BAEL-5768 - Coupling in Java (#11) (#12881)

* BAEL-5768 - Coupling in Java (#11)

* BAEL-5768 - Coupling in Java

patterns-modules/coupling/pom.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>patterns-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>coupling</artifactId>
+
+</project>

patterns-modules/coupling/src/main/java/com/baeldung/loose/CSVExport.java

@@ -0,0 +1,14 @@
+package com.baeldung.loose;
+
+import java.io.File;
+import java.util.List;
+
+public class CSVExport implements ExportMetadata {
+    @Override
+    public File export(List<Object> metadata) {
+        System.out.println("Exporting data...");
+        // Export Metadata
+        File outputCSV = null;
+        return outputCSV;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/ExportMetadata.java

@@ -0,0 +1,8 @@
+package com.baeldung.loose;
+
+import java.io.File;
+import java.util.List;
+
+public interface ExportMetadata {
+    File export(List<Object> metadata);
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/FetchMetadata.java

@@ -0,0 +1,7 @@
+package com.baeldung.loose;
+
+import java.util.List;
+
+public interface FetchMetadata {
+    List<Object> fetchMetadata();
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/JSONFetch.java

@@ -0,0 +1,12 @@
+package com.baeldung.loose;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class JSONFetch implements FetchMetadata{
+    @Override
+    public List<Object> fetchMetadata() {
+        System.out.println("Fetching some json data");
+        return new ArrayList<>();
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/MetadataCollector.java

@@ -0,0 +1,26 @@
+package com.baeldung.loose;
+
+import java.util.List;
+
+public class MetadataCollector {
+    private final FetchMetadata fetchMetadata;
+    private final ExportMetadata exportMetadata;
+
+    public MetadataCollector(FetchMetadata fetchMetadata, ExportMetadata exportMetadata) {
+        this.fetchMetadata = fetchMetadata;
+        this.exportMetadata = exportMetadata;
+    }
+
+    public void collectMetadata() {
+        List<Object> metadata = fetchMetadata.fetchMetadata();
+        exportMetadata.export(metadata);
+    }
+
+    public FetchMetadata getFetchMetadata() {
+        return fetchMetadata;
+    }
+
+    public ExportMetadata getExportMetadata() {
+        return exportMetadata;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/PDFExport.java

@@ -0,0 +1,14 @@
+package com.baeldung.loose;
+
+import java.io.File;
+import java.util.List;
+
+public class PDFExport implements ExportMetadata {
+    @Override
+    public File export(List<Object> metadata) {
+        System.out.println("PDF Export");
+        // Some logic
+        File outputPDF = null;
+        return outputPDF;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/loose/XMLFetch.java

@@ -0,0 +1,13 @@
+package com.baeldung.loose;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class XMLFetch implements FetchMetadata {
+    @Override
+    public List<Object> fetchMetadata() {
+        List<Object> metadata = new ArrayList<>();
+        // Do some stuff
+        return metadata;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/tight/CSVExport.java

@@ -0,0 +1,14 @@
+package com.baeldung.tight;
+
+import java.io.File;
+import java.util.List;
+
+public class CSVExport {
+
+    public File export(List<Object> metadata) {
+        System.out.println("Exporting data...");
+        // Export Metadata
+        File outputCSV = null;
+        return outputCSV;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/tight/JSONFetch.java

@@ -0,0 +1,12 @@
+package com.baeldung.tight;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class JSONFetch {
+    public List<Object> fetchMetadata() {
+        List<Object> metadata = new ArrayList<>();
+        // Do some stuff
+        return metadata;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/tight/MetadataCollector.java

