An Introduction to CDI (Contexts and Dependency Injection) (#4503)

* Initial Commit

* Update pom.xml

* Update TimeLoggerFactoryUnitTest.java

* Update PngFileEditorUnitTest.java

cdi/pom.xml

@@ -14,6 +14,24 @@
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-core</artifactId>
+            <version>1.3</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.10.0</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-context</artifactId>
@@ -42,4 +60,4 @@
         <weld-se-core.version>2.4.1.Final</weld-se-core.version>
     </properties>
 
-</project>
+</project>

cdi/src/main/java/com/baeldung/dependencyinjection/application/FileApplication.java

@@ -0,0 +1,18 @@
+package com.baeldung.dependencyinjection.application;
+
+import com.baeldung.dependencyinjection.imageprocessors.ImageFileProcessor;
+import org.jboss.weld.environment.se.Weld;
+import org.jboss.weld.environment.se.WeldContainer;
+
+public class FileApplication {
+    
+    public static void main(String[] args) {
+        Weld weld = new Weld();
+        WeldContainer container = weld.initialize();
+        ImageFileProcessor imageFileProcessor = container.select(ImageFileProcessor.class).get();
+        System.out.println(imageFileProcessor.openFile("file1.png"));
+        System.out.println(imageFileProcessor.writeFile("file1.png"));
+        System.out.println(imageFileProcessor.saveFile("file1.png"));
+        container.shutdown();
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/factories/TimeLoggerFactory.java

@@ -0,0 +1,14 @@
+package com.baeldung.dependencyinjection.factories;
+
+import com.baeldung.dependencyinjection.loggers.TimeLogger;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import javax.enterprise.inject.Produces;
+
+public class TimeLoggerFactory {
+    
+    @Produces
+    public TimeLogger getTimeLogger() {
+        return new TimeLogger(new SimpleDateFormat("HH:mm"), Calendar.getInstance());
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/imagefileeditors/GifFileEditor.java

@@ -0,0 +1,27 @@
+package com.baeldung.dependencyinjection.imagefileeditors;
+
+import com.baeldung.dependencyinjection.qualifiers.GifFileEditorQualifier;
+
+@GifFileEditorQualifier
+public class GifFileEditor implements ImageFileEditor {
+    
+    @Override
+    public String openFile(String fileName) {
+        return "Opening GIF file " + fileName;
+    }
+
+    @Override
+    public String editFile(String fileName) {
+        return "Editing GIF file " + fileName;
+    }
+    
+    @Override
+    public String writeFile(String fileName) {
+        return "Writing GIF file " + fileName;
+    }
+
+    @Override
+    public String saveFile(String fileName) {
+        return "Saving GIF file " + fileName;
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/imagefileeditors/ImageFileEditor.java

@@ -0,0 +1,12 @@
+package com.baeldung.dependencyinjection.imagefileeditors;
+
+public interface ImageFileEditor {
+    
+    String openFile(String fileName);
+    
+    String editFile(String fileName);
+    
+    String writeFile(String fileName);
+    
+    String saveFile(String fileName);
+}

cdi/src/main/java/com/baeldung/dependencyinjection/imagefileeditors/JpgFileEditor.java

@@ -0,0 +1,27 @@
+package com.baeldung.dependencyinjection.imagefileeditors;
+
+import com.baeldung.dependencyinjection.qualifiers.JpgFileEditorQualifier;
+
+@JpgFileEditorQualifier
+public class JpgFileEditor implements ImageFileEditor {
+   
+    @Override
+    public String openFile(String fileName) {
+        return "Opening JPG file " + fileName;
+    }
+
+    @Override
+    public String editFile(String fileName) {
+        return "Editing JPG file " + fileName;
+    }
+    
+    @Override
+    public String writeFile(String fileName) {
+        return "Writing JPG file " + fileName;
+    }
+
+    @Override
+    public String saveFile(String fileName) {
+        return "Saving JPG file " + fileName;
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/imagefileeditors/PngFileEditor.java

