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?
Related
I am on Spring Boot 2.0.6, where an entity pet do have a Lazy many-to-one relationship to another entity owner
Pet entity
#Entity
#Table(name = "pets")
public class Pet extends AbstractPersistable<Long> {
#NonNull
private String name;
private String birthday;
#JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id")
#JsonIdentityReference(alwaysAsId=true)
#JsonProperty("ownerId")
#ManyToOne(fetch=FetchType.LAZY)
private Owner owner;
But while submitting a request like /pets through a client(eg: PostMan), the controller.get() method run into an exception as is given below:-
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class java.lang.Long and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->com.petowner.entity.Pet["ownerId"])
at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77) ~[jackson-databind-2.9.7.jar:2.9.7]
at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1191) ~[jackson-databind-2.9.7.jar:2.9.7]
Controller.get implementation
#GetMapping("/pets")
public #ResponseBody List<Pet> get() {
List<Pet> pets = petRepository.findAll();
return pets;
}
My observations
Tried to invoke explicitly the getters within owner through pet to force the lazy-loading from the javaassist proxy object of owner within the pet. But did not work.
#GetMapping("/pets")
public #ResponseBody List<Pet> get() {
List<Pet> pets = petRepository.findAll();
pets.forEach( pet -> pet.getOwner().getId());
return pets;
}
Tried as suggested by this stackoverflow answer at https://stackoverflow.com/a/51129212/5107365 to have controller call to delegate to a service bean within the transaction scope to force lazy-loading. But that did not work too.
#Service
#Transactional(readOnly = true)
public class PetServiceImpl implements PetService {
#Autowired
private PetRepository petRepository;
#Override
public List<Pet> loadPets() {
List<Pet> pets = petRepository.findAll();
pets.forEach(pet -> pet.getOwner().getId());
return pets;
}
}
It works when Service/Controller returning a DTO created out from the entity. Obviously, the reason is JSON serializer get to work with a POJO instead of an ORM entity without any mock objects in it.
Changing the entity fetch mode to FetchType.EAGER would solve the problem, but I did not want to change it.
I am curious to know why it is thrown the exception in case of (1) and (2). Those should have forced the explicit loading of lazy objects.
Probably the answer might be connected to the life and scope of that javassist objects got created to maintain the lazy objects. Yet, wondering how would Jackson serializer not find a serializer for a java wrapper type like java.lang.Long. Please do rememeber here that the exception thrown did indicate that Jackson serializer got access to owner.getId as it recognised the type of the property ownerId as java.lang.Long.
Any clues would be highly appreciated.
Edit
The edited part from the accepted answer explains the causes. Suggestion to use a custom serializer is very useful one in case if I don't need to go in DTO's path.
I did a bit of scanning through the Jackson sources to dig down to the root causes. Thought to share that too.
Jackson caches most of the serialization metadata on first use. Logic related to the use case in discussion starts at this method com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(Collection<?> value, JsonGenerator g, SerializerProvider provider). And, the respective code snippet is:-
The statement serializer = _findAndAddDynamic(serializers, cc, provider) at Line #140 trigger the flow to assign serializers for pet-level properties while skipping ownerId to be later processed through serializer.serializeWithType at line #147.
Assigning of serializers is done at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.resolve(SerializerProvider provider) method. The respective snippet is shown below:-
Serializers are assigned at line #340 only for those properties which are confirmed as final through the check at line #333.
When owner comes here, its proxied properties are found to be of type com.fasterxml.jackson.databind.type.SimpleType. Had this associated entity been loaded eagerly, the proxied properties obviously won't be there. Instead, original properties would be found with the values that are typed with final classes like Long, String, etc. (just like the pet properties).
Wondering why can't Jackson address this from their end by using the getter's type instead of using that of the proxied property. Anyway, that could be a different topic to discuss :-)
This has to do with the way that Hibernate (internally what spring boot uses for JPA by default) hydrates objects. A lazy object is not loaded until some parameter of the object is requested. Hibernate returns a proxy which delegates to the dto after firing queries to hydrate the objects.
In your scenario, loading OwnerId does not help because it is the key via which you are referencing the owner object i.e. the OwnerId is already present in the Pet object, so the hydration will not take place.
In both 1 and 2, you have not actually loaded the owner object, so when Jackson tries to serialize it at the controller level it fails. In 3 and 4, the owner object has been loaded explicitly, which is why Jackson does not run into any issues.
If you want 2 to work then load some parameter of owner, other than id, and hibernate will hydrate the object, and then jackson will be able to serialize it.
Edited Answer
The problem here is with the default Jackson serializer. This inspects the class returned and fetches the value of each attribute via reflection. In the case of hibernate entities, the object returned is a delegator proxy class in which all parameters are null, but all getters are redirected to the contained instance. When the object is inspected, the values of each attribute are still null, which is defaulted to an error as explained here
So basically, you need to tell jackson how to serialize this object. You can do so by creating a serializer class
public class OwnerSerializer extends StdSerializer<Owner> {
public OwnerSerializer() {
this(null);
}
public OwnerSerializer(Class<Owner> t) {
super(t);
}
#Override
public void serialize(Owner value, JsonGenerator jgen, SerializerProvider provider)
throws IOException, JsonProcessingException {
jgen.writeStartObject();
jgen.writeNumberField("id", value.getId());
jgen.writeStringField("firstName", value.getFirstName());
jgen.writeStringField("lastName", value.getLastName());
jgen.writeEndObject();
}
}
And setting it as the default serializer for the object
#JsonSerialize(using = OwnerSerializer.class)
public class Owner extends AbstractPersistable<Long> {
Alternatively, you can create a new Object of type Owner from the proxy class, manually populate it and set it in the response.
