Java Example

• decorators

  • decorators/CompressionDecorator.java

    package refactoring_guru.decorator.example.decorators;
    
    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Base64;
    import java.util.zip.Deflater;
    import java.util.zip.DeflaterOutputStream;
    import java.util.zip.InflaterInputStream;
    
    public class CompressionDecorator extends DataSourceDecorator {
        private int compLevel = 6;
    
        public CompressionDecorator(DataSource source) {
            super(source);
        }
    
        public int getCompressionLevel() {
            return compLevel;
        }
    
        public void setCompressionLevel(int value) {
            compLevel = value;
        }
    
        @Override
        public void writeData(String data) {
            super.writeData(compress(data));
        }
    
        @Override
        public String readData() {
            return decompress(super.readData());
        }
    
        private String compress(String stringData) {
            byte[] data = stringData.getBytes();
            try {
                ByteArrayOutputStream bout = new ByteArrayOutputStream(512);
                DeflaterOutputStream dos = new DeflaterOutputStream(bout, new Deflater(compLevel));
                dos.write(data);
                dos.close();
                bout.close();
                return Base64.getEncoder().encodeToString(bout.toByteArray());
            } catch (IOException ex) {
                return null;
            }
        }
    
        private String decompress(String stringData) {
            byte[] data = Base64.getDecoder().decode(stringData);
            try {
                InputStream in = new ByteArrayInputStream(data);
                InflaterInputStream iin = new InflaterInputStream(in);
                ByteArrayOutputStream bout = new ByteArrayOutputStream(512);
                int b;
                while ((b = iin.read()) != -1) {
                    bout.write(b);
                }
                in.close();
                iin.close();
                bout.close();
                return new String(bout.toByteArray());
            } catch (IOException ex) {
                return null;
            }
        }
    }

  • decorators/DataSource.java

    package refactoring_guru.decorator.example.decorators;
    
    public interface DataSource {
        void writeData(String data);
    
        String readData();
    }

  • decorators/DataSourceDecorator.java

    package refactoring_guru.decorator.example.decorators;
    
    public class DataSourceDecorator implements DataSource {
        private DataSource wrappee;
    
        DataSourceDecorator(DataSource source) {
            this.wrappee = source;
        }
    
        @Override
        public void writeData(String data) {
            wrappee.writeData(data);
        }
    
        @Override
        public String readData() {
            return wrappee.readData();
        }
    }

  • decorators/EncryptionDecorator.java

    package refactoring_guru.decorator.example.decorators;
    
    import java.util.Base64;
    
    public class EncryptionDecorator extends DataSourceDecorator {
    
        public EncryptionDecorator(DataSource source) {
            super(source);
        }
    
        @Override
        public void writeData(String data) {
            super.writeData(encode(data));
        }
    
        @Override
        public String readData() {
            return decode(super.readData());
        }
    
        private String encode(String data) {
            byte[] result = data.getBytes();
            for (int i = 0; i < result.length; i++) {
                result[i] += (byte) 1;
            }
            return Base64.getEncoder().encodeToString(result);
        }
    
        private String decode(String data) {
            byte[] result = Base64.getDecoder().decode(data);
            for (int i = 0; i < result.length; i++) {
                result[i] -= (byte) 1;
            }
            return new String(result);
        }
    }

  • decorators/FileDataSource.java

    package refactoring_guru.decorator.example.decorators;
    
    import java.io.*;
    
    public class FileDataSource implements DataSource {
        private String name;
    
        public FileDataSource(String name) {
            this.name = name;
        }
    
        @Override
        public void writeData(String data) {
            File file = new File(name);
            try (OutputStream fos = new FileOutputStream(file)) {
                fos.write(data.getBytes(), 0, data.length());
            } catch (IOException ex) {
                System.out.println(ex.getMessage());
            }
        }
    
        @Override
        public String readData() {
            char[] buffer = null;
            File file = new File(name);
            try (FileReader reader = new FileReader(file)) {
                buffer = new char[(int) file.length()];
                reader.read(buffer);
            } catch (IOException ex) {
                System.out.println(ex.getMessage());
            }
            return new String(buffer);
        }
    }

• Demo.java

  package refactoring_guru.decorator.example;
  
  import refactoring_guru.decorator.example.decorators.*;
  
  public class Demo {
      public static void main(String[] args) {
          String salaryRecords = "Name,Salary\nJohn Smith,100000\nSteven Jobs,912000";
          DataSourceDecorator encoded = new CompressionDecorator(
                                          new EncryptionDecorator(
                                              new FileDataSource("out/OutputDemo.txt")));
          encoded.writeData(salaryRecords);
          DataSource plain = new FileDataSource("out/OutputDemo.txt");
  
          System.out.println("- Input ----------------");
          System.out.println(salaryRecords);
          System.out.println("- Encoded --------------");
          System.out.println(plain.readData());
          System.out.println("- Decoded --------------");
          System.out.println(encoded.readData());
      }
  }

  - Input ----------------
  Name,Salary
  John Smith,100000
  Steven Jobs,912000
  - Encoded --------------
  Zkt7e1Q5eU8yUm1Qe0ZsdHJ2VXp6dDBKVnhrUHtUe0sxRUYxQkJIdjVLTVZ0dVI5Q2IwOXFISmVUMU5rcENCQmdxRlByaD4+
  - Decoded --------------
  Name,Salary
  John Smith,100000
  Steven Jobs,912000