I am looking at extracting the root element of a JSON document. It looks like this is possible neither using JsonPointer nor JsonPath as my attempts to look up for such an expression has been unsuccessful. Any tips would be appreciated. TIA.
Sample document:
{
"MESSAGE1_ROOT_INPUT": {
"CTRL_SEG": "test"
}
}
The below using gson 2.9.0:
$.*~
produces:
{"CTRL_SEG": "test"}
while JSONPath Online produces this:
[
"MESSAGE1_ROOT_INPUT"
]
The attempt is to get text "MESSAGE1_ROOT_INPUT" using JsonPath/JsonPointer expression(s). Note that, extracting this the traditional (substring or regex on a stringified json text) way, would preferably be my last resort.
Background: We are building an API service that accepts JSON documents with different roots. Such as, MESSAGE2_ROOT_INPUT, MESSAGE3_ROOT_INPUT, etc. It is based on this, the routing of a message further will occur.
Supported/Employed Languages: Java/GSON Library/RegEx
Gson does not natively support JSONPath or JSON Pointer. However, you can quite efficiently obtain the name of the first property using JsonReader:
public static String getFirstPropertyName(Reader reader) throws IOException {
// Don't have to call JsonReader.close(); that would just close the provided reader
JsonReader jsonReader = new JsonReader(reader);
jsonReader.beginObject();
return jsonReader.nextName();
}
There are however two things to keep in mind:
This only reads the beginning of the JSON document; it neither verifies that the complete JSON document has valid syntax, nor checks if there might be more top-level properties
This consumes some data from the Reader; to further process the data you have to buffer the data to allow re-reading it again (you can also first store the JSON in a String and pass a StringReader to JsonReader)
I store a blob of Json in the datastore using JsonProperty.
I don't know the structure of the json data.
I am using endpoints proto datastore in order to retrieve my data.
The probleme is the json property is encoded in base64 and I want a plain json object.
For the example, the json data will be:
{
first: 1,
second: 2
}
My code looks something like:
import endpoints
from google.appengine.ext import ndb
from protorpc import remote
from endpoints_proto_datastore.ndb import EndpointsModel
class Model(EndpointsModel):
data = ndb.JsonProperty()
#endpoints.api(name='myapi', version='v1', description='My Sample API')
class DataEndpoint(remote.Service):
#Model.method(path='mymodel2', http_method='POST',
name='mymodel.insert')
def MyModelInsert(self, my_model):
my_model.data = {"first": 1, "second": 2}
my_model.put()
return my_model
#Model.method(path='mymodel/{entityKey}',
http_method='GET',
name='mymodel.get')
def getMyModel(self, model):
print(model.data)
return model
API = endpoints.api_server([DataEndpoint])
When I call the api for getting a model, I get:
POST /_ah/api/myapi/v1/mymodel2
{
"data": "eyJzZWNvbmQiOiAyLCAiZmlyc3QiOiAxfQ=="
}
where eyJzZWNvbmQiOiAyLCAiZmlyc3QiOiAxfQ== is the base64 encoded of {"second": 2, "first": 1}
And the print statement give me: {u'second': 2, u'first': 1}
So, in the method, I can explore the json blob data as a python dict.
But, in the api call, the data is encoded in base64.
I expeted the api call to give me:
{
'data': {
'second': 2,
'first': 1
}
}
How can I get this result?
After the discussion in the comments of your question, let me share with you a sample code that you can use in order to store a JSON object in Datastore (it will be stored as a string), and later retrieve it in such a way that:
It will show as plain JSON after the API call.
You will be able to parse it again to a Python dict using eval.
I hope I understood correctly your issue, and this helps you with it.
import endpoints
from google.appengine.ext import ndb
from protorpc import remote
from endpoints_proto_datastore.ndb import EndpointsModel
class Sample(EndpointsModel):
column1 = ndb.StringProperty()
column2 = ndb.IntegerProperty()
column3 = ndb.StringProperty()
#endpoints.api(name='myapi', version='v1', description='My Sample API')
class MyApi(remote.Service):
# URL: .../_ah/api/myapi/v1/mymodel - POSTS A NEW ENTITY
#Sample.method(path='mymodel', http_method='GET', name='Sample.insert')
def MyModelInsert(self, my_model):
dict={'first':1, 'second':2}
dict_str=str(dict)
my_model.column1="Year"
my_model.column2=2018
my_model.column3=dict_str
my_model.put()
return my_model
# URL: .../_ah/api/myapi/v1/mymodel/{ID} - RETRIEVES AN ENTITY BY ITS ID
#Sample.method(request_fields=('id',), path='mymodel/{id}', http_method='GET', name='Sample.get')
def MyModelGet(self, my_model):
if not my_model.from_datastore:
raise endpoints.NotFoundException('MyModel not found.')
dict=eval(my_model.column3)
print("This is the Python dict recovered from a string: {}".format(dict))
return my_model
application = endpoints.api_server([MyApi], restricted=False)
I have tested this code using the development server, but it should work the same in production using App Engine with Endpoints and Datastore.
After querying the first endpoint, it will create a new Entity which you will be able to find in Datastore, and which contains a property column3 with your JSON data in string format:
Then, if you use the ID of that entity to retrieve it, in your browser it will show the string without any strange encoding, just plain JSON:
And in the console, you will be able to see that this string can be converted to a Python dict (or also a JSON, using the json module if you prefer):
I hope I have not missed any point of what you want to achieve, but I think all the most important points are covered with this code: a property being a JSON object, store it in Datastore, retrieve it in a readable format, and being able to use it again as JSON/dict.
