Can I use complex types as query string params for the HttpGet request in Asp.NET Core MVC app?
I had a problem with it, when i try to pass the param as complex type, like this:
[Route("reportData")]
[HttpGet]
public List<dynamic> GetReportData(int reportId, int scope [FromQuery] ReportFilterMetadataDto filters)
{
...
}
all of properties in filters objects have null value. But if I pass filters like string and deserialize it into destination type, like this:
[Route("reportData")]
[HttpGet]
public List<dynamic> GetReportData(int reportId, int, string filters)
{
var result = JsonConvert.DeserializeObject<ReportFilterMetadataDto>(filters);
}
there are no problems. Is it necessary to implement custom serializer or configure asp net core app MVC, or use middleware to getting correct result. Maybe I done anything in the wrong way?
They are probably null due to a binding failure.
Try the following:
[HttpGet("reportData/{reportId}/{scope}")]
public List<dynamic> GetReportData(int reportId, int scope [FromQuery]
ReportFilterMetadataDto filters)
{
...
}
You can also have multiple FromQuery attributes. However, with the amount of information you are getting, maybe consider this method as Post and send get the dto FromBody.
Related
I be straight to the point. I am in the process of converting ASP.Net web services into DotNetCore 2.1 services. My question is very simple. How do I get json output from a string (with a GET verb)?
I'm new at this, but almost every piece of documentation and recommendations do not work with DotNetCore.
Obviously, the following will not work:
[HttpGet]
public string Get()
{
return "{\"country_code\":\"US\",\"country_name\":\"United States\",\"region_name\":\"California\",\"city_name\":\"Los Angeles\",\"latitude\":\"34.052230\",\"longitude\":\" - 118.243680\",\"zip_code\":\"90001\",\"time_zone\":\" - 08:00\"}";
}
I just need to convert this string (or tell the client) that I want the output in json. The following does not work either - got a squiggly line under the "Json(" method and, for the life of me, can't find a reference to make it go away (I pulled it from an example, so they must be using a 3rd party json parsing library or there's a reference that I'm missing)
[HttpGet]
public JsonResult Get()
{
return Json("{\"country_code\":\"US\",\"country_name\":\"United States\",\"region_name\":\"California\",\"city_name\":\"Los Angeles\",\"latitude\":\"34.052230\",\"longitude\":\" - 118.243680\",\"zip_code\":\"90001\",\"time_zone\":\" - 08:00\"}", "application/json");
}
Ideally, I'd like to serialize an object to json, but figured I'd start with something ridiculously simple.
Anywho, if anyone can help.
If you don't already have a strongly typed model, you can build an anonymous type and return that from the controller
Simple Example.
public class MyController: Controller {
[HttpGet]
public IActionResult Get() {
var model = new {
country_code = "US",
country_name = "United States",
region_name = "California",
city_name = "Los Angeles",
latitude = 34.052230,
longitude = -118.243680,
zip_code = 90001,
time_zone = "- 08:00"
};
return Ok(model); //200 OK with content
}
}
In more complex scenarios you would get your objects from a data source.
No library needed, the framework out of the box will serialize the object(s) into JSON for you by default unless otherwise configured.
If you insist on passing a manually formatted string then use the ContemntResult object. Pass it the string and the content type.
[HttpGet]
public IActionResult Get() {
string json = "{\"country_code\":\"US\",\"country_name\":\"United States\",\"region_name\":\"California\",\"city_name\":\"Los Angeles\",\"latitude\":\"34.052230\",\"longitude\":\" - 118.243680\",\"zip_code\":\"90001\",\"time_zone\":\" - 08:00\"}";
return Content(json, new MediaTypeHeaderValue("application/json"));
}
Reference Format response data in ASP.NET Core Web API
Forcing a Particular Format
If you would like to restrict the response formats for a specific action you can apply the
[Produces] filter. The [Produces] filter specifies the response
formats for a specific action (or controller). Like most Filters, this
can be applied at the action, controller, or global scope.
[Produces("application/json")]
public class AuthorsController
The [Produces] filter will force all actions within the
AuthorsController to return JSON-formatted responses, even if other
formatters were configured for the application and the client provided
an Accept header requesting a different, available format.
Don't return string but object. So result of your actions are json string this is why you will get string in JSON and not an object
Make sure that your client is sending header "Content-Type": "application/json".
[HttpGet]
public Address Get()
{
return new Address{ CountryCode = "US"} ;
}
Sometimes my ASP.NET Core API needs to return a simple value i.e. bool, int or string even though in most cases, I return complex objects/arrays as JSON.
I think for consistency purposes, it's a good idea to return even simple values as JSON. What's the easiest way to convert a simple value, whether it's bool or int into JSON?
My standard controller action looks like this -- see below -- which gives me the ability to return status codes as well as data. Therefore, I'd like to stick to that approach, rather than return JsonResult.
public async Task<IActionResult> Get()
{
// Some logic
return Ok(data);
}
I'm just trying to figure out the easiest way to convert my data into JSON, if it's not already in JSON format.
