We Keep Coding

Vaadin Table - AddNestedContainerProperty

public class LocationBasedRole extends AbstractEntity{
#ManyToMany(fetch=FetchType.LAZY)
private Set<Role> roles=new HashSet<Role>();
#ManyToMany(fetch=FetchType.LAZY)
private Set<Location> locations=new HashSet<Location>();
}
public class Role extends AbstractEntity{
private String name;
}
public class Location extends AbstractEntity{
private String location;
}
I have an entity named locationBasedRole which has 2 properties named roles and locations. Both roles and locations have a #ManyToMany relation with locationBasedRole.
Now I want to have one property of each in a Vaadin Table. It should be something like this,
public class UserForm extends OgsAbstractForm<User>{
MTable<LocationBasedRole> locationBasedRoleTable = new MTable<LocationBasedRole>().withHeight("100%").withWidth("100%");
#Override
protected Component createContent() {
Set<LocationBasedRole> lbRoles=new HashSet<LocationBasedRole>();
roles.addAll(locationBasedRoleFasade.findAll());
BeanItemContainer<LocationBasedRole> bean=new BeanItemContainer<LocationBasedRole>(LocationBasedRole.class);
//It returns an error on the next both lines and I know the reason, but don't know how to solve it.
// If it was no ManyToMany relation and the properties weren't a collection, it would work
bean.addNestedContainerProperty("roles.name");
bean.addNestedContainerProperty("locations.location");
bean.removeContainerProperty("persistent");
bean.removeContainerProperty("id");
bean.addAll(lbRoles);
locationBasedRoleTable.setContainerDataSource(bean);
return new VerticalLayout(locationBasedRoleTable);
}
}
When I remove the properties from the NestedContainerProperties it shows me at least something in the table.
bean.addNestedContainerProperty("roles");
bean.addNestedContainerProperty("locations");
I could use any help!
Thanks in advance!

So if I understand your question right, you want to have the Collections of your BeanItemContainer-Entity displayed in one column each?
I see two possibilities for that.
Option 1 - use a wrapper class for your Sets and use addNestedContainerBean
One possibility would be to not use Sets inside your LocationBasedRole but to use a wrapper class that extends HashSet.
Then you could use the addNestedContainerBean method.
I created a small example with the BeanItemContainer-Entity Team
public class Team {
private String teamName;
private Members teamMembers;
public String getTeamName() {
return teamName;
}
public void setTeamName(String teamName) {
this.teamName = teamName;
}
public Members getTeamMembers() {
return teamMembers;
}
public void setTeamMembers(Members teamMembers) {
this.teamMembers = teamMembers;
}
}
Which consists of a name and teamMembers. The latter is of type Members:
public class Members extends HashSet<TeamMember> {
public String getMembers() {
return this.stream()
.map(member -> member.getFirstName() + " " + member.getLastName())
.collect(Collectors.joining(","));
}
}
Which is a simple wrapper for the Set that contains instances of TeamMember:
public class TeamMember {
private String firstName;
private String lastName;
private Integer age;
// getters and setters
}
As you can see in the Members class, there is a method getMembers which returns a String, containing a comma separated list of the team members names.
If we now use addNestedContainerBean("teamMembers") Vaadin tries to display all properties contained in the class Members. Vaadin will think getMembers is a getter for a String property called members and so generate a column for it.
Vaadin will also display a column "empty" because it will find the isEmpty method of Set and think empty is a property to display in a column. So we tell Vaadin to remove that column.
The final code of my example looks like:
protected Component createContent() {
Set<Team> teams=new HashSet<>();
for (int teamCounter = 0; teamCounter < 5; teamCounter++) {
Team team = createTeam();
addMembersToTeam(5, team);
teams.add(team);
}
BeanItemContainer<Team> bean=new BeanItemContainer<>(Team.class);
bean.addNestedContainerBean("teamMembers");
bean.removeContainerProperty("teamMembers.empty");
bean.addAll(teams);
teamTable.setContainerDataSource(bean);
return new VerticalLayout(teamTable);
}
The result looks like:
Option 2 - create fake getters and use addNestedContainerProperty
The only thing you have to do for this is extend your BeanItemContainer-Entity (LocationBasedRole) and create a fake getter for each Set you want to be displayed in a column. In your example those two fake getters could be public String getTheRoles() and public String getTheLocations(). Then you can use bean.addNestedContainerProperty("theRoles") and bean.addNestedContainerProperty("theLocations").
In my example my TeamMember class (the counterpart to your Role / Location classes) would still look like in the option above:
public class TeamMember {
private String firstName;
private String lastName;
private Integer age;
// getters and setters
}
And my Team class (your LocationBasedRole) would look like:
public class Team {
private String teamName;
private Set<TeamMember> teamMembers;
public String getTeamName() {
return teamName;
}
public void setTeamName(String teamName) {
this.teamName = teamName;
}
public Set<TeamMember> getTeamMembers() {
return teamMembers;
}
public void setTeamMembers(Set<TeamMember> teamMembers) {
this.teamMembers = teamMembers;
}
public String getMembers() {
if (teamMembers != null) {
return teamMembers.stream()
.map(member -> member.getFirstName() + " " + member.getLastName())
.collect(Collectors.joining(","));
} else {
return "No members";
}
}
}
Now you can tell vaadin to add the (not existing) property "members" and Vaadin will find the getter getMembers and use this for generating the column. We also have to tell vaadin not to display the original "teamMembers" property. So the final code is:
protected Component createContent() {
Set<Team> teams=new HashSet<>();
for (int teamCounter = 0; teamCounter < 5; teamCounter++) {
Team team = createTeam();
addMembersToTeam(5, team);
teams.add(team);
}
BeanItemContainer<Team> bean=new BeanItemContainer<>(Team.class);
bean.addNestedContainerProperty("members");
bean.removeContainerProperty("teamMembers");
bean.addAll(teams);
teamTable.setContainerDataSource(bean);
return new VerticalLayout(teamTable);
}
and the result looks like:

