BAEL-1033 Introduction to StreamUtils (#2341)

* Evaluation article: Different Types of Bean Injection in Spring

* added tests & changed configuration to Java-based config

* removed xml config files

* rename unit tests

* BAEL-972 - Apache Commons Text

* remove code from evaluation article

* remove code from evaluation article

* BAEL-972 - Apache Commons Text - added another example

* BAEL-972 - Apache Commons Text - just indentation

* BAEL-994 - TemporalAdjuster in Java

* BAEL-994 - TemporalAdjuster in Java

* BAEL-994 - TemporalAdjuster in Java

* BAEL-994 - TemporalAdjuster in Java

* BAEL-994 - TemporalAdjuster in Java - fix problems

* BAEL-1033 Introduction to StreamUtils

* BAEL-1033 Introduction to StreamUtils

* BAEL-1033 Introduction to StreamUtils

* fix formatting

* BAEL-1033 minor refactor

spring-core/pom.xml

@@ -69,6 +69,11 @@
 			<version>${mockito.spring.boot.version}</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>commons-io</groupId>
+			<artifactId>commons-io</artifactId>
+			<version>${commons.io.version}</version>
+		</dependency>
 	</dependencies>
 
 	<build>
@@ -129,6 +134,7 @@
 		<guava.version>20.0</guava.version>
 		<maven-war-plugin.version>2.6</maven-war-plugin.version>
 		<lombok.version>1.16.12</lombok.version>
+		<commons.io.version>2.5</commons.io.version>
 	</properties>
 
 	<repositories>

spring-core/src/main/java/com/baeldung/streamutils/CopyStream.java

@@ -0,0 +1,22 @@
+package com.baeldung.streamutils;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.StringWriter;
+
+import org.apache.commons.io.IOUtils;
+import org.springframework.util.StreamUtils;
+
+public class CopyStream {
+    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);
+    }
+}

spring-core/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();
+    }
+}

spring-core/src/test/java/com/baeldung/streamutils/CopyStreamTest.java

@@ -0,0 +1,100 @@
+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.nio.charset.StandardCharsets;
+
+import static org.junit.Assert.assertEquals;
+import org.junit.Test;
+import org.springframework.util.StreamUtils;
+
+import static com.baeldung.streamutils.CopyStream.getStringFromInputStream;
+
+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));
+        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));
+        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));
+        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));
+        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));
+        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));
+        assertEquals(inputFileContent, content);
+    }
+
+}

spring-core/src/test/resources/input.txt

@@ -0,0 +1 @@
+This file is merely for testing.

spring-core/src/test/resources/output.txt

@@ -0,0 +1 @@
+Should be copied to OutputStream.