i'm coding a restService who can update some datas in a database via Nhibernate.
The service receive DTO objects from a client.
I'm using Automapper to map my Dto to NhibernateObject.
The problem is my DTO class reference itself. here an example :
public class UserDto
{
public String Name{get;set;}
public string Lastname{get;set;}
public UserDto UserOwner{get;set;}
}
here's my BusinessClass
public class User
{
public String Name{get;set;}
public string Lastname{get;set;}
public String Adress{get;set;}
public User UserOwner{get;set;}
}
Sometimes User object and UserOwner properties references the same object.
So when i do that
User usr = Automapper.Mapper.Map<UserDto,User>(myUserDtoObject); // this works fine
but when i do
Automapper.Mapper.Map(myUserdtoObject,MyUserNhibernateObject); // i've got a stackoverflowexception
I can use the first option but if i do that, when my new UserEntity returned by Map function is created the value of "Adress" properties is not set (UserDto does not contains it).
You need to use MaxDepth - AutoMapper doesn't know how far to go down your rabbit hole.
ForMember(dest => dest.UserOwner, opt => opt.MaxDepth(1))
This is important for NHibernate, which uses proxy objects to load indefinitely. The other option is to ignore the UserOwner member, but that's likely not your intent here.
Related
I'm trying to build a simple application with Quarkus. Currently, I have two entity classes, which are related one-to-many:
#Entity
public class Person extends PanacheEntity {
public String name;
public LocalDate birthdate;
#OneToMany(mappedBy = "person")
public List<Address> addresses;
public static Person findByNameFirst(String name) {
return find("name", name).firstResult();
}
}
#Entity
public class Address extends PanacheEntity {
public String street;
...etc...
#ManyToOne
public Person person;
}
These are used by a simple REST webservice, which should store a Person to the database, select it again an return it:
#GET
#Path("storePerson")
#Produces(MediaType.APPLICATION_JSON)
#Transactional
public Person storePerson(
#QueryParam("name")String name,
#QueryParam("birthdate")String birthdate)
{
LocalDate birth = LocalDate.parse(birthdate, DateTimeFormatter.BASIC_ISO_DATE);
Person person = new Person(name, birth);
person.persistAndFlush();
Person p2 = Person.findByNameFirst(name);
return p2;
}
When calling the webservice the first time, the result is a JSON object with the stored data, which is as expected. When called again, an internal server error is thrown:
org.hibernate.LazyInitializationException: Unable to perform requested lazy initialization [Person.addresses] - no session and settings disallow loading outside the Session
As I understand, the error is thrown because the transaction only lasts until the storePerson method ends, but the conversion to JSON is happening outside of the method.
How can I prevent this error? I have read about the hibernate parameter "enable_lazy_load_no_trans" but it seems it is not supported in Quakus' application.properties.
The idea is to use a mapper framework such as MapStruct.
We don't recommend to directly expose your entities for 2 reasons:
the issue you have,
API management in the long run: you might have to change your model and not your API or the opposite.
There is an example here: https://github.com/mapstruct/mapstruct-examples/tree/master/mapstruct-quarkus .
The Quarkus version used is a bit old but AFAICS it should still work with latest Quarkus.
You can make the error go away by using Hibernate.initialize(person.addresses), then the collection gets initialized before the transaction ends.
I'm currently trying to setup a database – using Java only. Given this simple class that might appear in the average social network app:
#Entity
class User {
#Id
private String email;
private String name;
private String otherInfo;
#ManyToMany
private List<User> contacts;
}
When the user logs in, he should receive the basic information and the list of contacts with their basic info, but not their contacts. To reduce the amount of boiler-plate code, I want to use a standard solution like Gson. However, even with lazy fetch the whole user is loaded on gson.toJson(user).
Therefore I thought of extracting the basic infos into a base class BasicUser and changing the contacts to List<BasicUser>. Now I only need to somehow circumwent the discriminator column when I fetch the contacts – of course they are all saved as complete users on the server. Unfortunately, I don't know how to archieve that. Any ideas?
If you need to get only part of the entity you can use projections. In your case it can be, for example, like this:
public interface BaseUser {
String getEmail();
String getName();
String getOtherInfo();
}
public interface UserRepo extends JpaRepository <User, String> {
List<BaseUser> findAllBy();
}
Using Jackson for serialization, the problem can be solved without writing custom serialization code. BasicUser contains the getters of the attributes, I want to serialize:
public interface BasicUser {
String getEmail();
String getFirstName();
String getLastName();
}
With a single annotation the contacts attribute is interpreted as a list of BasicUsers:
#Entity
public class User implements BasicUser {
#Id
private String email;
private String firstName;
private String lastName;
#ManyToMany
#JsonSerialize(contentAs = BasicUser.class)
private List<User> contacts = new ArrayList<>();
// ... implemented getters
}
You shouldn't have to modify your domain model just to accomodate a serialization library.
If you only want certain fields of a collection to be exposed to JSON, you could use Jackson with #JsonView (see here: How to serialize using #Jsonview with nested objects) not sure if Gson provides a similar feature as I have never used it extensively.