@@ -0,0 +1,27 @@
+package com.baeldung.dependencyinjection.imagefileeditors;
+
+import com.baeldung.dependencyinjection.qualifiers.PngFileEditorQualifier;
+
+@PngFileEditorQualifier
+public class PngFileEditor implements ImageFileEditor {
+   
+    @Override
+    public String openFile(String fileName) {
+        return "Opening PNG file " + fileName;
+    }
+
+    @Override
+    public String editFile(String fileName) {
+        return "Editing PNG file " + fileName;
+    }
+    
+    @Override
+    public String writeFile(String fileName) {
+        return "Writing PNG file " + fileName;
+    }
+
+    @Override
+    public String saveFile(String fileName) {
+        return "Saving PNG file " + fileName;
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/imageprocessors/ImageFileProcessor.java

@@ -0,0 +1,42 @@
+package com.baeldung.dependencyinjection.imageprocessors;
+
+import com.baeldung.dependencyinjection.loggers.TimeLogger;
+import com.baeldung.dependencyinjection.qualifiers.PngFileEditorQualifier;
+import javax.inject.Inject;
+import com.baeldung.dependencyinjection.imagefileeditors.ImageFileEditor;
+
+public class ImageFileProcessor {
+    
+    private final ImageFileEditor imageFileEditor;
+    private final TimeLogger timeLogger;
+    
+    @Inject
+    public ImageFileProcessor(@PngFileEditorQualifier ImageFileEditor imageFileEditor, TimeLogger timeLogger) {
+        this.imageFileEditor = imageFileEditor;
+        this.timeLogger = timeLogger;
+    }
+    
+    public ImageFileEditor getImageFileditor() {
+        return imageFileEditor;
+    }
+    
+    public TimeLogger getTimeLogger() {
+        return timeLogger;
+    }
+    
+    public String openFile(String fileName) {
+        return imageFileEditor.openFile(fileName) + " at: " + timeLogger.getTime();
+    }
+    
+    public String editFile(String fileName) {
+        return imageFileEditor.editFile(fileName) + " at: " + timeLogger.getTime();
+    }
+     
+    public String writeFile(String fileName) {
+        return imageFileEditor.writeFile(fileName) + " at: " + timeLogger.getTime();
+    }
+    
+    public String saveFile(String fileName) {
+        return imageFileEditor.saveFile(fileName)+ " at: " + timeLogger.getTime();
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/loggers/TimeLogger.java

@@ -0,0 +1,19 @@
+package com.baeldung.dependencyinjection.loggers;
+
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+
+public class TimeLogger {
+    
+    private final SimpleDateFormat dateFormat;
+    private final Calendar calendar;
+    
+    public TimeLogger(SimpleDateFormat dateFormat, Calendar calendar) {
+        this.dateFormat = dateFormat;
+        this.calendar = calendar;
+    }
+    
+    public String getTime() {
+        return dateFormat.format(calendar.getTime());
+    }
+}

cdi/src/main/java/com/baeldung/dependencyinjection/qualifiers/GifFileEditorQualifier.java

@@ -0,0 +1,12 @@
+package com.baeldung.dependencyinjection.qualifiers;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import javax.inject.Qualifier;
+
+@Qualifier
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE, ElementType.PARAMETER})
+public @interface GifFileEditorQualifier {}

cdi/src/main/java/com/baeldung/dependencyinjection/qualifiers/JpgFileEditorQualifier.java

@@ -0,0 +1,12 @@
+package com.baeldung.dependencyinjection.qualifiers;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import javax.inject.Qualifier;
+
+@Qualifier
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE, ElementType.PARAMETER})
+public @interface JpgFileEditorQualifier {}

cdi/src/main/java/com/baeldung/dependencyinjection/qualifiers/PngFileEditorQualifier.java

