Java Persistent Objects - Support for Data Types

Supported Java Types

When persisting a class, a persistence solution needs to know how to persist the types of each field in the class. Clearly a persistence solution can only support a finite number of Java types. It cannot know how to persist every possible type creatable. The JDO/JPA specifications define lists of types that are required to be supported by all implementations of those specifications. JDO uses terminology First-Class object (FCO) and Second-Class object (SCO) to categorize how these types are treated by the JDO implementation. Lets just explain what these mean.

FCO's are objects that have an identity in the datastore. They can be referred to. Examples of FCO's are an instance of a user-supplied class that is persistence capable.
SCO's are objects that do not have an identity in the datastore. They can't be referred to directly. They are aggregated to an FCO object and can be stored as part of the FCO object. SCO object can also contain FCO elements, like an FCO object has a SCO field of type Collection which contains FCO objects elements. Examples of SCO's are a field of type Date, that is typically stored as part of the FCO object.

If the type that you want to persist (as "SCO") is not listed below you can always add support for it via a JPOX plugin using the User-Types Plugin guide.

Supported First-Class (FCO) Types

JPOX currently supports objects that are PersistenceCapable as FCO. In addition it supports persisting fields of Interface or java.lang.Object type as FCO (since these are just references to PersistenceCapable objects).

Supported Second-Class (SCO) Types

The table below shows the currently supported SCO in JPOX (along with their JDBC type and default-fetch-group setting, whether they are queryable). It also shows the specifications which require support for the particular Java type. Please note that if your particular Java type is not listed below, it is possible for you to add support for it using a JPOX extension. It also shows whether a java type will be assigned a "proxy" object that allows detection of changes to the object. This is needed for things like Collections where you may add/remove elements and JPOX needs to know of updates. This use of a proxy will not affect your use of those types in any way. Please note that this list gives all JDBC types available with the various RDBMS adapters. The jdbc type in bold is the default type that will be used when "jdbc-type" is not specified in the MetaData (assuming that the RDBMS supports that JDBC type, and if not then JPOX will choose one itself). Some RDBMS adapters will only support some of these. The list will be improved in the future to add many more possibilities of persisting Java types using other JDBC types.

Java Type	Queryable	JDBC Type(s)
boolean		BIT, CHAR ('Y','N'), BOOLEAN, TINYINT, SMALLINT, NUMERIC
byte		TINYINT, SMALLINT, NUMERIC
char		CHAR, INTEGER, NUMERIC
double		DOUBLE, DECIMAL, FLOAT
float		FLOAT, REAL, DOUBLE, DECIMAL
int		INTEGER, BIGINT, NUMERIC
long		BIGINT, NUMERIC, DOUBLE, DECIMAL, INTEGER
short		SMALLINT, INTEGER, NUMERIC
boolean[]	[8]	LONGVARBINARY, BLOB
byte[]	[8]	LONGVARBINARY, BLOB
char[]	[8]	LONGVARBINARY, BLOB
double[]	[8]	LONGVARBINARY, BLOB
float[]	[8]	LONGVARBINARY, BLOB
int[]	[8]	LONGVARBINARY, BLOB
long[]	[8]	LONGVARBINARY, BLOB
short[]	[8]	LONGVARBINARY, BLOB
java.lang.Boolean		BIT, CHAR('Y','N'), BOOLEAN, TINYINT, SMALLINT
java.lang.Byte		TINYINT, SMALLINT, NUMERIC
java.lang.Character		CHAR, INTEGER, NUMERIC
java.lang.Double		DOUBLE, DECIMAL, FLOAT
java.lang.Float		FLOAT, REAL, DOUBLE, DECIMAL
java.lang.Integer		INTEGER, BIGINT, NUMERIC
java.lang.Long		BIGINT, NUMERIC, DOUBLE, DECIMAL, INTEGER
java.lang.Short		SMALLINT, INTEGER, NUMERIC
java.lang.Boolean[]	[8]	LONGVARBINARY, BLOB
java.lang.Byte[]	[8]	LONGVARBINARY, BLOB
java.lang.Character[]	[8]	LONGVARBINARY, BLOB
java.lang.Double[]	[8]	LONGVARBINARY, BLOB
java.lang.Float[]	[8]	LONGVARBINARY, BLOB
java.lang.Integer[]	[8]	LONGVARBINARY, BLOB
java.lang.Long[]	[8]	LONGVARBINARY, BLOB
java.lang.Short[]	[8]	LONGVARBINARY, BLOB
java.lang.Number
java.lang.Object		LONGVARBINARY, BLOB
java.lang.String		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.lang.String[]	[8]	LONGVARBINARY, BLOB
java.math.BigDecimal		DECIMAL, NUMERIC
java.math.BigInteger		NUMERIC, DECIMAL
java.math.BigDecimal[]	[8]	LONGVARBINARY, BLOB
java.math.BigInteger[]	[8]	LONGVARBINARY, BLOB
java.sql.Date		DATE, TIMESTAMP
java.sql.Time		TIME, TIMESTAMP
java.sql.Timestamp		TIMESTAMP
java.util.ArrayList
java.util.BitSet		LONGVARBINARY, BLOB
java.util.Calendar [5]		INTEGER, VARCHAR, CHAR
java.util.Collection
java.util.Currency		VARCHAR, CHAR
java.util.Date		TIMESTAMP, DATE, CHAR, BIGINT
java.util.Date[]	[8]	LONGVARBINARY, BLOB
java.util.GregorianCalendar [4]		INTEGER, VARCHAR, CHAR
java.util.HashMap
java.util.HashSet
java.util.Hashtable
java.util.LinkedHashMap [9]
java.util.LinkedHashSet [10]
java.util.LinkedList
java.util.List
java.util.Locale		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.util.Locale[]	[8]	LONGVARBINARY, BLOB
java.util.Map
java.util.Properties
java.util.PriorityQueue
java.util.Queue
java.util.Set
java.util.SortedMap [2]
java.util.SortedSet [1]
java.util.Stack
java.util.TimeZone		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.util.TreeMap [2]
java.util.TreeSet [1]
java.util.UUID		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.util.Vector
java.awt.Color [3]		INTEGER
java.awt.Point [4]		INTEGER
java.awt.image.BufferedImage [7]		LONGVARBINARY, BLOB
java.net.URI		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.net.URL		VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK, UNIQUEIDENTIFIER
java.io.Serializable		LONGVARBINARY, BLOB
javax.jdo.spi.PersistenceCapable		[embedded]
javax.jdo.spi.PersistenceCapable[]	[8]
java.lang.Enum [6]		LONGVARBINARY, BLOB, VARCHAR, INTEGER

