many-to-one（多对一）.docVIP

many-to-one（多对一） Multiple to one (many-to-one) elements can define a common association with another persistent class through the many-to-one element. The relational model is a multiple to one Association (in fact, an object reference): a foreign key of this table refers to the primary key field of the target table. many-to-one name= propertyName Column= column_name, column (optional): external field name. It can also be specified by nested column elements. Class= ClassName class (optional - default is the property type obtained by reflection): the name of the associated class. Cascade= cascade_style cascade (cascading) (optional): indicates which operations are cascaded from the parent object to the associated object. Fetch= join|select Fetch (optional - defaults to select): select one of the fetching (outer-join fetching) and the sequence select select (sequential). Update= true|false, insert=, true|false Update, insert (optional - default to true) specifies whether the corresponding field is included in the SQL statement for UPDATE and / or INSERT. If the two are false, then this is a purely exogenous (derived) association, and its value is mapped to the same (or multiple) field Certain other attributes are obtained or generated by trigger (triggers), or by other programs Property-ref= propertyNameFromAssociatedClass Property-ref: (optional) specifies an attribute of the associated class, which will correspond to the foreign key. If not specified, the primary key of the other partys associated class is used. Access= field|property|ClassName Access (optional - default is property): Hibernates policy for accessing attributes. Unique= true|false, not-null=, true|false Unique (optional): use DDL to generate a unique constraint for the foreign key field. In addition, this can also be used as the target attribute of property-ref. This allows the association to have one to one effect at the same time. Optimistic-lock= true|false Optimistic-lock (optional - defaults to t