I am getting a single entity by using a method fetchEntityByKey, after that I am loading navigation property for the entity by entityAspect.loadNavigationProperty. But loadNavigationProperty always make a call to the server, what I am wondering if I can first check it from cache, if it is exist then get it from there otherwise go the server. How is it possible? Here is my current code
return datacontext.getProjectById(projectId)
.then(function (data) {
vm.project = data;
vm.project.entityAspect.loadNavigationProperty('messages');
});
Here is a function that I encapsulated inside datacontext service.
function getProjectById(projectId) {
return manager.fetchEntityByKey('Project', projectId)
.then(querySucceeded, _queryFailed);
function querySucceeded(data) {
return data.entity;
}
}
Also, how is it possible to load navigation property with some limit. I don't want to have all records for navigation property at once for performance reason.
You can use the EntityQuery.fromEntityNavigation method to construct a query based on an entity and a navigationProperty . From there you can execute the resulting query locally, via the EntityManager.executeQueryLocally method. So in your example once you have a 'project' entity you can do the following.
var messagesNavProp = project.entityType.getProperty("messages");
var query = EntityQuery.fromEntityNavigation(project, messagesNavProp);
var messages = myEntityManager.executeQueryLocally(query);
You can also make use of the the EntityQuery.using method to toggle a query between remote and local execution, like this:
query = query.using(FetchStrategy.FromLocalCache);
vs
query = query.using(FetchStrategy.FromServer);
please take a look here: http://www.breezejs.com/sites/all/apidocs/classes/EntityManager.html
as you can see fetchEntityByKey ( typeName keyValues checkLocalCacheFirst ) also have a third optional param that you can use to tell breeze to first check the manager cache for that entity
hope this helps
When retrieving entities and metadata from the server my custom initializer functions are able to access thier navigation properties as expected. When exporting metadata and entities to localstorage and reimporting them the navigation properties are not available. I have ensured that the ctors and initializers are registered to the metadatastore before import as the methods are called. I took a look at the breeze source and it appears that the initialize functions are called prior to the item being fully populated and attached.
targetEntity = entityType._createEntityCore();
updateTargetFromRaw(targetEntity, rawEntity, dataProps, true);
if (newTempKeyValue !== undefined) {
// fixup pk
targetEntity.setProperty(entityType.keyProperties[0].name, newTempKeyValue);
// fixup foreign keys
if (newAspect.tempNavPropNames) {
newAspect.tempNavPropNames.forEach(function (npName) {
var np = entityType.getNavigationProperty(npName);
var fkPropName = np.relatedDataProperties[0].name;
var oldFkValue = targetEntity.getProperty(fkPropName);
var fk = new EntityKey(np.entityType, [oldFkValue]);
var newFkValue = tempKeyMap[fk.toString()];
targetEntity.setProperty(fkPropName, newFkValue);
});
}
}
*targetEntity.entityAspect._postInitialize();*
targetEntity = entityGroup.attachEntity(targetEntity, entityState);
if (entityChanged) {
entityChanged.publish({ entityAction: EntityAction.AttachOnImport, entity: targetEntity });
if (!entityState.isUnchanged()) {
entityGroup.entityManager._notifyStateChange(targetEntity, true);
}
}
}
if (targetEntity) {
targetEntity.entityAspect.entityState = entityState;
if (entityState.isModified()) {
targetEntity.entityAspect.originalValuesMap = newAspect.originalValues;
}
entityGroup.entityManager._linkRelatedEntities( targetEntity);
}
If I move the post initialize call below the ._linkRelatedEntities call it appears to work exactly as the query materialization
if (targetEntity) {
targetEntity.entityAspect.entityState = entityState;
if (entityState.isModified()) {
targetEntity.entityAspect.originalValuesMap = newAspect.originalValues;
}
entityGroup.entityManager._linkRelatedEntities( targetEntity);
*targetEntity.entityAspect._postInitialize();*
}
Am I missing something here? Is this the designed functionality? I have found a work around by passing in the EntityManager, setting the entityAspect manager and calling loadNavigationProperties however this seems redundant. Any insight fromt he Breeze folks would be greatly appreciated.
