Spring hibernate ManyToMany with extra fields

[Milan Strahinic]

I'm working on one demo project which has Driver and Licenses connected ManyToMany. Driver can have more licenses and one license can be connected to more drivers. This is not a driver licence. The license I am talking about is connected with the cargo that they can, or cannot transport. That is the way it should be.
Recently, I had one request to add two extra fields in this connection. Driver and License are connected ManyToMany by table Drivers_License. That extra filed goes to Drivers_License and that is expirationDate, and stateIssued.

This is the look of my database now.

Driver                          Driver_License                   License
-----------                     -------------------             --------------------
driverID                         driverID                         licenseID
driverName                       licenseID                        licenseName
driverNumber                     expirationDate    
driverDateOfBirth                stateIssued

The problem is that I need to break ManyToMany connection and create two OneToMany connections. I also need composite key to be made from driverID and licenseID.

This is the example of that I am talking about.
Hibernate Many-to-Many Association with Extra Columns in Join Table Example

Can you tell me if there is some complete example how to finish this using spring and hibernate, or maybe do you know some example that can handle this by using ManyToMany on a classical way?

[Dave Tolls]

The key to this is to get the Driver_License mapping correct.
The Driver and License ones should be easy after that as they will simply be standard OneToMany.

Have you created the composite key?

What does your DriverLicense class look like and maybe we can work through it?

[Milan Strahinic]

Here is my Driver:

@Entity
@Table(name="Driver")
public class Driver {
	
	@Id
	@GeneratedValue
	@Column(name = "driverID")
	private Integer driverID;
	
	private String firstName;
	
	private String	lastName;
	
	private String	middleInitials;
	
	@DateTimeFormat(pattern = "MM/dd/yyyy")
	private Date dateOfBirth;
	
	private String driverNumber;
	
	private String gender;
	
	
	//get & set
	
	public Integer getDriverID() {
		return driverID;
	}

	public void setDriverID(Integer driverID) {
		this.driverID = driverID;
	}

	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 String getMiddleInitials() {
		return middleInitials;
	}

	public void setMiddleInitials(String middleInitials) {
		this.middleInitials = middleInitials;
	}

	public Date getDateOfBirth() {
		return dateOfBirth;
	}

	public void setDateOfBirth(Date dateOfBirth) {
		this.dateOfBirth = dateOfBirth;
	}

	public String getDriverNumber() {
		return driverNumber;
	}

	public void setDriverNumber(String driverNumber) {
		this.driverNumber = driverNumber;
	}
	
	public String getGender() {
		return gender;
	}

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

	
    @ManyToMany(fetch = FetchType.LAZY, cascade=CascadeType.PERSIST)  
    @JoinTable(name="DRIVER_FLEET", 
    			joinColumns= { @JoinColumn(name="driverID")}, 
    			inverseJoinColumns={@JoinColumn(name="fleetID")}) 
	private List<Fleet> fleet = new ArrayList<Fleet>(); 
    public List<Fleet> getFleet() {
        return fleet;
    }
    public void setFleet(List<Fleet> fleet) {
        this.fleet = fleet;
    }
    
	@OneToMany(fetch = FetchType.LAZY, mappedBy = "id.driver", cascade = CascadeType.ALL)
	 private /*transient*/ List<DriverLicense> driverLicense = new ArrayList<DriverLicense>();
	 public List<DriverLicense> getDriverLicense() {
	   return driverLicense;
	 }
	 public void setDriverLicense(List<DriverLicense> driverLicense) {
	   this.driverLicense = driverLicense;
	 }
}

And here is my License:

@Entity
@Table(name="License")
public class License {
	
	@Id
	@GeneratedValue
	@Column(name = "licenseID")
	private Integer licenseID;
	
	@Column(name = "licenseName")
	private String licenseName;
	
	
	public Integer getLicenseID() {
		return licenseID;
	}
	public void setLicenseID(Integer licenseID) {
		this.licenseID = licenseID;
	}
	public String getLicenseName() {
		return licenseName;
	}
	public void setLicenseName(String licenseName) {
		this.licenseName = licenseName;
	} 
	
	@OneToMany(fetch = FetchType.LAZY, mappedBy = "id.license", cascade = CascadeType.ALL)
	private List<DriverLicense> driverLicense = new ArrayList<DriverLicense>();
	
    public List<DriverLicense> getDriverLicense() {
		 return driverLicense;
	}
	
    public void setDriverLicense(List<DriverLicense> driverLicense) {
		 this.driverLicense = driverLicense;
	}
}

Also DriverLicense has composite key so it is from two parts:

DriverLicenseID

@Embeddable
public class DriverLicenseID implements Serializable { 

	private static final long serialVersionUID = 1L;
	
