net.java.ao

Annotation Type ManyToMany

@Retention(value=RUNTIME)
@Target(value=METHOD)
public @interface ManyToMany

Marks a method as relevant only to a many-to-many relation. This informs ActiveObjects that the return value for the method in question should be determined from a many-to-many relation through the specified type onto the type in the return value. For example:

public interface Person {
     // ...
     
     @ManyToMany(Authorship.class)
     public Book[] getBooks();
 }

Thus the return value of the getBooks() method would be determined by a query something like the following:

SELECT bookID FROM authorships WHERE personID = ?

If the where() clause is specified, it will be used in addition to the base, necessary criterion to determine the returned entities. Thus, the many-to-many relation could be referenced in the following way:

public interface Person {
     // ...
     
     @ManyToMany(value=Authorship.class, where="deleted = FALSE")
     public Book[] getBooks();
 }

This would lead to a query like the following:

SELECT bookID FROM authorships WHERE personID = ? AND (deleted = FALSE)

The value() parameter is not optional.

Author:

Daniel Spiewak

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
Class<? extends RawEntity<?>>	value The type through which the many-to-many relation is defined.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String	reverse The name of the getter method in the joining entity that refers to the annotated entity.
String	through The name of the getter method in the joining entity that refers to the entities to be returned by the annotated method.
String	where A String clause allowing developer-specified additional conditions to be imposed on the relationship.

Element Detail

value

public abstract Class<? extends RawEntity<?>> value

The type through which the many-to-many relation is defined. For example, if a people table has a many-to-many relation on books, it would most likely be through an authorships table. Thus, the value of this parameter could be Authorship.class

reverse

public abstract String reverse

The name of the getter method in the joining entity that refers to the annotated entity.

If this is not specified, a warning will be logged at migration time, and ActiveObjects may behave in unexpected ways. Future versions of ActiveObjects may require that this property be specified.

See Also:

AO-325

Default:

""

through

public abstract String through

The name of the getter method in the joining entity that refers to the entities to be returned by the annotated method.

If this is not specified, a warning will be logged at migration time, and ActiveObjects may behave in unexpected ways. Future versions of ActiveObjects may require that this property be specified.

See Also:

AO-325

Default:

""

where

public abstract String where

A String clause allowing developer-specified additional conditions to be imposed on the relationship. The String must be a proper SQL WHERE clause:

"deleted = FALSE"

One must be extremely careful with this sort of thing though because sometimes (as is the case with the above sample), the unparameterized code may not execute as expected against every database (due to differences in typing and value handling). Thus, in all but non-trivial cases, defined implementations should be used.

See Also:

Implementation

Default:

""