JPA One-To-One Association Tutorial

Issue: BAEL-2394

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/HibernateUtil.java

@@ -0,0 +1,38 @@
+package com.baeldung.hibernate.onetoone;
+
+import org.hibernate.SessionFactory;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.service.ServiceRegistry;
+
+public class HibernateUtil {
+    private static SessionFactory sessionFactory;
+
+    private static SessionFactory buildSessionFactory(Strategy strategy) {
+        try {
+            // Create the SessionFactory from hibernate-annotation.cfg.xml
+            Configuration configuration = new Configuration();
+
+            for (Class<?> entityClass : strategy.getEntityClasses()) {
+                configuration.addAnnotatedClass(entityClass);
+            }
+            configuration.configure("one-to-one.cfg.xml");
+
+            ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties())
+                    .build();
+
+            SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
+
+            return sessionFactory;
+        } catch (Throwable ex) {
+            ex.printStackTrace();
+            throw new ExceptionInInitializerError(ex);
+        }
+    }
+
+    public static SessionFactory getSessionFactory(Strategy strategy) {
+        if (sessionFactory == null)
+            sessionFactory = buildSessionFactory(strategy);
+        return sessionFactory;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/Strategy.java

@@ -0,0 +1,25 @@
+package com.baeldung.hibernate.onetoone;
+
+
+import java.util.Arrays;
+import java.util.List;
+
+public enum Strategy {
+    //See that the classes belongs to different packages
+    FOREIGN_KEY(Arrays.asList(com.baeldung.hibernate.onetoone.foreignkeybased.User.class,
+            com.baeldung.hibernate.onetoone.foreignkeybased.Address.class)),
+    SHARED_PRIMARY_KEY(Arrays.asList(com.baeldung.hibernate.onetoone.sharedkeybased.User.class,
+            com.baeldung.hibernate.onetoone.sharedkeybased.Address.class)),
+    JOIN_TABLE_BASED(Arrays.asList(com.baeldung.hibernate.onetoone.jointablebased.Employee.class,
+            com.baeldung.hibernate.onetoone.jointablebased.WorkStation.class));
+
+    private List<Class<?>> entityClasses;
+
+    Strategy(List<Class<?>> entityClasses) {
+        this.entityClasses = entityClasses;
+    }
+
+    public List<Class<?>> getEntityClasses() {
+        return entityClasses;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/foreignkeybased/Address.java

@@ -0,0 +1,60 @@
+package com.baeldung.hibernate.onetoone.foreignkeybased;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "address")
+public class Address {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "street")
+    private String street;
+
+    @Column(name = "city")
+    private String city;
+
+    @OneToOne(mappedBy = "address")
+    private User user;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public User getUser() {
+        return user;
+    }
+
+    public void setUser(User user) {
+        this.user = user;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/foreignkeybased/User.java

@@ -0,0 +1,51 @@
+package com.baeldung.hibernate.onetoone.foreignkeybased;
+
+import javax.persistence.CascadeType;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "users")
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "username")
+    private String userName;
+
+    @OneToOne(cascade = CascadeType.ALL)
+     @JoinColumn(name = "address_id", referencedColumnName = "id")
+    private Address address;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getUserName() {
+        return userName;
+    }
+
+    public void setUserName(String userName) {
+        this.userName = userName;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/jointablebased/Employee.java

@@ -0,0 +1,53 @@
+package com.baeldung.hibernate.onetoone.jointablebased;
+
+import javax.persistence.CascadeType;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.JoinTable;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "employee")
+public class Employee {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "ename")
+    private String name;
+
+    @OneToOne(cascade = CascadeType.ALL)
+    @JoinTable(name = "emp_workstation", joinColumns = {@JoinColumn(name = "employee_id", referencedColumnName = "id")},
+            inverseJoinColumns = {@JoinColumn(name = "workstation_id", referencedColumnName = "id")})
+    private WorkStation workStation;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public WorkStation getWorkStation() {
+        return workStation;
+    }
+
+    public void setWorkStation(WorkStation workStation) {
+        this.workStation = workStation;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/jointablebased/WorkStation.java

@@ -0,0 +1,61 @@
+package com.baeldung.hibernate.onetoone.jointablebased;
+
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "workstation")
+public class WorkStation {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "workstation_number")
+    private Integer workstationNumber;
+
+    @Column(name = "floor")
+    private String floor;
+
+    @OneToOne(mappedBy = "workStation")
+    private Employee employee;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public Integer getWorkstationNumber() {
+        return workstationNumber;
+    }
+
+    public void setWorkstationNumber(Integer workstationNumber) {
+        this.workstationNumber = workstationNumber;
+    }
+
+    public String getFloor() {
+        return floor;
+    }
+
+    public void setFloor(String floor) {
+        this.floor = floor;
+    }
+
+    public Employee getEmployee() {
+        return employee;
+    }
+
+    public void setEmployee(Employee employee) {
+        this.employee = employee;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/sharedkeybased/Address.java

