I want to be able to perform an asynchronous task in java and be able to keep a completion (and if possible progress) monitor associated to the user's session. Is this possible, and if yes what is the way to do it?
Currently the task is implemented synchronously as a stateless session bean method, which is called from a jax-rs endpoint.
I looked at https://docs.oracle.com/javaee/7/tutorial/ejb-async001.htm but AsyncResult is not serializable so I guess I cannot add it to session.
Using the Spring annotation #Async, you can make any bean/method asynchronous.
The container will create a new thread and method will be executed asynchronously. You can as well pass a session object into this method and upon completion, you can mark an attribute in the session object.
Example:- https://spring.io/guides/gs/async-method/
JSF example, works in Wildfly:
1 inside in view (xhtml) we have an upload form and progress meter
<h:form>
<div align="justify">
<p:fileUpload style="width: auto" fileUploadListener="#{fileUploadCtrl.handleFileUpload}" mode="advanced" label="Please pick XLS file" update="messages" auto="true" sizeLimit="1000000" allowTypes="/(\.|\/)(xls|xlsx)$/" />
<p:growl id="messages" showDetail="false" life="4000"/>
</div>
</h:form>
<h:form id="wholeform">
<h:outputText id="statusot" value="#{fileUploadCtrl.message}" />
<p:spacer width="10" height="10"/>
<p:poll interval="1" listener="#{fileUploadCtrl.updateStatus}" update="wholeform" />
</h:form>
2 in controller, which is a managed bean, we process file and once a second update status
#ManagedBean
#ViewScoped
public class FileUploadCtrl {
#EJB
private SomeBusinessLogicClass model;
#EJB
private ProgressTracker progress;
private Future<List<String>> asyncResult;
private int progressId = 0;
private String message;
private boolean busy = false;
public void handleFileUpload(FileUploadEvent event) {
Set<String> ids = model.populate(event.getFile().getContents());
progressId = progress.newIndex();
asyncResult = model.process(ids);
busy = true;
FacesMessage message = new FacesMessage("Loaded " + ids.size() + " objects", "");
FacesContext.getCurrentInstance().addMessage(null, message);
}
public void updateStatus() {
if (!busy)
return;
try {
if (asyncResult.isDone()) {
List<String> r = asyncResult.get();
message = "Job done";
busy = false;
progress.delIndex(progressId);
} else {
message = progress.getIndex(progressId)+"-th element in work";
}
} catch (Exception e) {
System.out.println("updateStatus " + e.toString());
}
}
3 All business logic is in EJBs like SomeBusinessLogicClass or many others. Also we need a simple progress-manager EJB, I post it completely
#Singleton
public class ProgressTracker {
private Map<Integer,Integer> indexes = new HashMap<>();
public Map<Integer, Integer> getIndexes() {
return indexes;
}
public void setIndexes(Map<Integer, Integer> indexes) {
this.indexes = indexes;
}
public Integer newIndex() {
Integer size = indexes.size();
indexes.put(size,0);
return size;
}
public void incIndex(final Integer index) {
int old = indexes.get(index);
old++;
indexes.put(index,old);
}
public Integer getIndex(final Integer index) {
return indexes.get(index);
}
public void delIndex(Integer index) {
indexes.remove(index);
}
}
Maybe this example is not elegant, I'm almost newbie with frontends, but it is working and better, than nothing.
Related
I've recently started using Blazor. Is there a way to trigger form model validation only on submit, instead of live on each change?
Just for clarification, let's say I have something like this:
<EditForm Model="this" OnValidSubmit="SubmitForm">
<DataAnnotationsValidator />
<ValidationSummary />
<Label For="Name">Name</Label>
<InputText id="Name" name="Name" class="form-control" #bind-Value="Name"/>
<button type="submit">Save</button>
</EditForm>
#code {
[StringLength(10, ErrorMessage="Name too long")]
public string Name { get; set; }
private async Task SubmitForm()
{
// ...
