SortedSet can be viewed in a group of elements and they do not have a duplicate element and ascending order is maintained in its elements. By using <set> elements we can use them and the entity should have a Sortedset of values. As an example, we can have a freelancer who works for multiple companies on a shift basis. Here also the one-to-many relationship is seen as a freelancer can belong to multiple (many) companies.
Example Project
Project Structure:
This is a maven project. Let us see pom.xml
pom.xml
XML
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 <modelVersion>4.0.0</modelVersion> <groupId>HibernateSortedSetMapping</groupId> <artifactId>HibernateSortedSetMapping</artifactId> <version>0.0.1-SNAPSHOT</version> <build> <sourceDirectory>src</sourceDirectory> <resources> <resource> <directory>src</directory> <excludes> <exclude>**/*.java</exclude> </excludes> </resource> </resources> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <release>9</release> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>5.4.15.Final</version> </dependency> <!-- As we are connecting with MySQL, this is needed --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.34</version> </dependency> </dependencies> <properties> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> </properties></project> |
Let us start with POJO classes
Freelancer.java
Java
import java.util.SortedSet;public class Freelancer { // data members private int freelancerId; private String freelancerName; private int freelancerAge; private int pricePerHour; // As one freelancer works for multiple companies, let // us have that as SortedSet here for companies private SortedSet companies; public int getFreelancerId() { return freelancerId; } public void setFreelancerId(int freelancerId) { this.freelancerId = freelancerId; } public String getFreelancerName() { return freelancerName; } public void setFreelancerName(String freelancerName) { this.freelancerName = freelancerName; } public int getFreelancerAge() { return freelancerAge; } public void setFreelancerAge(int freelancerAge) { this.freelancerAge = freelancerAge; } public int getPricePerHour() { return pricePerHour; } public void setPricePerHour(int pricePerHour) { this.pricePerHour = pricePerHour; } public SortedSet getCompanies() { return companies; } public void setCompanies(SortedSet companies) { this.companies = companies; } // no argument constructor public Freelancer() {} // argument constructor public Freelancer(String freelancerName, int freelancerAge, int pricePerHour) { this.freelancerName = freelancerName; this.freelancerAge = freelancerAge; this.pricePerHour = pricePerHour; }} |
Company.java
Java
public class Company implements Comparable<Company> { private int companyId; private String companyName; public int getCompanyId() { return companyId; } public void setCompanyId(int companyId) { this.companyId = companyId; } public String getCompanyName() { return companyName; } public void setCompanyName(String companyName) { this.companyName = companyName; } public Company(String companyName) { this.companyName = companyName; } public Company() {} @Override // This method has to be implemented as we are following // SortedSet public int compareTo(Company company) { if (company == null) { return -1; } Comparable company1 = this.getCompanyName(); Comparable company2 = company.getCompanyName(); if (company1 == null) { return 1; } else if (company2 == null) { return -1; } else { return company1.compareTo(company2); } }} |
Let us see the configuration files
hibernate.cfg.xml
XML
<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"<hibernate-configuration> <session-factory> <!-- As we are connecting mysql, those driver classes, database name, username and password are specified Please change the information as per your requirement --> <!-- This property creates table in MySQL automatically according to the specifications given in mapping resource file which in turn maps to the POJO class --> <property name="hbm2ddl.auto">update</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.username">root</property> <property name="connection.password">admin</property> <!-- Helps to show the correct sql for each and every hibernate operation --> <property name="show_sql">true</property> <!-- We are going to connect language.hbm.xml and book.hbm.xml which has the table information about programmingLanguages and book which is present in mysql --> <mapping resource="freelancer.hbm.xml"/> <mapping resource="company.hbm.xml"/> </session-factory></hibernate-configuration> |
freelancer.hbm.xml
XML
