2.2.2. Mapping simple properties
2.2.2.1. Declaring basic property mappings
Every non static non transient property (field or method) of an entity bean is considered persistent, unless you annotate it as
@Transient. Not having an annotation for your property is equivalent to the appropriate @Basic annotation. The @Basic annotation allows you to declare the fetching strategy for a property:
public transient int counter; //transient property
private String firstname; //persistent property
@Transient
String getLengthInMeter() { ... } //transient property
String getName() {... } // persistent property
@Basic
int getLength() { ... } // persistent property
@Basic(fetch = FetchType.LAZY)
String getDetailedComment() { ... } // persistent property
@Temporal(TemporalType.TIME)
java.util.Date getDepartureTime() { ... } // persistent property
@Enumerated(EnumType.STRING)
Starred getNote() { ... } //enum persisted as String in databasecounter, a transient field, and lengthInMeter, a method annotated as @Transient, and will be ignored by the entity manager. name, length, and firstname properties are mapped persistent and eagerly fetched (the default for simple properties). The detailedComment property value will be lazily fetched from the database once a lazy property of the entity is accessed for the first time. Usually you do not need to lazy simple properties (not to be confused with lazy association fetching).
Note
To enable property level lazy fetching, your classes have to be instrumented: bytecode is added to the original one to enable such feature, please refer to the Hibernate reference documentation. If your classes are not instrumented, property level lazy loading is silently ignored.
The recommended alternative is to use the projection capability of EJB-QL or Criteria queries.
EJB3 support property mapping of all basic types supported by Hibernate (all basic Java types , their respective wrappers and serializable classes). Hibernate Annotations support out of the box Enum type mapping either into a ordinal column (saving the enum ordinal) or a string based column (saving the enum string representation): the persistence representation, defaulted to ordinal, can be overridden through the
@Enumerated annotation as shown in the note property example.
In core Java APIs, the temporal precision is not defined. When dealing with temporal data you might want to describe the expected precision in database. Temporal data can have
DATE, TIME, or TIMESTAMP precision (ie the actual date, only the time, or both). Use the @Temporal annotation to fine tune that.
@Lob indicates that the property should be persisted in a Blob or a Clob depending on the property type: java.sql.Clob, Character[], char[] and java.lang.String will be persisted in a Clob. java.sql.Blob, Byte[], byte[] and serializable type will be persisted in a Blob.
@Lob
public String getFullText() {
return fullText;
}
@Lob
public byte[] getFullCode() {
return fullCode;
}
If the property type implements
java.io.Serializable and is not a basic type, and if the property is not annotated with @Lob, then the Hibernate serializable type is used.
