Shulou(Shulou.com)06/02 Report--

This article mainly introduces "Hibernate case analysis". In daily operation, I believe many people have doubts about Hibernate case analysis. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts of "Hibernate case analysis". Next, please follow the editor to study!

Hibernate (currently in use version 3. 2) provides a variety of ways to generate primary keys. However, so many current generation methods may not meet our requirements. For example, increment can be used when it is convenient for an Hibernate instance, but not when it is clustered. For example, identity, sequence and native are the primary key generation methods provided by the data Bureau, which are often not needed by us, and they also show deficiencies in the program cross-database. And the primary key generated by the algorithm-based generation method is basically a string.

We now need a generation method: using Long as the primary key type, auto-increment, and support for clustering. Then we need to customize one of our primary key generators to implement it.

Hibernate instance code:

Package hibernate

Import java.io.Serializable

Import java.sql.Connection

Import java.sql.PreparedStatement

Import java.sql.ResultSet

Import java.sql.SQLException

Import java.util.Properties

Import org.apache.commons.logging.Log

Import org.apache.commons.logging.LogFactory

Import org.hibernate.HibernateException

Import org.hibernate.MappingException

Import org.hibernate.dialect.Dialect

Import org.hibernate.engine.SessionImplementor

Import org.hibernate.id.Configurable

Import org.hibernate.id.IdentifierGenerator

Import org.hibernate.id.PersistentIdentifierGenerator

Import org.hibernate.type.Type

Public class IncrementGenerator implements IdentifierGenerator, Configurable {

Private static final Log log = LogFactory.getLog (IncrementGenerator.class)

Private Long next

Private String sql

Public Serializable generate (SessionImplementor session, Object object)

Throws HibernateException {

If (sqlpercent null) {

GetNext (session.connection ())

}

Return next

}

Public void configure (Type type, Properties params, Dialect d)

Throws MappingException {

String table = params.getProperty ("table")

If (table==null) table= params.

GetProperty (PersistentIdentifierGenerator.TABLE)

String column = params.getProperty ("column")

If (column==null) column= params.

GetProperty (PersistentIdentifierGenerator.PK)

String schema = params.getProperty

(PersistentIdentifierGenerator.SCHEMA)

Sql = "select max (" + column + ") from" +

(schema==null? Table: schema +'.'+ table)

Log.info (sql)

}

Private void getNext (Connection conn) throws HibernateException {

Try {

PreparedStatement st = conn.prepareStatement (sql)

ResultSet rs = st.executeQuery ()

If (rs.next ()) {

Next = rs.getLong (1) + 1

}

Else {

Next = 1l

}

} catch (SQLException e)

{

Throw new HibernateException (e)

}

Finally {

Try {

Conn.close ()

} catch (SQLException e)

{

Throw new HibernateException (e)

}

}

}

}

Configuration:

Configure id in the corresponding hbm file as follows:

At this point, the study of "Hibernate case Analysis" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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