It is a little roundabout, but as a general practice you should not expose your DTO's externally anyway. The controller/domain should be decoupled from the storage layer.
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 have come across a problem of parsing json data . I am building project using spring boot based on REST api . When i have to parse data corresponding to domain then it is very easy , i use RequestBody in controller method with domain name but in current scenerio i have a list of domain in json form :
{
"data":[
{
"type":"abc",
"subtypes":[
{
"leftValue":"BEACH",
"rightValue":"MOUNTAIN",
"preferencePoint":60
},
{
"leftValue":"ADVENTURE",
"rightValue":"LEISURE",
"preferencePoint":60
}
]
},
{
"type":"mno",
"subtypes":[
{
"leftValue":"LUXURY",
"rightValue":"FUNCTIONAL",
"preferencePoint":60
},
{
"leftValue":"SENSIBLE",
"rightValue":"AGGRESIVE",
"preferencePoint":0
}
]
}
]
}
I am sending data in list where type is the property of class Type
and class Type has list of Subtypes class and subtype class contains leftValue and rightValue as enums
I am using spring boot which uses jackson liberary by default and i want to parse this data into corresponding Type class using Jackson. Can any one provide me solution.
It wasn't clear to me if you have static or dynamic payload.
Static payload
For static one, I would personally try to simplify your payload structure. But your structure would look like this. (I skipped getters and setters. You can generate them via Lombok library).
public class Subtype{
private String leftValue;
private String rightValue;
private int preferencePoint;
}
public class Type{
private String type;
private List<Subtype> subtypes;
}
public class Data{
private List<Type> data;
}
Then in your controller you inject Data type as #RequestBody.
Dynamic payload
For dynamic payload, there is option to inject LinkedHashMap<String, Object> as #RequestBody. Where value in that map is of type Object, which can be casted into another LinkedHashMap<String, Object> and therefore this approach support also nested objects. This can support infinite nesting this way. The only downside is that you need to cast Objects into correct types based on key from the map.
BTW, with pure Spring or Spring Boot I was always able to avoid explicit call against Jackson API, therefore I don't recommend to go down that path.
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.
I am trying to pass POST data from my jsp with jquery-ajax to my Spring-MVC controller function. The data is passed fine and I can print the JSON data when I use a String object to receive the RequestBody. But when I employ a DTO which has a List variable declared with its own objects the controller returns a '415 Unsupported Media Type Error' with the following statement,
The server refused this request because the request entity is in a format not supported by the requested resource for the requested method.
below given is the DTO class
public class anyClassDTO{
private String name;
private List<anyClassDTO> subList = new ArrayList<anyClassDTO>();
//getters and setters here
}
Now, here is the controller function
#RequestMapping(headers ={"Accept=application/json"}, value = "urlFromJsp", method = RequestMethod.POST)
public #ResponseBody
String addData (HttpServletRequest request,
#RequestBody List<anyClassDTO> dtoObject,
Model model)
{
return "{\"value\":\"true\"}";
}
Is it not possible for a list of objects to be received from the jsp page to a controller via AJAX?
Here is a set of sample data being passed from the jsp
[{"name":"module1","subList":[{"name":"chapter1","subList":[{"name":"subchapter1","subList":null}]}]},{"name":"module2","subList":[{"name":"chapter1","subList":[{"name":"subchapter1","subList":null}]}]}]
Make sure your AJAX request sets the request's Content-Type to application/json.
Spring typically uses a MappingJacksonHttpMessageConverter to convert the request body when you specify #RequestBody. This HttpMessageConverter only supports application/*+json type content types, so you have to make sure your request contains it.
Well, we could make it work as it is by adding a little more detail. Instead of receiving the #ResponseBody as a List object I created another DTO which holds a List object of the original DTO. So the second DTO is basically a dummy which receives the data from AJAX as a single object.
Like I have said in the question I have a DTO as follows
public class AnyClassDTO{
private String name;
private List<anyClassDTO> subList = new ArrayList<anyClassDTO>();
//getters and setters here
}
I created another DTO which holds a List of the above DTO
public class DummyDTO{
private List<AnyClassDTO> dummyObj;
//getters and setters here
}
Then in the controller I changed the function to
#RequestMapping(headers ={"Accept=application/json"}, value = "urlFromJsp", method = RequestMethod.POST)
public #ResponseBody
String addData (HttpServletRequest request,
#RequestBody DummyDTO dummyDTOObj,
Model model)
{
return "{\"value\":\"true\"}";
}
Earlier if I was sending a list directly from AJAX, now I am sending a stringified litteral with a variable which holds the whole data.
And it works like a charm!