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the other hand, foreign key fields must always be nullable.

 5

  A detailed description of the 

elements contained in the key field element follows: 

Table 9 4, key field Tags 

Tag Name 

Description 

Required 

field name 

This identifies the field to which this mapping applies.  This 

Yes 

name must match a primary key field of the current entity. 

column name 

Specifies the column name in which this primary key field 

No, default 

will be stored. If this is relationship uses 

depends on 

foreign key mapping, this column will be added to the table 

mapping type 

for the related entity.  If this relationship uses 

relation table mapping, this column is added to the 

relation table.  This element is not allowed for mapped 

dependent value class; instead use the property element 

described in Chapter 3 of the JBossCMP Documentation. 

jdbc type 

This is the JDBC type that is used when setting parameters 

Only required if 

in a JDBC PreparedStatement or loading data from a JDBC 

sql type is 

ResultSet. The valid types are defined in java.sql.Types. 

specified, default 

is based on 

datasource 

mapping 

sql type 

This is the SQL type that is used in create table statements 

Only required if 

for this field. Valid sql types are only limited by your 

jdbc type is 

database vendor. 

specified, default 

is based on 

datasource 

mapping 

F o r e i g n   K e y   M a p p i n g  

Foreign key mapping is the most common mapping style for one to one and one to many 

relationships, but is not allowed for many to many relationships. The foreign key mapping 

element is simply declared by adding an empty foreign key mapping element to the ejb 

relation element. 

5

 The current implementation of JBossCMP inserts a row into the database for a new entity between ejbCreate and ejbPostCreate.  Since the 

EJB specification does not allow a relationship to be modified until ejbPostCreate, a foreign key will be initially set to null.  There is a similar 

problem with removal.  This limitation will be removed in a future release. 

92