Looking at your code, I assume your application is supposed to be a service that needs to return some kind of data serialised in JSON.
Well, good news is ASP.NET Core already includes a data serialiser that would do the job for you.
You may need to set it up according to your needs.
For example, let's assume the following data class:
public class Data {
public string Name { get; }
public string Value { get; }
public bool IsValid { get; }
public Data(string name, string value, bool isValid) {
Name = name;
Value = value;
IsValid = isValid;
}
}
Then the following method in your Controller:
public async Task<IActionResult> Get() {
var data = new Data("sample name", "this is a value", true);
return Ok(data);
}
would return:
{
"name": "sample name",
"value": "this is a value",
"isValid": true
}
Even thought the standard serialisation behaviour may fit fine for very simple implementations, you may need more control on how your different data types should be serialised (and deserialised) by your application, especially when those do not exactly match the way you want to present the data back to the client. In this case you may want to use Custom Converters.
You can configure that when setting up MVC in the ConfigureServices(IServiceCollection services) method:
// Add framework services.
services.AddMvc().AddJsonOptions(jo => {
// sample serialiser setup
jo.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
jo.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
jo.SerializerSettings.MissingMemberHandling = MissingMemberHandling.Error;
// custom Converters
jo.SerializerSettings.Converters.Add(new MyCustomConverter());
});
Here you can read and learn more on how to setup and use Custom Converters.
I am used to JAX-RS and would like to have similar comfort when sending requests using Spring MVC and working with the responses, i.e. on the client side inside my tests.
On the server (controller) side I'm quite happy with the automatic conversion, i.e. it suffices to just return an object instance and have JSON in the resulting HTTP response sent to the client.
Could you tell me how to work around the manual process of converting objectInstance to jsonString or vice versa in these snippets? If possible, I'd also like to skip configuring the content type manually.
String jsonStringRequest = objectMapper.writeValueAsString(objectInstance);
ResultActions resultActions = mockMvc.perform(post(PATH)
.contentType(MediaType.APPLICATION_JSON)
.content(jsonStringRequest)
)
String jsonStringResponse = resultActions.andReturn().getResponse().getContentAsString();
Some objectInstanceResponse = objectMapper.readValue(jsonStringResponse, Some.class);
For comparison, with JAX-RS client API I can easily send an object using request.post(Entity.entity(objectInstance, MediaType.APPLICATION_JSON_TYPE) and read the response using response.readEntity(Some.class);
if you have lot's of response objects, you could create some generic JsonToObject mapper-factory. It could be then used to detect the object type from a generic response (all response objects inherit from the same generic class) and respond/log properly from a bad mapping attempt.
I do not have a code example at hand, but as a pseudocode:
public abstract GenericResponse {
public String responseClassName = null;
// get/set
}
In the server code, add the name of the actual response object to this class.
The JsonToObject factory
public ConverterFactory<T> {
private T objectType;
public ConverterFactory(T type) {
objectType = type;
}
public T convert(String jsonString) {
// Type check
GenericResponse genResp = mapper.readValue(result.getResponse().getContentAsString(),
GenericResponse.class);
if (objectType.getClass().getSimpleName().equals(genResp.getResponseClassName())) {
// ObjectMapper code
return mapper.readValue(result.getResponse().getContentAsString(),
objectType.class);
} else {
// Error handling
}
}
}
I think this could be extended to be used with annotation to do more automation magic with the response. (start checking with BeanPostProcessor)
#Component
public class AnnotationWorker implements BeanPostProcessor {
#Override
public Object postProcessBeforeInitialization(final Object bean, String name) throws BeansException {
ReflectionUtils.doWithFields(bean.getClass(), field -> {
// make the field accessible if defined private
ReflectionUtils.makeAccessible(field);
if (field.getAnnotation(MyAnnotation.class) != null) {
field.set(bean, log);
}
});
return bean;
}
}
The above code snippet is copied from my current project and it injects to fields, you need to change it so, that it works for methods, eg ... where you may need it.
Having this all implemented may be tricky and can't say it necessarily works even, but it's something to try if you don't mind a bit of educative work.
I'm having issues using Jackson to map a Javascript posted JSON array of hashes (Tag).
Here is the data received by the controller #RequestBody (It is send with correct json requestheader):
[{name=tag1}, {name=tag2}, {name=tag3}]
Here is the controller:
#RequestMapping(value = "purchases/{purchaseId}/tags", method = RequestMethod.POST, params = "manyTags")
#ResponseStatus(HttpStatus.CREATED)
public void createAll(#PathVariable("purchaseId") final Long purchaseId, #RequestBody final List<Tag> entities)
{
Purchase purchase = purchaseService.getById(purchaseId);
Set<Tag> tags = purchase.getTags();
purchaseService.updatePurchase(purchase);
}
When I debug and view the 'entities' value it shows as an ArrayList of generic objects, not as a list of objects of type 'Tag' as I would expect.