Is it correct to have static factory method to get a new instance with one field updated?

I think the title is self-descriptive but I will give an example to elaborate on my question. I have a DTO class with few fields (a CarDataTransferObj class in my example). In another class (let's call it class A) I need to create a new instance of that object few times, but with only one field updated (length field in my example). Given DTO must be immutable in class A. As there is "many" fields in the class CarDataTransferObj, I thought about following approach (to avoid repeating code in class A):
#Builder
public class CarDataTransferObj {
private Integer id;
private String color;
private String manufacturer;
private String model;
private String uniqueIdNr;
private Integer nrOfDoors;
private EngineType engineType;
private Integer length;
private Integer safetyLevel;
public static CarDataTransferObj newInstanceWithUpdatedLength(final CarDataTransferObj car, final Integer newLength) {
return CarDataTransferObj.builder()
.id(car.getId())
.color(car.getColor())
.manufacturer(car.getManufacturer())
.model(car.getModel())
.uniqueIdNr(car.getUniqueIdNr())
.nrOfDoors(car.getNrOfDoors())
.engineType(car.getEngineType())
.length(newLength)
.safetyLevel(car.getSafetyLevel())
.build();
}
}
For me it smells like a little anti-pattern usage of static factory methods. I am not sure whether it's acceptable or not, hence the question.
Is using static factory method in the presented way an anti-pattern, and should be avoided ?

In my searching, I didn't come across anyone calling this1 an anti-pattern.
However, it is clear that if you try to do this using a classic builder that is not specifically implemented to support this mode of operation .... it won't work. For instance, the example CarBuilderImpl in the Wikipedia article on the Builder design pattern puts the state into an eagerly created Car instance. The build() method simply returns that object. If you tried to reuse that builder in the way that you propose, you would end up modifying a Car that has already been built.
There is another problem you would need to worry about. In we modified the Wikipedia CarBuilder example to add actual wheels (rather than a number of wheels) to the Car being built, we have to worry about creating cars that share the same wheels.
You could address these things in a builder implementation, but it is unclear whether the benefits out-weigh the costs.
If you then transfer this thinking to doing this using a factory method, you come to a slightly different conclusion.
If you are doing this as a "one-off", that's probably OK. You have a specific need, the code is clunky ... but so is the problem.
If you needed to do this for lots of different parameters, or combinations of parameters, this is not going to scale.
If the objects that are created are mutable, then this approach is could be problematic in a multi-threaded environment depending on how you control access to the objects you are using as templates.
1 - There are no clear measurable criteria for whether something is an anti-pattern or not. It is a matter of opinion. Admittedly, for many anti-patterns, there will be wide-scale agreement on that opinion.

It seems a little inefficient to construct an entirely new instance via a builder every time you want to make a new copy with a small modification. More significantly, it sounds like the places where you need the class to be immutable are isolated to places like class A. Why not try something like this:
public interface ICarDataTransferObject {
public Integer GetId();
public String GetColor();
public String GetManufacturer();
public String GetModel();
public String GetUUID();
public Integer GetDoorCount();
public EngineType GetEngineType();
public Integer GetLength();
public Integer GetSafteyLevel();
}
public class CarDataTransferObject Implements ICarDataTransferObject {
private Integer _id;
private String _color;
private String _manufacturer;
private String _model;
private String _uniqueIdNr;
private Integer _nrOfDoors;
private EngineType _engineType;
private Integer _length;
private Integer _safetyLevel;
public Integer GetId() { return _id; }
public void SetId(Integer id) { _id = id; }
public String GetColor() { return _color; }
public void SetColor(String color) { _color = color; }
public String GetManufacturer() { return _manufacturer; }
public void SetManufacturer(String manufacturer) { _manufacturer = manufacturer; }
public String GetModel() { return _model; }
public void SetModel(String model) { _model = model; }
public String GetUUID() { return _uniqueIdNr; }
public void SetUUID(String uuid) { _uniqueIdNr = uuid; }
public Integer GetDoorCount() { return _nrOfDoors; }
public void SetDoorCount(Integer count) { _nrOfDoors = count; }
public EngineType GetEngineType() { return _engineType; }
public void SetEngineType(EngineType et) { _engineType = et; }
public Integer GetLength() { return _length; }
public void SetLength(Integer length) { _length = length; }
public Integer GetSafteyLevel() { return _safetyLevel; }
public void SetSafteyLevel(Integer level) { _safteyLevel = level; }
public CarDataTransferObject() {}
public CarDataTransferObject(ICarDataTransferObject other) { ... }
public ReadOnlyCarDataTransferObject AsReadOnly() {
return ReadOnlyCarDataTransferObject (this);
}
}
}
public class ReadOnlyCarDataTransferObject Implements ICarDataTransferObject {
private ICarDataTransferObject _dto = null;
public Integer GetId() { return _dto.GetId(); }
public String GetColor() { return _dto.GetColor(); }
public String GetManufacturer() { return _dto.GetManufacturer(); }
public String GetModel() { return _dto.GetModel(); }
public String GetUUID() { return _dto.GetUUID(); }
public Integer GetDoorCount() { return _dto.GetDoorCount(); }
public EngineType GetEngineType() { return _dto.GetEngineType(); }
public Integer GetLength() { return _dto.GetLength(); }
public Integer GetSafteyLevel() { return _dto.GetSafteyLevel; }
public ReadOnlyCarDataTransferObject (ICarDataTransferObject other) {
_dto = other;
}
}
Now when you want class A to have a copy no one can modify, just use the copy constructor and only expose a ReadOnly version of that copy.
public class A {
ICarDataTransferObject _dto;
ReadOnlyCarDataTransferObject _readOnlyDTO;
public ICarDataTransferObject GetDTO() { return _readOnlyDTO; }
public A(ICarDataTransferObject dto) {
_dto = new CarDataTransferObject(dto);
_readOnlyDTO = new ReadOnlyCarDataTransferObject(_dto);
}
}
You commonly see this approach in .NET applications.

