Add enumeration of supported Resource prefixes (e.g. classpath:).

Additionally, the enum defines operations on the Resource prefixes for convenience.

Resolves gh-92.

spring-geode/src/test/java/org/springframework/geode/core/io/support/ResourcePrefixUnitTests.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2020 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
+ *
+ *     https://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.geode.core.io.support;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+import org.springframework.core.io.ResourceLoader;
+
+/**
+ * Unit Tests for {@link ResourcePrefix}.
+ *
+ * @author John Blum
+ * @see org.junit.Test
+ * @since 1.3.1
+ */
+public class ResourcePrefixUnitTests {
+
+	@Test
+	public void fromReturnsResourcePrefix() {
+
+		assertThat(ResourcePrefix.from(ResourceLoader.CLASSPATH_URL_PREFIX))
+			.isEqualTo(ResourcePrefix.CLASSPATH_URL_PREFIX);
+
+		for (ResourcePrefix prefix : ResourcePrefix.values()) {
+			assertThat(ResourcePrefix.from(prefix.toString())).isEqualTo(prefix);
+		}
+	}
+
+	@Test
+	public void fromInvalidPrefixReturnsNull() {
+
+		assertThat(ResourcePrefix.from("ftp:")).isNull();
+		assertThat(ResourcePrefix.from("scp:")).isNull();
+		assertThat(ResourcePrefix.from("smtp:")).isNull();
+		assertThat(ResourcePrefix.from("  ")).isNull();
+		assertThat(ResourcePrefix.from("")).isNull();
+		assertThat(ResourcePrefix.from(null)).isNull();
+	}
+
+	@Test
+	public void getProtocolIsCorrect() {
+
+		assertThat(ResourcePrefix.CLASSPATH_URL_PREFIX.getProtocol()).isEqualTo("classpath");
+		assertThat(ResourcePrefix.FILESYSTEM_URL_PREFIX.getProtocol()).isEqualTo("file");
+		assertThat(ResourcePrefix.HTTP_URL_PREFIX.getProtocol()).isEqualTo("http");
+	}
+
+	@Test
+	public void toUrlPrefix() {
+
+		assertThat(ResourcePrefix.CLASSPATH_URL_PREFIX.toUrlPrefix()).isEqualTo("classpath:");
+		assertThat(ResourcePrefix.FILESYSTEM_URL_PREFIX.toUrlPrefix()).isEqualTo("file://");
+		assertThat(ResourcePrefix.HTTP_URL_PREFIX.toUrlPrefix()).isEqualTo("http://");
+	}
+}