[1] - java.util.SortedSet, java.util.TreeSet allow the specification of comparators via the "comparator-name" JPOX extension MetaData element (within <collection>). The headSet, tailSet, subSet methods are only supported when using cached collections.
[2] - java.util.SortedMap, java.util.TreeMap allow the specification of comparators via the "comparator-name" JPOX extension MetaData element (within <map>). The headMap, tailMap, subMap methods are only supported when using cached containers.
[3] - java.awt.Color - stored in 4 columns (red, green, blue, alpha). ColorSpace is not persisted.
[4] - java.awt.Point - stored in 2 columns (x and y).
[5] - java.util.Calendar - stored in 2 columns (milliseconds and timezone).
[6] - java.lang.Enum - by default, serialized into one column. Storing in VARCHAR or INTEGER data types is available via the "Java5" plugin. Queryable if stored in VARCHAR or INTEGER columns.
[7] - java.awt.image.BufferedImage is stored using JPG image format
[8] - Array types are queryable if not serialised, but stored to many rows
[9] - java.util.LinkedHashMap is stored without ordering, hence as just a Map currently
[10] - java.util.LinkedHashSet is stored without ordering, hence as just a Set currently

Additional Information Second-Class (SCO) Types

Java Type	JDBC Type	Database	Additional Information
java.lang.String	DATALINK	DB2	By default uses the SQL function: DLURLCOMPLETEONLY to fetch the column from database. This setting can be overwritten by the select-function extension. See the MetaData reference.
java.lang.String	VARCHAR	Oracle	Oracle treats an empty string equals null. To workaround, JPOX replaces the empty string with the character \u0001.
java.lang.String	UNIQUEIDENTIFIER	MSSQL

Supported Spatial Types

The table below shows the currently supported Spatial SCO in JPOX.

Java Type	Spec.	DFG?	Persistent?	Proxied?	Queryable	JDBC Type(s)	Plug-in
oracle.spatial.geometry.JGeometry [1]						SDO_GEOMETRY	SpatialOracle

[1] - oracle.spatial.geometry.JGeometry dirty check mechanism is limited to immutable mode, it means, if you change a JGeometry object field, you must reassign it to the owner object field to make sure changes are propaged to the database.