I have an existing web application that uses EF and POCO objects. I want to improve the client experience by exposing some of my objects through WCF(JSON). I have this working fine but where I am unsure is how to handle derived objects(not sure if that is the correct term) or IEnumerable anonymous objects if you will.
Let's say I have 3 tables structured like so:
Templates
ID
Template
Groups
ID
Group
Instances
ID
TemplateID
GroupID
This is obviously a one-to-many type relationship. I have my navigation properties setup correctly and getting strongly typed object properties works great. However, how do I send serialized anonymous type object(s) over the wire. Like an object that sends all instances that are equal to groupid=1 and include the names of the template and the object.
Am I missing something or do I have to create another class object for WCF that would look like this:
WCF Object
InstanceID
TemplateID
TemplateName
GroupID
GroupName
I guess I could alter my tables to account for this but that seems wrong too. I know that IEnumerable objects can't be serialized and I know that throw away objects are probably not the way to go either. I want to do this the right way but I am not sure how to go about it.
Your suggestions are appreciated.
Regards
Based on what you're doing, I'd suggest looking at OData with WCF Data Services. You state that you want to be able to send all instances where the groupid=1 - OData is great at this type of filtering.
If you're want to stick with your current approach and not use OData, then my first question is why are you sending back anonymous types at all? You can do what you are seeking (all instances with a groupid=1) without sending back an anonymous type. In your select clause you just create new instances of your concrete objects rather than newing up anonymous types. If your query is really just filtering and not executing any meaningful projection with the selct to anonymous type, then I don't see any reason to send back your anonymous type at all.
Related
Here's my problem.
I'm using SOAP to retrieve information from a third-party web service.
Response time is too high, so I was planning on using JSON instead, at least in a couple of methods.
For this I'm using DataContractJsonSerializer, but I seem to be having some trouble.
For example, in SOAP there's a method called getAvailablePublic with returns an object of type getAvailablePublicResponse.
There's an equivalent for this method in JSON, which also returns a an object of type getAvailablePublicResponse.
In order to deserialize the information I needed to create a couple of data contracts, and here are my concerns:
Do I really need to create a DataContract? Why can't I use getAvailablePublicResponse object from asmx?
The problem is that if I create a DataContract, I need to use a different name other than getAvailablePublicResponse, as I would have two objects with the same name (the one created by me, and the one from SOAP), and this would require making several changes in my solution.
Hope this makes sense.
Thanks.
Can you post your client code that is making the call to the web service? I don't know what you are using now, but I'm a fan of RestSharp for making remote calls and serializing JSON to C# classes. Something like this:
RestClient client = new RestClient("http://some.domain.com/someservice?someparam=yes");
var results = client.Execute<MyGreatDTOClass>(new RestRequest(Method.GET));
I'm developing my first Spring 3 webapp. In Spring 2, we used to have formBackingObject load data from the database, then let Spring binding update some of the fields, and then onSubmit would persist those changes.
In Spring 3 it seems I have two options:
Let the user edit 100% of the persistent object. This would mean that the object's ID would need to be a hidden field
Create a form object which holds the editable data, and then map that onto the persistent object on submit
The first option is not truly an option, we cannot let the user edit all fields, and we'd rather not present data in hidden fields where anyone capable of pressing F12 can alter the values.
The second option seems like a decent design approach. However, it appears that it requires to essentially clone every editable, persistent class.
#Entity
public class Company {
private String uuid; // not editable!
.. 30 other properties, 2 are not editable
}
public class CompanyForm {
.. 28 of above properties
}
and then some mapping mechanism with lots of
public void map(CompanyForm cf, Company c) {
cf.setName(c.getName());
.. 27 other set(get())
}
I'm praying this is not the "as designed" approach of Spring's MVC binding. However, all tutorial I've found so far are terribly trivial and implement option 1 from above. Does anyone have some suggestions for implementing option 2?