Thanks,
Brad
Not sure but this issue might be related to a bug that we just fixed in Breeze 1.4.1 available now.
I am working on a Hottowel project and I want to format some data passed on from database to Breeze, but it looks like the ctor is not getting registered.
What am I doing wrong?
In datacontext.js:
var manager = configureManager();
function configureManager() {
var mng = new breeze.EntityManager('breeze/data');
breeze.NamingConvention.camelCase.setAsDefault();
model.configureMetadataStore(mng.metadataStore);
return mng;
}
In model.js:
function configureMetadataStore(metadataStore) {
metadataStore.registerEntityTypeCtor
('UserInfo', null, userInfoInitializer);
}
function userInfoInitializer() {
if (this.Email == "")
this.Email = '---';
this.CreateDate = formatDateTime(this.CreateDate);
}
function formatDateTime(DateTime) {
return moment.utc(DateTime).format('DD. MM. YYYY. [у] hh:mm');
}
Datacontext has a reference to model, the data is transferred from database and appears on the screen, but is not formatted. console.log() calls from userInfoInitializer() are not appearing.
When I am constructing an entity, my constructor needs to have an entity to construct. I have not tried your above code but I believe that Breeze passes an entity in and you need to give that entity properties. Using this. MAY work but it is the first thing that stands out to me.
function userInfoInitializer(user) {
if (user.Email == "")
user.Email = "---";
2nd - What is your entity named in your model? Is it UserInfo or just User? You probably already know this but you need to make sure when you are adding a constructor you use the properly named Entity.
3rd - If you are using camelCase then you need to leave the first letter of the property lowercase. Ex . user.email and user.createDate.
Last, I can't tell if you are creating a 'createDate' in the constructor or that is being passed from your model. If it is indeed a property you are creating I would recommend making it an knockout observable or computed property. If it is coming from the database then you need to do something like
if (!user.createDate) { } //set it
Remember that all of the entities being returned from the database will be given that property, so if you have entities that already have a createDate in your example you are overriding that date. If you want to set createDate to now then I would move that into your method where you are creating the object.
I’m trying save some entities using breeze.js. Breeze is working fine and it saves all the changes as required. However, I have trouble validating and ensuring authorization is the server side. From what I’ve gather so far I guess the only way to do this is via examining the JObject passed into save bundles and constructing corresponding objects on the server side. I have to do this (instead of relying Breeze.SaveChanges as I have some logic on the server side). How do I do this? And how do I construct the Breeze.WebApi. SaveResult?
Idea of any other way of solving this problem is also very welcome
This should be done by implementing a custom EFContextProvider.
The code below implements a custom EFContextProvider for the Northwind database and was taken directly from the documentation on the breeze.com website .
public class NorthwindContextProvider: EFContextProvider<NorthwindIBContext> {
public NorthwindContextProvider() : base() { }
protected override bool BeforeSaveEntity(EntityInfo entityInfo) {
// return false if we don’t want the entity saved.
// prohibit any additions of entities of type 'Role'
if (entityInfo.Entity.GetType() == typeof(Role)
&& entityInfo.EntityState == EntityState.Added) {
return false;
} else {
return true;
}
}
protected override Dictionary<Type, List<EntityInfo>> BeforeSaveEntities(Dictionary<Type, List<EntityInfo>> saveMap) {
// return a map of those entities we want saved.
return saveMap;
}
}
#jaq316 is correct: a custom EFContextProvider is the place to intercept changes coming from the client. It is the place to both authorize and validate them . The documentation has more details. The essence of it is that you scrutinize the proposed changes within your overrides of the BeforeSaveEntity and BeforeSaveEntities virtual methods; alternatively you can attach handlers to the BeforeSaveEntityDelegate and BeforeSaveEntitiesDelegate.
