Convert MavenFilteringHack, Groovy to Java

buildSrc/src/main/java/org/elasticsearch/gradle/MavenFilteringHack.java

@@ -0,0 +1,43 @@
+/*
+     * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+     * or more contributor license agreements. Licensed under the Elastic License
+     * 2.0 and the Server Side Public License, v 1; you may not use this file except
+     * in compliance with, at your election, the Elastic License 2.0 or the Server
+     * Side Public License, v 1.
+     */
+package org.elasticsearch.gradle;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.apache.tools.ant.filters.ReplaceTokens;
+import org.gradle.api.file.CopySpec;
+
+/**
+ * Gradle provides "expansion" functionality using groovy's SimpleTemplatingEngine (TODO: check name).
+ * However, it allows substitutions of the form {@code $foo} (no curlies). Rest tests provide
+ * some substitution from the test runner, which this form is used for.
+ *
+ * This class provides a helper to do maven filtering, where only the form {@code $\{foo\}} is supported.
+ *
+ * TODO: we should get rid of this hack, and make the rest tests use some other identifier
+ * for builtin vars
+ */
+public class MavenFilteringHack {
+    /**
+     * Adds a filter to the given copy spec that will substitute maven variables.
+     *
+     */
+    static void filter(CopySpec copySpec, Map<Object, Object> substitutions) {
+        Map<String, String> mavenSubstitutions = new LinkedHashMap<>();
+        Map<String, Object> argMap = new LinkedHashMap<>();
+
+        substitutions.forEach((k, v) -> mavenSubstitutions.put("{" + k.toString(), v.toString()));
+
+        argMap.put("tokens", mavenSubstitutions);
+        argMap.put("beginToken", "$");
+        argMap.put("endToken", "}");
+
+        copySpec.filter(argMap, ReplaceTokens.class);
+    }
+}