Java Persistence/Basic Attributes - Wikibooks, open books for an open world

A basic attribute is one where the attribute class is a simple type such as String, Number, Date or a primitive. A basic attribute's value can map directly to the column value in the database. The following table summarizes the basic types and the database types they map to. Java type Database type Number (BigDecimal, BigInteger, Integer, Double, Long, Float, Short, Byte) NUMERIC (NUMBER, INT, LONG, FLOAT, DOUBLE) int, long, float, double, short, byte NUMERIC (NUMBER, INT, LONG, FLOAT,

LOBs, BLOBs, CLOBs and Serialization

A LOB is a Large OBject, such as a BLOB (Binary LOB), or a CLOB (Character LOB). It is a database type that can store a large binary or string value, as the normal VARCHAR or VARBINARY types typically have size limitations. A LOB is often stored as a locator in the database table, with the actual data stored outside of the table. In Java a CLOB will normally map to a String, and a BLOB will normally map to a byte[], although a BLOB may also represent some serialized object.

By default in JPA any Serializable attribute that is not a relationship or a basic type (String, Number, temporal, primitive), will be serialized to a BLOB field.

Column Definition and Schema Generation

The columnDefinition attribute of Column can be used to override the default database type used, or enhance the type definition with constraints or other such DDL. The length, scale and precision can also be set to override defaults. Since the defaults for the length are just defaults, it is normally a good idea to set these to be correct for your data model's expected data, to avoid data truncation. The unique attribute can be used to define a unique constraint on the column, most JPA providers will automatically define primary key and foreign key constraints based on the Id and relationship mappings.

 @Column(name="S_TIME", columnDefinition="TIMESTAMPTZ")
 private Calendar startTime;

 @Column(name = "START_DATE", columnDefinition = "DATE DEFAULT CURRENT_DATE")
 private java.sql.Date startDate;

@Column(columnDefinition="varchar2(20)")



With @Lob I always end up with a LONGTEXTin MySQL.

To get TEXT I declare it that ways (JPA 2.0):
@Column(columnDefinition = "TEXT")
private String text

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