So here is my thought on this one, since I am not using a ContextProvider at all. I am utilizing a SQL back-end and Ninject to inject a repository dependency into each controller I have. I have more items than the demo for "Todos" and want separate controllers out there and repositories as well. If I created the ContextProvider as shown by the breeze docs I would have one ContextProvider file with all the entities in it. This would be huge. If I separated them into separate contexts I would duplicating code in all the overrides.
Here is my Save Changes method in ContactFormController.cs :
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
var sr = new SaveResult() { KeyMappings = new List<KeyMapping>(), Entities = new List<object>()};
dynamic entity = saveBundle["entities"][0];
ContactForm form = entity.ToObject<ContactForm>();
EntityState state = entity.entityAspect.entityState;
switch (state)
{
case EntityState.Added:
KeyMapping mapping = new KeyMapping(){EntityTypeName = typeof(ContactForm).ToString(), TempValue = form.Id };
var validationErrors = _contactFormService.ProcessContactForm(ref form).Cast<object>().ToList();
//if we succeed then update the mappings
if (validationErrors.Count == 0)
{
//setup the new mappings
mapping.RealValue = form.Id;
sr.KeyMappings.Add(mapping);
//link the entity
sr.Entities.Add(form);
}
else
{
sr.Errors = validationErrors;
}
break;
}
return sr;
}
I dynamically change the endpoints before saves on the client side so that each controller in my webapi has a SaveChanges() method. I then call into the appropriate repository to process the backend functions as needed. This way I can run mock code or actual SQL changes depending on the repo injected.
If their are errors on the Processing of the form then we cast our custom List list to a List and assign it to the Errors property of the SaveResult. If there are no errors we send back the new key mappings to be updated on the client.
Ideally I want to reduce all the code in this controller and perhaps abstract it out to a utility method so there is less repeat in every controller. I like this method because then I can create normal repositories and not have them depend on a ContextProvider. Breeze independent at that point.
I have an object which has a circular reference to another object. Given the relationship between these objects this is the right design.
To Illustrate
Machine => Customer => Machine
As is expected I run into an issue when I try to use Json to serialize a machine or customer object. What I am unsure of is how to resolve this issue as I don't want to break the relationship between the Machine and Customer objects. What are the options for resolving this issue?
Edit
Presently I am using Json method provided by the Controller base class. So the serialization I am doing is as basic as:
Json(machineForm);
Update:
Do not try to use NonSerializedAttribute, as the JavaScriptSerializer apparently ignores it.
Instead, use the ScriptIgnoreAttribute in System.Web.Script.Serialization.
public class Machine
{
public string Customer { get; set; }
// Other members
// ...
}
public class Customer
{
[ScriptIgnore]
public Machine Machine { get; set; } // Parent reference?
// Other members
// ...
}
This way, when you toss a Machine into the Json method, it will traverse the relationship from Machine to Customer but will not try to go back from Customer to Machine.
The relationship is still there for your code to do as it pleases with, but the JavaScriptSerializer (used by the Json method) will ignore it.
I'm answering this despite its age because it is the 3rd result (currently) from Google for "json.encode circular reference" and although I don't agree with the answers (completely) above, in that using the ScriptIgnoreAttribute assumes that you won't anywhere in your code want to traverse the relationship in the other direction for some JSON. I don't believe in locking down your model because of one use case.
It did inspire me to use this simple solution.
Since you're working in a View in MVC, you have the Model and you want to simply assign the Model to the ViewData.Model within your controller, go ahead and use a LINQ query within your View to flatten the data nicely removing the offending circular reference for the particular JSON you want like this:
var jsonMachines = from m in machineForm
select new { m.X, m.Y, // other Machine properties you desire
Customer = new { m.Customer.Id, m.Customer.Name, // other Customer properties you desire
}};
return Json(jsonMachines);
Or if the Machine -> Customer relationship is 1..* -> * then try:
var jsonMachines = from m in machineForm
select new { m.X, m.Y, // other machine properties you desire
Customers = new List<Customer>(
(from c in m.Customers
select new Customer()
{
Id = c.Id,
Name = c.Name,
// Other Customer properties you desire
}).Cast<Customer>())
};
return Json(jsonMachines);
Based on txl's answer you have to
disable lazy loading and proxy creation and you can use the normal methods to get your data.
