Inverse, cascade, lazy, unsaved-Value

 

This example is constructed to illustrate some advanced configurations of Hibernate and their related mechanisms during the test:
There are three classes: category. Java, prodcuct. Java, and configurationtest. java. The third class is used for testing.
Category. Java code:

1. Package unsaved_value;
2. Import ......
3. Public class category {
4. Private integer ID;
5. Private string name;
6. Private string description;
7. Private set Products;
8. Public category (){
9. Id = NULL;
10. Name = NULL;
11. Description = NULL;
12. Products = new hashset ();
13. }
14. Public void addproduct (product P ){
15. Products. Add (P );
16. }
17. // ********** Setter and getter
18. ........
19. }
    

 
Product. Java code:
 

1. Package unsaved_value;
2. Public class product {
3. Private integer ID;
4. Private string name;
5. Private category;
6. Private string description;
7. Public Product (){
9. }
10. // ******* Getter and setter
11. .........
12. }

Configurationtest. Java

1. Public void testsave () throws exception {
2. CATEGORY Category = new category ();
3. Category. setname ("Java programming book 2 ");
4. Category. setdescription ("programming classic books 2 ");
5. Product pro = new product ();
6. Pro. setname ("Java programming ideology 2 ");
7. Pro. setdescription ("Chinese Version 4 2 ");
8. Pro. setcategory (category );
9. Category. addproduct (Pro );
10. Transaction Tx = session. begintransaction ();
11. Assert (session! = NULL) :( "session is null ");
12. Session. Save (category );
13. TX. Commit ();
14. }

Category represents the product catalog, while product represents the product. Obviously, category and product are one-to-multiple relationships. There are two ways for hibernate to map one-to-multiple relationships. One is one-to-one, and the other is two-way. Compared with the two, the two-way one-to-multiple advantage is reflected in two aspects: first, it is also very obvious that because of the two-way association, we will be more convenient in actual business logic, for example, we can retrieve all the products under a category and find out which product belongs. Second, bidirectional relationships are more advantageous in accessing databases than unidirectional ones. This will be discussed later in inverse.
. Two-way Association is the only "disadvantage" of one-way Association, because two-way association needs to write more ing files than one-way Association. This is not a problem. Two-way Association is used to map these two databases:

1. Category. HBM. xml:
2. Version = "1.0" encoding = "UTF-8"?>
4. Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd>
5. <Hibernate-mapping package = "unsaved_value">
6. <Class name = "category" table = "category">
7. <ID name = "ID" column = "ID">
8. <Generator class = "native">