@@ -0,0 +1,60 @@
+package com.baeldung.hibernate.onetoone.sharedkeybased;
+
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.MapsId;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "address")
+public class Address {
+
+    @Id
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "street")
+    private String street;
+
+    @Column(name = "city")
+    private String city;
+
+    @OneToOne
+    @MapsId
+    private User user;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public User getUser() {
+        return user;
+    }
+
+    public void setUser(User user) {
+        this.user = user;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/hibernate/onetoone/sharedkeybased/User.java

@@ -0,0 +1,50 @@
+package com.baeldung.hibernate.onetoone.sharedkeybased;
+
+
+import javax.persistence.CascadeType;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.OneToOne;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "users")
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "username")
+    private String userName;
+
+    @OneToOne(mappedBy = "user", cascade = CascadeType.ALL)
+    private Address address;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getUserName() {
+        return userName;
+    }
+
+    public void setUserName(String userName) {
+        this.userName = userName;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+}

persistence-modules/spring-hibernate-5/src/main/resources/one-to-one.cfg.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE hibernate-configuration PUBLIC
+        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
+        "http://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
+<hibernate-configuration>
+    <session-factory>
+        <property name="hibernate.connection.driver_class">org.h2.Driver</property>
+        <property name="hibernate.connection.password"></property>
+        <property name="hibernate.connection.url">jdbc:h2:mem:spring_hibernate_one_to_one</property>
+        <property name="hibernate.connection.username">sa</property>
+        <property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property>
+        <property name="hibernate.current_session_context_class">thread</property>
+        <property name="hibernate.show_sql">true</property>
+        <property name="hibernate.hbm2ddl.auto">create-drop</property>
+    </session-factory>
+</hibernate-configuration>

persistence-modules/spring-hibernate-5/src/test/java/com/baeldung/hibernate/onetoone/HibernateOneToOneAnnotationFKBasedIntegrationTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.hibernate.onetoone;
+
+import com.baeldung.hibernate.onetoone.foreignkeybased.Address;
+import com.baeldung.hibernate.onetoone.foreignkeybased.User;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class HibernateOneToOneAnnotationFKBasedIntegrationTest {
+
+    private static SessionFactory sessionFactory;
+
+    private Session session;
+
+    @BeforeClass
+    public static void beforeTests() {
+        sessionFactory = HibernateUtil.getSessionFactory(Strategy.FOREIGN_KEY);
+    }
+
+    @Before
+    public void setUp() {
+        session = sessionFactory.openSession();
+        session.beginTransaction();
+    }
+
+    @Test
+    public void givenData_whenInsert_thenCreates1to1relationship() {
+        User user = new User();
+        user.setUserName("alice@baeldung.com");
+
+        Address address = new Address();
+        address.setStreet("FK Street");
+        address.setCity("FK City");
+
+        address.setUser(user);
+        user.setAddress(address);
+
+        //Address entry will automatically be created by hibernate, since cascade type is specified as ALL
+        session.persist(user);
+        session.getTransaction().commit();
+
+        assert1to1InsertedData();
+    }
+
+    private void assert1to1InsertedData() {
+        @SuppressWarnings("unchecked")
+        List<User> userList = session.createQuery("FROM User").list();
+
+        assertNotNull(userList);
+        assertEquals(1, userList.size());
+
+        User user = userList.get(0);
+        assertEquals("alice@baeldung.com", user.getUserName());
+
+        Address address = user.getAddress();
+        assertNotNull(address);
+        assertEquals("FK Street", address.getStreet());
+        assertEquals("FK City", address.getCity());
+
+    }
+
+    @After
+    public void tearDown() {
+        session.close();
+    }
+
+    @AfterClass
+    public static void afterTests() {
+        sessionFactory.close();
+    }
+}