// send a POST request
}
}
By default, it seems like the validity of the field and the error messages displayed in the ValidationSummary get re-evaluated on every change of the text input (e.g. as soon as I delete the 11th character from the input, the "too long" message disappears).
I would prefer if the displayed messages would remain frozen until the Submit button is clicked.
I suppose it would be possible to implement it by removing the ValidationSummary component and implementing a custom solution (e.g. displaying a List of error messages that's refreshed only on submit), but I was wondering if there is some idiomatic solution that I'm not aware of.
When validation occurs is controlled by the Validator you're using.
There are two events that you can receive from EditContext:
OnValidationRequested is invoked either when EditContext.Validate is called or as part of the form submission process.
OnFieldChanged is invoked every time a field value is changed.
A validator uses these events to trigger it's validation process, and outputs the results to the EditContext's ValidationMessageStore.
DataAnnotationsValidator wires up for both events and triggers validation whenever either is invoked.
There are other validators out there, and writing your own is not too difficult. Other than those from the usual control suppliers, there's Blazored, or mine. Mine is documented here - https://shauncurtis.github.io/articles/Blazor-Form-Validation.html. it has a DoValidationOnFieldChange setting!
#enet's answer sparked an alternative answer. Build your own DataAnnotationsValidator.
Here's the EditContext Extensions code. It's a modified version of the original MS Code with some extra control arguments.
using Microsoft.AspNetCore.Components.Forms;
using System.Collections.Concurrent;
using System.ComponentModel.DataAnnotations;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using System.Reflection.Metadata;
using System.Runtime.InteropServices;
namespace StackOverflowAnswers;
public static class EditContextCustomValidationExtensions
{
public static IDisposable EnableCustomValidation(this EditContext editContext, bool doFieldValidation, bool clearMessageStore)
=> new DataAnnotationsEventSubscriptions(editContext, doFieldValidation, clearMessageStore);
private static event Action? OnClearCache;
private static void ClearCache(Type[]? _)
=> OnClearCache?.Invoke();
private sealed class DataAnnotationsEventSubscriptions : IDisposable
{
private static readonly ConcurrentDictionary<(Type ModelType, string FieldName), PropertyInfo?> _propertyInfoCache = new();
private readonly EditContext _editContext;
private readonly ValidationMessageStore _messages;
private bool _doFieldValidation;
private bool _clearMessageStore;
public DataAnnotationsEventSubscriptions(EditContext editContext, bool doFieldValidation, bool clearMessageStore)
{
_doFieldValidation = doFieldValidation;
_clearMessageStore = clearMessageStore;
_editContext = editContext ?? throw new ArgumentNullException(nameof(editContext));
_messages = new ValidationMessageStore(_editContext);
if (doFieldValidation)
_editContext.OnFieldChanged += OnFieldChanged;
_editContext.OnValidationRequested += OnValidationRequested;
if (MetadataUpdater.IsSupported)
{
OnClearCache += ClearCache;
}
}
private void OnFieldChanged(object? sender, FieldChangedEventArgs eventArgs)
{
var fieldIdentifier = eventArgs.FieldIdentifier;
if (TryGetValidatableProperty(fieldIdentifier, out var propertyInfo))
{
var propertyValue = propertyInfo.GetValue(fieldIdentifier.Model);
var validationContext = new ValidationContext(fieldIdentifier.Model)
{
MemberName = propertyInfo.Name
};
var results = new List<ValidationResult>();
Validator.TryValidateProperty(propertyValue, validationContext, results);
_messages.Clear(fieldIdentifier);
foreach (var result in CollectionsMarshal.AsSpan(results))
{
_messages.Add(fieldIdentifier, result.ErrorMessage!);
