uk.ac.cam.cl.databases.moviedb

Class MovieDB

java.lang.Object

uk.ac.cam.cl.databases.moviedb.MovieDB

All Implemented Interfaces:

AutoCloseable

public class MovieDB
extends Object
implements AutoCloseable

An example database using a JSON document data model, with data derived from IMDb. It stores two kinds of object: Movie and Person.

The database is embedded in-process (not a network service), and implemented using Berkeley DB Java Edition. The records in the database are JSON strings, which are mapped to Java objects using GSON.

The database has two primary key indexes (looking up a person or a movie by ID), and two secondary indexes (looking up a person by name, or looking up a movie by title).

You can open the database in a specified directory on disk using open(String). When you have finished using the database, you should close it using close(), which clears up any locks and pending writes, and shuts down background threads. The easiest way of doing this is with a try-with-resources statement, which takes advantage of the AutoCloseable interface:

try (MovieDB database = MovieDB.open("document-db")) {
    ... // use the database
}

Method Summary

Modifier and Type	Method and Description
void	close() Closes the database cleanly and shuts down its background threads.
Iterable<Person>	getByNamePrefix(String namePrefix) Scans over a set of people whose name begins with the specified string.
Iterable<Movie>	getByTitlePrefix(String titlePrefix) Scans over a set of movies whose title begins with the specified string.
Movie	getMovieById(int id) Looks up a movie by its unique identifier.
Person	getPersonById(int id) Looks up a person by their unique identifier.
static MovieDB	open(String dataDir) Opens the database, stored in the specified directory.
void	putMovie(String json) Inserts a movie into the database, given as a JSON string.
void	putPerson(String json) Inserts a person into the database, given as a JSON string.

Methods inherited from class java.lang.Object

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

Method Detail

open

public static MovieDB open(String dataDir)

Opens the database, stored in the specified directory.

Parameters:

dataDir - The directory in which to store the data files.

putMovie

public void putMovie(String json)

Inserts a movie into the database, given as a JSON string.

Parameters:

json - The JSON document representing the movie.

putPerson

public void putPerson(String json)

Inserts a person into the database, given as a JSON string.

Parameters:

json - The JSON document representing the person.

getMovieById

public Movie getMovieById(int id)

Looks up a movie by its unique identifier.

Parameters:

id - The identifier of the movie to search for.

Returns:

The requested movie, or null if there is none with the given id.

getPersonById

public Person getPersonById(int id)

Looks up a person by their unique identifier.

Parameters:

id - The identifier of the person to search for.

Returns:

The requested person, or null if there is none with the given id.

getByTitlePrefix

public Iterable<Movie> getByTitlePrefix(String titlePrefix)

Scans over a set of movies whose title begins with the specified string. See Movie.getTitle() for notes on how the title is formatted. The search is case-sensitive.

You need to iterate all the way to the end, because the iterator maintains a cursor in the database that is closed when the iterator has no more items remaining. Stopping iteration early would leak cursors.

Parameters:

titlePrefix - The beginning of the title to search for.

Returns:

Sequence of movies matching the search condition.

getByNamePrefix

public Iterable<Person> getByNamePrefix(String namePrefix)

Scans over a set of people whose name begins with the specified string. See Person.getName() for notes on how the name is formatted. The search is case-sensitive.

You need to iterate all the way to the end, because the iterator maintains a cursor in the database that is closed when the iterator has no more items remaining. Stopping iteration early would leak cursors.

Parameters:

namePrefix - The beginning of the name to search for.

Returns:

Sequence of people matching the search condition.

close

public void close()

Closes the database cleanly and shuts down its background threads. This method is called automatically if you use MovieDB in a try-with-resources statement.

Specified by:

close in interface AutoCloseable