Package org.syncany.chunk

Class Transformer

  • Direct Known Subclasses:
    CipherTransformer, GzipTransformer, NoTransformer
    public abstract class Transformer
extends java.lang.Object
    A transformer combines one or many stream-transforming OutputStreams and InputStreams. Implementations might provide functionality to encrypt or compress output streams, and to decrypt or uncompress a corresponding input stream.

    Transformers can be chained in order to allow multiple consecutive output-/input stream transformers to be applied to a stream.

    A transformer can be instantiated using its implementation-specific constructor, or by calling its default constructor and initializing it using the init() method. Depending on the implementation, varying settings must be passed.

    • Constructor Summary

      Constructors 
      Constructor Description
      Transformer()
      Creates a new transformer object (no next transformer)
      Transformer​(Transformer nextTransformer)
      Create a new transformer, with a nested/chained transformer that will be be applied after this transformer.

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      abstract java.io.InputStream createInputStream​(java.io.InputStream in)
      Creates a strea-transforming InputStream.
      abstract java.io.OutputStream createOutputStream​(java.io.OutputStream out)
      Create a stream-transforming OutputStream.
      static Transformer getInstance​(java.lang.String type)
      Instantiates a transformer by its name using the default constructor.
      abstract void init​(java.util.Map<java.lang.String,​java.lang.String> settings)
      If a transformer is instantiated via the default constructor (e.g.
      void setNextTransformer​(Transformer nextTransformer)  
      abstract java.lang.String toString()
      An implementation of a transformer must override this method to identify the type of transformer and/or its settings.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • Transformer

        public Transformer()
        Creates a new transformer object (no next transformer)

      • Transformer

        public Transformer​(Transformer nextTransformer)
        Create a new transformer, with a nested/chained transformer that will be be applied after this transformer.
        Parameters:
        nextTransformer - The next transformer (to be applied after this transformer)

    • Method Detail

      • init

        public abstract void init​(java.util.Map<java.lang.String,​java.lang.String> settings)
                   throws java.lang.Exception
        If a transformer is instantiated via the default constructor (e.g. via a config file), it must be initialized using this method. The settings passed to the method depend on the implementation of the transformer.
        Parameters:
        settings - Implementation-specific setting map
        Throws:
        java.lang.Exception - If the given settings are invalid or insufficient for instantiation

      • createOutputStream

        public abstract java.io.OutputStream createOutputStream​(java.io.OutputStream out)
                                                 throws java.io.IOException
        Create a stream-transforming OutputStream. Depending on the implementation, the bytes written to the output stream might be encrypted, compressed, etc.
        Parameters:
        out - Original output stream which is transformed by this transformer
        Returns:
        Returns a transformed output stream
        Throws:
        java.io.IOException - If an exception occurs when instantiating or writing to the stream

      • createInputStream

        public abstract java.io.InputStream createInputStream​(java.io.InputStream in)
                                               throws java.io.IOException
        Creates a strea-transforming InputStream. Depending on the implementation, the bytes read from the input stream are uncompressed, decrypted, etc.
        Parameters:
        in - Original input stream which is transformed by this transformer
        Returns:
        Returns a transformed input stream
        Throws:
        java.io.IOException - If an exception occurs when instantiating or reading from the stream

      • toString

        public abstract java.lang.String toString()
        An implementation of a transformer must override this method to identify the type of transformer and/or its settings.
        Overrides:
        toString in class java.lang.Object

      • getInstance

        public static Transformer getInstance​(java.lang.String type)
                               throws java.lang.Exception
        Instantiates a transformer by its name using the default constructor. After creating a new transformer, it must be initialized using the init() method.

        The given type attribute is mapped to fully qualified class name (FQCN) of the form org.syncany.chunk.XTransformer, where X is the camel-cased type attribute.

        Parameters:
        type - Type/name of the transformer (corresponds to its camel case class name)
        Returns:
        Returns a new transformer
        Throws:
        java.lang.Exception - If the FQCN cannot be found or the class cannot be instantiated