Consolidate matrix vars parsing in HttpRequestPathHelper

Restore matrix variable parsing code not resorting to the use of
WebUtils which brings Servlet API dependencies with it.

Instead the parsing logic is now exposed through HttpRequestPathHelper
which already contained the decoding logic and also the knowledge of
whether to decode the parsed variables or not.

Issue: SPR-15397

spring-web/src/test/java/org/springframework/web/server/support/HttpRequestPathHelperTests.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2002-2017 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 org.springframework.web.server.support;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+
+import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.server.ServerWebExchange;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Unit tests for {@link HttpRequestPathHelper}.
+ * @author Rossen Stoyanchev
+ */
+public class HttpRequestPathHelperTests {
+
+
+	@Test
+	public void parseMatrixVariables() {
+
+		HttpRequestPathHelper pathHelper = new HttpRequestPathHelper();
+		ServerWebExchange exchange = MockServerHttpRequest.get("").toExchange();
+		MultiValueMap<String, String> variables;
+
+		variables = pathHelper.parseMatrixVariables(exchange, null);
+		assertEquals(0, variables.size());
+
+		variables = pathHelper.parseMatrixVariables(exchange, "year");
+		assertEquals(1, variables.size());
+		assertEquals("", variables.getFirst("year"));
+
+		variables = pathHelper.parseMatrixVariables(exchange, "year=2012");
+		assertEquals(1, variables.size());
+		assertEquals("2012", variables.getFirst("year"));
+
+		variables = pathHelper.parseMatrixVariables(exchange, "year=2012;colors=red,blue,green");
+		assertEquals(2, variables.size());
+		assertEquals(Arrays.asList("red", "blue", "green"), variables.get("colors"));
+		assertEquals("2012", variables.getFirst("year"));
+
+		variables = pathHelper.parseMatrixVariables(exchange, ";year=2012;colors=red,blue,green;");
+		assertEquals(2, variables.size());
+		assertEquals(Arrays.asList("red", "blue", "green"), variables.get("colors"));
+		assertEquals("2012", variables.getFirst("year"));
+
+		variables = pathHelper.parseMatrixVariables(exchange, "colors=red;colors=blue;colors=green");
+		assertEquals(1, variables.size());
+		assertEquals(Arrays.asList("red", "blue", "green"), variables.get("colors"));
+	}
+
+	@Test
+	public void parseMatrixVariablesAndDecode() {
+
+		HttpRequestPathHelper pathHelper = new HttpRequestPathHelper();
+		pathHelper.setUrlDecode(false);
+
+		ServerWebExchange exchange = MockServerHttpRequest.get("").toExchange();
+		MultiValueMap<String, String> variables;
+
+		variables = pathHelper.parseMatrixVariables(exchange, "mvar=a%2fb");
+		assertEquals(1, variables.size());
+		assertEquals("a/b", variables.getFirst("mvar"));
+	}
+
+}