<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE hibernate-mapping SYSTEM<hibernate-mapping> <!-- In MySQL, 'freelancer' table is created if it is not there and it should have 4 attributes namely freelancerId, freelancerName, freelancerAge and pricePerHour --> <class name="com.gfg.sortedsetmapping.pojo.Freelancer" table="freelancer"> <id name="freelancerId" type="int" column="freelancerId"> <generator class="native"></generator> </id> <property name="freelancerName" column="freelancerName" type="string"/> <property name="freelancerAge" column="freelancerAge" type="int"/> <property name="pricePerHour" column="pricePerHour" type="int"/> <!-- We are following SortedSet Pattern. Hence should provide 'set' and also 'sort' nature Here one to many relationship is followed and it denote a key column as well --> <set name="companies" cascade="all" sort="natural"> <key column="freelancerId"/> <one-to-many class="com.gfg.sortedsetmapping.pojo.Company"/> </set> </class> </hibernate-mapping> |
company.hbm.xml
XML
<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE hibernate-mapping SYSTEM <!-- In MySQL, 'company' table is created if it is not there and it should have 2 attributes namely companyId and companyName --><hibernate-mapping> <class name="com.gfg.sortedsetmapping.pojo.Company" table="company"> <id name="companyId" type="int" column="companyId"> <generator class="native"></generator> </id> <property name="companyName" column="companyName" type="string"></property> </class> </hibernate-mapping> |
SortedSetMappingPatternOfStoringData.java
Java
import com.gfg.sortedsetmapping.pojo.Company;import com.gfg.sortedsetmapping.pojo.Freelancer;import java.util.List;import java.util.Set;import java.util.TreeSet;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;public class SortedSetMappingPatternOfStoringData { private static SessionFactory factory; public static void main(String[] args) { try { factory = new Configuration() .configure() .buildSessionFactory(); } catch (Throwable ex) { System.err.println( "Failed to create sessionFactory object." + ex); throw new ExceptionInInitializerError(ex); } // As one freelancer works for multiple companies, // via TreeSet we can represent that TreeSet companySet1 = new TreeSet(); companySet1.add(new Company("Company A")); companySet1.add(new Company("Company B")); TreeSet companySet2 = new TreeSet(); companySet2.add(new Company("Company A")); companySet2.add(new Company("Company C")); companySet2.add(new Company("Company E")); // Create the Freelancer object. Freelancer freelancer1 = new Freelancer("Freelancer A", 20, 1000); freelancer1.setCompanies( companySet1); // Freelancer A associated to 2 // companies Freelancer freelancer2 = new Freelancer("Freelancer B", 20, 2000); freelancer2.setCompanies( companySet2); // Freelancer B associated to 2 // companies SortedSetMappingPatternOfStoringData sortedMapMappingPatternOfStoringData = new SortedSetMappingPatternOfStoringData(); // insert freelancer object. Integer freelancerId1 = sortedMapMappingPatternOfStoringData .addFreelancer(freelancer1); Integer freelancerId2 = sortedMapMappingPatternOfStoringData .addFreelancer(freelancer2); // show all Language and book details object. sortedMapMappingPatternOfStoringData .listFreelancerAndCompanyDetails(); } public Integer addFreelancer(Freelancer freelancer) { Session session = factory.openSession(); Transaction tx = null; Integer languageId = null; try { tx = session.beginTransaction(); languageId = (Integer)session.save(freelancer); tx.commit(); } catch (HibernateException e) { if (tx != null) tx.rollback(); e.printStackTrace(); } finally { session.close(); } return languageId; } // Method to list all the freelancers and company detail public void listFreelancerAndCompanyDetails() { Session session = factory.openSession(); Transaction tx = null; try { tx = session.beginTransaction(); List<Freelancer> freelancers = session.createQuery("FROM Freelancer") .list(); for (Freelancer freelancer : freelancers) { System.out.println( "Freelancer Name: " + freelancer.getFreelancerName()); System.out.println( "Freelancer Age: " + freelancer.getFreelancerAge()); System.out.println( "Price Per Hour: " + freelancer.getPricePerHour()); Set<Company> companies = freelancer.getCompanies(); for (Company company : companies) { System.out.println( "Company Name:" + company.getCompanyName()); } } tx.commit(); } catch (HibernateException e) { if (tx != null) tx.rollback(); e.printStackTrace(); } finally { session.close(); } }} |
On execution of the project.
Output:
Conclusion
The one-to-many relationship can be easily depicted via SortedSet and from the output, it is proved that no duplicate elements and ascending order is maintained in the output.
