Study of Hibernate. Akash Ravindra. Khapare

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(IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering Study f Hibernate Akash Ravindra. Khapare Dept Name: Cmputer Science & Engineering Cllege: H.V.P.M S, C.O.E.T, Amravati Amravati, India E-mail: akashkhapare@gmail.

1 (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering Study f Hibernate Akash Ravindra. Khapare Dept Name: Cmputer Science & Engineering Cllege: H.V.P.M S, C.O.E.T, Amravati Amravati, India akashkhapare@gmail.cm Abstract:-Generally we use Object Oriented Prgramming with the relatinal databases. Thus there is a mismatch between the bjects and the relatinal databases as relatinal databases are in the frm f tables which need t be mapped with the bjects f Object Oriented technlgy. S the slutin t avid this mismatch is t prvide Object Relatinal Mapping (ORM) which will create a virtual Object Oriented Database (OOD). Hibernate, an pen surce persistent framewrk prvides an Object Relatinal Mapping fr JAVA. I. Intrductin Hibernate is an pen surce bject/relatinal mapping tl fr Java. Hibernate lets yu develp persistent classes fllwing cmmn Java idim - including assciatin, inheritance, plymrphism, cmpsitin and the Java cllectins framewrk. Hibernate nt nly takes care f the mapping frm Java classes t database tables (and frm Java data types t SQL data types), but als prvides data query and retrieval facilities and can significantly reduce develpment time therwise spent with manual data handling in SQL and JDBC.Hibernates gal is t relieve the develper frm 95 percent f cmmn data persistence related prgramming tasks. Hibernate makes use f persistent bjects cmmnly called as POJO (POJO = "Plain Old Java Object".) alng with XML mapping dcuments fr persisting bjects t the database layer. The term POJO refers t a nrmal Java bjects that des nt serve any ther special rle r implement any special interfaces f any f the Java framewrks (EJB, JDBC, JDO). II. Histry Of Hibernate Hibernate was started in 2001 by Gavin King with clleagues frm Cirrus Technlgies as an alternative t using EJB2-style entity beans. Its riginal gal was t ffer better persistence capabilities than ffered by EJB2 by simplifying the cmplexities and supplementing missing features. In early 2003, the Hibernate develpment team began Hibernate2 releases, which ffered many significant imprvements ver the first release. JBss, Inc. (nw part f Red Hat) later hired the lead Hibernate develpers in rder t further its develpment. In 2005, Hibernate versin 3.0 was released. Key features included a new Interceptr/Callback architecture, user defined filters, and JDK 5.0 Anntatins (Java's metadata feature). As f 2010, Hibernate 3 (versin and up) was a certified implementatin f the Java Persistence API 2.0 specificatin via a wrapper fr the Cre mdule which prvides cnfrmity with the JSR 317 standard. In Dec 2011, Hibernate Cre Final was released. This includes new features such as multi-tenancy supprt, intrductin f ServiceRegistry (a majr change in hw Hibernate builds and manages "services"), better Sessin pening frm SessinFactry, imprved integratin via rg.hibernate.integratr.spi.integratr and aut discvery, internatinalizatin supprt and message cdes in lgging, and a clearer split between API, SPI and IJIRSE/Vl 3. Iss.2/ Page 25

2 (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering implementatin classes. In Dec 2012, Hibernate ORM Final was released. In 2012, develpment was started n Hibernate 5. III. ORM Overview JDBC stands fr Java Database Cnnectivity and prvides a set f Java API fr accessing the relatinal databases frm Java prgram. These Java APIs enables Java prgrams t execute SQL statements and interact with any SQL cmpliant database. JDBC prvides a flexible architecture t write a database independent applicatin that can run n different platfrms and interact with different DBMS withut any mdificatin. Prs and Cns f JDBC Prs f JDBC Clean and simple SQL prcessing Gd perfrmance with large data Very gd fr small applicatins Simple syntax s easy t learn Cns f JDBC Cmplex if it is used in large prjects Large prgramming verhead Query is DBMS specific Why Object Relatinal Mapping (ORM)? When we wrk with an bject-riented systems, there's a mismatch between the bject mdel and the relatinal database. RDBMSs represent data in a tabular frmat whereas bject-riented languages, such as Java r C# represent it as an intercnnected graph f bjects. First prblem, what if we need t mdify the design f ur database after having develped few pages r ur applicatin? Secnd, Lading and string bjects in a relatinal database expses us t the fllwing five mismatch prblems impedance mismatches prblem is ccurred. Mismatch 1) Granularity Smetimes yu will have an bject mdel which has mre classes than the number f crrespnding tables in the database. 2) Inheritance RDBMSs d nt define anything similar t Inheritance which is a natural paradigm in bject-riented prgramming languages. 3) Identity A RDBMS defines exactly ne ntin f 'sameness': the primary key. Java, hwever, defines bth bject identity (a==b) and bject equality (a.equals(b)). 4) Assciatins Object-riented languages represent assciatins using bject references where as a RDBMS represents an assciatin as a freign key clumn. 5) Navigatin The ways yu access bjects in Java and in a RDBMS are fundamentally different. The Object-Relatinal Mapping (ORM) is the slutin t handle all the abve impedance mismatches. What is ORM? IJIRSE/Vl 3. Iss.2/ Page 26

(IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering ORM stands fr Object-Relatinal Mapping (ORM) is a prgramming technique fr cnverting data between relatinal databases and

3 (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering ORM stands fr Object-Relatinal Mapping (ORM) is a prgramming technique fr cnverting data between relatinal databases and bject riented prgramming languages such as Java, C# etc. An ORM system has fllwing advantages. Hides details f SQL queries frm OO lgic. Transactin management and autmatic key generatin Fast develpment f applicatin. Let s business cde access bjects rather than DB tables. IV. Architecture Hibernate The Hibernate architecture is layered t keep yu islated frm having t knw the underlying APIs. Hibernate makes use f the database and cnfiguratin data t prvide persistence services (and persistent bjects) t the applicatin. Fllwing is a detailed view f the Hibernate Applicatin Architecture with few imprtant cre classes. 3 Hibernate uses varius existing Java APIs, like JDBC, Java Transactin API(JTA), and Java Naming and Directry Interface (JNDI). JDBC prvides a rudimentary level f abstractin f functinality cmmn t relatinal databases, allwing almst any database with a JDBC driver t be supprted by Hibernate. JNDI and JTA allw Hibernate t be integrated with J2EE applicatin servers. Fllwing sectin gives brief descriptin f each f the class bjects invlved in Hibernate Applicatin Architecture. Cnfiguratin Object The Cnfiguratin bject is the first Hibernate bject yu create in any Hibernate applicatin and usually created nly nce during applicatin initializatin. It represents a cnfiguratin r prperties file required by the Hibernate. Database Cnnectin: This is handled thrugh ne r mre cnfiguratin files supprted by Hibernate. These files are hibernate.prpertiesand hibernate.cfg.xml. creates the cnnectin between the Java classes and database tables. SessinFactry Object Cnfiguratin bject is used t create a SessinFactrybject which inturn cnfigures Hibernate fr the applicatin using the supplied cnfiguratin file and allws fr a Sessin bject t be instantiated. The SessinFactryis a thread safe bject and used by all the threads f an applicatin. The SessinFactryis heavy weight bject s usually it is created during applicatin start up and kept fr later use. Yu wuld need ne SessinFactrybject per database using a separate cnfiguratin file. S if yu are using multiple databases then yu wuld have t create multiple SessinFactrybjects. Sessin Object a Sessin is used t get a physical cnnectin with a database. The Sessin bject is light weight and designed t be instantiated each time an interactin is needed with the database. Persistent bjects are saved and retrieved thrugh a Sessin bject. The sessin bjects shuld nt be kept pen fr a lng time because they are nt usually thread safe and they shuld be created and destryed them as needed. Transactin Object A Transactin represents a unit f wrk with the database and mst f the RDBMS supprts transactin functinality. Transactins in Hibernate are handled by an underlying transactin manager and transactin (frm JDBC r JTA). This is an ptinal bject and Hibernate applicatins may chse nt t use this interface, instead managing transactins in their wn applicatin cde. Query Object Query bjects IJIRSE/Vl 3. Iss.2/ Page 27

