In both association and aggregation, one class maintains a reference to another class.
Then, does constructor injection imply composition?
Going by the same logic, is it safe to say that setter injection leads to an association, and not an aggregation?
An aggregation is merely another representation of an association. So setter injection leads to an association and aggregation -- as does constructor injection.
It's debatable as to whether constructor injection implies composition since, according to a strict interpretation of composition, the class itself must be responsible for both the construction and destruction of the composite class.
At java code level if you have a class 2 and Class 3 this the expected code.
Traditional association 0..1 to 0..1 gives the following code:
public class Class2 {
private Class3 class3;
public Class3 getClass3() {
return class3;
}
public void setClass3(Class3 class3) {
this.class3 = class3;
}
}
Class 3 is the same code as Class 2.
Please note that association are related to attributes and not to methods therefore if we decide not to use accessors then the code would only be:
public class **Class2** {
private Class3 class3;
Aggregation 1 to many gives the following code:
import java.util.Collection;
import java.util.Iterator;
public class Class2 {
private Collection<Class3> class3 = null;
public Collection<Class3> getClass3() {
return class3;
}
public Iterator<Class3> class3Iterator() {
return class3.iterator();
}
public boolean isClass3Empty() {
return class3.isEmpty();
}
public boolean containsClass3(Class3 class3) {
return this.class3.contains(class3);
}
public boolean containsAllClass3(Collection<Class3> class3) {
return this.class3.containsAll(class3);
}
public int class3Size() {
return class3.size();
}
public Class3[] class3ToArray() {
return class3.toArray(new Class3[class3.size()]);
}
public void setClass3(Collection<Class3> class3) {
this.class3 = class3;
}
public boolean addClass3(Class3 class3) {
return this.class3.add(class3);
}
public boolean removeClass3(Class3 class3) {
return this.class3.remove(class3);
}
public void clearClass3() {
this.class3.clear();
}
}
public class Class3 {
private Class2 class2 = null;
public Class2 getClass2() {
return class2;
}
public void setClass2(Class2 class2) {
this.class2 = class2;
}
}
Hope this helps
Related
I am using springfox version 2.9.2 and swagger annotations 1.5.x. The ApiModel annotations support the discriminator, subTypes and parent attribute which are required to make polymorphism work but I am not seeing the correct apidocs generated to enable polymorphism.
Here is my annotated code.
#RestController
#RequestMapping("/api/vehicles")
public class VehicleController {
private static final Logger LOGGER = LoggerFactory.getLogger(VehicleController.class);
#PostMapping(consumes = {MediaType.APPLICATION_JSON_UTF8_VALUE})
void post(#RequestBody Vehicle anyVehicle) {
LOGGER.info("Vehicle : {}", anyVehicle);
}
}
#ApiModel(discriminator = "type", subTypes = {Car.class, Bike.class})
public class Vehicle {
String brand;
String type;
public String getBrand() {
return brand;
}
public void setBrand(String brand) {
this.brand = brand;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
}
#ApiModel(parent = Vehicle.class)
public class Car extends Vehicle {
int noOfDoors;
boolean powerWindows;
public int getNoOfDoors() {
return noOfDoors;
}
public void setNoOfDoors(int noOfDoors) {
this.noOfDoors = noOfDoors;
}
public boolean isPowerWindows() {
return powerWindows;
}
public void setPowerWindows(boolean powerWindows) {
this.powerWindows = powerWindows;
}
}
#ApiModel(parent = Vehicle.class)
public class Bike extends Vehicle {
boolean pillion;
public boolean isPillion() {
return pillion;
}
public void setPillion(boolean pillion) {
this.pillion = pillion;
}
}
When the docs get generated is basically shows one endpoint which handles a POST request and takes in a Vehicle as the model.
Is what I am doing here supposed to work? Can someone point me to a working example of this with SpringFox that I can look at?
Support for discriminator is not available in Swagger UI yet. You can follow these issues for status updates:
Discriminator does not switch schema
subTypes not displayed in model
I have following code snipped and I tried to test it using typemock but got InvalidCast exception. ISomeClass is just an interface and SomeClass implements that interface. UseOfSomeClass is another class which uses SomeClass and its constructor takes SomeClass as parameter. I need to test UseOfSomeClass. How do I inject a typemock fake object into a class constructor?
public interface ISomeClass
{
void DoSomething();
}
public class SomeClass : ISomeClass
{
public void DoSomething()
{
Console.WriteLine("Do something!");
}
}
public class UseOfSomeClass
{
public SomeClass SomeClassProperty { get; set; }
public bool IsChecked { get; set; }
public UseOfSomeClass(SomeClass someClass)
{
SomeClassProperty = someClass;
}
public void MyMethod()
{
SomeClassProperty.DoSomething();
IsChecked = true;
}
}
Then test:
[TestClass]
public class UseOfSomeClassTest
{
[TestMethod]
public void TestMethod1()
{
var fakeSomeClass = Isolate.Fake.Instance<ISomeClass>();
var use = new UseOfSomeClass((SomeClass)fakeSomeClass);
use.MyMethod();
Assert.IsTrue(use.IsChecked);
}
}
Thanks!
Typemock Isolator allows you to mock concrete classes, so there's no need to fake ISomeClass in your test case. You can just fake SomeClass and send it as a parameter to the ctor.
[TestMethod, Isolated]
public void TestMethod1()
{
var fakeSomeClass = Isolate.Fake.Instance<SomeClass>();
var use = new UseOfSomeClass(fakeSomeClass);
use.MyMethod();
Assert.IsTrue(use.IsChecked);
}
At the moment I have a Base class that contains a member I would like to inject. However, I would like the concrete type of this member to depend on the Subclass being instantiated. What I am aiming for is something along these lines:
public interface StringInterface {
public String getString();
}
public class HelloStringConcrete implements StringInterface {
public String getString() {
return "Hello";
}
}
public class WorldStringConcrete implements StringInterface {
public String getString() {
return "World";
}
}
public abstract class Base {
#Inject StringInterface member;
public Base() {
// Assume access to object graph
MyObjectGraph.get().inject(this);
}
public void printSomething() {
System.out.println(member.getString());
}
}
public class SubclassHello extends Base {}
public class SubclassWorld extends Base {}
#Module(injects = {SubclassHello.class})
public class HelloModule {
#Provides StringInterface provideStringInterface() {
return new HelloStringConcrete();
}
}
#Module(injects = {SubclassWorld.class})
public class WorldModule {
#Provides StringInterface provideStringInterface() {
return new WorldStringConcrete();
}
}
So now what I would like to do is something along the lines of:
#Module(
includes = {
HelloModule.class,
WorldModule.class
}
)
public class BigModule {}
// Somewhere in another piece of code...
objectGraph = ObjectGraph.create(new BigModule());
// In yet another piece of code...
SubclassHello hello = new SubclassHello();
SubclassWorld world = new SubclassWorld();
hello.printSomething();
world.printSomething();
// Hopefully would result in :
// Hello
// World
This type of setup won't work though, because including two modules with the same provider will result in a duplicate provider error at compile time. It would be cool to see a solution to this problem without introducing #Named or #Qualifer annotations, or using scoped graph extensions via graph.plus() because these strategies necessarily introduce coupling to the subclasses
This is possible but I think the code I've attached below is more coupled than using scoped graphs or annotations. Basically you can use constructor injection to inject concrete dependencies to your
SubclassHello and SubclassWorld.
public abstract class Base {
private final StringInterface member;
public Base(StringInterface member) {
this.member = member;
}
...
}
#Module(injects = {SubclassWorld.class})
public class WorldModule {
#Provides
WorldStringConcrete provideStringInterface() {
return new WorldStringConcrete();
}
}
public class SubclassWorld extends Base {
#Inject
public SubclassWorld(WorldStringConcrete worldStringConcrete) {
super(worldStringConcrete);
}
}
#Module(injects = {SubclassHello.class})
public class HelloModule {
#Provides
HelloStringConcrete provideStringInterface() {
return new HelloStringConcrete();
}
}
public class SubclassHello extends Base {
#Inject
public SubclassHello(HelloStringConcrete helloStringConcrete) {
super(helloStringConcrete);
}
}
// Somewhere in another piece of code...
ObjectGraph objectGraph = ObjectGraph.create(new BigModule());
// In yet another piece of code...
SubclassHello hello = objectGraph.get(SubclassHello.class);
SubclassWorld world = objectGraph.get(SubclassWorld.class);
I don't think there are other solutions. How could Dagger find out which StringInterface implementations should be injected to the concrete classes?
I have successfully setup a simple mvc application that lists teams. I'm using Ninject to inject the appropriate repository depending on the controller (thanks to stack overflow ;). All looks good, except that the repository code looks exactly the same. And I know that's wrong. So my TeamRepository has two classes (for now).
public class SwimTeamRepository : ITeamRepository<SwimTeam>
{
private readonly Table<SwimTeam> _teamTable;
public SwimTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SwimTeam>());
}
public IQueryable<SwimTeam> Team
{
get { return _teamTable; }
}
}
public class SoccerTeamRepository : ITeamRepository<SoccerTeam>
{
private readonly Table<SoccerTeam> _teamTable;
public SoccerTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SoccerTeam>());
}
public IQueryable<SoccerTeam> Team
{
get { return _teamTable; }
}
}
They look exactly the same except for the Class and Table name, so clearly I need to re-factor this. What would be the best approach here? Singleton? Factory Method?
Thanks in advance!
You could use generics:
public interface ITeamRepository<T>
{
}
public class TeamRepository<TTeam> : ITeamRepository<TTeam>
where TTeam : Team
{
private readonly Table<TTeam> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<TTeam>());
}
public IQueryable<TTeam> Team
{
get { return _teamTable; }
}
}
public class Team
{
}
public class SwimTeam : Team
{
}
Then use it like so...
public void MyMethod()
{
var repository = new TeamRepository<SwimTeam>();
}
...and set up your IoC container w/ Ninject like so...
public class MyModule : NinjectModule
{
public override void Load()
{
Bind<ITeamRepository<SwimTeam>>
.To<TeamRepository<SwimTeam>>();
}
}
public void MyMethod()
{
var repository = kernel.Get<ITeamRepository<SwimTeam>>();
}
If you want to get REAL generic and have a single repository for ALL of your mapped classes, you can do something like this:
public interface IRepository
{
IQueryable<T> Get<T>() where T : class, new();
}
public class Repository : IRepository, IDisposable
{
private DataContext _dataContext;
public Repository(string connectionString)
{
_dataContext = new DataContext(connectionString);
}
public IQueryable<T> Get<T>()
where T : class, new()
{
return _dataContext.GetTable<T>().AsQueryable();
}
public void Dispose()
{
if (_dataContext != null)
{
_dataContext.Dispose();
_dataContext = null;
}
}
}
...which you could call like so (after setting up your Ninject container)...
using (var repository = kernel.Get<IRepository>())
{
var swimTeam = repository.Get<SwimTeam>();
}
Since Ninject takes care of the life-cycle management of your objects, you don't HAVE to wrap the repository in a using statement. In fact, you don't want to use a using statement there at all if you plan to use the repository more than once within the scope of its lifetime. Ninject will automatically dispose of it when it's life-cycle ends.
Here's a good article by Rob Conery on using this kind of technique to reduce the friction of using different ORMs.
EDIT by keeg:
I Think
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : Team {}
Should be
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : class {}
Please correct if I'm wrong.
Is this what you want?
public class TeamRepository : ITeamRepository<T>
{
private readonly Table<T> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<T>());
}
public IQueryable<T> Team
{
get { return _teamTable; }
}
}
PLEASE: If my question isn't clear, please tell me and I'll try to rephrase it
I need [Default Constructor] in LogOnModel, so it can't be removed.
LoadModel+ModelFactory and LogOnModel are physically in different files in different projects AND project2 has reference to project1 and NOT vice versa.
1 - Let say that
type=typeof(LogOnModel). When ObjectFactory.GetInstance(t) is called I want it to call the
parameterized constructor of LogOnModel and pass it the #params
2 - If I'll add to the parameterized constructor of LogOnModel another parameter,for example
public LogOnModel(string param, IPageService pageService)
so ObjectFacytory should call this constructor without any problems
How to configure/initiate ObjectFactory, so this will work?
Thank you
EDITED
//Project1/file1.cs
public void LoadModel(Type type, string param)
{
var factory = new ModelFactory();
var model = factory.Get(type, **param**);
}
public class ModelFactory : IModelFactory
{
public PageModel Get(Type t, **string param**)
{
//NOW I NEED SOMEHOW TO PASS **param** TO EVERY INSTANCE THAT INHERITS FROM **PageModel**
return ObjectFactory.GetInstance(t) as PageModel;
}
}
//Project2/file2.cs
public class LogOnModel : PageModel
{
public LogOnModel()
{
}
public LogOnModel(string param)
{
}
}
public class Model2 : PageModel
{
public LogOnModel()
{
}
public LogOnModel(string param)
{
}
}
public class Model3 : PageModel
{
public LogOnModel()
{
}
public LogOnModel(string param)
{
}
}
StructureMap will use the constructor with the most parameters by default, so that part is easy. Then you just need to configure the value of param like so:
ObjectFactory.Initialize(i => {
i.For<LogOnModel>().Use<LogOnModel>();
});
When you call the container, use the with method to pass in your parameter:
return ObjectFactory.With("param").EqualTo(param).GetInstance(t) as PageModel;