Handle mixture of encoded and unencoded chars in JarURLConnection

Previously, JarURLConnection would corrupt a URL that contained a
mixture of encoded and unencoded double-byte characters. URLs that
only contained unencoded double-byte characters were not affected as
they are passed through as-is.

This commit updates JarURLConnection.JarEntryName to correctly handle
characters with a value that won't fit in a single signed byte (a
value greater than 127). Such characters are now URL encoded and then
written to the output stream as multiple bytes.

Closes gh-5194

spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/JarEntryNameTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2016 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.boot.loader.jar;
+
+import java.io.UnsupportedEncodingException;
+
+import org.junit.Test;
+
+import org.springframework.boot.loader.jar.JarURLConnection.JarEntryName;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link JarEntryName}.
+ *
+ * @author Andy Wilkinson
+ */
+public class JarEntryNameTests {
+
+	@Test
+	public void basicName() {
+		assertThat(new JarEntryName("a/b/C.class").toString()).isEqualTo("a/b/C.class");
+	}
+
+	@Test
+	public void nameWithSingleByteEncodedCharacters() {
+		assertThat(new JarEntryName("%61/%62/%43.class").toString())
+				.isEqualTo("a/b/C.class");
+	}
+
+	@Test
+	public void nameWithDoubleByteEncodedCharacters() {
+		assertThat(new JarEntryName("%c3%a1/b/C.class").toString())
+				.isEqualTo("\u00e1/b/C.class");
+	}
+
+	@Test
+	public void nameWithMixtureOfEncodedAndUnencodedDoubleByteCharacters()
+			throws UnsupportedEncodingException {
+		assertThat(new JarEntryName("%c3%a1/b/\u00c7.class").toString())
+				.isEqualTo("\u00e1/b/\u00c7.class");
+	}
+
+}