I am learning a course topic reflection and metadata from nest documentation. They used #setmetadata('roles') but I don't know metadata come from and when they are used?
I don't know metadata come from
First lets explain what metadata generally means.
Metadata in general means data about data. Its a description of the data in more simpler terms (for e.g data about an image). Taking an example from here.
They used #setmetadata('roles').
Nest provides the ability to attach custom data to route handlers through #SetMetadata. Its a way to declaratively define and store data about your controller(endpoint).
#SetMetadata stores the key value pairs. For example,
SetMetadata('IS_PUBLIC_KEY', true)
findAll(#Query() paginationQuery: PaginationQueryDto) {
return this.testService.findAll(paginationQuery);
}
Here I am setting a key IS_PUBLIC_KEY with a value set to true.
In this scenario you are defining a key named role (most probably and it seems it may be missing a value) which will define what certain types or role can access this controller.
When they are used?
You can use it when you want to define the Guards. For instance, I am using the above findAll controller as a public api. In my guard implementation, I check and see if the value of IsPublic is true then allow any consumer to consume the API.
canActivate(
context: ExecutionContext,
): boolean | Promise<boolean> | Observable<boolean> {
const isPublic = this.reflector.get('IS_PUBLIC_KEY', context.getHandler());
if (isPublic) {
return true;
}
}
Hope this answers your question.
https://docs.nestjs.com/fundamentals/execution-context#reflection-and-metadata:
The #SetMetadata() decorator is imported from the #nestjs/common package.
Related
I need to query a property of Saga Data class to get a list. It is stored on SqlPersistance table [Data] column as a serialized object.
Think about a scenario that my SagaData has a property called UserName, so I want to query every saga related to that user.
In a sloppy way, I can query the column content, get the list and can create Saga objects out of the content, by querying like:
SELECT [Id]
,[Correlation_TaskId]
,[Metadata]
,[Data]
,[PersistenceVersion]
,[SagaTypeVersion]
,[Concurrency]
FROM [myWonderfulDb].[dbo].[MyWonderfulPeristanceTable]
where JSON_VALUE(Data,'$.Username') = 'arthur'
but I am looking for an elegant way to do it by possibly using NserviceBus API's.
There is a SagaFinder implementation described in ParticularSoftware documentation (link: https://docs.particular.net/persistence/sql/saga-finder) but this returns only one object which does not perfectly fit into my scenario.
Here how it is implemented in the documentation:
class SqlServerSagaFinder :
IFindSagas<MySagaData>.Using<MyMessage>
{
public Task<MySagaData> FindBy(MyMessage message, SynchronizedStorageSession session, ReadOnlyContextBag context)
{
return session.GetSagaData<MySagaData>(
context: context,
whereClause: "JSON_VALUE(Data,'$.PropertyPathInJson') = #propertyValue",
appendParameters: (builder, append) =>
{
var parameter = builder();
parameter.ParameterName = "propertyValue";
parameter.Value = message.PropertyValue;
append(parameter);
});
}
}
Any ideas appreciated. Thank you!
We have guidance about querying saga state available at
https://docs.particular.net/nservicebus/sagas/#querying-saga-data
In short, you can query the saga data, there is no out of the box way provided by NServiceBus because we recommend using a different approach instead:
the saga to publish events containing the required data and have handlers that process these events and store the data in one or more read model(s) for querying purposes.
The major points why we don't recommend it is in my viewpoint these two
By exposing the data outside of the safeguards of the business logic in the saga the risk is that the data is not treated as
read-only. Eventually, a component tries to bypass the saga and
directly modify the data.
Querying the data might require additional indexes, resources etc. which need to be managed by the component issuing the query.
Those additional resources can influence saga performance.
The only purpose of the SagaFinder is to find a single instance of a certain saga that correlates with the incoming message. I'm not aware of any framework functionalities to query saga (data) instances.
When the key is a composite of id1, id2 in a GemFire Region and the Region is partitioned with id1, what is the best way of getting all the rows whose key matched id1.
Couple of options that we are thinking of:
Create another index on id1. If we do that, we are wondering if it goes against all Partition Regions?
Write data aware Function and Filter by (id1, null) to target specific Partition Region. Use index in local Region by using QueryService?
Can you please let me know if there is any other way to achieve the query by partial key.
Well, it could be implemented (optimally) by using a combination of #1 and #2 in your "options" above (depending on whether your application domain object also stored/referenced the key, which would be the case if you were using SD[G] Repositories.
