Hibernate composite-id or multiple primary keys concept in hibernate

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<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <!-- <session-factory> <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property> hibernate word is optional <property name="connection.url">jdbc:oracle:thin:@localhost:1521:ORCL</property> <property name="hibernate.connection.username">kcv</property> <property name="hibernate.connection.password">kcv</property> <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property> <property name="show_sql">true</property> <mapping resource="Employee.hbm.xml"/> </session-factory> --> <session-factory> <property name="hibernate.current_session_context_class">thread</property> <property name="hbm2ddl.auto">create</property> <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property> <property name="connection.url">jdbc:postgresql://localhost:5432/hibernate</property> <property name="connection.username">postgres</property> <property name="connection.password">password</property> <property name="connection.driver_class">org.postgresql.Driver</property> <property name="show_sql">true</property> <property name="format_sql">true</property> <property name="use_sql_comments">true</property> <mapping resource="Certificate.hbm.xml" /> </session-factory> </hibernate-configuration>

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.cv.hibernate.composite.model"> <class name="Employee" table="COMPOSITE_EMPLOYEE_SET" > <id name="id" type="int" column="id"> <generator class="native" /> </id> <set name="certificates" cascade="all"> <key column="eid" /> <one-to-many class="Certificate"/> </set> <property name="firstName" column="first_name" type="string" /> <property name="lastName" column="last_name" type="string" /> <property name="salary" column="salary" type="int" /> </class> </hibernate-mapping>

package com.cv.hibernate.composite; import java.util.HashSet; import org.apache.log4j.Logger; import org.hibernate.Session; import org.hibernate.Transaction; import com.cv.hibernate.composite.model.Certificate; import com.cv.hibernate.composite.model.Employee; import com.cv.hibernate.composite.util.HibernateUtil; /**  * @author Chandra Vardhan  */ public class CompositeIdTest {   private final static Logger logger = Logger.getLogger(CompositeIdTest.class);   public static void main(String[] args) {     Session session = HibernateUtil.getSession();     Transaction tx = session.beginTransaction();     HashSet<Certificate> set1 = new HashSet<Certificate>();     set1.add(new Certificate(1, "MTECH"));     set1.add(new Certificate(2, "BTECH"));     Employee employee = new Employee("CV", "KODAM", 405);     employee.setCertificates(set1);     session.saveOrUpdate(employee);     logger.info("Saved successfully...");     tx.commit();     HibernateUtil.closeSession();   } }

package com.cv.hibernate.composite.model; import java.io.Serializable; /**  * @author Chandra Vardhan  */ public class Certificate implements Serializable {   private int id;   private String name;   public Certificate() {   }   public Certificate(String name) {     this.name = name;   }   public Certificate(int i, String name) {     this.id =i;     this.name = name;   }   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 boolean equals(Object obj) {     if (obj == null)       return false;     if (!this.getClass().equals(obj.getClass()))       return false;     Certificate obj2 = (Certificate) obj;     if ((this.id == obj2.getId()) && (this.name.equals(obj2.getName()))) {       return true;     }     return false;   }   public int hashCode() {     int tmp = 0;     tmp = (id + name).hashCode();     return tmp;   } }

package com.cv.hibernate.composite.model; import java.io.Serializable; import java.util.Set; /**  * @author Chandra Vardhan  */ public class Employee  implements Serializable{   private int id;   private String firstName;;   private String lastName;   private int salary;   private Set<Certificate> certificates;   public Employee() {   }   public Employee(String fname, String lname, int salary) {     this.firstName = fname;     this.lastName = lname;     this.salary = salary;   }   public int getId() {     return id;   }   public void setId(int id) {     this.id = id;   }   public String getFirstName() {     return firstName;   }   public void setFirstName(String first_name) {     this.firstName = first_name;   }   public String getLastName() {     return lastName;   }   public void setLastName(String last_name) {     this.lastName = last_name;   }   public int getSalary() {     return salary;   }   public void setSalary(int salary) {     this.salary = salary;   }   public Set<Certificate> getCertificates() {     return certificates;   }   public void setCertificates(Set<Certificate> certificates) {     this.certificates = certificates;   } }