Thanks, Simon
DataBinder API
Note that there are potential security implications in failing to set an array of allowed fields. In the case of HTTP form POST data for example, malicious clients can attempt to subvert an application by supplying values for fields or properties that do not exist on the form. In some cases this could lead to illegal data being set on command objects or their nested objects. For this reason, it is highly recommended to specify the allowedFields property on the DataBinder.
You can use it together with option 1
A pragmatic way would be to just ignore the non editable fields on the update statement.
I have actually circumvented this in the past by using a #ModelAttribute annotation and detecting the PK on the request, if you do it this way Spring will use the object that is returned from #ModelAttribute and automatically copy the submitted object to it.
It's kind of a hack and not obvious to someone who comes in to maintain the code though.
I am creating a mobile app that will connect to a zendamf implementation to retrive certain information to store and display to the user.
There are multiple php classes on the gateway to handle things like users, Orders, Products etc.
Therefore I would have a package called remotehandler with classes under it, remotehandler.orders remotehandler.product, remotehandler.users. Which would mean for each class I could do the following:
instead of creating a connection for each type of call I want to make lots of times I was thinking that it might be better to create a wrapper class for each call family I.E
Users
createUser - calls a php function to create the user
DeleteUser
UpdateUser
after some searching I came accross this post
http://flexdevtips.blogspot.com/2009/05/using-flex-and-amfphp-without-services.html
which shows how to deal with netconnection in code. but it is written if you are planning on making a single call.
Does anyone have any ideas or example on how I could turn this in to a class that would allow me to specific different source(php class functions).
Thanks
JaChNo
Simply expose a property on your Class (let's call it source) as a getter/setter pair that, when set, changes the source of the RemoteObject.
However, I find it is better to have a different Service Class for each return type I expect, because I can then mock the service and just drop in the mock when I am working on things that don't require a live connection to the database (such as skinning).
I will try to be as concise as possible. I'm using Flex/Hibernate technologies for my app. I also use Cairngorm micro-architecture for Flex. Because i'm beginner, i have probably misunderstand something about Caringorm's ModelLocator purpose. I have following problem...
Suppose that we have next data model:
USER ----------------> TOPIC -------------> COMMENT
1 M 1 M
User can start many topics, topics can have many comments etc. It is pretty simple model, just for example. In hibernate, i use EAGER fetching strategy for unidirectional USER->TOPIC and TOPIC->COMMENT relations(here is no question about best practices etc, this is just example of problem).
My ModelLocator looks like this:
...
public class ModelLocator ....
{
//private instance, private constructor, getInstance() etc...
...
//app state
public var users:ArrayCollection;
public var selectedUser:UserVO;
public var selectedTopic:TopicVO;
}
Because i use eager fetching, i can 'walk' through all object graph on my Flex client without hitting the database. This is ok as long as i don't need to insert, update, or delete some of the domain instances. But when that comes, problems with synchronization arise.
For example, if i want to show details about some user from some UserListView, when user(actor) select that user in list, i will take selected index in UserList, get element from users ArrayCollection in ModelLocator at selected index and show details about selected user.
When i want to insert new User, ok, I will save that user in database and in IResponder result method i will add that user in ModelLocator.users ArrayCollection.
But, when i want to add new topic for some user, if i still want to use convenience of EAGER fetching, i need to reload user list again... And to add topic to selected user... And if user is in some other location(indirectly), i need to insert topic there also.
Update is even worst. In that case i need to write even some logic...
My question: is this good way of using ModelLocator in Cairngorm? It seems to me that, because of mentioned, EAGER fetching is somehow pointless. In case of using EAGER fetching, synchronization on Flex client can become big problem. Should I always hit database in order to manipulate with my domain model?
EDIT:
It seems that i didn't make myself clear enough. Excuse me for that.
Ok, i use Spring in technology stack also and DTO(DVO) pattern with flex/spring (de)serializer, but i just wanted to stay out of that because i'm trying to point out how do you stay synchronized with database state in your flex app. I don't even mention multi-user scenario and poling/pushing topic which is, maybe, my solution because i use standard request-response mechanism. I didn't provide some concrete code, because this seems conceptual problem for me, and i use standard Cairngorm terms in order to explain pseudo-names which i use for class names, var names etc.