This might be best explained with the docs and an example, particularly using the PartitionResolver interface Javadoc.
Say your "composite" Key was implemented as follows:
class CompositeKey implements PartitionResolver {
private final Object idOne;
private final Object idTwo;
CompositeKey(Object idOne, Object idTwo) {
// argument validation as necessary
this.idOne = idOne;
this.idTwo = idTwo;
}
public String getName() {
return "MyCompositeKeyPartitionResolver";
}
public Object getRoutingObject() {
return idOne;
}
}
Then, you could invoke a Function that queries the results you desire by using...
Execution execution = FunctionService.onRegion("PartitionRegionName");
Optionally, you could use the returned Execution to filter on just the (complex) Keys you wanted to query (further qualify) when invoking the Function...
ComplexKey filter = { .. };
execution.withFilter(Arrays.stream(filter).collect(Collectors.toSet()));
Of course, this is problematic if you do not know your keys in advance.
Then you might prefer to use the ComplexKey to identify your application domain object, which is necessary when using SD[G]'s Repository abstraction/extension:
#Region("MyPartitionRegion")
class ApplicationDomainObject {
#Id
CompositeKey identifier;
...
}
And then, you can code your Function to operate on the "local data set" of the Partition Region. That is, when a data node in the cluster hosts the same Partition Region (PR), then it will only operate on the data set in the "bucket" for that PR, which is accomplished by doing the following:
class QueryPartitionRegionFunction implements Function {
public void execute(FunctionContext<Object> functionContext) {
RegionFunctionContext regionFunctionContext =
(RegionFunctionContext) functionContext;
Region<ComplexKey, ApplicationDomainObject> localDataSet =
PartitionRegionHelper.getLocalDataForContext(regionFunctionContext);
SelectResults<?> resultSet =
localDataSet.query(String.format("identifier.idTwo = %s",
regionFunctionContext.getArguments);
// process result set and use ResultSender to send results
}
}
Of course, all of this is much easier to do using SDG's Function annotation support (i.e. implementing and invoking your Function anyway).
Note that, when you invoke the Function, onRegion using the GemFire's FunctionService, or more conveniently with SDG's annotation support for Function Execution, like so:
#OnRegion("MyPartitionRegion")
interface MyPartitionRegionFunctions {
#FunctionId("QueryPartitionRegion")
<return-type> queryPartitionRegion(..);
}
Then..
Object resultSet = myPartitionRegionFunctions.queryPartitionRegion(..);
Then, the FunctionContext will be a RegionFunctionContext (because you executed the Function on the PR, which executes on all nodes in the cluster hosting the PR).
Additionally, you use the PartitionRegionHelper.getLocalDataForContext(:RegionFunctionContext) to get the local data set of the PR (i.e. the bucket, or just the shard of data in the entire PR (across all nodes) hosted by that node, which would be based your "custom" PartitionResolver).
You can then query to further qualify, or filter the data of interests. You can see that I queried (or further qualified) by idTwo, which was not part of the PartitionResolver implementation. Additionally, this would only be required in the (OQL) query predicate if you did not specify Keys in your Filter with the Execution (since, I think, that would take the entire "Key" (idOne & idTwo) into account, based on our properly implemented Object.equals() method of your ComplexKey class).
But, if you did not know the keys in advance and/or (especially if) you are using SD[G]'s Repositories, then the ComplexKey would be part of your application domain abject, which you could then Index, and query on (as shown above: identifier.idTwo = ?).
Hope this helps!
NOTE: I have not test any of this, but hopefully it will point you in the right direction and/or give you further ideas.
In relay, when using REQUIRED_CHILDREN like so:
return [{
type: 'REQUIRED_CHILDREN',
children: [
Relay.QL`
fragment on Payload {
myConnection (first: 50) {
edges {
node {
${fragment}
}
}
}
}
`
]
}]
and reading off the response through the onSuccess callback:
Relay.Store.commitUpdate(
new AboveMutation({ }), { onFailure, onSuccess }
)
the response turns the property myConnection into a hashed name (i.e. __myConnection652K), which presumably is used to prevent connection/list conflicts inside the relay store.
However, since this is a REQUIRED_CHILDREN and I'm manually reading myConnection, it just prevents access to it.
Is there an way to get the actual property names when using the onSuccess callback?