package com.cv.hibernate.composite.util; import org.apache.log4j.Logger; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; /**  * Configures and provides access to Hibernate sessions, tied to the current  * thread of execution. Follows the Thread Local Session pattern, see  * {@link http://hibernate.org/42.html }.  */ public class HibernateUtil {   private final static Logger logger = Logger.getLogger(HibernateUtil.class);   /**    * Location of hibernate.cfg.xml file. Location should be on the classpath    * as Hibernate uses #resourceAsStream style lookup for its configuration    * file. The default classpath location of the hibernate config file is in    * the default package. Use #setConfigFile() to update the location of the    * configuration file for the current session.    */   private static String CONFIG_FILE_LOCATION = "hibernate.cfg.xml";   private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();   private static Configuration configuration = new Configuration();   private static SessionFactory sessionFactory;   static {     try {       configuration = configuration.configure(CONFIG_FILE_LOCATION);       StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()           .applySettings(configuration.getProperties());       sessionFactory = configuration.buildSessionFactory(builder.build());       logger.info("%%%% Connection successful %%%%");     } catch (Exception e) {       logger.error("%%%% Error Creating SessionFactory %%%%");       e.printStackTrace();     }   }   private HibernateUtil() {   }   /**    * Returns the ThreadLocal Session instance. Lazy initialize the    * <code>SessionFactory</code> if needed.    *    * @return Session    * @throws HibernateException    */   public static Session getSession() throws HibernateException {     Session session = (Session) threadLocal.get();     if (session == null || !session.isOpen()) {       if (sessionFactory == null) {         rebuildSessionFactory();       }       session = (sessionFactory != null) ? sessionFactory.openSession() : null;       threadLocal.set(session);     }     return session;   }   /**    * Rebuild hibernate session factory    *    */   public static void rebuildSessionFactory() {     try {       configuration = configuration.configure(CONFIG_FILE_LOCATION);       StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()           .applySettings(configuration.getProperties());       sessionFactory = configuration.buildSessionFactory(builder.build());       logger.info("%%%% Connection successful %%%%");     } catch (Exception e) {       logger.error("%%%% Error Creating SessionFactory %%%%");       e.printStackTrace();     }   }   /**    * Close the single hibernate session instance.    *    * @throws HibernateException    */   public static void closeSession() throws HibernateException {     Session session = (Session) threadLocal.get();     threadLocal.set(null);     if (session != null) {       session.close();       System.exit(0);     }   }   /**    * return session factory    *    */   public static SessionFactory getSessionFactory() {     return sessionFactory;   }   /**    * return hibernate configuration    *    */   public static Configuration getConfiguration() {     return configuration;   } }

#By default enabling Console appender # Root logger option log4j.rootLogger=INFO, stdout # Redirect log messages to console log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target=System.out log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%-5p [%c]:%L -->> %m%n # Redirect log messages to a log file #log4j.appender.file=org.apache.log4j.RollingFileAppender #log4j.appender.file.File=C:\\servlet-application.log #log4j.appender.file.MaxFileSize=5MB #log4j.appender.file.MaxBackupIndex=10 #log4j.appender.file.layout=org.apache.log4j.PatternLayout #log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.cv.hibernate.composite</groupId> <artifactId>HibernateCompositeIdwithMultipleKey</artifactId> <version>1.0</version> <dependencies> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>4.3.5.Final</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-c3p0</artifactId> <version>4.3.5.Final</version> </dependency> <dependency> <artifactId>hibernate-core</artifactId> <groupId>org.hibernate</groupId> <version>4.3.5.Final</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>4.2.0.Final</version> </dependency> <dependency> <groupId>org.hibernate.common</groupId> <artifactId>hibernate-commons-annotations</artifactId> <version>4.0.4.Final</version> </dependency> <dependency> <groupId>org.hibernate.javax.persistence</groupId> <artifactId>hibernate-jpa-2.0-api</artifactId> <version>1.0.1.Final</version> </dependency> <dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>1.0.0.GA</version> provided </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.6.4</version> </dependency> <dependency> <groupId>org.jboss.logging</groupId> <artifactId>jboss-logging</artifactId> <version>3.1.0.CR2</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.6.4</version> </dependency> <dependency> <groupId>postgresql</groupId> <artifactId>postgresql</artifactId> <version>9.1-901.jdbc4</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>1.7.5</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.3</version> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> </plugins> </build> </project>