}
// We have to notify even if there were no messages before and are still no messages now,
// because the "state" that changed might be the completion of some async validation task
_editContext.NotifyValidationStateChanged();
}
}
private void OnValidationRequested(object? sender, ValidationRequestedEventArgs e)
{
var validationContext = new ValidationContext(_editContext.Model);
var validationResults = new List<ValidationResult>();
Validator.TryValidateObject(_editContext.Model, validationContext, validationResults, true);
// Transfer results to the ValidationMessageStore
_messages.Clear();
foreach (var validationResult in validationResults)
{
if (validationResult == null)
{
continue;
}
var hasMemberNames = false;
foreach (var memberName in validationResult.MemberNames)
{
hasMemberNames = true;
_messages.Add(_editContext.Field(memberName), validationResult.ErrorMessage!);
}
if (!hasMemberNames)
{
_messages.Add(new FieldIdentifier(_editContext.Model, fieldName: string.Empty), validationResult.ErrorMessage!);
}
}
_editContext.NotifyValidationStateChanged();
}
public void Dispose()
{
if (_clearMessageStore)
_messages.Clear();
if (_doFieldValidation)
_editContext.OnFieldChanged -= OnFieldChanged;
_editContext.OnValidationRequested -= OnValidationRequested;
_editContext.NotifyValidationStateChanged();
if (MetadataUpdater.IsSupported)
{
OnClearCache -= ClearCache;
}
}
private static bool TryGetValidatableProperty(in FieldIdentifier fieldIdentifier, [NotNullWhen(true)] out PropertyInfo? propertyInfo)
{
var cacheKey = (ModelType: fieldIdentifier.Model.GetType(), fieldIdentifier.FieldName);
if (!_propertyInfoCache.TryGetValue(cacheKey, out propertyInfo))
{
// DataAnnotations only validates public properties, so that's all we'll look for
// If we can't find it, cache 'null' so we don't have to try again next time
propertyInfo = cacheKey.ModelType.GetProperty(cacheKey.FieldName);
// No need to lock, because it doesn't matter if we write the same value twice
_propertyInfoCache[cacheKey] = propertyInfo;
}
return propertyInfo != null;
}
internal void ClearCache()
=> _propertyInfoCache.Clear();
}
}
And the CustomValidation component:
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Forms;
namespace StackOverflowAnswers;
public class CustomValidation : ComponentBase, IDisposable
{
private IDisposable? _subscriptions;
private EditContext? _originalEditContext;
[CascadingParameter] EditContext? CurrentEditContext { get; set; }
[Parameter] public bool DoEditValidation { get; set; } = false;
/// <inheritdoc />
protected override void OnInitialized()
{
if (CurrentEditContext == null)
{
throw new InvalidOperationException($"{nameof(DataAnnotationsValidator)} requires a cascading " +
$"parameter of type {nameof(EditContext)}. For example, you can use {nameof(DataAnnotationsValidator)} " +
$"inside an EditForm.");
}
_subscriptions = CurrentEditContext.EnableCustomValidation(DoEditValidation, true);
_originalEditContext = CurrentEditContext;
}
/// <inheritdoc />
protected override void OnParametersSet()
{
if (CurrentEditContext != _originalEditContext)
{
// While we could support this, there's no known use case presently. Since InputBase doesn't support it,
// it's more understandable to have the same restriction.
throw new InvalidOperationException($"{GetType()} does not support changing the " +
$"{nameof(EditContext)} dynamically.");
}
}
/// <inheritdoc/>
protected virtual void Dispose(bool disposing)
{
}
void IDisposable.Dispose()
{
_subscriptions?.Dispose();
_subscriptions = null;
Dispose(disposing: true);
}
}
You can use it like this:
<EditForm EditContext=this.editContext OnValidSubmit=OnValidSubmit>
<CustomValidation DoEditValidation=false/>
#*<DataAnnotationsValidator/>*#
<div class="row">
<div class="col-2">
Date:
</div>
<div class="col-10">
<InputDate #bind-Value=this.Record.Date></InputDate>
</div>
</div>
.......