@@ -0,0 +1,35 @@
+package com.baeldung.tight;
+
+import java.util.List;
+
+public class MetadataCollector {
+    private XMLFetch xmlFetch = new XMLFetch();
+    private JSONFetch jsonFetch = new JSONFetch();
+    private CSVExport csvExport = new CSVExport();
+    private PDFExport pdfExport = new PDFExport();
+
+    public void collectMetadata() {
+        List<Object> metadata = xmlFetch.fetchMetadata();
+        csvExport.export(metadata);
+    }
+
+    public void collectMetadata(int inputType, int outputType) {
+        if (outputType == 1) {
+            List<Object> metadata = null;
+            if (inputType == 1) {
+                metadata = xmlFetch.fetchMetadata();
+            } else {
+                metadata = jsonFetch.fetchMetadata();
+            }
+            csvExport.export(metadata);
+        } else {
+            List<Object> metadata = null;
+            if (inputType == 1) {
+                metadata = xmlFetch.fetchMetadata();
+            } else {
+                metadata = jsonFetch.fetchMetadata();
+            }
+            pdfExport.export(metadata);
+        }
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/tight/PDFExport.java

@@ -0,0 +1,13 @@
+package com.baeldung.tight;
+
+import java.io.File;
+import java.util.List;
+
+public class PDFExport {
+    public File export(List<Object> metadata) {
+        System.out.println("Exporting data...");
+        // Export Metadata
+        File outputPDF = null;
+        return outputPDF;
+    }
+}

patterns-modules/coupling/src/main/java/com/baeldung/tight/XMLFetch.java

@@ -0,0 +1,12 @@
+package com.baeldung.tight;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class XMLFetch {
+    public List<Object> fetchMetadata() {
+        List<Object> metadata = new ArrayList<>();
+        // Do some stuff
+        return metadata;
+    }
+}

patterns-modules/coupling/src/test/java/com/baeldung/loose/LooselyCouplingUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.loose;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class LooselyCouplingUnitTest {
+
+    @Test
+    public void givenMetadataCollector_thenCollectMetadataXMLAndExportCSV() {
+        FetchMetadata metadata = new XMLFetch();
+        ExportMetadata exportMetadata = new CSVExport();
+        MetadataCollector collector = new MetadataCollector(metadata, exportMetadata);
+        collector.collectMetadata();
+        assertTrue(collector.getExportMetadata() instanceof CSVExport);
+        assertTrue(collector.getFetchMetadata() instanceof XMLFetch);
+    }
+
+    @Test
+    public void givenMetadataCollector_thenCollectMetadataUsingJSONAndExportPDF() {
+        FetchMetadata metadata = new JSONFetch();
+        ExportMetadata exportMetadata = new PDFExport();
+        MetadataCollector collector = new MetadataCollector(metadata, exportMetadata);
+        collector.collectMetadata();
+        assertTrue(collector.getExportMetadata() instanceof PDFExport);
+        assertTrue(collector.getFetchMetadata() instanceof JSONFetch);
+    }
+
+    @Test
+    public void givenMetadataCollector_thenCollectMetadataUsingXMLAndExportPDF() {
+        FetchMetadata metadata = new XMLFetch();
+        ExportMetadata exportMetadata = new PDFExport();
+        MetadataCollector collector = new MetadataCollector(metadata, exportMetadata);
+        collector.collectMetadata();
+        assertTrue(collector.getExportMetadata() instanceof PDFExport);
+        assertTrue(collector.getFetchMetadata() instanceof XMLFetch);
+    }
+}

patterns-modules/coupling/src/test/java/com/baeldung/tight/TightlyCouplingUnitTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.tight;
+
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.mock;
+
+import org.junit.jupiter.api.Test;
+
+class TightlyCouplingUnitTest {
+
+    @Test
+    public void givenMetadataCollector_thenCollectMetadata() {
+        MetadataCollector collector = mock(MetadataCollector.class);
+        doNothing().when(collector)
+            .collectMetadata();
+    }
+
+    @Test
+    public void givenMetadataCollectorWithDifferentInput_thenCollectMetadata() {
+        MetadataCollector collector = new MetadataCollector();
+        collector.collectMetadata(1, 1);
+    }
+}

patterns-modules/pom.xml

@@ -29,6 +29,7 @@
         <module>solid</module>
         <module>clean-architecture</module>
         <module>enterprise-patterns</module>
+        <module>coupling</module>
     </modules>
 
     <dependencyManagement>