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"} ;
}
Related
I'm developing a Rest Client using Spring Boot and Spring Framework (spring-boot-starter-parent 2.1.6.RELEASE)
I have a class representing a response object as shown below:
public class ValidateResponse {
private String ResponseCode;
private String ResponseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
I'm creating a web-hook for an external api and I need to return a JSON object to for a specific endpoint (the JSON object properties must start with uppercase(s)). I'm calling returning the object from a PostMapping method nested in a RequestMapping root path:
#PostMapping("hooks/validate")
public ValidateResponse responseObj(#RequestHeader Map<String, String> headersObj) {
ValidateResponse response = new ValidateResponse("000000", "Success");
logger.info("Endpoint = hooks/validate | Request Headers = {}", headersObj);
return response;
}
However, when I hit the endpoint from postman I'm getting duplicate varialbes
{
"ResponseCode": "000000",
"ResponseDesc": "Success",
"responseCode": "000000",
"responseDesc": "Success"
}
I understand that the pojo-json conversion is handled by spring but I don't understand why the conversion is yielding duplicate variables.
Note: I know the ResponseDesc and the ResponseCode are not declared using the best standards for naming variables (camelCasing).
I've done some digging and according to the Java Language Specification
An identifier is an unlimited-length sequence of Java letters and Java digits, the first of which must be a Java letter.
and
The "Java letters" include uppercase and lowercase ASCII Latin letters A-Z (\u0041-\u005a), and a-z (\u0061-\u007a), and, for historical reasons, the ASCII underscore (_, or \u005f) and dollar sign ($, or \u0024). The $ character should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.
So, I'm assuming its syntactically correct to define a variable using the Camelcase format [Need clarification on this].
I'm considering having to create the JSON object manually but I'd like to know the cause of this behaviour first. Any pointers are appreciated.
Jackson deserializes all the public fields that it comes across. However if you want Jackson to return the response in your expected element names (in your case elements starting with capital letters), make the fields private and annotate them with the #JsonProperty(expected_name_here). Your class file will typically looks as shown below
public class ValidateResponse {
#JsonProperty("ResponseDesc")
private String responseCode;
#JsonProperty("ResponseDesc")
private String responseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
Note: The getters and setters for these fields should be public, otherwise Jackson won't see anything to deserialize in the class.
public class ValidateResponse {
#JsonProperty("ResponseDesc")
public String responseCode;
#JsonProperty("ResponseDesc")
public String responseDesc;
//getters and setters
//constructors using fields
//empty constructor
}
This must fix your problem, however I do not know the reason as it requires deep Jackson investigation.
EDIT
I found out the reason.
The field got duplicated because in you case you had:
2 public fields named in upper case -> they are to be processed by jackson
2 getters getResponseCode and getResponseDesc -> they are to be resolved
as accessors for properties responseCode and responseDesc accordingly.
Summing this up - you have 4 properties resolved by Jackson. Simply making your fields private will resolve your issue, however I still advise using JsonProperty approach.
I added a com.google.code.gson dependency in the projects pom.xml file to configure Spring Boot to use Gson (instead of the default jackson).
The Json object returned from the hooks/validate endpoint must have its property names starting with a capital letter. Using a java class to generate the response object was resulting to camelCased property names so I resolved to create the JSON response object manually. Here's the code for creating the custom JSON object:
public ResponseEntity<String> responseObj(#RequestHeader Map<String, String> headersObj) {
HttpHeaders responseHeaders = new HttpHeaders();
responseHeaders.setContentType(MediaType.APPLICATION_JSON);
JsonObject response = new JsonObject();
response.addProperty("ResponseCode", "00000000");
response.addProperty("ResponseDesc" , "Success");
logger.info("Endpoint = hooks/validate | Request Headers = {}", headersObj);
return ResponseEntity.ok().headers(responseHeaders).body(response.toString());
}
Note The JSON object is returned as a String so the response from the endpoint must have an additional header to define MediaType to inform the calling system that the response is in JSON format:
responseHeaders.setContentType(MediaType.APPLICATION_JSON);
then add the header to the response:
return ResponseEntity.ok().headers(responseHeaders).body(response.toString());
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'm using Google Http Client and Jackson to query data to backend (JSON API).