I'll try to 'simplify' again: you have flex client for administration of above mentioned domain(CRUD for each of domain classes), you have ListOfUsersView(shows list of users with basic infos about them), UserDetailsView(shows user details and list of user topics with delete option for each of topic), InsertNewUserTopicView(form to insert new topic) etc.
Each of view which displays some infos is synchronized with ModelLocator state variables, for example:
ListOfUsersView ------binded to------> users:ArrayCollection in ModelLocator
UserDetailsView ------binded to------> selectedUser:UserVO in ModelLocator
etc.
View state transition look like this:
ListOfUsersView----detailsClick---->UserDetailsView---insertTopic--->InsertTopicView
So when i click on "Details" button in ListOfUsersView, in my logic, i get index of selected row in ListOfUsers, after that i take UserVO object from users:ArrayCollection in ModelLocator at mentioned index, after that i set that UserVO object as selectedUser:UserVO in ModelLocator and after that i change view state to UserDetailsView(it shows user details and selectedUser.topics) which is synchronized with selectedUser:UserVO in ModelLocator.
Now, i click "Insert new topic" button on UserDetailsView which results in InsertTopicView form. I enter some data, click "Save topic"(after successful save, UserDetailsView is shown again) and problem arise.
Because of my EAGER-ly fetched objects, i didn't hit the database in mentioned transitions and because of that there are two places for which i need to be concerned when insert new topic for selected user: one is instance of selectedUser object in users:ArrayCollection (because my logic select users from that collection and shows them in UserDetailsView), and second is selectedUser:UserVO(in order to sync UserDetailsView which comes after successfull save operation).
So, again my question arises... Should i hit database in every transition, should i reload users:ArrayCollection and selectedUser:UserVO after save in order to synchronize database state with flex client, should i take saved topic and on client side, without hitting the database, programmatically pass all places which i need to update or...?
It seems to me that EAGER-ly fetched object with their associations is not good idea. Am i wrong?
Or, to 'simplify' :) again, what should you do in the mentioned scenario? So, you need to handle click on "Save topic" button, and now what...?
Again, i really try to explain this as plastic as possible because i'm confused with this. So, please forgive me for my long post.
From my point of view the point isn't in fetching mode itself but in client/server interaction. From my previous experience with it I've finally found some disadvantages of using pure domain objects (especially with eager fetching) for client/server interaction:
You have to pass all the child collections maybe without necessity to use them on a client side. In your case it is very likely you'll display topics and comments not for all users you get from server. The most like situation you need to display user list then display topics for one of the selected users and then comments for one of the selected topics. But in current implementation you receive all the topics and comments even if they are not needed to display. It is very possible you'll receive all your DB in a single query.
Another problem is it can be very insecure to get all the user data (or some other data) with all fields (emails, addresses, passwords, credit card numbers etc).
I think there can be other reasons not to use pure domain objects especially with eager fetching.
I suggest you to introduce some Mapper (or Assembler) layer to convert your domain objects to Data Transfer Objects aka DTO. So every query to your service layer will receive data from your DAO or Active Record and then convert it to corresponding DTO using corresponding Mapper. So you can get user list without private data and query some additional user details with a separate query.
On a client side you can use these DTOs directly or convert them into client domain objects. You can do it in your Cairngorm responders.
This way you can avoid a lot of your client side problems which you described.
For a Mapper layer you can use Dozer library or create your own lightweight mappers.
Hope this helps!
EDIT
What about your details I'd prefer to get user list with necessary displayable fields like first name and last name (to display in list). Say a list of SimpleUserRepresentationDTO.
Then if user requests user details for editing you request UserDetailsDTO for that user and fill tour selectedUser fields in model with it. The same is for topics.
The only problem is displaying list of users after user details editing. You can:
Request the whole list again. The advantage is you can display changes performed by other users. But if the list is too long it can be very ineffective to query all the users each time even if they are SimpleUserRepresentationDTO with minimal data.
