we'll
need that in the short term), or even typed properties (not included here).
> Provide a single entry point for configuration
> ----------------------------------------------
>
> Key: MNG-7914
> URL: https://issues.apache.org/jira/browse/MNG-7914
> Project: Maven
> Issue Type: New Feature
> Reporter: Guillaume Nodet
> Priority: Major
> Fix For: 4.0.x-candidate
>
>
> Looking at MNG-7772, this should not require any code change, but it's all
> about configuration.
> I propose to load / interpolate the following files:
> * {{${maven.home}/conf/maven.user.properties}}
> * {{${maven.home}/conf/maven.system.properties}}
> Those files would be used to load additional user properties and system
> properties for Maven. In addition to the simple interpolation mechanism, we
> should provide two enhancements using special keys {{{}$\{includes{}}}} and
> {{{}$\{optionals{}}}} which would be used to load additional referenced
> configuration files such as:
> {{ ${optionals} = ${user.home}/.m2/maven.user.properties,
> ${session.rootDirectory}/.mvn/maven.user.properties}}
> Being loaded early when Maven is loaded, those files could reference
> directories to load extensions from:
> {{{}maven.core.extensions.directories =
> ${session.rootDirectory}/.mvn/extensions.xml,{}}}{{{}${user.home}/.m2/extensions.xml,${maven.home}/extensions.xml{}}}
>
> In various places, the maven code could be simplified and offer more
> configuration points at the same time.
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