Hibernate 4th-hibernate _ set ing

Hibernate set ing Demo:

Prerequisites:

Book [ID, name, authors], there may be n authors, so set is used here;

The object class has one book. There are two tables: tbook and tauthors;

1: Model:

package model;import java.util.Set;public class Book {private int id;private String name;private Set<String> authors;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<String> getAuthors() {return authors;}public void setAuthors(Set<String> authors) {this.authors = authors;}}

2: ing file of book: HBM. xml

<class name="Book" table="TBook" lazy="false">        <id name="id">            <generator class="native"/>        </id>        <property name="name" column="bookName"/>        <set name="authors" table="TAuthors">        <key column="id" />        <element column="authorName" type="string" not-null="true" length="30"/>        </set>    </class>

Note the following two points:

* State that not-null = "true" will automatically generate the primary key [ID, authorname] for you only when the tauthors table is generated; otherwise, the table has no primary key;

* If length = "30" is not specified, the following error occurs. Primary Key Generation fails. Therefore, you must specify a smaller value;

 not-null="true" length="30"

1218 [main] ERROR org.hibernate.tool.hbm2ddl.SchemaUpdate - Unsuccessful: create table TAuthors (id integer not null, topicName varchar(255) not null, primary key (id, topicName))1218 [main] ERROR org.hibernate.tool.hbm2ddl.SchemaUpdate - Specified key was too long; max key length is 767 bytes

3. Dao:

/** add */public void addPerson(Book p){Session session=null;Transaction tran=null;try {session=HibernateUtil.getSession();tran=session.beginTransaction();session.save(p);tran.commit();} catch (HibernateException e) {tran.rollback();e.printStackTrace();}finally{if(session!=null && session.isOpen()){session.close();}}}

4: Service:

        BookDao dao=new BookDao();/** add */public void add(Book p){dao.addPerson(p);}

5: JUnit test:

@ Test public void testadd () {Book p = New Book (); p. setname ("Java core technology"); set <string> authors = new hashset <string> (); authors. add ("cay S. horstmann "); authors. add ("Gary Cornell"); p. setauthors (authors); manager. add (p );}

6: final database result:

Mysql> select * From tbook; + ---- + ------------------ + | ID | bookname | + ---- + ------------------ + | 1 | Java core technology | + ---- + ------------------ + 1 row in setmysql> select * From tauthors; + ---- + --------------- + | ID | authorname | + ---- + ----------------- + | 1 | Cay S. horstmann | 1 | Gary Cornell | + ---- + --------------- + 2 rows in Set

DDL statement of the table:

CREATE TABLE `tbook` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `bookName` varchar(255) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8--------------------------------------------------------------------CREATE TABLE `tauthors` (  `id` int(11) NOT NULL,  `authorName` varchar(30) NOT NULL,  PRIMARY KEY (`id`,`authorName`),  KEY `FK529261547AAF8BC9` (`id`),  CONSTRAINT `FK529261547AAF8BC9` FOREIGN KEY (`id`) REFERENCES `tbook` (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8

That's all;