From f1c7b8b2b01512ee243f0c493932d325af0afd76 Mon Sep 17 00:00:00 2001
From: rajatgarg <rajatgarg@adobe.com>
Date: Sun, 3 Sep 2023 03:59:20 +0530
Subject: [PATCH] Add getting Extension from MIME type of a file

---
 core-java-modules/core-java-io/pom.xml        | 11 +++++
 .../ExtensionFromMimeTypeUnitTest.java        | 47 +++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 core-java-modules/core-java-io/src/test/java/com/baeldung/extension/ExtensionFromMimeTypeUnitTest.java

diff --git a/core-java-modules/core-java-io/pom.xml b/core-java-modules/core-java-io/pom.xml
index 59952c2d9e..53762d7547 100644
--- a/core-java-modules/core-java-io/pom.xml
+++ b/core-java-modules/core-java-io/pom.xml
@@ -43,6 +43,17 @@
             <version>${angus-activation.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.jodd</groupId>
+            <artifactId>jodd-util</artifactId>
+            <version>6.2.1</version>
+        </dependency>
+        <dependency>
+            <groupId>com.j256.simplemagic</groupId>
+            <artifactId>simplemagic</artifactId>
+            <version>1.17</version>
+        </dependency>
+
     </dependencies>
 
     <build>
diff --git a/core-java-modules/core-java-io/src/test/java/com/baeldung/extension/ExtensionFromMimeTypeUnitTest.java b/core-java-modules/core-java-io/src/test/java/com/baeldung/extension/ExtensionFromMimeTypeUnitTest.java
new file mode 100644
index 0000000000..0a22e2defb
--- /dev/null
+++ b/core-java-modules/core-java-io/src/test/java/com/baeldung/extension/ExtensionFromMimeTypeUnitTest.java
@@ -0,0 +1,47 @@
+package com.baeldung.extension;
+
+import static org.junit.Assert.assertEquals;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.tika.mime.MimeType;
+import org.apache.tika.mime.MimeTypeException;
+import org.apache.tika.mime.MimeTypes;
+import org.junit.Test;
+
+import com.j256.simplemagic.ContentInfo;
+
+public class ExtensionFromMimeTypeUnitTest {
+    public static final String PNG_EXT = "image/png";
+    @Test
+    public void whenUsingTika_thenGetFileExtension() throws MimeTypeException {
+        MimeTypes allTypes = MimeTypes.getDefaultMimeTypes();
+        MimeType type = allTypes.forName(PNG_EXT);
+        String extension = type.getExtension();
+        assertEquals(".png", extension);
+    }
+
+    @Test
+    public void  whenUsingJodd_thenGetFileExtension() {
+        String fileExtension = jodd.net.MimeTypes.findExtensionsByMimeTypes(PNG_EXT,false)[0];
+        assertEquals("png", fileExtension);
+    }
+
+    @Test
+    public void whenUsingMimetypesFileTypeMap_thenGetFileExtension() {
+        ContentInfo contentInfo = new ContentInfo("", PNG_EXT, "", true);
+        String[] fileExtensions = contentInfo.getFileExtensions();
+        assertEquals("png", fileExtensions[0]);
+    }
+
+    @Test
+    public void whenUsingCustomLogic_thenGetFileExtension() {
+        Map<String, String> mimeToExtensionMap = new HashMap<>();
+        mimeToExtensionMap.put("application/pdf", "pdf");
+        mimeToExtensionMap.put("image/jpeg", "jpg");
+        mimeToExtensionMap.put("image/png", "png");
+        String fileExtension = mimeToExtensionMap.get(PNG_EXT);
+        if (fileExtension!= null)
+            assertEquals("png", fileExtension);
+    }
+}