hibernate中casecade和inverse的区别

原文地址：http://www.mkyong.com/hibernate/different-between-cascade-and-inverse/#

Many Hibernate developers are confuse about the cascade option and inverse keyword. In some ways..they really look quite similar at the beginning, both are related with relationship.

Cascade vs inverse

However, there is no relationship between cascade and inverse, both are totally different notions.

1. inverse

This is used to decide which side is the relationship owner to manage the relationship (insert or update of the foreign key column).

Example

In this example, the relationship owner is belong to stockDailyRecords (inverse=true).

Markup

<!-- Stock.hbm.xml -->
<hibernate-mapping>
    <class name="com.mkyong.common.Stock" table="stock" ...>
    ...
    <set name="stockDailyRecords" table="stock_daily_record" inverse="true">
        <key>
            <column name="STOCK_ID" not-null="true" />
        </key>
        <one-to-many class="com.mkyong.common.StockDailyRecord" />
    </set>
    ...

When you save or update the stock object

Java

session.save(stock);
session.update(stock);

Hibernate will only insert or update the STOCK table, no update on the foreign key column. More detail example here…

2. cascade

In cascade, after one operation (save, update and delete) is done, it decide whether it need to call other operations (save, update and delete) on another entities which has relationship with each other.

Example

In this example, the cascade=”save-update” is declare on stockDailyRecords.

Markup

<!-- Stock.hbm.xml -->
<hibernate-mapping>
    <class name="com.mkyong.common.Stock" table="stock" ...>
    ...
    <set name="stockDailyRecords" table="stock_daily_record" 
        cascade="save-update" inverse="true">
        <key>
            <column name="STOCK_ID" not-null="true" />
        </key>
        <one-to-many class="com.mkyong.common.StockDailyRecord" />
    </set>
    ...

When you save or update the stock object

Java

session.save(stock);
session.update(stock);

It will inserted or updated the record into STOCK table and call another insert or update statement (cascade=”save-update”) on StockDailyRecord. More detail example here…

Conclusion

In short, the “inverse” is decide which side will update the foreign key, while “cascade” is decide what’s the follow by operation should execute. Both are look quite similar in relationship, but it’s totally two different things. Hibernate developers are worth to spend time to research on it, because misunderstand the concept or misuse it will bring serious performance or data integrity issue in your application.

Reference

1. inverse=”true” example and explanation
2. cascade example – save, update and delete