Module com.renomad.minum
Package com.renomad.minum.database

Class DbData<T>

java.lang.Object
com.renomad.minum.database.DbData<T>
Direct Known Subclasses:
Inmate
public abstract class DbData<T> extends Object
An abstract data type meant to be used with Db

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    DbData()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    protected abstract T
    deserialize(String serializedText)
    deserializes the text back into an object.
    protected abstract long
    getIndex()
    We need an index so that each piece of data is distinct, even if it has the same data.
    protected abstract String
    serialize()
    Serializes this object into a string representation.
    protected abstract void
    setIndex(long index)
    It is necessary for this method to exist because it is used by the Db code to add the new index into this data.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • DbData

      protected DbData()

  • Method Details

    • serialize

      protected abstract String serialize()
      Serializes this object into a string representation. It will be the values of this object as strings, encoded with URL encoding, separated by pipe symbols.

      An example: 

              import static com.renomad.minum.utils.SerializationUtils.serializeHelper;

        public String serialize() {
            return serializeHelper(index, a, b);
        }
      Returns:
      this type serialized to a string - use SerializationUtils.serializeHelper(Object[])
      See Also:

    • deserialize

      protected abstract T deserialize(String serializedText)
      deserializes the text back into an object. See helper method SerializationUtils.deserializeHelper(String) to split a serialized string into tokens for rebuilding the object. See also serialize()

      An example: 

              import static com.renomad.minum.utils.SerializationUtils.deserializeHelper;

        public Foo deserialize(String serializedText) {
            final var tokens =  deserializeHelper(serializedText);
            return new Foo(
                    Integer.parseInt(tokens.get(0)),
                    Integer.parseInt(tokens.get(1)),
                    tokens.get(2)
                    );
        }
      Parameters:
      serializedText - the serialized string
      Returns:
      this type deserialized from a string
      See Also:

    • getIndex

      protected abstract long getIndex()
      We need an index so that each piece of data is distinct, even if it has the same data.
      Returns:
      an index for this data, used to name a file for this particular instance of data

    • setIndex

      protected abstract void setIndex(long index)
      It is necessary for this method to exist because it is used by the Db code to add the new index into this data.

      Let me unpack that a bit.

      The way our database works, it's expected that when you are creating a new instance of data, you won't know its index yet, because that is something the database manages for you.

      The index is an AtomicLong value that allows us to create new data without worrying about race conditions between threads (that is, we don't have to worry about two threads accidentally adding the same index value to two different datas).

      This value is also used as the name for the file of this data stored on disk.