BAEL-5942 Code changes (#13147)

* BAEL-5942 Code changes

* BAEL-5942 Code changes

* BAEL-5942 Code updates from Review

* BAEL-5942 Code updates from Review

* BAEL-5942 Code updates from Review

* BAEL-5942 Code updates from Review

* BAEL-5942 Code updates from Review

* BAEL-5942 Code updates from Review

* BAEL-5942 Test updates from Review

* BAEL-5942 Test updates from Review

* BAEL-5942 Test updates from Review

spring-web-modules/spring-mvc-file/src/main/java/com/baeldung/Application.java

@@ -0,0 +1,11 @@
+package com.baeldung;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class Application {
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+}

spring-web-modules/spring-mvc-file/src/main/java/com/baeldung/file/CustomMultipartFile.java

@@ -0,0 +1,60 @@
+package com.baeldung.file;
+
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.springframework.web.multipart.MultipartFile;
+
+public class CustomMultipartFile implements MultipartFile {
+    private byte[] input;
+
+    public CustomMultipartFile(byte[] input) {
+        this.input = input;
+    }
+
+    @Override
+    public String getName() {
+        return null;
+    }
+
+    @Override
+    public String getOriginalFilename() {
+        return null;
+    }
+
+    @Override
+    public String getContentType() {
+        return null;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return input == null || input.length == 0;
+    }
+
+    @Override
+    public long getSize() {
+        return input.length;
+    }
+
+    @Override
+    public byte[] getBytes() throws IOException {
+        return input;
+    }
+
+    @Override
+    public InputStream getInputStream() throws IOException {
+        return new ByteArrayInputStream(input);
+    }
+
+    @Override
+    public void transferTo(File destination) throws IOException, IllegalStateException {
+        try(FileOutputStream fos = new FileOutputStream(destination)) {
+            fos.write(input);
+        }
+    }
+
+}

spring-web-modules/spring-mvc-file/src/test/java/com/baeldung/file/CustomMultipartFileUnitTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.file;
+
+import java.io.IOException;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockMultipartFile;
+
+class CustomMultipartFileUnitTest {
+
+    @Test
+    void whenProvidingByteArray_thenMultipartFileCreated() throws IOException {
+        byte[] inputArray = "Test String".getBytes();
+        CustomMultipartFile customMultipartFile = new CustomMultipartFile(inputArray);
+        Assertions.assertFalse(customMultipartFile.isEmpty());
+        Assertions.assertArrayEquals(inputArray, customMultipartFile.getBytes());
+        Assertions.assertEquals(inputArray.length, customMultipartFile.getSize());
+    }
+
+    @Test
+    void whenProvidingEmptyByteArray_thenMockMultipartFileIsEmpty() throws IOException {
+        byte[] inputArray = "".getBytes();
+        MockMultipartFile mockMultipartFile = new MockMultipartFile("tempFileName", inputArray);
+        Assertions.assertTrue(mockMultipartFile.isEmpty());
+    }
+
+    @Test
+    void whenProvidingNullByteArray_thenMockMultipartFileIsEmpty() throws IOException {
+        byte[] inputArray = null;
+        MockMultipartFile mockMultipartFile = new MockMultipartFile("tempFileName", inputArray);
+        Assertions.assertTrue(mockMultipartFile.isEmpty());
+    }
+
+    @Test
+    void whenProvidingByteArray_thenMultipartFileInputSizeMatches() throws IOException {
+        byte[] inputArray = "Testing String".getBytes();
+        CustomMultipartFile customMultipartFile = new CustomMultipartFile(inputArray);
+        Assertions.assertEquals(inputArray.length, customMultipartFile.getSize());
+    }
+
+    @Test
+    void whenProvidingByteArray_thenMockMultipartFileCreated() throws IOException {
+        byte[] inputArray = "Test String".getBytes();
+        MockMultipartFile mockMultipartFile = new MockMultipartFile("tempFileName", inputArray);
+        Assertions.assertFalse(mockMultipartFile.isEmpty());
+        Assertions.assertArrayEquals(inputArray, mockMultipartFile.getBytes());
+        Assertions.assertEquals(inputArray.length, mockMultipartFile.getSize());
+    }
+}