I have the following dependency chain:
IUserAppService
IUserDomainService
IUserRepository
IUserDataContext - UserDataContextImpl(string conn)
All interfaces above and implementations are registered in a Windsor Castle container. When I use one connection string, everything works fine.
Now we want to support multiple databases, In UserAppServiceImpl.cs, we want to get different IUserRepository (different IUserDatabaseContext) according to userId as below:
// UserAppServiceImpl.cs
public UserInfo GetUserInfo(long userId)
{
var connStr = userId % 2 == 0 ? "conn1" : "conn2";
//var repo = container.Resolve<IUserRepository>(....)
}
How can I pass the argument connStr to UserDataContextImpl?
Since the connection string is runtime data in your case, it should not be injected directly into the constructor of your components, as explained here. Since however the connection string is contextual data, it would be awkward to pass it along all public methods in your object graph.
Instead, you should hide it behind an abstraction that allows you to retrieve the proper value for the current request. For instance:
public interface ISqlConnectionFactory
{
SqlConnection Open();
}
An implementation of the ISqlConnectionFactory itself could depend on a dependency that allows retrieving the current user id:
public interface IUserContext
{
int UserId { get; }
}
Such connection factory might therefore look like this:
public class SqlConnectionFactory : ISqlConnectionFactory
{
private readonly IUserContext userContext;
private readonly string con1;
private readonly string con2;
public SqlConnectionFactory(IUserContext userContext,
string con1, string con2) {
...
}
public SqlConnection Open() {
var connStr = userContext.UserId % 2 == 0 ? "conn1" : "conn2";
var con = new SqlConnection(connStr);
con.Open();
return con;
}
}
This leaves us with an IUserContext implementation. Such implementation will depend on the type of application we are building. For ASP.NET it might look like this:
public class AspNetUserContext : IUserContext
{
public string UserId => int.Parse(HttpContext.Current.Session["UserId"]);
}
You have to start from the beginning of your dependency resolver and resolve all of your derived dependencies to a "named" resolution.
Github code link:https://github.com/castleproject/Windsor/blob/master/docs/inline-dependencies.md
Example:
I have my IDataContext for MSSQL and another for MySQL.
This example is in Unity, but I am sure Windsor can do this.
container.RegisterType(Of IDataContextAsync, dbEntities)("db", New InjectionConstructor())
container.RegisterType(Of IUnitOfWorkAsync, UnitOfWork)("UnitOfWork", New InjectionConstructor(New ResolvedParameter(Of IDataContextAsync)("db")))
'Exceptions example
container.RegisterType(Of IRepositoryAsync(Of Exception), Repository(Of Exception))("iExceptionRepository",
New InjectionConstructor(New ResolvedParameter(Of IDataContextAsync)("db"),
New ResolvedParameter(Of IUnitOfWorkAsync)("UnitOfWork")))
sql container
container.RegisterType(Of IDataContextAsync, DataMart)(New HierarchicalLifetimeManager)
container.RegisterType(Of IUnitOfWorkAsync, UnitOfWork)(New HierarchicalLifetimeManager)
'brands
container.RegisterType(Of IRepositoryAsync(Of Brand), Repository(Of Brand))
controller code:
No changes required at the controller level.
results:
I can now have my MSSQL context do its work and MySQL do its work without any developer having to understand my container configuration. The developer simply consumes the correct service and everything is implemented.
I am writing a REST web service and I am using Spring 4 with annotation-based configuration.
I am also using Spring security for HTTP Basic authentication and authorization.
I have an ItemRestPresentation class purely used for the presentation layer whose instances are created in my controller method using instances of another class called Item (the actual domain object). ItemRestPresentationinstances get converted to the following JSON by my controller method:
ItemRestPresentation class:
public class ItemRestPresentation {
private String name;
private String description;
private boolean canDelete;
// ... private constructor, public getters and public static factory method to create an ItemRestPresentation instance from an Item instance
}
Generated JSON :
{
"name" : "item1",
"description": "Sample item for testing",
"canDelete" : true
}
Is it possible to use Spring Security ACL to set the canDelete member of the ItemRestPresentation instance to the correct value depending on whether the current user has permission to delete it?
I try to write a demo with WCF (REST) Service, and I use LinqToSQL as my db operator.
When I try to pub [DataContract] or [Serializable] on top of my domain object, it cannot be serialized to JSON. I only can get a pair of '{}' in my browser. After removing [DataContract] or [Serializable] attribute, it become normal again.
[DataContract]
public partial class MyDoc{ } // a Linq To SQL domain class
get method:
[WebGet(UriTemplate = "GetMyDoc/{docID}",ResponseFormat=WebMessageFormat.Json)]
[ServiceKnownType(typeof(MyDoc))]
public WcfRESTfulTest.Db.MyDoc GetMyDoc(string docID)
{
WcfRESTfulTest.Db.DbDataContext db = new DbDataContext();
var query = db.MyDocs.Where(d => d.DocID.Equals(Int32.Parse(docID)));
return query.FirstOrDefault();
}
If you don't use the [DataContract] attribute, all public properties will be serialized. If you do use it, you'll have to opt-in the properties you want to serialize, using the [DataMember] attribute.