DataNucleus
Access Platform
Persistence
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. This support can be conveniently split into two parts

  • An object that can be referred-to (object reference, providing a relation) and that has an "identity" - First Class Object (FCO) . JDO2 requires an implementation to support PersistenceCapable types, as well as object/interface fields that refer to PersistenceCapable objects. JPA1 requires support for fields that are entity types. DataNucleus provides support for JDO2/JPA1 FCOs
  • An object that does not have an "identity" - Second Class Object (SCO) . This is something like a String or Date field in a class. It can also be a Collection, that contains other objects. DataNucleus provides full support for JDO2/JPA1 SCOs, as well as support for many more types. Indeed, if the type that you want to persist (as "SCO") is not listed below you can always add support for it via a DataNucleus plugin using the RDBMS Java Types Plugin guide


Supported First-Class (FCO) Types

DataNucleus 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 java types in DataNucleus (and the specifications requiring its support). The table also shows the default-fetch-group (DFG) setting for that Java type (so whether it is retrieved by default when retrieving an object with a field of that type), whether the field is persisted by default (if it is "false" then you would have to add persistence-modifier="persistent" to the field for it to be persisted by JDO), and whether the java type is replaced by a wrapper (or proxy) type that intercepts all methods that change the object internally (this is used for dirty detection, and is most common with collections/maps. You will see no difference when using the field of this type. The final column lists the DataNucleus jar where you will find support for this type

Java Type Spec. DFG? Persistent? Proxied? PK? Plugin
boolean datanucleus-core
byte datanucleus-core
char datanucleus-core
double datanucleus-core
float datanucleus-core
int datanucleus-core
long datanucleus-core
short datanucleus-core
boolean[] datanucleus-core
byte[] datanucleus-core
char[] datanucleus-core
double[] datanucleus-core
float[] datanucleus-core
int[] datanucleus-core
long[] datanucleus-core
short[] datanucleus-core
java.lang.Boolean datanucleus-core
java.lang.Byte datanucleus-core
java.lang.Character datanucleus-core
java.lang.Double datanucleus-core
java.lang.Float datanucleus-core
java.lang.Integer datanucleus-core
java.lang.Long datanucleus-core
java.lang.Short datanucleus-core
java.lang.Boolean[] datanucleus-core
java.lang.Byte[] datanucleus-core
java.lang.Character[] datanucleus-core
java.lang.Double[] datanucleus-core
java.lang.Float[] datanucleus-core
java.lang.Integer[] datanucleus-core
java.lang.Long[] datanucleus-core
java.lang.Short[] datanucleus-core
java.lang.Number [4] datanucleus-core
java.lang.Object datanucleus-core
java.lang.String datanucleus-core
java.lang.StringBuffer [3] datanucleus-core
java.lang.String[] datanucleus-core
java.math.BigDecimal datanucleus-core
java.math.BigInteger datanucleus-core
java.math.BigDecimal[] datanucleus-core
java.math.BigInteger[] datanucleus-core
java.sql.Date datanucleus-core
java.sql.Time datanucleus-core
java.sql.Timestamp datanucleus-core
java.util.ArrayList datanucleus-core
java.util.BitSet datanucleus-core
java.util.Calendar datanucleus-core
java.util.Collection datanucleus-core
java.util.Currency datanucleus-core
java.util.Date datanucleus-core
java.util.Date[] datanucleus-core
java.util.GregorianCalendar [7] datanucleus-core
java.util.HashMap datanucleus-core
java.util.HashSet datanucleus-core
java.util.Hashtable datanucleus-core
java.util.LinkedHashMap [5] datanucleus-core
java.util.LinkedHashSet [6] datanucleus-core
java.util.LinkedList datanucleus-core
java.util.List datanucleus-core
java.util.Locale datanucleus-core
java.util.Locale[] datanucleus-core
java.util.Map datanucleus-core
java.util.Properties datanucleus-core
java.util.PriorityQueue datanucleus-core
java.util.Queue datanucleus-core
java.util.Set datanucleus-core
java.util.SortedMap [2] datanucleus-core
java.util.SortedSet [1] datanucleus-core
java.util.Stack datanucleus-core
java.util.TimeZone datanucleus-core
java.util.TreeMap [2] datanucleus-core
java.util.TreeSet [1] datanucleus-core
java.util.UUID datanucleus-core
java.util.Vector datanucleus-core
java.awt.Color datanucleus-core
java.awt.Point datanucleus-core
java.awt.image.BufferedImage datanucleus-core
java.net.URI datanucleus-core
java.net.URL datanucleus-core
java.io.Serializable datanucleus-core
javax.jdo.spi.PersistenceCapable datanucleus-core
javax.jdo.spi.PersistenceCapable[] datanucleus-core
java.lang.Enum datanucleus-java5
java.lang.Enum[] datanucleus-java5
  • [1] - java.util.SortedSet , java.util.TreeSet allow the specification of comparators via the "comparator-name" DataNucleus 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" DataNucleus extension MetaData element (within <map>). The headMap, tailMap, subMap methods are only supported when using cached containers.
  • [3] - java.lang.StringBuffer dirty check mechanism is limited to immutable mode, it means, if you change a StringBuffer object field, you must reassign it to the owner object field to make sure changes are propagated to the database.
  • [4] - java.lang.Number will be stored in a column capable of storing a BigDecimal, and will store to the precision of the object to be persisted. On reading back the object will be returned typically as a BigDecimal since there is no mechanism for determing the type of the object that was stored.
  • [5] - java.util.LinkedHashMap treated as a Map currently. No List-ordering is supported.
  • [6] - java.util.LinkedHashSet treated as a Set currently. No List-ordering is supported.
  • [7] - java.util.Calendar can be stored into two columns (millisecs, Timezone) or into a single column (Timestamp). The single column option is not guaranteed to preserve the TimeZone of the input Calendar.


Supporting additional types

Other DataNucleus plugins, for example RDBMS Spatial add on support for other Java types. You can also make use of the Java types extension and easily add support for your own types.