@@ -0,0 +1,12 @@
+package com.baeldung.dependencyinjection.qualifiers;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import javax.inject.Qualifier;
+
+@Qualifier
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE, ElementType.PARAMETER})
+public @interface PngFileEditorQualifier {}

cdi/src/test/java/com/baeldung/test/dependencyinjection/GifFileEditorUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.imagefileeditors.GifFileEditor;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class GifFileEditorUnitTest {
+    
+    private static GifFileEditor gifFileEditor;
+    
+    
+    @BeforeClass
+    public static void setGifFileEditorInstance() {
+        gifFileEditor = new GifFileEditor();
+    }
+    
+    @Test
+    public void givenGifFileEditorlInstance_whenCalledopenFile_thenOneAssertion() {
+        assertThat(gifFileEditor.openFile("file1.gif")).isEqualTo("Opening GIF file file1.gif");
+    }
+    
+    @Test
+    public void givenGifFileEditorlInstance_whenCallededitFile_thenOneAssertion() {
+        assertThat(gifFileEditor.editFile("file1.gif")).isEqualTo("Editing GIF file file1.gif");
+    }
+    
+    @Test
+    public void givenGifFileEditorInstance_whenCalledwriteFile_thenOneAssertion() {
+        assertThat(gifFileEditor.writeFile("file1.gif")).isEqualTo("Writing GIF file file1.gif");
+    }
+    
+    @Test
+    public void givenGifFileEditorInstance_whenCalledsaveFile_thenOneAssertion() {
+        assertThat(gifFileEditor.saveFile("file1.gif")).isEqualTo("Saving GIF file file1.gif");
+    }
+}

cdi/src/test/java/com/baeldung/test/dependencyinjection/ImageProcessorUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.imagefileeditors.GifFileEditor;
+import com.baeldung.dependencyinjection.imagefileeditors.JpgFileEditor;
+import com.baeldung.dependencyinjection.imagefileeditors.PngFileEditor;
+import com.baeldung.dependencyinjection.imageprocessors.ImageFileProcessor;
+import com.baeldung.dependencyinjection.loggers.TimeLogger;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.jboss.weld.environment.se.Weld;
+import org.jboss.weld.environment.se.WeldContainer;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class ImageProcessorUnitTest {
+    
+    private static ImageFileProcessor imageFileProcessor;
+    private static SimpleDateFormat dateFormat;
+    private static Calendar calendar;
+    
+    
+    @BeforeClass
+    public static void setImageProcessorInstance() {
+        Weld weld = new Weld();
+        WeldContainer container = weld.initialize();
+        imageFileProcessor = container.select(ImageFileProcessor.class).get();
+        container.shutdown();
+    }
+    
+    @BeforeClass
+    public static void setSimpleDateFormatInstance() {
+        dateFormat = new SimpleDateFormat("HH:mm");
+    }
+    
+    @BeforeClass
+    public static void setCalendarInstance() {
+        calendar = Calendar.getInstance();
+    }
+    
+    @Test
+    public void givenImageProcessorInstance_whenInjectedPngFileEditorandTimeLoggerInstances_thenTwoAssertions() {
+        assertThat(imageFileProcessor.getImageFileditor()).isInstanceOf(PngFileEditor.class);
+        assertThat(imageFileProcessor.getTimeLogger()).isInstanceOf(TimeLogger.class);
+    }
+    
+    @Test
+    public void givenImageProcessorInstance_whenCalledopenFile_thenOneAssertion() {
+        String currentTime = dateFormat.format(calendar.getTime());
+        assertThat(imageFileProcessor.openFile("file1.png")).isEqualTo("Opening PNG file file1.png at: " + currentTime);
+    }
+    
+    @Test
+    public void givenImageProcessorInstance_whenCallededitFile_thenOneAssertion() {
+        String currentTime = dateFormat.format(calendar.getTime());
+        assertThat(imageFileProcessor.editFile("file1.png")).isEqualTo("Editing PNG file file1.png at: " + currentTime);
+    }
+    
+    @Test
+    public void givenImageProcessorInstance_whenCalledwriteFile_thenOneAssertion() {
+        String currentTime = dateFormat.format(calendar.getTime());
+        assertThat(imageFileProcessor.writeFile("file1.png")).isEqualTo("Writing PNG file file1.png at: " + currentTime);
+    }
+    
+    @Test
+    public void givenImageProcessorInstance_whenCalledsaveFile_thenOneAssertion() {
+        String currentTime = dateFormat.format(calendar.getTime());
+        assertThat(imageFileProcessor.saveFile("file1.png")).isEqualTo("Saving PNG file file1.png at: " + currentTime);
+    }
+}