When you get success from server on user details saving you can find corresponding user in model's user list and replace changed details there.
Tell you the truth, there's no good way of using Cairngorm. It's a crap framework.
I'm not too sure exactly what you mean by eager fetching (or what exactly is your problem), but whatever it is, it's still a request/response kind of deal and this shouldn't be a problem per say unless you're not doing something right; in which case I can't see your code.
As for frameworks, I recommend you look at RobotLegs or Parsley.
Look at the "dpHibernate" project. It implements "lazy loading" on the Flex client.
I am building a site in which we are making moderate use of email templates. As in, HTML templates which we pass tokens into like {UserName}, {Email}, {NameFirst}, etc.
I am struggling with where to store these, as far as best practice goes. I'll first show the approach I took, and I'd be really excited to hear some expert perspective as a far as alternate approaches.
I created HTML templates in a folder called /Templates/.
I call a static method in my service layer, which takes in the following arguments:
UserName
UserID
Email
TemplatePath ("~/Templates")
Email Subject
Within the service layer I have my static method SendUserEmail() which makes use of a Template class - which takes a path, loads it as a string, and has a AddToken() Method.
Within my static SendUserEmail(), I build the token list off of the method signature, and send the email.
This makes for a quite long method call in my actual usage, especially since I am calling from the web.config the "TemplatePath", and "Email Subject". I could create a utility that has a shorter method call than the ConfigurationManager.AppSettings, but my concern is more that I don't usually see method signatures this long and I feel like it's because I'm doing something wrong.
This technique works great for the emails I have now, which at the most are using the first 3 tokens. However in the future I will have more tokens to pass in, and I'm just wondering what approach to take.
Do I create methods specific to the email needing to be sent? ie. SendNewUserRegistration(), SendMarketingMaterial(), and each has a different signature for the parameters?
I am using ASP.NET Membership, which contains probably the extend of all the fields I'll ever need. There are three main objects, aspnet_User, aspnet_Mebership and aspnet_profile. If it was all contained in one object, I would have just passed that in. Is there performance concerns with passing in all 3, to get all the fields I need? That is versus just passing in aspnet_User.UserID, aspnet_User.Email, etc?
I could see passing in a dictionary with the token entries, but I'm just wondering if that is too much to ask the calling page?
Is there a way to stick these in a config file of it's own called Templates.config, which has tags like -
<Templates>
<EmailTemplate Name="New User Registration">
<Tokens>
<UserName>
<UserID>
<Email>
</Tokens>
<Message Subject="Hi welcome...">
Hi {UserName}...
</Message>
</EmailTemplate>
</Templates>
I guess the main reason I'm asking, is because I'm having a hard time determining where the responsibility should be as far as determining what template to use, and how to pass in parameters. Is it OK if the calling page has to build the dictionary of TokenName, TokenValue? Or should the method take each in as a defined parameter? This looks out of place in the web.config, because I have 2 entries for and , and it feels like it should look more nested.
Thank you. Any techniques or suggestions of an objective approach I can use to ask whether my approach is OK.
First of all I would like to suggest you to use NVelocity as a template engine. As for main problem I think you can create an abstract class MailMessage and derive each one for every needed message (with unique template). So you will use this like following:
MailMessage message = new UserRegistrationMessage(tokens);
//some code that sends this message
Going this way you force each concrete XXXMessage class to be responsible for storing a template and filling it with the given tokens. How to deal with tokens? The simpliest way is to create a dictionary before passing it to the message, so each concrete message class will know how to deal with passed dictionary and what tokens it should contain, but you also need to remember what tokens it should contain. Another way (I like it more) is to create a general abstract type TokenSet and a derived one for every needed unique set of tokens. For example you can create a UserMessageTokenSet : TokenSet and several properties in it:
UserNameToken
SomeUserProfileDataToken
etc. So using this way you will always know, what data you should set for each token set and
UserRegistrationMessage will know what to take from this tokenSet.
There are a lot of ways to go. If you will describe you task better I think I will try suggest you something more concrete. But general idea is listed above. Hope it helps =)