My code is experiencing a problem that I suspect may be self-inflicted. So I should probably answer this question first. Can I/how do I observe a LiveData object that is returned from a Dao that is based on a inner join query and a List parameter?
Unfortunately I do not yet have "10 reputation" on Stackoverflow, so apparently I cannot embed an image. But here is my ERD snapshot as it may help you see how my Entities are tying together: https://i.ibb.co/9YW0Vbx/Screenshot-at-2019-04-06-13-04-43.png
PrayerListFragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mTagViewModel = ViewModelProviders.of(this).get(TagViewModel.class);
mPrayerTagViewModel =
ViewModelProviders.of(this).get(PrayerTagViewModel.class);
...
//Update the tag list with the selected tags
mTagViewModel.getSelectedTags().observe(this, new Observer<List<Tag>>() {
#Override
public void onChanged(#Nullable List<Tag> tags) {
if(tags.size() > 0) {
mPrayerTagViewModel.setTagList(tags);
}
}
});
//Observe whatever prayers the view model has to show us
mPrayerTagViewModel.getPrayers().observe(this, new Observer<List<Prayer>>() {
#Override
public void onChanged(#Nullable List<Prayer> prayers) {
mPrayersAdapter.setPrayers(prayers);
}
});
...
}
PrayerTagViewModel
...
private List<String> mTagNames = new ArrayList<>();
...
public LiveData<List<Prayer>> getPrayers() { return getPrayersForTags(mTagNames); }
...
public void setTagList(List<Tag> tags) {
mTagNames = new ArrayList<>();
for (Tag tag: tags) {
mTagNames.add(tag.getName());
}
}
ITagDAO
This returns LiveData objects that I have no trouble observing:
#Query("SELECT * FROM tag_table ORDER BY name")
LiveData<List<Tag>> getAll();
#Query("SELECT * FROM tag_table WHERE selected ORDER BY name")
LiveData<List<Tag>> getSelected();
IPrayerTagDAO
But I am running into issues observing this, so I want to first make sure it is valid syntax:
#Query("SELECT * FROM prayer_table " +
"INNER JOIN prayertag_table " +
"ON summary=fk_summary " +
"WHERE fk_name IN (:names)")
LiveData<List<Prayer>> getPrayersForTags(final List<String> names);
If it is valid syntax, am I possibly losing my observable in my fragment because the call to getPrayers() in PrayerTagViewModel returns a new ViewModel, i.e. a different ViewModel than the one I have started observing in the fragment??
Persistence paid off! I had a sneaky suspicion the mysterious Transformations.switchMap could resolve my issue, but only after a lot more reading did I realize how.
PrayerTagViewModel (modified)
...
private PrayerTagRepository mPrayerTagRepository;
private MutableLiveData<List<String>> mTags = new MutableLiveData<>();
private LiveData<List<Prayer>> mPrayers =
Transformations.switchMap(mTags, mTags -> getPrayersForTags(mTags));
public PrayerTagViewModel(#NonNull Application application) {
super(application);
mPrayerTagRepository = PrayerTagRepository.getRepository(application);
}
...
public LiveData<List<Prayer>> getPrayersForTags(final List<String> names) {
return mPrayerTagRepository.getPrayersForTags(names);
}
public LiveData<List<Prayer>> getPrayers() { return mPrayers; }
...
public void setTagList(List<Tag> tags) {
List<String> tagNames = new ArrayList<>();
for (Tag tag: tags)
tagNames.add(tag.getName());
mTags.setValue(tagNames);
}
PrayersListFragment (modified)
...
//Update the tag list with the selected tags
mTagViewModel.getSelectedTags().observe(this, new Observer<List<Tag>>() {
#Override
public void onChanged(#Nullable List<Tag> tags) {
Log.i(this.getClass().getName(),"onChanged :: Tag size = " + tags.size());
if(tags.size() > 0)
mPrayerTagViewModel.setTagList(tags);
}
});
//Observe whatever prayers the view model has to show us
mPrayerTagViewModel.getPrayers().observe(this,
prayers -> mPrayersAdapter.setPrayers(prayers));
Solution: The switchMap lets my Fragment observe a dynamically changing LiveData (actually a MutableLiveData) from my ViewModel.
i start to use Spring MVC and i have a trouble. I want to get the value of a hashmap with the key. The object ProtoStatus contains a hashmap who i want to get value. I have this error :
org.thymeleaf.exceptions.TemplateProcessingException: Exception
evaluating SpringEL expression: "protoStatus.status.get(30000)"
(template: "protoStatusPage" - line 18, col 21)
public class ProtoStatus
{
public HashMap<String, String> status;
public void computeStatus()
{
this.status = new HashMap();
for (int i=30000; i<30032; i++)
{
this.status.put(String.valueOf(i), String.valueOf(ServerChecker.Check("192.168.0.1", i)));
}
}
public void setStatus(HashMap status)
{
this.status = status;
}
public HashMap getStatus()
{
return this.status;
}
public String getStatus(int key)
{
return (String) this.status.get(key);
}
}
The Spring MVC part :
#PostMapping("/")
public String submit(#ModelAttribute User user, #ModelAttribute ProtoStatus protoStatus)
{
protoStatus = new ProtoStatus();
protoStatus.computeStatus();
return "protoStatusPage";
}
And Finaly, in the template protoStatusPage.html, i want to get the value for key 30000:
<p th:text="${protoStatus.status.get(30000)}" />
Your status attribute is null by default. It only becomes non-null when you call computeStatus(). But you're never calling it on the ProtoStatus used by the view:
protoStatus = new ProtoStatus();
protoStatus.computeStatus();
Instead, you create a different one, and call computeStatus() on that one, that is then immediately eligible to garbage collection.
Also, you have a Map<String, String>, but your getStatus() method, and the expression in your view, tries to get something out of it usig a key of type Integer. That will always return null.
Your HashMap<String,String> contains both the String object. So you have to call using
Replace this line
<p th:text="${protoStatus.status.get(30000)}" />
with
<p th:text="${protoStatus.status.get('30000')}" />
Using VS2012/.NET 4.5 I am creating a custom activity which implements a Receive child activity (as an implementation child). The parameters are in the example below fixed to just one: OutValue of type Guid.
I really would love to access the value of incoming parameter value in ReceiveDone, because I need to work with it and transform it before returning it from the activity. Please ignore that I am currently using a Guid, it still fails to access the value with and InvalidOperationException:
An Activity can only get the location of arguments which it owns. Activity 'TestActivity' is trying to get the location of argument 'OutValue' which is owned by activity 'Wait for
workflow start request [Internal for TestActivity]'
I have tried everything I could think of, but am stupefied. There must be a way to do this very simple thing?
public class TestActivity : NativeActivity<Guid>
{
protected override void CacheMetadata(NativeActivityMetadata metadata)
{
var content = ReceiveParametersContent.Create(new Dictionary<string, OutArgument>()
{
// How to access the runtime value of this inside TestActivity?
{"OutValue", new OutArgument<Guid>()}
});
startReceiver = new Receive()
{
DisplayName = string.Format("Wait for workflow start request [Internal for {0}]", this.DisplayName),
CanCreateInstance = true,
ServiceContractName = XName.Get("IStartService", Namespace),
OperationName = "Start",
Content = content
};
foreach (KeyValuePair<string, OutArgument> keyValuePair in content.Parameters)
{
metadata.AddImportedChild(keyValuePair.Value.Expression);
}
metadata.AddImplementationChild(startReceiver);
}
protected override void Execute(NativeActivityContext context)
{
context.ScheduleActivity(startReceiver, ReceiveDone);
}
private void ReceiveDone(NativeActivityContext context, ActivityInstance completedInstance)
{
var receive = completedInstance.Activity as Receive;
ReceiveParametersContent content = receive.Content as ReceiveParametersContent;
try
{
// This causes InvalidOperationException.
// An Activity can only get the location of arguments which it owns.
// Activity 'TestActivity' is trying to get the location of argument 'OutValue'
// which is owned by activity 'Wait for workflow start request [Internal for TestActivity]'
var parmValue = content.Parameters["OutValue"].Get(context);
}
catch (Exception)
{ }
}
private Receive startReceiver;
private const string Namespace = "http://company.namespace";
}
Use internal variables to pass values between internal activities.
Although not directly related to your code, see the example below which should give you the idea:
public sealed class CustomNativeActivity : NativeActivity<int>
{
private Variable<int> internalVar;
private Assign<int> internalAssign;
protected override void CacheMetadata(NativeActivityMetadata metadata)
{
base.CacheMetadata(metadata);
internalVar = new Variable<int>("intInternalVar", 10);
metadata.AddImplementationVariable(internalVar);
internalAssign = new Assign<int>
{
To = internalVar,
Value = 12345
};
metadata.AddImplementationChild(internalAssign);
}
protected override void Execute(NativeActivityContext context)
{
context.ScheduleActivity(internalAssign, (activityContext, instance) =>
{
// Use internalVar value, which was seted by previous activity
var value = internalVar.Get(activityContext);
Result.Set(activityContext, value);
});
}
}
Calling the above activity:
WorkflowInvoker.Invoke<int>(new CustomNativeActivity());
Will output:
12345
Edit:
In your case your OutArgument will be the internalVar
new OutArgument<int>(internalVar);
You need to use OutArgument and them to variables. See the code example with the documentation.
I may have tried everything I thought of, but I am stubborn and refuse to give up, so I kept on thinking ;)
I here have changed my example to use a Data class as a parameter instead (it does not change anything in itself, but I needed that in my real world example).
This code below is now a working example on how to access the incoming data. The use of an implementation Variable is the key:
runtimeVariable = new Variable<Data>();
metadata.AddImplementationVariable(runtimeVariable);
And the OutArgument:
new OutArgument<Data>(runtimeVariable)
I can then access the value with:
// Here dataValue will get the incoming value.
var dataValue = runtimeVariable.Get(context);
I haven't seen an example elsewhere, which does exactly this. Hope it will be of use to any one but me.
The code:
[DataContract]
public class Data
{
[DataMember]
Guid Property1 { get; set; }
[DataMember]
int Property2 { get; set; }
}
public class TestActivity : NativeActivity<Guid>
{
public ReceiveContent Content { get; set; }
protected override void CacheMetadata(NativeActivityMetadata metadata)
{
runtimeVariable = new Variable<Data>();
metadata.AddImplementationVariable(runtimeVariable);
Content = ReceiveParametersContent.Create(new Dictionary<string, OutArgument>()
{
{"OutValue", new OutArgument<Data> (runtimeVariable)}
});
startReceiver = new Receive()
{
DisplayName = string.Format("Wait for workflow start request [Internal for {0}]", this.DisplayName),
CanCreateInstance = true,
ServiceContractName = XName.Get("IStartService", Namespace),
OperationName = "Start",
Content = Content
};
metadata.AddImplementationChild(startReceiver);
}
protected override void Execute(NativeActivityContext context)
{
context.ScheduleActivity(startReceiver, ReceiveDone);
}
private void ReceiveDone(NativeActivityContext context, ActivityInstance completedInstance)
{
// Here dataValue will get the incoming value.
var dataValue = runtimeVariable.Get(context);
}
private Receive startReceiver;
private Variable<Data> runtimeVariable;
private const string Namespace = "http://company.namespace";
}
In Martin Fowler's "Patterns of Enterprise Application Architecture"
is described approach for organizing DAL like a set of mappers for entities. Each has it's own IdentityMap storing specific entity.
