BAEL-1033 Introduction to StreamUtils

libraries/src/main/java/com/baeldung/streamutils/DrainStream.java

@@ -0,0 +1,11 @@
+package com.baeldung.streamutils;
+
+import java.io.InputStream;
+
+import org.springframework.util.StreamUtils;
+
+public class DrainStream {
+	public InputStream getInputStream() {
+		return StreamUtils.emptyInput();
+	}
+}

libraries/src/test/java/com/baeldung/streamutils/CopyStreamTest.java

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+package com.baeldung.streamutils;
+
+import static org.junit.Assert.assertTrue;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.StringWriter;
+import java.nio.charset.StandardCharsets;
+
+import org.apache.commons.io.IOUtils;
+import org.junit.Assert;
+import org.junit.Test;
+import org.springframework.util.StreamUtils;
+
+public class CopyStreamTest {
+
+	@Test
+	public void whenCopyInputStreamToOutputStream_thenCorrect() throws IOException {
+		String inputFileName = "src/test/resources/input.txt";
+		String outputFileName = "src/test/resources/output.txt";
+		File outputFile = new File(outputFileName);
+		InputStream in = new FileInputStream(inputFileName);
+		OutputStream out = new FileOutputStream(outputFileName);
+
+		StreamUtils.copy(in, out);
+
+		assertTrue(outputFile.exists());
+		String inputFileContent = getStringFromInputStream(new FileInputStream(inputFileName));
+		String outputFileContent = getStringFromInputStream(new FileInputStream(outputFileName));
+		Assert.assertEquals(inputFileContent, outputFileContent);
+	}
+
+	@Test
+	public void whenCopyRangeOfInputStreamToOutputStream_thenCorrect() throws IOException {
+		String inputFileName = "src/test/resources/input.txt";
+		String outputFileName = "src/test/resources/output.txt";
+		File outputFile = new File(outputFileName);
+		InputStream in = new FileInputStream(inputFileName);
+		OutputStream out = new FileOutputStream(outputFileName);
+
+		StreamUtils.copyRange(in, out, 1, 10);
+
+		assertTrue(outputFile.exists());
+		String inputFileContent = getStringFromInputStream(new FileInputStream(inputFileName));
+		String outputFileContent = getStringFromInputStream(new FileInputStream(outputFileName));
+		Assert.assertEquals(inputFileContent.substring(1, 11), outputFileContent);
+	}
+
+	@Test
+	public void whenCopyStringToOutputStream_thenCorrect() throws IOException {
+		String string = "Should be copied to OutputStream.";
+		String outputFileName = "src/test/resources/output.txt";
+		File outputFile = new File(outputFileName);
+		OutputStream out = new FileOutputStream("src/test/resources/output.txt");
+
+		StreamUtils.copy(string, StandardCharsets.UTF_8, out);
+
+		assertTrue(outputFile.exists());
+		String outputFileContent = getStringFromInputStream(new FileInputStream(outputFileName));
+		Assert.assertEquals(outputFileContent, string);
+	}
+
+	@Test
+	public void whenCopyInputStreamToString_thenCorrect() throws IOException {
+		String inputFileName = "src/test/resources/input.txt";
+		InputStream is = new FileInputStream(inputFileName);
+		String content = StreamUtils.copyToString(is, StandardCharsets.UTF_8);
+
+		String inputFileContent = getStringFromInputStream(new FileInputStream(inputFileName));
+		Assert.assertEquals(inputFileContent, content);
+	}
+
+	@Test
+	public void whenCopyByteArrayToOutputStream_thenCorrect() throws IOException {
+		String outputFileName = "src/test/resources/output.txt";
+		String string = "Should be copied to OutputStream.";
+		byte[] byteArray = string.getBytes();
+		OutputStream out = new FileOutputStream("src/test/resources/output.txt");
+
+		StreamUtils.copy(byteArray, out);
+		String outputFileContent = getStringFromInputStream(new FileInputStream(outputFileName));
+		Assert.assertEquals(outputFileContent, string);
+	}
+
+	@Test
+	public void whenCopyInputStreamToByteArray_thenCorrect() throws IOException {
+		String inputFileName = "src/test/resources/input.txt";
+		InputStream in = new FileInputStream(inputFileName);
+		byte[] out = StreamUtils.copyToByteArray(in);
+
+		String content = new String(out);
+		String inputFileContent = getStringFromInputStream(new FileInputStream(inputFileName));
+		Assert.assertEquals(inputFileContent, content);
+	}
+
+	public static String getStringFromInputStream(InputStream input) throws IOException {
+		StringWriter writer = new StringWriter();
+		IOUtils.copy(input, writer, "UTF-8");
+		return writer.toString();
+	}
+	
+	public InputStream getNonClosingInputStream() throws IOException {
+	    InputStream in = new FileInputStream("src/test/resources/input.txt");
+	    return StreamUtils.nonClosing(in);
+	}
+}

libraries/src/test/resources/input.txt

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+This file is merely for testing.

libraries/src/test/resources/output.txt

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+Should be copied to OutputStream.