hibernate online tutorials for Beginers

Information about hibernate online tutorials for Beginers

Published on September 24, 2014

Author: quontra123

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PowerPoint Presentation: Quontra solutions http://www.quontrasolutions.com Call us : (404)-900-9988 Hibernate Tutorials PowerPoint Presentation: Hibernate Introduction Why to use Hibernate Steps to use/configure hibernate in an application simple case study Transaction in Hibernate Using Criteria in Hibernate Caching in Hibernate CONTENT PowerPoint Presentation: Hibernate Introduction: Hibernate is a powerful, high performance object/relational persistence and query service. Hibernate lets you develop persistent classes following object-oriented idiom - including association, inheritance, polymorphism, composition, and collections. Hibernate allows you to express queries in its own portable SQL extension (HQL), as well as in native SQL, or with an object-oriented Criteria and Example API.   Object/Relational Mapping Hibernate Dual-Layer Cache Architecture Highly scalable architecture J2EE integration Object Relational tool ( JDO, Hibernate, and iBatis SQL Maps, TopLink)   Hibernate supports these following databases: PowerPoint Presentation: Why to use Hibernate In traditional approach: Too many SQL statements Manually handled associations Database dependent Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Hibernate architecture PowerPoint Presentation: Steps to use/configure hibernate in an application: A . Installing the Hibernate core and support JAR libraries into your project B. Creating a Hibernate.cfg.xml file to describe how to access your database C. Selecting appropriate SQL Dialect for the database. D. Creating individual mapping descriptor files for each persistable Java classes PowerPoint Presentation: A. Install the Hibernate core and JAR libraries PowerPoint Presentation: B. Creating a Hibernate.cfg.xml : Before Hibernate can retrieve and persist objects for us, we need to tell it the settings about our application. For example, which kind of objects are persistent objects? Which kind of database are we using? How to connect to the database? What is the size of Connection pool? There are three ways to configure Hibernate in total: 1.       XML configuration 2.        programmatic configuration 3.        properties file configuration. PowerPoint Presentation: XML Configuration Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: C. Selecting appropriate SQL Dialect for the database. The dialect property determines the dialect to be used when generating queries. Hibernate supports dialects for all popular Relational Database Management Systems (RDBMS), such as DB2 or Oracle™. Therefore, for example, if you use Oracle during development and want to move to DB2 in production, changes will only be required in the hibernate.cfg.xml file. PowerPoint Presentation: A.     Creating individual mapping/descriptor files for each persistable Java classes/Table in DB JAVA XML RDBMS POJO Class HBM File A Table PowerPoint Presentation: A Table in Database       CREATE TABLE BOOK (   ISBN VARCHAR(50) NOT NULL,   NAME VARCHAR(100) NOT NULL,   PRICE INT NOT NULL,   PRIMARY KEY (ISBN)   ); PowerPoint Presentation: Java (POJO): PowerPoint Presentation: Hibernate-mapping: (*.hbm.xml) 0 PowerPoint Presentation: 4 simple case study [email protected] www.quontrasolutions.com Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: simple case study Creating global session factory: For an application using Hibernate as O/R mapping framework, a global session factory should be created and accessed through a particular interface. Here we use a static variable for storing the session factory. It is initialized in a static block when this class is loaded for the first time. PowerPoint Presentation: Using the SessionFactory in Application:   SessionFactory factory = HibernateUtil .getSessionFactory();   Session session = factory.openSession();   try { //………………….. // Using the session to retrieve objects //………………………………. } finally { session.close(); } SessionFactorys are immutable. The behaviour of a SessionFactory is controlled by properties supplied at configuration time. PowerPoint Presentation: Retrieving objects   Book book = (Book) session.load(Book.class, isbn); or Book book = (Book) session.get(Book.class, isbn);   What’s the difference between load() and get() ? The first difference is that when the given ID could not be found, load() will throw an exception “org.hibernate.ObjectNotFoundException”, while get() will return a null object. The second difference is that load() just returns a proxy by default and database won’t be hit until the proxy is first invoked. The get() will hit the database immediately. PowerPoint Presentation: Using HQL (Hibernate Query Language): If you are sure that there will be only one object matching, you can use the uniqueResult() method to retrieve the unique result object. So, the code would appear as: PowerPoint Presentation: persisting Objects:   For saving a newly created object, we can use the save() method. Hibernate will issue an INSERT statement.   session.save(book);   For updating an existing object, we can use the update() method. Hibernate will issue an UPDATE statement.   session.update(book);   For deleting an existing object, we can use the delete() method. Hibernate will issue a DELETE statement.   