for example in my ASP.NET WebApplication:
//AbstractMapper - superclass for all mappers in DAL
public abstract class AbstractMapper
{
private readonly string _connectionString;
protected string ConnectionString
{
get { return _connectionString; }
}
private readonly DbProviderFactory _dbFactory;
protected DbProviderFactory DBFactory
{
get { return _dbFactory; }
}
#region LoadedObjects (IdentityMap)
protected Hashtable LoadedObjects = new Hashtable();
public void RegisterObject(long id, DomainObject obj)
{
LoadedObjects[id] = obj;
}
public void UnregisterObject(long id)
{
LoadedObjects.Remove(id);
}
#endregion
public AbstractMapper(string connectionString, DbProviderFactory dbFactory)
{
_connectionString = connectionString;
_dbFactory = dbFactory;
}
protected virtual string DBTable
{
get
{
throw new NotImplementedException("database table is not defined in class " + this.GetType());
}
}
protected virtual T Find<T>(long id, IDbTransaction tr = null) where T : DomainObject
{
if (id == 0)
return null;
T result = (T)LoadedObjects[id];
if (result != null)
return result;
IDbConnection cn = GetConnection(tr);
IDbCommand cmd = CreateCommand(GetFindStatement(id), cn, tr);
IDataReader rs = null;
try
{
OpenConnection(cn, tr);
rs = cmd.ExecuteReader(CommandBehavior.SingleRow);
result = (rs.Read()) ? Load<T>(rs) : null;
}
catch (DbException ex)
{
throw new DALException("Error while loading an object by id in class " + this.GetType(), ex);
}
finally
{
CleanUpDBResources(cmd, cn, tr, rs);
}
return result;
}
protected virtual T Load<T>(IDataReader rs) where T : DomainObject
{
long id = GetReaderLong(rs["ID"]);
T result = (T)LoadedObjects[id];
if (result != null)
return result;
result = (T)DoLoad(id, rs);
RegisterObject(id, result);
return result;
}
// another CRUD here ...
}
// Specific Mapper for entity Account
public class AccountMapper : AbstractMapper
{
internal override string DBTable
{
get { return "Account"; }
}
public AccountMapper(string connectionString, DbProviderFactory dbFactory) : base(connectionString, dbFactory) { }
public Account Find(long id)
{
return Find<Account>(id);
}
public override DomainObject DoLoad(long id, IDataReader rs)
{
Account account = new Account(id);
account.Name = GetReaderString(rs["Name"]);
account.Value = GetReaderDecimal(rs["Value"]);
account.CurrencyID = GetReaderLong(rs["CurrencyID"]);
return account;
}
// ...
}
The question is: where to store these mappers? How system services (entities) should call mappers?
I decided to create MapperRegistry containing all mappers. So services can call mappers like:
public class AccountService : DomainService
{
public static Account FindAccount(long accountID)
{
if (accountID > 0)
return MapperRegistry.AccountMapper.Find(accountID);
return null;
}
...
}
But where can I store MapperRegistry instance? I see following variants, but don't like any of them:
MapperRegistry is global for application (Singleton)
Not applicable because of necessity of synchronization in multi-thread ASP.NET application (at least Martin says that only mad can choose this variant)
MapperRegistry per Session
Seems not so good too. All ORMs (NHibernate, LINQ to SQL, EntityFramework) masters advise to use DataContext (NHibernateSession, ObjectContext) per Request and not to store context in Session.
Also in my WebApp almost all requests are AJAX-requests to EntityController.asmx (with attribute ScriptService) returning JSON. And session is not allowed.
MapperRegistry per Request
There are a lot of separate AJAX calls. In this case life cycle of MapperRegistry will be too small. So the data almost always will be retrieved from database, as a result - low performance.
Dear Experts, please help me with architectural solution.