Update:
I think you should have a look at the list of available Property Types yourself, in order to find which one fits your requirements better. However, as an additional note, I have done a quick test working with a StructuredProperty (a property inside another property), by adding these modifications to the code:
#Define the nested model (your JSON object)
class Structured(EndpointsModel):
first = ndb.IntegerProperty()
second = ndb.IntegerProperty()
#Here I added a new property for simplicity; remember, StackOverflow does not write code for you :)
class Sample(EndpointsModel):
column1 = ndb.StringProperty()
column2 = ndb.IntegerProperty()
column3 = ndb.StringProperty()
column4 = ndb.StructuredProperty(Structured)
#Modify this endpoint definition to add a new property
#Sample.method(request_fields=('id',), path='mymodel/{id}', http_method='GET', name='Sample.get')
def MyModelGet(self, my_model):
if not my_model.from_datastore:
raise endpoints.NotFoundException('MyModel not found.')
#Add the new nested property here
dict=eval(my_model.column3)
my_model.column4=dict
print(json.dumps(my_model.column3))
print("This is the Python dict recovered from a string: {}".format(dict))
return my_model
With these changes, the response of the call to the endpoint looks like:
Now column4 is a JSON object itself (although it is not printed in-line, I do not think that should be a problem.
I hope this helps too. If this is not the exact behavior you want, maybe should play around with the Property Types available, but I do not think there is one type to which you can print a Python dict (or JSON object) without previously converting it to a String.
I want to write an API ReST endpoint, using Spring 4.0 and Groovy, such that the #RequestBody parameter can be any generic JSON input, and it will be mapped to a Groovy JsonSlurper so that I can simply access the data via the slurper.
The benefit here being that I can send various JSON documents to my endpoint without having to define a DTO object for every format that I might send.
Currently my method looks like this (and works):
#RequestMapping(value = "/{id}", method = RequestMethod.PUT, consumes = MediaType.APPLICATION_JSON_VALUE)
ResponseEntity<String> putTest(#RequestBody ExampleDTO dto) {
def json = new groovy.json.JsonBuilder()
json(
id: dto.id,
name: dto.name
);
return new ResponseEntity(json.content, HttpStatus.OK);
}
But what I want, is to get rid of the "ExampleDTO" object, and just have any JSON that is passed in get mapped straight into a JsonSlurper, or something that I can input into a JsonSlurper, so that I can access the fields of the input object like so:
def json = new JsonSlurper().parseText(input);
String exampleName = json.name;
I initially thought I could just accept a String instead of ExampleDTO, and then slurp the String, but then I have been running into a plethora of issues in my AngularJS client, trying to send my JSON objects as strings to the API endpoint. I'm met with an annoying need to escape all of the double quotes and surround the entire JSON string with double quotes. Then I run into issues if any of my data has quotes or various special characters in it. It just doesn't seem like a clean or reliable solution.
I open to anything that will cleanly translate my AngularJS JSON objects into valid Strings, or anything I can do in the ReST method that will allow JSON input without mapping it to a specific object.
Thanks in advance!
Tonya
I have a method in my main controller that return a string that I want to render as JSON.
So I am importing "import grails.converters.JSON" and calling
myMethod() as JSON
, and it works fine. But when I need to get some details of the json response in my integration test.
So in my integration test I have:
void testfoo() {
def bar = controller.myMethod();
def bar.name; //fails
JSON.parse(bar.toString()).name; // doesn't fail
....
..
}
any idea why I need to convert it to a string and then again to a JSON, since it already a JSON?
The value you get back from your method is a grails.converters.JSON, which is not a directly accessible JSON tree as such, but simply an object that knows how to serialize itself as JSON when required. If you want direct access to the JSON tree structure then you need to tell the grails.converters.JSON object to serialize itself and then pass that JSON to JSON.parse to turn it into a JSONElement (or one of its subclasses, in this case presumably a JSONObject).
I am trying to access a REST Service in my MVC application.I am calling getJSON method to get the data from a controller which internally calls the REST service which returns data in json format.But I am getting the a lot of "\ in my output of DownLoadString method and my return Json is not returning proper JSON data and hence my client side script is not able to access the JSON properties.
My Script in my view is
$.getJSON("#Url.Action("GetManufacturers", "Home")",function(data){
console.debug("Status is : "+data.Status)
});
My Action method looks like this
public ActionResult GetManufacturers()
{
string restURL ="http://mytestserver/myapi/Manufacturers";
using (var client = new WebClient())
{
var data = client.DownloadString(restURL);
//data variable gets "\" everywhere
return Json(data,JsonRequestBehavior.AllowGet);
}
}
I used visual studio breakpoints in my action method and i am seeing a lot of \"
And i checked what is coming out to my getJSON callback and the JSON tab is empty.
But my response tab has content like this
I belive if there is no \", i would be able to parse it nicely.
I used fiddler to see whether i am getting correct (JSON format) data from my REST service and it seems fine.
Can anyone help me to tackle this ? I would like to return proper JSON from my action method. Sometime i may want to read the json properties in the C# code itself. I saw some example of doing it with DataContractJsonSerializer. But that needs a concrete type to be converted to. I don't want to do that. because other clients would also access my RESTService and how will expect them to write a fake entity for this ?
You need to return the data as is:
public ActionResult GetManufacturers()
{
string restURL ="http://mytestserver/myapi/Manufacturers";
using (var client = new WebClient())
{
var data = client.DownloadString(restURL);
return Content(data, "application/json");
}
}