I need to pass parameters (one Java bean object). The object might have few or lot of field. Initially I attempt to pass it as content as follow:
HttpRequest request = requestFactory.buildGetRequest(getUrl(api)).setContent(new JsonCContent(jsonFactory, params));
However, I'm not allowed to set the HTTP content in GET operation.
Any suggestion how can I pass these parameters?
Under one condition:
I don't want to write a util method to convert this object into string of URL parameters. But if there's already reusable API to do it, that would be fine.
I need generic solution if possible. Because I'm going to apply this to 600 JSON API calls.
My last alternative would be to change backend to expect POST request instead of GET, then I perform POST operation on the client side.
Thanks
Instead of extends GenericUrl, you can use GenericUrl.put (inherit from GenericData) to set query parameters. For example:
GenericUrl genericUrl = new GenericUrl("http://yourapi.com/request");
genericUrl.put("user", "user name");
genericUrl.put("token", "token values");
HttpRequest request = requestFactory.buildGetRequest(genericUrl);
It seems like the expected usage is to extend the URL class you are using for your buildGetRequest() call. For instance, let's say you wanted to provide two extra query parameters called "user" and "token". You could do this with the following:
HttpRequest request = requestFactory.buildGetRequest(
new CustomUrl("http://www.yourserver.com").setUser(userId).setToken(token));
where the CustomUrl class is defined as:
public class CustomUrl extends GenericUrl {
public CustomUrl(String encodedUrl) {
super(encodedUrl);
}
#Key("user")
private String mUserId;
#Key("token")
private String mToken;
public CustomUrl setUser(String userId) {
mUserId = userId;
return this;
}
public CustomUrl setToken(String token) {
mToken = token;
return this;
}
}
The values are not necessary for the #Key annotations, but will be used as the name of the respective query parameters if provided. If omitted, the name of the variable will be used instead (see example)
Check google-http-client's javadoc for more info.
For some reason, I haven't found any normal way to do the following:
I want to Post a json object, and add additional parameters to the call (in this case, an authentication token).
This is a simple RESTful server in myUrl/server, which should give access to different resources of a "person" in the url myUrl/server/person/personCode/resourceName.
GET is easy, and requires no object, only parameters.
The problem arrises when I get to POST - how do I attach the JSON, and keep the other parameters as well?
The class (much has been removed for clarity and proprietary reasons...):
//Handles the person's resources
#Path("/person/{personCode}/{resourceName}")
public class PersonResourceProvider {
#GET
#Produces("application/json")
public String getPersonResource(#PathParam("personCode") String personCode, #PathParam("resourceName") String resourceName, #DefaultValue("") #QueryParam("auth_token") String auth_token) throws UnhandledResourceException, UnauthorizedAccessException {
//Authenticates the user in some way, throwing an exception when needed...
authenticate(personCode, auth_token, resourceName);
//Returns the resource somehow...
}
#POST
#Produces("application/json")
public String postPersonResource(#PathParam("personCode") String personCode, #PathParam("resourceName") String resourceName, #DefaultValue("") #QueryParam("resourceData") String resourceData, #DefaultValue("") #QueryParam("auth_token") String auth_token) throws UnhandledResourceException, UnauthorizedAccessException {
//Again, authenticating
authenticate(personCode, auth_token, resourceName);
//Post the given resource
}
}
Now, the GET method works perfectly, when you go to
myUrl/person/personCode/resourceName, it gives me the correct resource.
The auth_token is used with every single call to the server (for now, authentication is done by comparing with a predefined string), so it's needed. All the other parameters are provided through the path, except for the authentication token, which should not be in the path as it does not relate to the identity of the required resource.
