Class IndexedObjectDatabase

java.lang.Object
com.coyotegulch.jisp.ObjectDatabaseFile
com.coyotegulch.jisp.IndexedObjectDatabase
public class IndexedObjectDatabase extends ObjectDatabaseFile
The IndexedObjectDatabase class provides a mechanism for using a key value to an object serialized to a file.

A IndexedObjectDatabase object encapsulates access to a ObjectDatabaseFile via a set of ObjectIndexs. When an object is stored, it is associated with a key value by storing the key and an object reference in each attached ObjectIndex. Objects may then be retrieved either by providing a key and index pair, or through an iterator created for an index associated with the database.

Rationale: The Java Database Connection (JDBC) is often overkill for many applications. Sun designed JDBC to access enterprise-level database systems, such as DB2, SQL Server, and Oracle. Those systems, while very flexible and expansive, come with a high price tag, both in terms of system requirements and database overhead. BTreeDatabase provides a simpler tool for associating "key" information with data in external storage.

See Also:

  • Constructor Details

    • IndexedObjectDatabase

      public IndexedObjectDatabase(String filename, boolean is_new) throws IOException
      Opens an existing IndexedObjectDatabase, using a supplied file name.
      Parameters:
      filename - The name of an external database file containing serialized objects. If filename exists, it is opened; otherwise, the constructor creates the file and initializes it.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class

  • Method Details

    • attachIndex

      public void attachIndex(ObjectIndex index)
      Attaches an index object to this database. This index will be updated for every object recorded in the database.
      Parameters:
      index - An ObjectIndex to be associated with this database.
      See Also:

    • removeIndex

      public void removeIndex(ObjectIndex index)
      Removes the association of an index with this database. The index will no longer be updated for objects recorded in the database.
      Parameters:
      index - An ObjectIndex that should no longer be associated with this database.
      See Also:

    • insert

      public void insert(KeyObject[] key, Serializable obj) throws IOException, ClassNotFoundException
      Write a new object to the database, associating it with the provided keys.
      Parameters:
      key - The key values associated with obj. There must be one key for each attached index; the keys are associated with the indexes in order of attachment; in other words, the first key is associated with the first index attached, etc.
      obj - The object to be stored in the database.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class
      ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type
      DatabaseException - when an error occurs during database processing
      See Also:

    • write

      public void write(KeyObject[] key, Serializable obj) throws IOException, ClassNotFoundException
      Writes an object to the database, associating it with the provided key, replacing an existing object with a new one.
      Parameters:
      key - key values associated with obj. There must be one key for each attached index; the keys are associated with the indexes in order of attachment; in other words, the first key is associated with the first index attached, etc.
      obj - record object to be stored in the database.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class
      ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type
      DatabaseException - when an error occurs during database processing
      See Also:

    • read

      public Object read(KeyObject key, ObjectIndex index) throws IOException, ClassNotFoundException
      Read the object associated with a given key.
      Parameters:
      key - key identifying the record to be read
      index - index used to retrieve the object by key.
      Returns:
      The record object associated with key, or null if no such object could be found.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class
      ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type
      DatabaseException - when an error occurs during database processing
      See Also:

    • read

      public Object read(IndexIterator iterator) throws IOException, ClassNotFoundException
      Read the object associated with a given iterator.
      Parameters:
      iterator - a BTreeIterator pointing to the requested record
      Returns:
      The record object associated with iterator, or null if the iterator was invalid or no such record could be found.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class
      ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type
      DatabaseException - when an error occurs during database processing
      See Also:

    • remove

      public void remove(KeyObject[] key) throws IOException, DatabaseException, ClassNotFoundException
      Delete the record associated with a given key.

      Parameters:
      key - array of keys identifying the record to be deleted.
      index - index used to retrive the object by key.
      Throws:
      IOException - when an I/O exception is thrown by an underlying java.io.* class
      ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type
      DatabaseException - when an error occurs during database processing
      See Also: