I have two pojo objects: Husband, Wife which reference each other.
Husband.java
public class Husband {
private String name;
private int age;
private String man;
private Wife wife;
// getter, setter, builder, constructor are removed for berevity
}
Wife.java
public class Wife {
private String name;
private int age;
private String woman;
private Husband husband;
// getter, setter, builder, constructor are removed for berevity
}
I've created simple typeMap rulings for both objects, where the referenced object is skipped.
My test class:
public class ModelTest {
#Test
public void test() {
ModelMapper modelMapper = new ModelMapper();
TypeMap<Wife, Wife> typeWife = modelMapper.createTypeMap(Wife.class, Wife.class);
typeWife.addMappings(mapper -> {
mapper.skip(Wife::setHusband);
});
TypeMap<Husband, Husband> typeHusband = modelMapper.createTypeMap(Husband.class, Husband.class);
typeHusband.addMappings(mapper -> {
mapper.skip(Husband::setWife);
});
Wife wife = Wife.builder().age(25).name("Sarah").woman("good woman").build();
Husband husband = Husband.builder().age(28).name("Imtiaz").man("good man").build();
wife.setHusband(husband);
husband.setWife(wife);
Husband updatedHusband = Husband.builder().age(28).name("Imtiaz Shakil").man("slightly good man").build();
modelMapper.map(updatedHusband, husband);
System.out.println(husband.toString());
System.out.println(husband.getWife().toString());
}
}
When mapping updatedHusband to husband, setWife() method is not skipped. But, if we I remove typeWife mapping from modelMapper the code works fine.
I'm using ModelMapper 1.1.3
Thanks.
Edit:
I think the problem is with the mappings modelmapper generates. When I print the mappings of each typeMap this is what I get:
[PropertyMapping[Wife.age -> Wife.age], PropertyMapping[ -> Wife.husband], PropertyMapping[Wife.name -> Wife.name], PropertyMapping[Wife.woman -> Wife.woman]]
[PropertyMapping[Husband.age -> Husband.age], PropertyMapping[Husband.man -> Husband.man], PropertyMapping[Husband.name -> Husband.name], PropertyMapping[ -> Husband.wife], PropertyMapping[Husband.wife.age -> Husband.wife.age], PropertyMapping[Husband.wife -> Husband.wife.husband], PropertyMapping[Husband.wife.name -> Husband.wife.name], PropertyMapping[Husband.wife.woman -> Husband.wife.woman]]
TypeMap typeHusband picks mapping from typeWife during mapping process.
The problem is fixed in v2.1.0.
Thanks to the developers for their great work!
Related
I'm trying to implement inheritance with Kotlin and JPA. My abstract base class (annotated with #Entity) holds the ID (annotated with #Id and #GeneratedValue) and other metadata, like createDate, etc. I'm getting several errors from Hibernate, one for each field except the ID:
org.hibernate.tuple.entity.PojoEntityTuplizer - HHH000112: Getters of lazy classes cannot be final: com.example.BaseEntity.createDate
As I've read I need to include the open keyword for each property.
I have 3 questions regarding this:
Why do I have to do that in the superclass, and don't need in subclass? I'm not overriding those properties.
Why isn't it complaining about the ID?
It seems to work without the open keyword, then why is the error logged?
Edit:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
abstract class BaseEntity(
#Id #GeneratedValue(strategy = GenerationType.IDENTITY) val id: Long = 0,
val createdAt: Instant = Instant.now()
)
#Entity
class SubClass(
val someProperty: String = ""
) : BaseEntity()
I'm using the JPA plugin for Gradle, which I believe creates the noarg constructor, that's why I don't have to specify everything nullable.
Thank you!
The logged error has to do with lazy loading.
Hibernate extends entities at runtime to enable it. It is done by intercepting an access to properties when an entity is loaded lazily.
Kotlin has flipped the rules and all classes are final by default there. It is the reason why we're advised to add an open keyword.
If a property is not open hibernate cannot intercept access to it because final methods cannot be overridden. Hence the error.
Why isn't it complaining about the ID?
Because #Id is always loaded. There is no need to intercept access to it.
It seems to work without the open keyword, then why is the error logged?
The key word here is seems. It may introduce subtle bugs.
Consider the following #Entity:
#Entity
public class Book {
#Id
private Long id;
private String title;
public final Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public final String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
And the #Test:
#Test
public void test() {
EntityManager entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
// signal here
Book book = new Book();
book.setId(1L);
book.setTitle("myTitle");
entityManager.persist(book);
// noise
entityManager.getTransaction().commit();
entityManager.close();
entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
// signal
Book reference = entityManager.getReference(Book.class, 1L);
String title = reference.getTitle();
assertNull(title); // passes
entityManager.getTransaction().commit();
entityManager.close();
}
This test passes but it should not (and fails if getTitle is not final).
This would be hard to notice
Why do I have to do that in the superclass, and don't need in subclass? I'm not overriding those properties.
Looks like Hibernate gives up when it sees final #Entity.
Add open to SubClass and you will the precious:
2019-05-02 23:27:27.500 ERROR 5609 --- [ main] o.h.tuple.entity.PojoEntityTuplizer : HHH000112: Getters of lazy classes cannot be final: com.caco3.hibernateanswer.SubClass.someProperty
See also:
final methods on entity silently breaks lazy proxy loading
How to avoid initializing HibernateProxy when invoking toString() on it? - my old question (note that Hibernate uses Byte Buddy these days).
PS
Did you forget to include #MappedSuperclass on BaseEntity?
Without the annotation it should fail with something like:
org.hibernate.AnnotationException: No identifier specified for entity: com.caco3.hibernateanswer.SubClass
Let us take the following JSON response which I want to return from my REST service,
{
"id" : 123,
"name" : "ABC",
}
For the above JSON response, I can create a POJO class like,
public class Student{
private long id;
private String name;
//getters and setters
}
So, I can write a GET service to return the Student object which will be then transformed as JSON.
#GET
#Produces(MediaType.APPLICATION_JSON)
public Response get(){
Student student = new Student();
student.setId(123);
student.setName("ABC");
return Response.ok(student).build();
}
It works fine. Now I want to introduce optional parameters to my JSON response as follows,
{
"id" : 123,
"name" : "ABC",
"params" : {"param1":"xxx","param2":342}
}
Here the params in the JSON response is an Object type and the attributes of that object are not fixed. It will vary for every request like sometime it can have 3 attributes and sometime it will have none. I don't know how to create my POJO class for this requirement. Can anybody suggest me a way how to do it?
Unless you don't need anything special, you should design it as like:
public class Student{
private long id;
private String name;
//getters and setters
private Map<String, String> parameters = new HashMap<>();
public void add(String key, String value) {
parameters.put(key, value);
}
public void addAll(Map<String, String> map) {
parameters.putAll(map);
}
}
If you need type safety then the design is little bit complicated a consider using something like:
class StudentParameters {
long param1;
String param2;
}
and Student:
public class Student{
private long id;
private String name;
//getters and setters
private StudentParameters studentParameters;
public setStudentParameters(final StudentParameters studentParameters) {
this.studentParameters = studentParameters;
}
}
Do not create complex hierarchies e.g Map<List<List>, List<List>> it will complicate whole structure.
I'm using the adapter support in Autofac to convert multiple types to a desired type. I also want to preserve the keys/names/metadata attached to the adapter input types, so that they exist with the same values on the adapter output types - this is needed for using IIndex<,> to resolve instances by name.
I can't figure out how to propagate the keys/names/metadata through the adapter function, since the adapter function runs during component construction, and the metadata needs to be propagated when the container is built.
Here's an example xunit test, which fails:
/// <summary>
/// Unit test to figure out how to propagate keys through adapters.
/// </summary>
public sealed class AutofacAdapterTest
{
public class A
{
public A(string key)
{
Key = key;
}
public string Key { get; private set; }
}
public class B
{
public B(string name)
{
Name = name;
}
public string Name { get; private set; }
}
public class C : B
{
public C(string name)
: base(name)
{}
}
public class LookerUpper
{
private readonly IIndex<string, B> _bIndex;
public LookerUpper(IIndex<string, B> bIndex)
{
_bIndex = bIndex;
}
public B LookupByName(string name)
{
return _bIndex[name];
}
}
[Fact]
public void TestPropagateKeysThroughAdapters()
{
var builder = new ContainerBuilder();
// Register named types
builder.RegisterType<A>().Named<A>("A").WithParameter("key", "A");
builder.RegisterType<B>().Named<B>("B").WithParameter("name", "B");
builder.RegisterType<C>().Named<C>("C").Named<B>("C").WithParameter("name", "C");
// Adapter to convert an A to a B, since it's not a subclass
builder.RegisterAdapter<A, B>((c, a) => new B(a.Key));
// Register LookerUpper, which is the only top-level type that needs to be autowired
builder.RegisterType<LookerUpper>();
var container = builder.Build();
var lookerUpper = container.Resolve<LookerUpper>();
// Test expected results
Assert.Equal("A", lookerUpper.LookupByName("A").Name);
Assert.IsType<B>(lookerUpper.LookupByName("A")); // A should have been adapted to a B
Assert.Equal("B", lookerUpper.LookupByName("B").Name);
Assert.IsType<B>(lookerUpper.LookupByName("B"));
Assert.Equal("C", lookerUpper.LookupByName("C").Name);
Assert.IsType<C>(lookerUpper.LookupByName("C"));
Assert.Throws<ComponentNotRegisteredException>(() => lookerUpper.LookupByName("D"));
}
}
The statement lookerUpper.LookupByName("A") fails with a ComponentNotRegisteredException, because the name value "A" is not propagated through the adapter function (which adapts A -> B ). If the first two lines of Asserts are commented out, the rest of the test works as expected.
I found a workable solution to this problem by using Autofac Metadata instead of Autofac keys or names. For the call to RegisterAdapter<TFrom, TTo>(Func<TFrom,TTo>), metadata is propagated from the IComponentRegistration for TFrom to the IComponentRegistration for TTo; however the keys/names are not propagated. The omission of keys may be a bug or by design, I'll file a bug with autofac to figure out which is the case and follow up.
The unfortunate part about using metadata is I can't use an IIndex<string, B> constructor parameter, so I had to use an IEnumerable<Meta<Lazy<B>>> parameter and create my own dictionary of string -> Lazy<B> to provide similiar functionality to IIndex. Here's the code that works:
/// <summary>
/// Unit test to figure out how to propagate keys through adapters.
/// </summary>
public sealed class AutofacAdapterTest
{
internal const string LookupKey = "lookup";
public class A
{
public A(string key)
{
Key = key;
}
public string Key { get; private set; }
}
public class B
{
public B(string name)
{
Name = name;
}
public string Name { get; private set; }
}
public class C : B
{
public C(string name)
: base(name)
{}
}
public class LookerUpper
{
private readonly IDictionary<string, Lazy<B>> _bLookup;
public LookerUpper(IEnumerable<Meta<Lazy<B>>> bMetas)
{
_bLookup = bMetas.ToDictionary(meta => meta.Metadata[LookupKey].ToString(), meta => meta.Value);
}
public B LookupByName(string name)
{
return _bLookup[name].Value;
}
}
[Fact]
public void TestPropagateKeysThroughAdapters()
{
var builder = new ContainerBuilder();
// Register types that will be looked up; attach metadata for the lookup key
builder.Register((c) => new A("A")).WithMetadata(LookupKey, "A");
builder.Register((c) => new B("B")).WithMetadata(LookupKey, "B");
builder.Register((c) => new C("C")).AsSelf().As<B>().WithMetadata(LookupKey, "C");
// Adapter to convert an A to a B, since it's not a subclass
builder.RegisterAdapter<A, B>((c, a) => new B(a.Key));
// Register LookerUpper, which is the only top-level type that needs to be autowired
builder.RegisterType<LookerUpper>();
var container = builder.Build();
var lookerUpper = container.Resolve<LookerUpper>();
// Test expected results
Assert.Equal("A", lookerUpper.LookupByName("A").Name);
Assert.IsType<B>(lookerUpper.LookupByName("A")); // A should have been adapted to a B
Assert.Equal("B", lookerUpper.LookupByName("B").Name);
Assert.IsType<B>(lookerUpper.LookupByName("B"));
Assert.Equal("C", lookerUpper.LookupByName("C").Name);
Assert.IsType<C>(lookerUpper.LookupByName("C"));
Assert.Throws<KeyNotFoundException>(() => lookerUpper.LookupByName("D"));
}
}
It should also be possible to create an IRegistrationSource and some extension methods that extend what is done in RegisterAdapter<TFrom, TTo>, such that the keys in TFrom are propagated to TTo - that would be an ideal solution, but potentially more work to maintain, so I'll probably stick with this.
It was fixed in Autofac version 3.5.1.
Link to the bug
Link to the fix
class Person{
private String name;
private int age;
private String gender;
//......
}
class Student extends Person{
private String id;
private String schoolBelongTo;
//......
}
public void showInfoOf(Person person){
System.out.println(person.getName());
//......
}
When using function "showInfoOf" ,if an object of Peron is used as the param,OK.However,if it is the type Student,I cannot get access to the field id and schoolBelongTo.
So I am confused ,how to ?
Actually, I want to know is this one of its(Interface oriented programming's or Supper class oriented programming's) disadvantages???
Two possible solutions:
You can programatically check the type in showInfoOf (Person), and use a cast to access & print the desired fields; or,
You can define a method on Person which will print/provide the desired info -- and either replace showPersonInfo() with that entirely, or call it into it. This is the more OO way.
Example:
abstract class Person {
private String name;
private int age;
private String gender;
public void printInfo() {
System.out.println( name);
}
}
class Student extends Person{
private String id;
private String schoolBelongTo;
#Override
public void printInfo() {
super.printInfo();
System.out.println( id);
System.out.println( schoolBelongTo);
}
}
public void showInfoOf (Person person){
person.printInfo();
}
In this example, all functionality has moved to Person.printInfo() and there is no real functionality remaining in showInfoOf (Person).
However in the real-world, you'd probably want move versatility in a Person.provideInfo() function -- perhaps returning a LinkedHashMap of fields & values (since unlabelled values on their own, are not great design).
The showInfoOf (Person) function could then handle formatting & printing the values to the specific requirement, leaving the Person.provideInfo() function general & multi-purpose.
in showInfoOf() you would have to check that person is of type Student, then cast it as a Student to get id or schoolBelongsTo
I'm dynamically creating my DbContext by iterating over any entities that inherit from EntityBase and adding them to my Context:
private void AddEntities(DbModelBuilder modelBuilder)
{
var entityMethod = typeof(DbModelBuilder).GetMethod("Entity");
foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
{
var entityTypes = assembly.GetTypes()
.Where(x => x.IsSubclassOf(typeof(EntityBase)) && !x.IsAbstract);
foreach (var type in entityTypes)
{
dynamic entityConfiguration = entityMethod.MakeGenericMethod(type).Invoke(modelBuilder, new object[] { });
EntityBase entity = (EntityBase)Activator.CreateInstance(type);
//Add any specific mappings that this class has defined
entity.OnModelCreating(entityConfiguration);
}
}
}
That way, I can have many namespaces but just one generic repository in my base namespace that's used everywhere. Also, in apps that make use of multiple namespaces, the base repository will already be setup to use all the entities in all the loaded namespaces. My problem is, I don't want to make EntityFramework.dll a dependency of every namespace in the company. So I'm calling OnModelCreating and passing the EntityTypeConfiguration to the class so it can add any mappings. This works fine and here's how I can add a mapping to tell the model that my "Description" property comes from a column called "Descriptor":
class Widget... {
public override void OnModelCreating(dynamic entity)
{
System.Linq.Expressions.Expression<Func<Widget, string>> tmp =
x => x.Description;
entity.Property(tmp).HasColumnName("Descriptor");
}
The good thing is, my entity class has no reference to EF, this method is only called once, when the context is created and if we scrap EF and go to something else in the future, my classes won't have all sorts of attributes specific to EF in them.
The problem is, it's super ugly. How can I let the model know about column mappings and keys in a simpler way than creating these Expressions to get properties to map without hard coding references to EF all over my poco classes?
You could define your own Attributes and use these to control the configuration within OnModelCreating(). You should be able to gain (using reflection) all the details you need for column mapping in one linq query a second query for the creation of the key.
public class DatabaseNameAttribute : Attribute
{
private readonly string _name;
public DatabaseNameAttribute(string name)
{
_name = name;
}
public string Name
{
get
{
return _name;
}
}
}
public class KeySequenceAttribute : Attribute
{
private readonly int _sequence;
public KeySequenceAttribute(int sequence)
{
_sequence = sequence;
}
public int Sequence
{
get
{
return _sequence;
}
}
}
[DatabaseName("BlogEntry")]
public class Post
{
[DatabaseName("BlogId")]
[KeySequence(1)]
public int id { get; set; }
[DatabaseName("Description")]
public string text { get; set; }
}