    @ManyToOne
    @JoinColumn(name="driverID")
    private Driver driver;
    public Driver getDriver() {
        return driver;
    }
 
    public void setDriver(Driver driver) {
        this.driver = driver;
    }
 
    @ManyToOne
    private License license;
    public License getLicense() {
        return license;
    }
 
    public void setLicense(License license) {
        this.license = license;
    } 
}

DriverLicense

@Entity
@Table(name="DRIVER_LICENSE")
@AssociationOverrides({
    @AssociationOverride(name = "id.driver",
        joinColumns = @JoinColumn(name = "driverID")),
    @AssociationOverride(name = "id.license",
        joinColumns = @JoinColumn(name = "licenseID")) })
public class DriverLicense {
 
	// composite-id key
	@EmbeddedId
    private DriverLicenseID id = new DriverLicenseID();
    
    @Column(name = "expirationDate")
    private Date expirationDate;
    
    @Column(name = "stateIssued")
    private String stateIssued;
	
    public DriverLicenseID getId() {
        return id;
    }
 
    public void setId(DriverLicenseID id) {
        this.id = id;
    }
 
    @Transient
    public Driver getDriver() {
        return getId().getDriver();
    }
 
    public void setDriver(Driver driver) {
        getId().setDriver(driver);
    }
 
    @Transient
    public License getLicense() {
        return getId().getLicense();
    }
 
    public void setLicense(License license) {
        getId().setLicense(license);
    }
 
    @Temporal(TemporalType.DATE)
    @Column(name = "expirationDate")
    public Date getExpirationDate() {
        return expirationDate;
    }
 
    public void setExpirationDate(Date expirationDate) {
        this.expirationDate = expirationDate;
    } 
    
    public String getStateIssued() {
        return stateIssued;
    }
 
    public void setStateIssued(String stateIssued) {
        this.stateIssued = stateIssued;
    }
}

My problem is that in dao layer I have problems with DriverLicense get method.
Those two methods return null values somehow.

@Override
	@SuppressWarnings("unchecked")
	public List<DriverLicense> getDriverLicense() {
		List<DriverLicense> list = getCurrentSession().createQuery("from DriverLicense").list();
		return list;
	}
	
	@Override
	public License getLicense(DriverLicenseID id) {
		DriverLicense driverLicense = (DriverLicense) getCurrentSession().get(DriverLicense.class, id);
		License license = driverLicense.getLicense();
		return license;
	}

Maybe I am doing something wrong. Don't know what is the right way to work with composite key.

[Tim Holloway]

I think that a lot of confusion might be avoided if your "License" object was renamed to something like "TransportLicense". It's psychologically confusing to call it "License" and doubly so if there's a real Driver's License in the mixture.

[Milan Strahinic]

Do you have any good example, that can be found on internet, and that has Entities, hibernate, spring and GUI? I was searching but there are a lot of examples without GUI. I think that my problems are connected with Entities.

[Milan Strahinic]

Ok. Like I promised here is my solution.

For my particular problem I have chosen this : http://www.codejava.net/frameworks/hibernate/hibernate-many-to-many-association-with-extra-columns-in-join-table-example

This solves work with hibernate. I have also used DTO to repack beans. This example here has one mistake, and that is that they are not using LAZY in composite ID creation. That is why this example has infinite loop problem.

Here is my code that solves this.

Driver entity

@OneToMany(fetch = FetchType.LAZY, mappedBy = "id.driver", cascade = CascadeType.ALL)

 private List<DriverLicense> driverLicense = new ArrayList<DriverLicense>();

 public List<DriverLicense> getDriverLicense() {
   return driverLicense;

 public void setDriverLicense(List<DriverLicense> driverLicense) {
   this.driverLicense = driverLicense;
 }

DriverLicenseID (my composite key)

@Embeddable
public class DriverLicenseID implements Serializable { 

    private static final long serialVersionUID = 1L;

    @ManyToOne(fetch = FetchType.LAZY, cascade=CascadeType.ALL) 
    @JoinColumn(name="driverID")
    private Driver driver;

    public Driver getDriver() {
        return driver;
    }

    public void setDriver(Driver driver) {
        this.driver = driver;
    }

    @ManyToOne(fetch = FetchType.LAZY, cascade=CascadeType.ALL)
    private License license;

    public License getLicense() {
        return license;
    }

    public void setLicense(License license) {
        this.license = license;
    } 
}

License entity

@OneToMany(fetch = FetchType.LAZY, mappedBy = "id.license", cascade = CascadeType.ALL)

    private List<DriverLicense> driverLicense = new ArrayList<DriverLicense>();

    public List<DriverLicense> getDriverLicense() {
         return driverLicense;
    }

    public void setDriverLicense(List<DriverLicense> driverLicense) {
         this.driverLicense = driverLicense;
    }