While it is debatable whether your static method is an anti-pattern or not, it surely won't scale for combinations of different attributes. Nonetheless, even if it's not an anti-pattern, I think there is a better way to accomplish what you need.
There's a variant of the traditional builder pattern that, instead of creating a new empty builder, accepts an already built object and creates an already initialized builder. Once you create the builder this way, you simply change the length attribute in the builder. Finally, build the object. In plain code (no Lombok, sorry) it could be like this:
public class CarDataTransferObj {
private Integer id;
private String color;
// other attributes omitted for brevity
private Integer length;
// Private constructor for builder
private CarDataTransferObj(Builder builder) {
this.id = builder.id;
this.color = builder.color;
this.length = builder.length;
}
// Traditional factory method to create and return builder
public static Builder builder() {
return new Builder();
}
// Factory method to create and return builder initialized from an instance
public static Builder builder(CarDataTransferObj car) {
Builder builder = builder();
builder.id = car.id;
builder.color = car.color;
builder.length = car.length;
return builder;
}
// getters
public static class Builder {
private Integer id;
private String color;
private Integer length;
private Builder() { }
public Builder withId(Integer id) { this.id = id; return this; }
public Builder withColor(String color) { this.color = color; return this; }
public Builder withLength(Integer length) { this.length = length; return this; }
public CarDataTransferObj build() {
return new CarDataTransferObj(this);
}
}
}
Now with all this infrastructure in place, you can do what you want as easy as:
CarDataTransferObj originalCar = ... // get the original car from somewhere
CarDataTransferObj newCar = CarDataTransferObj.builder(originalCar)
.withLength(newLength)
.build();
This approach has the advantage that it scales well (it can be used to change any combination of parameters). Maybe all this builder's code seems boilerplate, but I use an IntelliJ plugin to create the builder with two keystrokes (including the variant factory method that accepts a built instance to create an initialized builder).

I'm still new to java but..
I guess making a copy method which takes the CarDataTransferObj object variables and sets their values to another CarDataTransferObj object variables and changing the the length using it's setter method would be better idea
Example:
public class CarDataTransferObj {
private Integer id;
private String color;
private String manufacturer;
private String model;
private String uniqueIdNr;
private Integer nrOfDoors;
private EngineType engineType;
private Integer length;
private Integer safetyLevel;
public void Copy(CarDataTransferObj copy) { //Could add another parameter here to be the new length
copy.setId(id);
copy.set(color);
copy.setManufacturer(manufacturer);
copy.setModel(model);
copy.setUniqueIdNr(uniqueIdNr));
copy.setNrOfDoors(nrOfDoors));
copy.setEngineType(engineType));
copy.setLength(length);
copy.setSafetyLevel(safetyLevel));
}
}
public class SomeOtherClass {
CarDataTransferObj car1 = new CarDataTransferObj(); //Using this way made you able to use the constructor for a more useful thing
//You set the variables you want for car1 here
CarDataTransferObj car2 = new CarDataTransferObj();
car1.Copy(car2)
car2.setLength(newLength) //Set the new length here
}

Combine two methods. int cannot be dereferenced

If a woman has a partner, erase that partner's partner.
I need to retrieve her partner then make that partner single.
How do I combine getPartner() with erasePartner()
if (w.hasPartner() == true) {
w.getPartner().erasePartner();
}
import java.util.*;
public class Person {
public static final int NOBODY = -1;
private String name;
private List<Integer> preferences;
private List<Integer> oldPreferences;
private int partner;
public Person(String name) {
this.name = name;
preferences = new ArrayList<Integer>();
oldPreferences = new ArrayList<Integer>();
erasePartner();
}
public void erasePartner() {
partner = NOBODY;
}
public boolean hasPartner() {
return partner != NOBODY;
}
public int getPartner() {
return partner;
}
public void setPartner(int partner) {
this.partner = partner;
}
public String getName() {
return name;
}
public boolean hasChoices() {
return !preferences.isEmpty();
}
public int getFirstChoice() {
return preferences.get(0);
}
public void addChoice(int person) {
preferences.add(person);
oldPreferences.add(person);
}
public List<Integer> getChoices() {
return preferences;
}
public int getPartnerRank() {
return oldPreferences.indexOf(partner) + 1;
}
}

Right now you have partner as an int. You cannot call methods on an int since it is a primitive type. However this doesn't make much sense in your context since you are erasing w's partner and not the partner's partner. Instead just call:
if (w.hasPartner() == true) {
w.erasePartner();
}
Also your code doesn't make much sense. Why is the partner an int? Why wouldn't it be a Person object. You could change your code to:
private Person partner;
And
public Person getPartner() {
return partner;
}
So that partner points to another Person object instead of an int

You need to be able to get the Persona that the partner field corresponds to if you want to erase the partner's partner.
Given the code that you have, every Person should have a corresponding id that is an int, which is the value the partner field stores. You'll need some way to store these mappings such as a Map<Integer, Persona> that lives outside the Person class, and whenever you create a Person you have to put it in the map along with its id (which you can generate however you like as long as it's unique).
With this map you can then access the Person that corresponds to the partner int and erase its partner
if (w.hasParter()) {
Person partner = personMap.get(w.getPartner());
partner.erasePartner()
}
assuming the partner exists in the map (which you may want to check for).