session.delete(book); PowerPoint Presentation: Id Generation in Hibernate Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: ID generation in Hibernate   There are three approaches to set ID:   a. Sequence Identity c. Native [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: ID generation in Hibernate   There are three approaches to set ID:   a.Sequence To generate an ID is to use an auto-incremented sequence number. For some kinds of databases (including HSQLDB), we can use a sequence/generator to generate this sequence number: PowerPoint Presentation: b. Identity: To generate an auto-incremented sequence number is to use an identity column of a table. Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: c. Native: most suitable strategy to use for your database Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: primary key generation using multiple columns: Table: Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Java (POJO Class) Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Mapping (an HBM file) Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: 5. Transaction in Hibernate: [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Transaction in Hibernate: PowerPoint Presentation: Example : select Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Example : update Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Example : delete [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: 6 Using Criteria in Hibernate [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Sometimes we need to build up a query dynamically in our application, e.g. for an advanced search function.“Criteria Queries” is an alternative way of HQL query.The traditional method of doing this is to generate a HQL statement, or SQL statement if not using Hibernate, by string concatenation. The problem for this method is making your code hard to maintain because of the hard reading statement fragments. Traditinal approach: if (startDate != null) { if (firstClause) { query = query + " where "; } else { query = query + " and "; query += " s.date >= '" + startDate + "'"; } // And so on... Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Hibernate Criteria: Criteria criteria = session.createCriteria(Book.class); if (startDate != null) { criteria.add(Expression.ge("date",startDate); } if (endDate != null) { criteria.add(Expression.le("date",endDate); } List results = criteria.list(); [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: SELECT * FROM ORDERS WHERE ORDER_ID=’1092’; In Cretira it would become: List orders= session.createCriteria(Order.class) .add(Restrictions.eq(“orderId”,”1092”)) .list(); SELECT O.*, P.* FROM ORDERS O, PRODUCT P WHERE O.ORDER_ID=P.ORDER_ID AND P.ID=’1111’; Would become List orders = session.createCriteria(Order.class) .setFetchMode(“products”,FetchMode.JOIN) .add(Restrictions.eq(“id”,”1111”)) .list(); [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: This criteria query corresponds to the following HQL query: from Book book where book.name = 'Hibernate for Beginners' Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Restriction .between is used to apply a "between" constraint to the field. Restriction .eq is used to apply an "equal" constraint to the field. Restriction .ge is used to apply a "greater than or equal" constraint to the field. Restriction .gt is used to apply a "greater than" constraint to the field. Restriction .idEq is used to apply an "equal" constraint to the identifier property. Restriction .in is used to apply an "in" constraint to the field. Restriction .isNotNull is used to apply an "is not null" constraint to the field. Restriction .isNull is used to apply an "is null" constraint to the field. Restriction .ne is used to apply a "not equal" constraint to the field. IN : criteria.add(Restrictions .in ("newCourseID", courseIDs)); PowerPoint Presentation:   7. Caching in Hibernate: Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: Hibernate supports the caching of persistent objects at different levels: 1 st level of caching 2 nd Level of caching Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: 1 st level of caching:   Suppose we get an object with same identifier for two times within a session, will Hibernate query the database for two times?  Call us : (404)-900-9988 www.quontrasolutions.com PowerPoint Presentation: If we inspect the SQL statements executed by Hibernate, we will find that only one database query is made. That means Hibernate is caching our objects in the same session. This kind of caching is called “first level caching”, whose caching scope is a session.   But how about getting an object with same identifier for two times in two different sessions? Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: 2 nd Level of caching: [email protected] www.quontrasolutions.com Call us : (404)-900-9988 Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation:  We will find that two database queries are made. That means Hibernate is not caching the persistent objects across different sessions by default. We need to turn on this “second level caching” whose caching scope is a session factory . Call us : (404)-900-9988 [email protected] www.quontrasolutions.com PowerPoint Presentation: To enable 2 nd level of caching, update the ‘hibernate.cfg.xml’ To monitor the caching activities of Hibernate at runtime, we can add the following line to the log4j configuration file “log4j.properties”.   log4j.logger.org.hibernate.cache=debug PowerPoint Presentation: [email protected] www.quontrasolutions.com Call us : (404)-900-9988 [email protected] www.quontrasolutions.com To Know More In-depth Knowledge Contact us Call Now 404)-900-9988   Email: [email protected] http ://www.quontrasolutions.com Quontra Solutions

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