cdi/src/test/java/com/baeldung/test/dependencyinjection/JpgFileEditorUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.imagefileeditors.JpgFileEditor;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class JpgFileEditorUnitTest {
+    
+    private static JpgFileEditor jpgFileUtil;
+    
+    
+    @BeforeClass
+    public static void setJpgFileEditorInstance() {
+        jpgFileUtil = new JpgFileEditor();
+    }
+    
+    @Test
+    public void givenJpgFileEditorInstance_whenCalledopenFile_thenOneAssertion() {
+        assertThat(jpgFileUtil.openFile("file1.jpg")).isEqualTo("Opening JPG file file1.jpg");
+    }
+    
+    @Test
+    public void givenJpgFileEditorlInstance_whenCallededitFile_thenOneAssertion() {
+        assertThat(jpgFileUtil.editFile("file1.gif")).isEqualTo("Editing JPG file file1.gif");
+    }
+    
+    @Test
+    public void givenJpgFileEditorInstance_whenCalledwriteFile_thenOneAssertion() {
+        assertThat(jpgFileUtil.writeFile("file1.jpg")).isEqualTo("Writing JPG file file1.jpg");
+    }
+    
+    @Test
+    public void givenJpgFileEditorInstance_whenCalledsaveFile_thenOneAssertion() {
+        assertThat(jpgFileUtil.saveFile("file1.jpg")).isEqualTo("Saving JPG file file1.jpg");
+    }
+}

cdi/src/test/java/com/baeldung/test/dependencyinjection/PngFileEditorUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.imagefileeditors.PngFileEditor;
+import com.baeldung.dependencyinjection.qualifiers.PngFileEditorQualifier;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+@PngFileEditorQualifier
+public class PngFileEditorUnitTest {
+    
+    private static PngFileEditor pngFileEditor;
+    
+    
+    @BeforeClass
+    public static void setPngFileEditorInstance() {
+        pngFileEditor = new PngFileEditor();
+    }
+    
+    @Test
+    public void givenPngFileEditorInstance_whenCalledopenFile_thenOneAssertion() {
+        assertThat(pngFileEditor.openFile("file1.png")).isEqualTo("Opening PNG file file1.png");
+    }
+    
+    @Test
+    public void givenPngFileEditorInstance_whenCallededitFile_thenOneAssertion() {
+        assertThat(pngFileEditor.editFile("file1.png")).isEqualTo("Editing PNG file file1.png");
+    }
+    
+    @Test
+    public void givenPngFileEditorInstance_whenCalledwriteFile_thenOneAssertion() {
+        assertThat(pngFileEditor.writeFile("file1.png")).isEqualTo("Writing PNG file file1.png");
+    }
+    
+    @Test
+    public void givenPngFileEditorInstance_whenCalledsaveFile_thenOneAssertion() {
+        assertThat(pngFileEditor.saveFile("file1.png")).isEqualTo("Saving PNG file file1.png");
+    }
+}

cdi/src/test/java/com/baeldung/test/dependencyinjection/TimeLoggerFactoryUnitTest.java

@@ -0,0 +1,15 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.factories.TimeLoggerFactory;
+import com.baeldung.dependencyinjection.loggers.TimeLogger;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class TimeLoggerFactoryUnitTest {
+    
+    @Test
+    public void givenTimeLoggerFactory_whenCalledgetTimeLogger_thenOneAssertion() {
+        TimeLoggerFactory timeLoggerFactory = new TimeLoggerFactory();
+        assertThat(timeLoggerFactory.getTimeLogger()).isInstanceOf(TimeLogger.class);
+    }
+}

cdi/src/test/java/com/baeldung/test/dependencyinjection/TimeLoggerUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.test.dependencyinjection;
+
+import com.baeldung.dependencyinjection.loggers.TimeLogger;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class TimeLoggerUnitTest {
+    
+    
+    @Test
+    public void givenTimeLoggerInstance_whenCalledgetLogTime_thenOneAssertion() {
+        SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm");
+        Calendar calendar = Calendar.getInstance();
+        TimeLogger timeLogger = new TimeLogger(dateFormat, calendar);
+        String currentTime = dateFormat.format(calendar.getTime());
+        assertThat(timeLogger.getTime()).isEqualTo(currentTime);
+    }
+}