Ensure HTTP classes don't close streams

Prior to this commit several HTTP classes made use of FileCopyUtils
when reading from or writing to streams. This has the unfortunate
side effect of closing streams that should really be left open.

The problem is particularly noticeable when dealing with a
FormHttpMessageConverter that is writing a multi-part response.

Relevant HTTP classes have now been refactored to make use of a new
StreamUtils class that works in a similar way FileCopyUtils but does
not close streams.

The NonClosingOutputStream class from SimpleStreamingClientHttpRequest
has also been refactored to a StreamUtils method.

Issue: SPR-10095

spring-core/src/test/java/org/springframework/util/StreamUtilsTests.java

@@ -0,0 +1,129 @@
+/*
+ * Copyright 2002-2013 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.util;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.charset.Charset;
+import java.util.Random;
+import java.util.UUID;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.InOrder;
+
+/**
+ * Tests for {@link StreamUtils}.
+ *
+ * @author Phillip Webb
+ */
+public class StreamUtilsTests {
+
+	private byte[] bytes = new byte[StreamUtils.BUFFER_SIZE + 10];
+
+	private String string = "";
+
+	@Before
+	public void setup() {
+		new Random().nextBytes(bytes);
+		while (string.length() < StreamUtils.BUFFER_SIZE + 10) {
+			string += UUID.randomUUID().toString();
+		}
+	}
+
+	@Test
+	public void copyToByteArray() throws Exception {
+		InputStream inputStream = spy(new ByteArrayInputStream(bytes));
+		byte[] actual = StreamUtils.copyToByteArray(inputStream);
+		assertThat(actual, equalTo(bytes));
+		verify(inputStream, never()).close();
+	}
+
+	@Test
+	public void copyToString() throws Exception {
+		Charset charset = Charset.defaultCharset();
+		InputStream inputStream = spy(new ByteArrayInputStream(string.getBytes(charset)));
+		String actual = StreamUtils.copyToString(inputStream, charset);
+		assertThat(actual, equalTo(string));
+		verify(inputStream, never()).close();
+	}
+
+	@Test
+	public void copyBytes() throws Exception {
+		ByteArrayOutputStream out = spy(new ByteArrayOutputStream());
+		StreamUtils.copy(bytes, out);
+		assertThat(out.toByteArray(), equalTo(bytes));
+		verify(out, never()).close();
+	}
+
+	@Test
+	public void copyString() throws Exception {
+		Charset charset = Charset.defaultCharset();
+		ByteArrayOutputStream out = spy(new ByteArrayOutputStream());
+		StreamUtils.copy(string, charset, out);
+		assertThat(out.toByteArray(), equalTo(string.getBytes(charset)));
+		verify(out, never()).close();
+	}
+
+	@Test
+	public void copyStream() throws Exception {
+		ByteArrayOutputStream out = spy(new ByteArrayOutputStream());
+		StreamUtils.copy(new ByteArrayInputStream(bytes), out);
+		assertThat(out.toByteArray(), equalTo(bytes));
+		verify(out, never()).close();
+	}
+
+	@Test
+	public void nonClosingInputStream() throws Exception {
+		InputStream source = mock(InputStream.class);
+		InputStream nonClosing = StreamUtils.nonClosing(source);
+		nonClosing.read();
+		nonClosing.read(bytes);
+		nonClosing.read(bytes, 1, 2);
+		nonClosing.close();
+		InOrder ordered = inOrder(source);
+		ordered.verify(source).read();
+		ordered.verify(source).read(bytes, 0, bytes.length);
+		ordered.verify(source).read(bytes, 1, 2);
+		ordered.verify(source, never()).close();
+	}
+
+	@Test
+	public void nonClosingOutputStream() throws Exception {
+		OutputStream source = mock(OutputStream.class);
+		OutputStream nonClosing = StreamUtils.nonClosing(source);
+		nonClosing.write(1);
+		nonClosing.write(bytes);
+		nonClosing.write(bytes, 1, 2);
+		nonClosing.close();
+		InOrder ordered = inOrder(source);
+		ordered.verify(source).write(1);
+		ordered.verify(source).write(bytes, 0, bytes.length);
+		ordered.verify(source).write(bytes, 1, 2);
+		ordered.verify(source, never()).close();
+	}
+}