Okay I kinda figured it out. I did it another way. Goes through each person and test's to see if person p is partner with firstChoice then deletes the p's partner. Kinda long way it seems but it works :)
for (Person p : list1) {
if (p.getPartner() == firstChoice) {
p.erasePartner();
}

How can I implement these 2 simple queries using Spring data JPA with the "query creation from method names" strategy?

I am pretty new in Spring Data and I have to write what in the official documentation seems to be called Query creation from method names, here the reference:https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.query-methods.query-creation
As you can see in the previous example show the creation of a query by the definition of a method name, for example:
List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);
that I think return a list of Person object that have a specific email affress and a specific lastname.
So I am trying to do the same thing in my project that use Hibernate as JPA provider.
In my project I have this Twb1012Regione entity class that map the anagrafiche.TWB1012_REGIONE on the database:
#Entity
#Table(name="anagrafiche.TWB1012_REGIONE")
#NamedQuery(name="Twb1012Regione.findAll", query="SELECT t FROM Twb1012Regione t")
public class Twb1012Regione implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name="COD_REG")
private String codReg;
#Column(name="COD_ARE_GEO")
private String codAreGeo;
#Column(name="COD_CIT")
private String codCit;
#Column(name="COD_IST")
private int codIst;
#Column(name="COD_PGM_ULT_MOV")
private String codPgmUltMov;
#Column(name="COD_UTE_ULT_MOV")
private String codUteUltMov;
#Temporal(TemporalType.TIMESTAMP)
#Column(name="DAT_ORA_ULT_MOV")
private Date datOraUltMov;
#Column(name="DES_REG")
private String desReg;
//bi-directional many-to-one association to Tpg1029Provnuoist
#OneToMany(mappedBy="twb1012Regione")
private List<Tpg1029Provnuoist> tpg1029Provnuoists;
//bi-directional many-to-one association to Twb1013Provincia
#OneToMany(mappedBy="twb1012Regione")
private List<Twb1013Provincia> twb1013Provincias;
public Twb1012Regione() {
}
public String getCodReg() {
return this.codReg;
}
public void setCodReg(String codReg) {
this.codReg = codReg;
}
public String getCodAreGeo() {
return this.codAreGeo;
}
public void setCodAreGeo(String codAreGeo) {
this.codAreGeo = codAreGeo;
}
public String getCodCit() {
return this.codCit;
}
public void setCodCit(String codCit) {
this.codCit = codCit;
}
public int getCodIst() {
return this.codIst;
}
public void setCodIst(int codIst) {
this.codIst = codIst;
}
public String getCodPgmUltMov() {
return this.codPgmUltMov;
}
public void setCodPgmUltMov(String codPgmUltMov) {
this.codPgmUltMov = codPgmUltMov;
}
public String getCodUteUltMov() {
return this.codUteUltMov;
}
public void setCodUteUltMov(String codUteUltMov) {
this.codUteUltMov = codUteUltMov;
}
public Date getDatOraUltMov() {
return this.datOraUltMov;
}
public void setDatOraUltMov(Date datOraUltMov) {
this.datOraUltMov = datOraUltMov;
}
public String getDesReg() {
return this.desReg;
}
public void setDesReg(String desReg) {
this.desReg = desReg;
}
public List<Tpg1029Provnuoist> getTpg1029Provnuoists() {
return this.tpg1029Provnuoists;
}
public void setTpg1029Provnuoists(List<Tpg1029Provnuoist> tpg1029Provnuoists) {
this.tpg1029Provnuoists = tpg1029Provnuoists;
}
public Tpg1029Provnuoist addTpg1029Provnuoist(Tpg1029Provnuoist tpg1029Provnuoist) {
getTpg1029Provnuoists().add(tpg1029Provnuoist);
tpg1029Provnuoist.setTwb1012Regione(this);
return tpg1029Provnuoist;
}
public Tpg1029Provnuoist removeTpg1029Provnuoist(Tpg1029Provnuoist tpg1029Provnuoist) {
getTpg1029Provnuoists().remove(tpg1029Provnuoist);
tpg1029Provnuoist.setTwb1012Regione(null);
return tpg1029Provnuoist;
}
public List<Twb1013Provincia> getTwb1013Provincias() {
return this.twb1013Provincias;
}
public void setTwb1013Provincias(List<Twb1013Provincia> twb1013Provincias) {
this.twb1013Provincias = twb1013Provincias;
}
public Twb1013Provincia addTwb1013Provincia(Twb1013Provincia twb1013Provincia) {
getTwb1013Provincias().add(twb1013Provincia);
twb1013Provincia.setTwb1012Regione(this);
return twb1013Provincia;
}
public Twb1013Provincia removeTwb1013Provincia(Twb1013Provincia twb1013Provincia) {
getTwb1013Provincias().remove(twb1013Provincia);
twb1013Provincia.setTwb1012Regione(null);
return twb1013Provincia;
}
}
So, into my project I have defined a Twb1012RegioneRepository interface that is my repository class defined on the previous Twb1012Regione entity class:
#RepositoryDefinition(domainClass=Twb1012Regione.class, idClass=String.class)
public interface Twb1012RegioneRepository extends JpaRepository<Twb1012Regione, String> {
// I have to implement it
}
Now my problem is that I want to create 2 methods (that implement 2 queries by method name as described by the previous tutorial) that perform the following tasks:
1) Return the list of all the Twb1012Regione representing all the record of the TWB1012_REGIONE table on the DB.
2) Given a specific id (the value of the String codReg field, PK of the Twb1012Regione class) I want to obtain the Twb1012Regione object associated to this record.
How can I implement these queries? I have some difficulties to do it
Tnx