Example:
//Retrieve Items with Json:
public JsonResult Search(string id = "")
{
db.Configuration.LazyLoadingEnabled = false;
db.Configuration.ProxyCreationEnabled = false;
var res = db.Table.Where(a => a.Name.Contains(id)).Take(8);
return Json(res, JsonRequestBehavior.AllowGet);
}
Use to have the same problem. I have created a simple extension method, that "flattens" L2E objects into an IDictionary. An IDictionary is serialized correctly by the JavaScriptSerializer. The resulting Json is the same as directly serializing the object.
Since I limit the level of serialization, circular references are avoided. It also will not include 1->n linked tables (Entitysets).
private static IDictionary<string, object> JsonFlatten(object data, int maxLevel, int currLevel) {
var result = new Dictionary<string, object>();
var myType = data.GetType();
var myAssembly = myType.Assembly;
var props = myType.GetProperties();
foreach (var prop in props) {
// Remove EntityKey etc.
if (prop.Name.StartsWith("Entity")) {
continue;
}
if (prop.Name.EndsWith("Reference")) {
continue;
}
// Do not include lookups to linked tables
Type typeOfProp = prop.PropertyType;
if (typeOfProp.Name.StartsWith("EntityCollection")) {
continue;
}
// If the type is from my assembly == custom type
// include it, but flattened
if (typeOfProp.Assembly == myAssembly) {
if (currLevel < maxLevel) {
result.Add(prop.Name, JsonFlatten(prop.GetValue(data, null), maxLevel, currLevel + 1));
}
} else {
result.Add(prop.Name, prop.GetValue(data, null));
}
}
return result;
}
public static IDictionary<string, object> JsonFlatten(this Controller controller, object data, int maxLevel = 2) {
return JsonFlatten(data, maxLevel, 1);
}
My Action method looks like this:
public JsonResult AsJson(int id) {
var data = Find(id);
var result = this.JsonFlatten(data);
return Json(result, JsonRequestBehavior.AllowGet);
}
In the Entity Framework version 4, there is an option available: ObjectContextOptions.LazyLoadingEnabled
Setting it to false should avoid the 'circular reference' issue. However, you will have to explicitly load the navigation properties that you want to include.
see: http://msdn.microsoft.com/en-us/library/bb896272.aspx
Since, to my knowledge, you cannot serialize object references, but only copies you could try employing a bit of a dirty hack that goes something like this:
Customer should serialize its Machine reference as the machine's id
When you deserialize the json code you can then run a simple function on top of it that transforms those id's into proper references.
You need to decide which is the "root" object. Say the machine is the root, then the customer is a sub-object of machine. When you serialise machine, it will serialise the customer as a sub-object in the JSON, and when the customer is serialised, it will NOT serialise it's back-reference to the machine. When your code deserialises the machine, it will deserialise the machine's customer sub-object and reinstate the back-reference from the customer to the machine.
Most serialisation libraries provide some kind of hook to modify how deserialisation is performed for each class. You'd need to use that hook to modify deserialisation for the machine class to reinstate the backreference in the machine's customer. Exactly what that hook is depends on the JSON library you are using.
I've had the same problem this week as well, and could not use anonymous types because I needed to implement an interface asking for a List<MyType>. After making a diagram showing all relationships with navigability, I found out that MyType had a bidirectional relationship with MyObject which caused this circular reference, since they both saved each other.
After deciding that MyObject did not really need to know MyType, and thereby making it a unidirectional relationship this problem was solved.
What I have done is a bit radical, but I don't need the property, which makes the nasty circular-reference-causing error, so I have set it to null before serializing.
SessionTickets result = GetTicketsSession();
foreach(var r in result.Tickets)
{
r.TicketTypes = null; //those two were creating the problem
r.SelectedTicketType = null;
}
return Json(result);
If you really need your properties, you can create a viewmodel which does not hold circular references, but maybe keeps some Id of the important element, that you could use later for restoring the original value.