How can I get jackson to map a passed array of objects to a list of obejcts of type 'Tag'?
Thanks
It sounds like Spring is not passing full type information for some reason, but rather a type-erased version, as if declaration was something like List<?> tag. I don't know what can be done to fully resolve this (may need something from Spring integration team), but one work-around is to define your own type like:
static class TagList extends ArrayList<Tag> { }
and use that instead. This will retain generic parameterization through super-type declarations so that even if Spring only passes equivalent of TagList.class, Jackson can figure out the Tag parameter.
Another way to do this is to rather obtain an array than a List, as follows:
#RequestBody Tag[] entities
Jackson requires a default constructor with no parameters on custom Objects, so you'll need to simply add a default constructor to your Tag class.
In your case simply add to your Tag class:
public Tag(){}
I have successfully set up a quick test of creating a "REST-like" service that returns an object serialized to JSON, and that was quite easy and quick (based on this article).
But while returning JSON-ified objects was easy as peach, I have yet to see any examples dealing with input parameters that are not primitives. How can I pass in a complex object as an argument? I am using Apache CXF, but examples using other frameworks like Jackson are welcome too :)
Client side would probably be something like building a javascript object, pass it into JSON.stringify(complexObj), and pass that string as one of the parameters.
The service would probably look something like this
#Service("myService")
class RestService {
#GET
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(#QueryParam("foo") double foo, #QueryParam("bar") double bar,
#QueryParam("object") MyComplex object) throws WebServiceException {
...
}
}
Sending serialized objects as parameters would probably quickly touch the 2KB URL-limit imposed by Internet Explorer. Would you recommend using POST in these cases, and would I need to change much in the function definitions?
After digging a bit I quickly found out there are basically two options:
Option 1
You pass a "wrapper object" containing all the other parameters to the service. You might need to annotate this wrapper class with JAXB annotations like #XmlRootElement in order for this to work with the Jettison based provider, but if you use Jackson in stead there is no need. Just set the content type to the right type and the right message body reader will be invoked.
This will only work for POST type services of course (AFAIK).
Example
This is just an example of turning the service mentioned in the original question into one using a wrapper object.
#Service("myService")
class RestService {
#POST
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(
/**
* Using "" will inject all form params directly into a ParamsWrapper
* #see http://cxf.apache.org/docs/jax-rs-basics.html
*/
#FormParam("") FooBarParamsWrapper wrapper
) throws WebServiceException {
doSomething(wrapper.foo);
}
}
class ParamsWrapper {
double foo, bar;
MyComplexObject object;
}
Option 2
You can provide some special string format that you pack your objects into and then implement either a constructor taking a string, a static valueOf(String s) or a static fromString(String s) in the class that will take this string and create an object from it. Or quite similar, create a ParameterHandler that does exactly the same.
AFAIK, only the second version will allow you to call your services from a browser using JSONP (since JSONP is a trick restricted to GET). I chose this route to be able to pass arrays of complex objects in the URI.
As an example of how this works, take the following domain class and service
Example
#GET
#Path("myService")
public void myService(#QueryParam("a") MyClass [] myVals) {
//do something
}
class MyClass {
public int foo;
public int bar;
/** Deserializes an Object of class MyClass from its JSON representation */
public static MyClass fromString(String jsonRepresentation) {
ObjectMapper mapper = new ObjectMapper(); //Jackson's JSON marshaller
MyClass o= null;
try {
o = mapper.readValue(jsonRepresentation, MyClass.class );
} catch (IOException e) {
throw new WebApplicationException()
}
return o;
}
}
A URI http://my-server.com/myService?a={"foo":1, "bar":2}&a={"foo":100, "bar":200} would in this case be deserialized into an array composed of two MyClass objects.
2019 comment:
Seeing that this answer still gets some hits in 2019, I feel I should comment. In hindsight, I would not recomment option 2, as going through these steps just to be able to be able to do GET calls adds complexity that's probably not worth it. If your service takes such complex input, you will probably not be able to utilize client side caching anyway, due to the number of permutations of your input. I'd just go for configuring proper Cross-Origin-Sharing (CORS) headers on the server and POST the input. Then focus on caching whatever you can on the server.
The accepted answer is missing #BeanParam. See
https://docs.jboss.org/resteasy/docs/3.0-rc-1/javadocs/javax/ws/rs/BeanParam.html
for further details. It allows you to define query params inside a wrapper object.
E.g.
public class TestPOJO {
#QueryParam("someQueryParam")
private boolean someQueryParam;
public boolean isSomeQueryParam() {
return someQueryParam;
}
public boolean setSomeQueryParam(boolean value) {
this.someQueryParam = value;
}
}
... // inside the Resource class
#GET
#Path("test")
public Response getTest(#BeanParam TestPOJO testPOJO) {
...
}
the best and simplest solution is to send your object as a json string and in server side implement a method which will decode that json and map to the specified object as per your need.. and yes it`s better to use POST.