When I get to POST, it's a problem.
I know there's a way to tell the method it consumes a JSON, but in that case, what will happen to the other parameters (auth_token is one of them)?
Should I use Multipart?
Another related question, this is the first time I've designed such a server, is this design correct?
Thanks!
I am not sure I understand what you are trying to achieve. Let me try explain a few things - hope it will be relevant to your question:
#QueryParam injects parameters which are part of your path - i.e. the part of the URL that goes after "?".
E.g. if you have a URL like this:
http://yourserver.com/person/personCode/resourceName?resourceData=abc&token=1234
Then there would be 2 query params - one named resourceData with value "abc" and the other one named token with value "1234".
If you are passing an entity in the POST request, and that entity is of application/json type, you can simply annotate your post method using #Consumes("application/json") annotation and add another parameter to your method, which does not need to be annotated at all.
That parameter can be either a String (in that case Jersey would pass a raw JSON string and you would have to parse it yourself) or it can be a java bean annotated with #XmlRootElement annotation - in that case (if you also include jersey-json module on your classpath) Jersey will try to unmarshall the json string into that object using JAXB. You can also use Jackson or Jettison libraries to do that - see this section of Jersey User Guide for more info: http://jersey.java.net/nonav/documentation/latest/json.html
Found!
Client side:
Client c = Client.create();
WebResource service = c.resource("www.yourserver.com/");
String s = service.path("test/personCode/resourceName")
.queryParam("auth_token", "auth")
.type("text/plain")
.post(String.class, jsonString);
Server side:
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.WebResource;
#Path("/test/{personCode}/{resourceName}")
public class TestResourceProvider {
#POST
#Consumes("text/plain")
#Produces("application/json")
public String postUserResource(String jsonString,
#PathParam("personCode") String personCode,
#PathParam("resourceName") String resourceName,
#QueryParam("auth_token") String auth_token)
throws UnhandledResourceException {
//Do whatever...
}
}
In my case, I will parse the json I get in the server depending on the resource name, but you can also pass the object itself, and make the server consume an "application/json".
I'm trying to set up an action in ASP.NET MVC 3 to handle the payload of a mercurial webhook request - in this case, generated by Kiln.
The payload is JSON, but unfortunately it is sent as a URL encoded form value with the content type application/x-www-form-urlencoded, because apparently using application/json and sending it unencoded with no parameter name would make it too easy and um... standard.
This means that I can't just use the new JsonValueProviderFactory because it only picks up requests using the standard application/json content type. And of course I can't just kludge the factory to also pick up application/x-www-form-urlencoded requests too, because I need those requests to use the form data value provider everywhere else in my app that's actually receiving form data and not JSON.
So, is there a way I can specify that a ValueProvider or ValueProviderFactory should only be used for a specific action or route?
If you create a specific controller to handle these webhook requests, you can assign your unique ValueProvider when you instantiate your controller.
public class KilnController : Controller
{
public KilnController()
{
this.ValueProvider = MyCustomValueProvider;
}
...
}
This should fulfill your need for a custom ValueProvider for these requests.
Turns out that IValueProvider was not the particular bit of extensibility I was looking for - I just needed to use a quick IModelBinder implementation I found courtesy of James Hughes. It needed a little tweaking to cover pulling something out of the form:
public class JsonFormModelBinder : IModelBinder
{
#region [ ModelBinder Members ]
Object IModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
HttpRequestBase request = controllerContext.HttpContext.Request;
var jsonStringData = request.Form[bindingContext.ModelName];
if (jsonStringData != null) return JsonConvert.DeserializeObject(jsonStringData, bindingContext.ModelType);
else return null;
}
#endregion
}
And the usage:
[HttpPost]
public ActionResult WebHook([ModelBinder(typeof(JsonFormModelBinder))] WebHookMessage payload)
{
return Content("OK");
}