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As we saw in the Types Guide JPOX supports the persistence of a large range of Java field types.
With RDBMS datastores, we have the notion of tables/columns in the datastore and so each Java type is mapped across to
a column or a set of columns in a table. It is important to understand this mapping when mapping to an existing schema
for example. In RDBMS datastores a java type is stored using JDBC types. JPOX supports the use of the vast majority of the
available JDBC types.
When persisting a Java type in general it is persisted into a single column. For example a String will be persisted
into a VARCHAR column by default. Some types (e.g Color) have more information to store than we can conveniently
persist into a single column and so use multiple columns. Other types (e.g Collection) store their information in other
ways, such as foreign keys.
This table shows the Java types we saw earlier and whether they can be queried using JDOQL queries, and what
JDBC types can be used to store them in your RDBMS datastore. Not all RDBMS datastores support all
of these options. While JPOX always tries to provide a complete list sometimes this is impossible
due to limitations in the underlying JDBC driver
| Java Type | Number
Columns | Queryable | JDBC Type(s) |
|---|
| boolean | 1 |  | BIT, CHAR ('Y','N'), BOOLEAN, TINYINT, SMALLINT, NUMERIC | | byte | 1 | | TINYINT, SMALLINT, NUMERIC | | char | 1 | | CHAR, INTEGER, NUMERIC | | double | 1 | | DOUBLE, DECIMAL, FLOAT | | float | 1 | | FLOAT, REAL, DOUBLE, DECIMAL | | int | 1 | | INTEGER, BIGINT, NUMERIC | | long | 1 | | BIGINT, NUMERIC, DOUBLE, DECIMAL, INTEGER | | short | 1 | | SMALLINT, INTEGER, NUMERIC | | boolean[] | 1 | [6] | LONGVARBINARY, BLOB | | byte[] | 1 | [6] | LONGVARBINARY, BLOB | | char[] | 1 | [6] | LONGVARBINARY, BLOB | | double[] | 1 | [6] | LONGVARBINARY, BLOB | | float[] | 1 | [6] | LONGVARBINARY, BLOB | | int[] | 1 | [6] | LONGVARBINARY, BLOB | | long[] | 1 | [6] | LONGVARBINARY, BLOB | | short[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Boolean | 1 | | BIT, CHAR('Y','N'), BOOLEAN, TINYINT, SMALLINT | | java.lang.Byte | 1 | | TINYINT, SMALLINT, NUMERIC | | java.lang.Character | 1 | | CHAR, INTEGER, NUMERIC | | java.lang.Double | 1 | | DOUBLE, DECIMAL, FLOAT | | java.lang.Float | 1 | | FLOAT, REAL, DOUBLE, DECIMAL | | java.lang.Integer | 1 | | INTEGER, BIGINT, NUMERIC | | java.lang.Long | 1 | | BIGINT, NUMERIC, DOUBLE, DECIMAL, INTEGER | | java.lang.Short | 1 | | SMALLINT, INTEGER, NUMERIC | | java.lang.Boolean[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Byte[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Character[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Double[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Float[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Integer[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Long[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Short[] | 1 | [6] | LONGVARBINARY, BLOB | | java.lang.Number | 1 | | | | java.lang.Object | 1 | | LONGVARBINARY, BLOB | | java.lang.String [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.lang.StringBuffer [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.lang.String[] | 1 | [6] | LONGVARBINARY, BLOB | | java.math.BigDecimal | 1 | | DECIMAL, NUMERIC | | java.math.BigInteger | 1 | | NUMERIC, DECIMAL | | java.math.BigDecimal[] | 1 | [6] | LONGVARBINARY, BLOB | | java.math.BigInteger[] | 1 | [6] | LONGVARBINARY, BLOB | | java.sql.Date | 1 | | DATE, TIMESTAMP | | java.sql.Time | 1 | | TIME, TIMESTAMP | | java.sql.Timestamp | 1 | | TIMESTAMP | | java.util.ArrayList | 0 | | | | java.util.BitSet | 0 |  | LONGVARBINARY, BLOB | | java.util.Calendar [3] | 1 or 2 | | INTEGER, VARCHAR, CHAR | | java.util.Collection | 0 | | | | java.util.Currency | 1 | | VARCHAR, CHAR | | java.util.Date | 1 | | TIMESTAMP, DATE, CHAR, BIGINT | | java.util.Date[] | 1 | [6] | LONGVARBINARY, BLOB | | java.util.GregorianCalendar [2] | 1 or 2 | | INTEGER, VARCHAR, CHAR | | java.util.HashMap | 0 | | | | java.util.HashSet | 0 | | | | java.util.Hashtable | 0 | | | | java.util.LinkedHashMap | 0 | | | | java.util.LinkedHashSet | 0 | | | | java.util.LinkedList | 0 | | | | java.util.List | 0 | | | | java.util.Locale [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.util.Locale[] | 1 | [6] | LONGVARBINARY, BLOB | | java.util.Map | 0 | | | | java.util.Properties | 0 | | | | java.util.PriorityQueue | 0 | | | | java.util.Queue | 0 | | | | java.util.Set | 0 | | | | java.util.SortedMap | 0 | | | | java.util.SortedSet | 0 | | | | java.util.Stack | 0 | | | | java.util.TimeZone [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.util.TreeMap | 0 | | | | java.util.TreeSet | 0 | | | | java.util.UUID [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.util.Vector | 0 | | | | java.awt.Color [1] | 4 | | INTEGER | | java.awt.Point [2] | 2 | | INTEGER | | java.awt.image.BufferedImage [5] | 1 | | LONGVARBINARY, BLOB | | java.net.URI [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.net.URL [9] | 1 | | VARCHAR, CHAR, LONGVARCHAR, CLOB, BLOB, DATALINK [7], UNIQUEIDENTIFIER [8], XMLTYPE [10] | | java.io.Serializable | 1 | | LONGVARBINARY, BLOB | | javax.jdo.spi.PersistenceCapable | 1 | | [embedded] | | javax.jdo.spi.PersistenceCapable[] | 1 | [6] | | | java.lang.Enum [4] | 1 | | LONGVARBINARY, BLOB, VARCHAR, INTEGER |
- [1] - java.awt.Color - stored in 4 columns (red, green, blue, alpha). ColorSpace is not persisted.
- [2] - java.awt.Point - stored in 2 columns (x and y).
- [3] - java.util.Calendar - stored in 2 columns (milliseconds and timezone).
- [4] - 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.
- [5] - java.awt.image.BufferedImage is stored using JPG image format
- [6] - Array types are queryable if not serialised, but stored to many rows
- [7] - DATALINK JDBC type supported on DB2 only. Uses the SQL function DLURLCOMPLETEONLY to fetch from
the datastore. You can override this using the select-function extension. See the
JDO MetaData reference.
- [8] - UNIQUEIDENTIFIER JDBC type supported on MSSQL only.
- [9] - Oracle treats an empty string as the same as NULL. To workaround this limitation JPOX
replaces the empty string with the character \u0001.
- [10] - XMLTYPE JDBC type supported on Oracle only, and is included in the "jpox-xmltypeoracle" plugin.
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