commits decorator design pattern.

Author: ali4j

src/main/java/com/designpatterns/structural/decorator/CompressingDecorator.java

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+package com.designpatterns.structural.decorator;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.zip.GZIPOutputStream;
+
+/**
+ * this is one of the concrete decorators
+ */
+public class CompressingDecorator extends SenderDecorator {
+
+    public CompressingDecorator(Sender sender) {
+        super(sender);
+    }
+
+    @Override
+    public String send(String content) {
+        String compressedContent = new String(compressContent(content));
+        super.send(compressedContent);
+        return compressedContent;
+    }
+
+    private byte[] compressContent(String content) {
+        try{
+            ByteArrayOutputStream baostream = new ByteArrayOutputStream();
+            OutputStream outStream = new GZIPOutputStream(baostream);
+            outStream.write(content.getBytes("UTF-8"));
+            outStream.close();
+            byte[] compressedBytes = baostream.toByteArray(); // toString not always possible
+            return compressedBytes;
+        } catch (IOException e) {
+            throw new RuntimeException("exception happened while compressing email content");
+
+        }
+    }
+
+
+}

src/main/java/com/designpatterns/structural/decorator/EmailSender.java

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+package com.designpatterns.structural.decorator;
+
+/**
+ * this is the class which should be decorated without any modification
+ */
+public class EmailSender implements Sender {
+    @Override
+    public String send(String content) {
+        System.out.println("sending \"" + content  + "\" as email");
+        return content;
+    }
+}

src/main/java/com/designpatterns/structural/decorator/EncodingDecorator.java

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+package com.designpatterns.structural.decorator;
+
+import java.util.Base64;
+
+/**
+ * this is another concrete decorator.
+ */
+public class EncodingDecorator extends SenderDecorator {
+
+    public EncodingDecorator(Sender sender) {
+        super(sender);
+    }
+
+    @Override
+    public String send(String content) {
+        String encodedContent = encodeContent(content);
+        super.send(encodedContent);
+        return encodedContent;
+    }
+
+    private String encodeContent(String content){
+        return Base64.getEncoder().encodeToString(content.getBytes());
+    }
+}

src/main/java/com/designpatterns/structural/decorator/Sender.java

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+package com.designpatterns.structural.decorator;
+
+public interface Sender {
+    String send(String content);
+}

src/main/java/com/designpatterns/structural/decorator/SenderDecorator.java

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+package com.designpatterns.structural.decorator;
+
+/**
+ * this is the base decorator.
+ */
+public class SenderDecorator implements Sender {
+    private Sender sender;
+
+    public SenderDecorator(Sender sender) {
+        this.sender = sender;
+    }
+
+    @Override
+    public String send(String content) {
+        return this.sender.send(content);
+    }
+}