Just as Ahmad wrote: using REQUIRED_CHILDREN means you're not going to store the results. The consequence of it is that data supplied to the callback is in raw shape (nearly as it came from server) and data masking does not applies.
Despite not storing the data, it seems to be no reason (though core team member's opinion would be certainly more appropriate here) not to convert it to client style shape. This is the newest type of mutation, so there is a chance such feature was accidentally omitted. This is normal that queries are transformed to the server style shape, the opposite transformation could take place as well. However until now is has not been needed - while saving the data to the store and updating components props, transformation was made meanwhile. Currently most of Relay team is highly focused on rewriting much of the implementation, so I would not expect this issue to be improved very soon.
So again, solution proposed by Ahmed to convert type to GraphQLList seems to be the easiest and most reliable. If for any reason you want to stand by connection, there is an option to take GraphQL fragment supplied as children (actually its parsed form stored in __cachedFragment__ attribute of that original fragment) and traverse it to obtain the serializationKey for desired field (eg __myConnection652K).
I have a REST interface endpoint like
POST /items/12345/actions
I utilize a generic actions sub collection to be apply to apply changes to 12345 which are not easily mapped to the content or direct other sub collections of it.
My question is the following: Since there could be multiple different action types I identify the action by a JSON property of the content of an uploaded document.
How do I select a action by a part of the JSON body of the request. Is there something possible like...
[Route("api/v1/items")
public class ItemsController : Controller
{
[HttpPost("{id}/actions")]
[CheckJsonBody("type", "ActionA")]
public ActionResult DoActionA(int id, ActionA a)
{
// do something
}
[HttpPost("{id}/actions")]
[CheckJsonBody("type", "ActionB")]
public ActionResult DoActionB(int id, ActionB b)
{
// do something
}
}
The request would look like ...
{
"type": "ActionA",
"abc": "xyz"
}
I have digged myself up into the code till Microsoft.AspNetCore.Mvc.ActionConstraints.ActionMethodSelectorAttribute (GitHub).
However starting from there, I am a bit lost to reach a high-performance solution. Do I need to decode the body or is that something which is already done at that time the constraint is evaluated?
ps: And yes, I know I could handle them in one action and do a switch on the "type" property.
An ASP.NET team member was so friendly to direct me to an answer: In the ActionMethodSelectorAttribute you can read the body into a memory stream, read till the property for the selection filter. Then you seek the memory stream to zero and replace it in the request (for later model binding). You can cache the criteria value in HttpContext.Items to speed it up if you use the same property for multiple actions.
I'm designing a REST API and am looking for the recommended best practice for updating object graphs. My question is best explained in an example, so let's say that I have a GET resource as follows:
URI: /people/123
This URI returns an object graph like this:
{
"name":"Johnny",
"country":{"id":100,"name":"Canada"},
"likes":[
{"id":5,"name":"Fruit"},
{"id":100,"name":"Sports"}
]
}
When allowing the API consumer to update this resource, how would you expect the object to be updated via PUT or PATCH? Updating the "name" property is pretty straightforward, but I'm not certain about "country" or "likes", as the consumer can only only change the relationship to other objects and not create new ones.
Here is one way to request the update:
{
"name":"Bob",
"countryId":200
"likeIds":[3,10,22]
}
This update will change the resource to the following:
{
"name":"Bob",
"country":{"id":200,"name":"United States of America"},
"likes":[
{"id":3,"name":"Cars"},
{"id":10,"name":"Planes"},
{"id":22,"name":"Real Estate"}
]
}
This design explicitly and clearly asks the consumer to only update the "IDs" of the "Person", but I'm concerned that the object graph for a PUT/PATCH looks different than the GET, making the API hard to learn and remember. So another option is to request the PUT/PATCH as follows:
{
"name":"Bob",
"country":{"id":100},
"likes":[
{"id":3},
{"id":10},
{"id":22}
]
}
This will yield the same change as the previous update and does not alter the object graph. However, it doesn't make it clear to the API consumer that only the "IDs" can be updated.
In this scenario, which approach is recommended?
In my opinion you should stay with the same structure for both, GET and PUT requests. Why? Because it's quite common to map JSON/XML data into objects, and most (if not all) software that do the actual mapping work best if JSON schema is always the same.
So your webservice should accept a following JSON code:
{
"name":"Joe",
"country":{"id":200,"name":"United States of America"},
"likes":[
{"id":5,"name":"Fruit"}
]
}
However it doesn't have to take into account the country name and may focus only on the country id.