@MappedSuperclass
public class BaseEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "id", nullable = false)
    private long id;

    @UpdateTimestamp @Column(name = "update_timestamp", nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    private Date updateTimestamp;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public Date getUpdateTimestamp() {
        return updateTimestamp;
    }

    public void setUpdateTimestamp(Date updateTimestamp) {
        this.updateTimestamp = updateTimestamp;
    }
}

@Entity @Table(name = "USER_ACCOUNT")
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
@AttributeOverride(name = "id", column = @Column(name="user_id"))
public class UserAccount extends BaseEntity {
    private static final long serialVersionUID = 1234567890L;

    @Column(name = "username", unique = true)   //username has to be unique
    private String username;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @Column(name = "age")
    private int age;

    @Column(name = "gender")
    private String gender;

    @Column(name = "password")
    private String password;

    @OneToMany(mappedBy = "userAccountRolePk.role", cascade = CascadeType.ALL)
    private Set<UserAccountRole> userAccountRoles = new HashSet<>();

    public Set<UserAccountRole> getUserAccountRoles() {
        return userAccountRoles;
    }

    public void setUserAccountRoles(Set<UserAccountRole> r) {
        this.userAccountRoles = r;
    }

    public void addUserAccountRoles(UserAccountRole r) {
        this.userAccountRoles.add(r);
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }
}

@Entity
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
@AttributeOverride(name = "id", column = @Column(name="role_id"))
public class Role extends BaseEntity {
    private static final long serialVersionUID = 1234567893L;

    @Column(name = "name")
    private String name;

    @Column(name = "description")
    private String description;

    /* if true, then cannot be updated by users or rest api */
    @Column(name = "immutable")
    private boolean immutable;

    @OneToMany(mappedBy = "rolePriviledgePk.role", cascade = CascadeType.ALL)
    private Set<RolePriviledge> rolePriviledges = new HashSet<>();

    public Set<RolePriviledge> getRolePriviledges() {
        return rolePriviledges;
    }

    public void setRolePriviledges(Set<RolePriviledge> rolePriviledges) {
        this.rolePriviledges = rolePriviledges;
    }

    public void addRolePriviledges(RolePriviledge rolePriviledge) {
        this.rolePriviledges.add(rolePriviledge);
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public boolean isImmutable() {
        return immutable;
    }

    public void setImmutable(boolean immutable) {
        this.immutable = immutable;
    }

    public static long getSerialversionuid() {
        return serialVersionUID;
    }
}

@Entity
@Table(name = "USERACCOUNT_ROLES")
@AssociationOverrides(
    { @AssociationOverride(name = "userAccountRolePk.userAccount",
        joinColumns = @JoinColumn(name = "USER_ID")),
    @AssociationOverride(name = "userAccountRolePk.role",
        joinColumns = @JoinColumn(name = "ROLE_ID"))
})
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class UserAccountRole extends BaseEntity {
    //composite primary key
    @EmbeddedId
    private UserAccountRolePk userAccountRolePk = new UserAccountRolePk();

    //additional fields if any (updateTimeStamp inherited from BaseEntity)
    private boolean immutable;

    public UserAccountRolePk getUserAccountRolePk() {
        return userAccountRolePk;
    }

    public void setUserAccountRolePk(UserAccountRolePk pk) {
        this.userAccountRolePk = pk;
    }

    @Transient
    public UserAccount getUserAccount() {
        return getUserAccountRolePk().getUserAccount();
    }

    public void setUserAccount(UserAccount u) {
        getUserAccountRolePk().setUserAccount(u);
    }

    @Transient
    public Role getRole() {
        return getUserAccountRolePk().getRole();
    }

    public void setRole(Role p) {
        getUserAccountRolePk().setRole(p);
    }

    public boolean isImmutable() {
        return immutable;
    }

    public void setImmutable(boolean immutable) {
        this.immutable = immutable;
    }
}

@Embeddable
public class UserAccountRolePk {
    @ManyToOne(cascade = CascadeType.ALL)
    private UserAccount userAccount;

    @ManyToOne(cascade = CascadeType.ALL)
    private Role role;

    public Role getRole() {
        return role;
    }

    public void setRole(Role role) {
        this.role = role;
    }

    public UserAccount getUserAccount() {
        return userAccount;
    }

    public void setUserAccount(UserAccount x) {
        this.userAccount = x;
    }

    public boolean equals(Object o) {
        if(o == null || o.getClass() != this.getClass()) {
            return false;
        }

        UserAccountRolePk pk = (UserAccountRolePk) o;
        if(this.getRole().equals(pk.getRole()) && this.getUserAccount().equals(pk.getUserAccount())) {
            return true;
        }

        return false;
    }

    public int hashCode() {
        return new Long(this.getRole().getId() + this.getUserAccount().getId()).hashCode();
    }
}

java.lang.IllegalArgumentException: This class [class demo.rbacapp.entity.UserAccountRole] does not define an IdClass
    at org.hibernate.jpa.internal.metamodel.AbstractIdentifiableType.getIdClassAttributes (AbstractIdentifiableType.java:183)
    at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation$IdMetadata.<init> (JpaMetamodelEntityInformation.java:253)
    at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation.<init> (JpaMetamodelEntityInformation.java:84)
    at org.springframework.data.jpa.repository.support.JpaEntityInformationSupport.getEntityInformation (JpaEntityInformationSupport.java:68)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getEntityInformation (JpaRepositoryFactory.java:173)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository (JpaRepositoryFactory.java:106)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository (JpaRepositoryFactory.java:88)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository (RepositoryFactorySupport.java:198)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn (RepositoryFactoryBeanSupport.java:277)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet (RepositoryFactoryBeanSupport.java:263)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet (JpaRepositoryFactoryBean.java:101)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods (AbstractAutowireCapableBeanFactory.java:1687)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean (AbstractAutowireCapableBeanFactory.java:1624)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:555)