persistence-modules/spring-hibernate-5/src/test/java/com/baeldung/hibernate/onetoone/HibernateOneToOneAnnotationJTBasedIntegrationTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.hibernate.onetoone;
+
+import com.baeldung.hibernate.onetoone.jointablebased.Employee;
+import com.baeldung.hibernate.onetoone.jointablebased.WorkStation;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class HibernateOneToOneAnnotationJTBasedIntegrationTest {
+
+    private static SessionFactory sessionFactory;
+
+    private Session session;
+
+    @BeforeClass
+    public static void beforeTests() {
+        sessionFactory = HibernateUtil.getSessionFactory(Strategy.JOIN_TABLE_BASED);
+    }
+
+    @Before
+    public void setUp() {
+        session = sessionFactory.openSession();
+        session.beginTransaction();
+    }
+
+    @Test
+    public void givenData_whenInsert_thenCreates1to1relationship() {
+        Employee employee = new Employee();
+        employee.setName("bob@baeldung.com");
+
+        WorkStation workStation = new WorkStation();
+        workStation.setWorkstationNumber(626);
+        workStation.setFloor("Sixth Floor");
+
+
+        employee.setWorkStation(workStation);
+        workStation.setEmployee(employee);
+
+        session.persist(employee);
+        session.getTransaction().commit();
+
+        assert1to1InsertedData();
+    }
+
+    private void assert1to1InsertedData() {
+        @SuppressWarnings("unchecked")
+        List<Employee> employeeList = session.createQuery("FROM Employee").list();
+        assertNotNull(employeeList);
+        assertEquals(1, employeeList.size());
+
+        Employee employee = employeeList.get(0);
+        assertEquals("bob@baeldung.com", employee.getName());
+
+        WorkStation workStation = employee.getWorkStation();
+
+        assertNotNull(workStation);
+        assertEquals((long) 626, (long) workStation.getWorkstationNumber());
+        assertEquals("Sixth Floor", workStation.getFloor());
+
+    }
+
+    @After
+    public void tearDown() {
+        session.close();
+    }
+
+    @AfterClass
+    public static void afterTests() {
+        sessionFactory.close();
+    }
+}

persistence-modules/spring-hibernate-5/src/test/java/com/baeldung/hibernate/onetoone/HibernateOneToOneAnnotationSPKBasedIntegrationTest.java

@@ -0,0 +1,79 @@
+package com.baeldung.hibernate.onetoone;
+
+import com.baeldung.hibernate.onetoone.sharedkeybased.Address;
+import com.baeldung.hibernate.onetoone.sharedkeybased.User;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class HibernateOneToOneAnnotationSPKBasedIntegrationTest {
+
+    private static SessionFactory sessionFactory;
+
+    private Session session;
+
+    @BeforeClass
+    public static void beforeTests() {
+        sessionFactory = HibernateUtil.getSessionFactory(Strategy.SHARED_PRIMARY_KEY);
+    }
+
+    @Before
+    public void setUp() {
+        session = sessionFactory.openSession();
+        session.beginTransaction();
+    }
+
+    @Test
+    public void givenData_whenInsert_thenCreates1to1relationship() {
+        User user = new User();
+        user.setUserName("alice@baeldung.com");
+
+        Address address = new Address();
+        address.setStreet("SPK Street");
+        address.setCity("SPK City");
+
+        address.setUser(user);
+        user.setAddress(address);
+
+        //Address entry will automatically be created by hibernate, since cascade type is specified as ALL
+        session.persist(user);
+        session.getTransaction().commit();
+
+        assert1to1InsertedData();
+    }
+
+
+    private void assert1to1InsertedData() {
+        @SuppressWarnings("unchecked")
+        List<User> userList = session.createQuery("FROM User").list();
+        assertNotNull(userList);
+        assertEquals(1, userList.size());
+
+        User user = userList.get(0);
+        assertEquals("alice@baeldung.com", user.getUserName());
+
+        Address address = user.getAddress();
+        assertNotNull(address);
+        assertEquals("SPK Street", address.getStreet());
+        assertEquals("SPK City", address.getCity());
+    }
+
+    @After
+    public void tearDown() {
+        session.close();
+    }
+
+    @AfterClass
+    public static void afterTests() {
+        sessionFactory.close();
+    }
+}

persistence-modules/spring-hibernate-5/src/test/resources/one-to-one.cfg.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE hibernate-configuration PUBLIC
+		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
+		"http://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
+<hibernate-configuration>
+    <session-factory>
+        <property name="hibernate.connection.driver_class">org.h2.Driver</property>
+        <property name="hibernate.connection.password"></property>
+        <property name="hibernate.connection.url">jdbc:h2:mem:spring_hibernate_one_to_one</property>
+        <property name="hibernate.connection.username">sa</property>
+        <property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property>
+        <property name="hibernate.current_session_context_class">thread</property>
+        <property name="hibernate.show_sql">true</property>
+        <property name="hibernate.hbm2ddl.auto">create-drop</property>
+    </session-factory>
+</hibernate-configuration>