4 (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering use SQL r Hibernate Query Language (HQL) string t retrieve data frm the database and create bjects. A Query instance is used t bind query parameters, limit the number f results returned by the query, and finally t execute the query. Criteria Object Criteria bject are used t create and execute bject riented criteria queries t retrieve bjects. V. Hibernate Mapping An Object/relatinal mappings are usually defined in an XML dcument. This mapping file instructs Hibernate hw t map the defined class r classes t the database tables. Thugh many Hibernate users chse t write the XML by hand, a number f tls exist t generate the mapping dcument. These include XDclet, Middlegen and AndrMDA fr advanced Hibernate users. public class Emplyee { private int id; private String firstname; private String lastname; private int salary; public Emplyee() { public Emplyee(String fname, String lname, int salary) { this.firstname = fname; this.lastname = lname; this.salary = salary; public int getid() { return id; public vid setid( int id ) { this.id = id; public String getfirstname() { return firstname; public vid setfirstname( String first_name ) { this.firstname = first_name; public String getlastname() { return lastname; public vid setlastname( String last_name ) { this.lastname = last_name; public int getsalary() { return salary; IJIRSE/Vl 3. Iss.2/ Page 28

5 public vid setsalary( int salary ) { this.salary = salary; (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering There wuld be ne table crrespnding t each bject yu are willing t prvide persistence. Cnsider abve bjects need t be stred and retrieved int the fllwing RDBMS table: create table EMPLOYEE ( id INT NOT NULL aut_increment, first_name VARCHAR(20) default NULL, last_name VARCHAR(20) default NULL, salary INT default NULL, PRIMARY KEY (id) ); Based n the tw abve entities we can define fllwing mapping file which instructs Hibernate hw t map the defined class r classes t the database tables. <?xml versin="1.0" encding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" " <hibernate-mapping> <class name="emplyee" table="employee"> <meta attribute="class-descriptin"> This class cntains the emplyee detail. </meta> <id name="id" type="int" clumn="id"> <generatr class="native"/> </id> <prperty name="firstname" clumn="first_name" type="string"/> <prperty name="lastname" clumn="last_name" type="string"/> <prperty name="salary" clumn="salary" type="int"/> </class> </hibernate-mapping> Yu shuld save the mapping dcument in a file with the frmat <classname>.hbm.xml. We saved ur mapping dcument in the file Emplyee.hbm.xml. Let us see little detail abut the mapping elements used in the mapping file: The mapping dcument is an XML dcument having <hibernate-mapping> as the rt element which cntains all the <class> elements. The <class> elements are used t define specific mappings frm a Java classes t the database tables. The Java class name is specified using the name attribute f the class element and the database table name is specified using the table attribute. IJIRSE/Vl 3. Iss.2/ Page 29

6 (IJIRSE) Internatinal Jurnal f Innvative Research in Science & Engineering The <meta> element is ptinal element and can be used t create the class descriptin. The <id> element maps the unique ID attribute in class t the primary key f the database table. The name attribute f the id element refers t the prperty in the class and the clumn attribute refers t the clumn in the database table. The type attribute hlds the hibernate mapping type, this mapping types will cnvert frm Java t SQL data type. The <generatr> element within the id element is used t autmatically generate the primary key values. Set the class attribute f the generatr element is set t native t let hibernate pick up either identity, sequence t create primary key depending upn the capabilities f the underlying database. The <prperty> element is used t map a Java class prperty t a clumn in the database table. The name attribute f the element refers t the prperty in the class and the clumn attribute refers t the clumn in the database table. The type attribute hlds the hibernate mapping type, this mapping types will cnvert frm Java t SQL data type. VI. Advantages Of Hibernate Hibernate takes care f mapping Java classes t database tables using XML files. Prvides simple APIs fr string and retrieving Java bjects directly t and frm the database. If there is change in Database r in any table then the nly need t change XML file prperties. Abstract away the unfamiliar SQL types and prvide us t wrk arund familiar Java Objects. A real gd Caching Mechanism fr faster retrieval f data. Yur applicatin supprt almst relatinal databases. Cnclusin Hibernate is an Object-relatinal mapping (ORM) tl. Object-relatinal mapping r ORM is a prgramming methd fr mapping the bjects t the relatinal mdel where entities/classes are mapped t tables, instances are mapped t rws and attributes f instances are mapped t clumns f table. Hibernate is persistence framewrk which is used t persist data frm Java envirnment t database. Thus Virtual bject Oriented database is created. References [1] Bhushan S. Sapre, Rhan V. Thakare, Santsh V. Kakade, Dr. B. B. Mesh ram, Design and Applicatin f the Hibernate Persistence Layer Data Reprt System using JasperReprts, (IJEIT)Vlume 1, Issue 5, May 2012 [2] [3] [4] [5] IJIRSE/Vl 3. Iss.2/ Page 30

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