JDBC

IO Framework

Chaining IO Streams

• Each IO stream object performs a specific task.
  • FileOutputStream -- Write the given bytes into the file (on disk).
  • BufferedOutputStream -- Hold multiple elements in a temporary buffer before flushing it to underlying stream/device. Improves performance.
  • DataOutputStream -- Convert primitive types into sequence of bytes. Inherited from DataOutput interface.
  • ObjectOutputStream -- Convert object into sequence of bytes. Inherited from ObjectOutput interface.
  • PrintStream -- Convert given input into formatted output.
  • Note that input streams does the counterpart of OutputStream class hierarchy.
• Streams can be chained to fulfil application requirements.

Primitive types IO

• DataInputStream & DataOutputStream -- convert primitive types from/to bytes
  • primitive type --> DataOutputStream --> bytes --> FileOutputStream --> file.
    • DataOutput interface provides methods for conversion - writeInt(), writeUTF(), writeDouble(), ...
  • primitive type <-- DataInputStream <-- bytes <-- FileInputStream <-- file.
    • DataInput interface provides methods for conversion - readInt(), readUTF(), readDouble(), ...

DataOutput/DataInput interface

interface DataOutput
  writeUTF(String s)
  writeInt(int i)
  writeDouble(double d)
  writeShort(short s)
  ...

interface DataInput
  String readUTF()
  int readInt()
  double readDouble()
  short readShort()
  ...

Serialization

• ObjectInputStream & ObjectOutputStream -- convert java object from/to bytes
  • Java object --> ObjectOutputStream --> bytes --> FileOutputStream --> file.
    • ObjectOutput interface provides method for conversion - writeObject().
  • Java object <-- ObjectInputStream <-- bytes <-- FileInputStream <-- file.
    • ObjectInput interface provides methods for conversion - readObject().
• Converting state of object into a sequence of bytes is referred as Serialization. The sequence of bytes includes object data as well as metadata.
• Serialized data can be further saved into a file (using FileOutputStream) or sent over the network (Marshalling process).
• Converting (serialized) bytes back to the Java object is referred as Deserialization.