You don't need to implement the methods. The Spring Data Repository API will construct query for you as the JpaRepository already has following methods:
List findAll(Iterable ids)
T getOne(ID id)
That's the whole point with the Spring Data Repository - To reduce the boiler plate code that you write.

How to forbid creation of two class objects with the same parameters?

friends and colleagues. I have following class:
public class Department {
private String departmentName;
private int moneyForDepartment;
public Department(String departmentName, int moneyForDepartment){
if (moneyForDepartment < 0){
throw new IllegalArgumentException("invalid value");
}
this.departmentName = departmentName;
this.moneyForDepartment = moneyForDepartment;
}
public Department(){
}
public String getDepartmentName() {
return departmentName;
}
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}
public int getMoneyForDepartment() {
return moneyForDepartment;
}
public void setMoneyForDepartment(int moneyForDepartment) {
this.moneyForDepartment = moneyForDepartment;
}
}
and for example i will create two objects of this class:
Department dep1 = new Department("Storage", 100000);
Department dep2 = new Department("Storage", 200000);
Please tell me how can i forbid to create class object in case when object of this class with the same first parameter is already exists ?

It's probably not a good idea to do that globally across your entire application (in static state), because then testing becomes difficult. Instead, create a factory for your Department class, maybe looking something like this:
public class Department {
private Department(String departmentName, int moneyForDepartment) { ... }
...
public static class Factory {
private Set<String> seenDepartmentNames = new HashSet<>();
public Department create(String departmentName, int moneyForDepartment) {
if (!seenDepartmentNames.add(departmentName)) {
throw new IllegalArgumentException("Department already created");
}
return new Department(departmentName, moneyForDepartment);
}
}
}
This forces all construction to go through the Factory, since the Department constructor is private. Just use one Factory across your application, and you can still create new ones for testing without running into problems.

You could create a static field in the Department class and keep a Set with the department names already used:
public class Department {
private static final Set<String> usedDepartmentNames = new HashSet<>();
...
}
Then, in the constructor, do:
public Department(String departmentName, int moneyForDepartment) {
if (usedDepartmentNames.contains(departmentName)) {
throw new IllegalArgumentException("Department already exists");
}
if (moneyForDepartment < 0){
throw new IllegalArgumentException("invalid value");
}
this.departmentName = departmentName;
this.moneyForDepartment = moneyForDepartment;
usedDepartmentNames.add(departmentName);
}