I have a Problem to insert a document via Api to my ES 8.0.0.
In my IndexTemplate I defined a mapping of a property called [Data] of type "flattend".
For "normal" JSON-Objects it works fine. But when I try to insert a plain string literal (for example "test") or a number (for example 4) I get a "400 Bad Request". JSONLint says it's a valid JSON!!
{
....
"Data": "test",
....
}
Can i configure ES to accept such kind of JSON for type "flattened"??
As Elasticsearch document mentions:
The flattened type provides an alternative approach, where the entire
object is mapped as a single field. Given an object, the flattened
mapping will parse out its leaf values and index them into one field
as keywords.
So, the value provided for the "flattened" field type should be a JsonObject.
Hence, below works as where "full_name" is of type "flattened"
"full_name":{
"name":"nishikant"
}
But below does not
"full_name":"nishikant".
Same has been given in exception
"reason" : "Failed to parse object: expecting token of type [START_OBJECT] but found [VALUE_STRING]"
I have a tuple consisting of an String and a Uuid that I serialize using serde_json:
let log_and_id = (String::from("Test string"), test_id);
let log_and_id_serialized = serde_json::to_string(&log_and_id)
.expect("Serialization failed");
//After serialization (debug print): "[\"Test string\",\"32a8e12d-69d2-421d-a52e-1ee76cc03ed5\"]"
Then I transfer this serialized value over the network and receive a BytesMut (serialized_tuple) on the other end, which I try to deserialize:
//Bytesmut value (debug print): b"\"[\\\"Test string\\\",\\\"32a8e12d-69d2-421d-a52e-1ee76cc03ed5\\\"]\""
let (log, operation_state_id) = serde_json::from_slice::<(String, Uuid)>(&serialized_tuple)?;
But I get the following error:
ERROR actix_http::response] Internal Server Error: SerdeError(Error("invalid type: string \"[\\\"Test string\\\",\\\"32a8e12d-69d2-421d-a52e-1ee76cc03ed5\\\"]\", expected a tuple of size 2", line: 1, column: 68))
(De)serializing single objects this way used to work in other parts of this code, so what could cause it to fail when used with tuples?
You don't have a serialized tuple, but a serialized serialized tuple.
I mean the serialization of the tuple, which was a JSON string, was again serialized.
You can check this with this code (playground):
let serialized_tuple = b"\"[\\\"Test string\\\",\\\"32a8e12d-69d2-421d-a52e-1ee76cc03ed5\\\"]\"";
let serialized_tuple: String = serde_json::from_slice(serialized_tuple).unwrap();
let (log, operation_state_id) = serde_json::from_slice::<(String, String)>(serialized_tuple.as_bytes()).unwrap();
which produces the desired tuple.
Of course, rather than deserializing twice, you should remove the unnecessary serialization from your application (it's not in the code you've shown).
So my problem is presenting as a type-matching of sorts; I have code that queries a database, and returns an array of string type. When I attempt to validate against my JSON message returned from a web service, one of the values is a primitive integer (without the double-quotes), and the validation is failing, as it is stating: Expected: iterable containing {"1", "1", "1", "1", "1"}Actual: [1, 1, 1, 1, 1]I'm using the contains matcher to validate a ListArray of values against many returned by the query. My assumption is that the Actual is being evaluated as an integer, but the values to validate against (Expected) are String. I've been racking my brain attempting the HasToString or hasItem matchers but I think that would just parse toString if the target is a single value.I guess my ultimate question is, is there a way to force Hamcrest to evaluate the JSON data as a String, or implicitly/explicitly cast the Expected to the evaluated type?Thanks in advance.
So, I acutally think I figured this one out; what I ended up doing was performing a toString(). on the extracted ArrayList of objects, which gave me string values; code example below:
ArrayList<String> myObj = response.path(jsonField);
String[] myObjStr = new String[myObj.size()];
int x = 0;
for (Object obj : myObj){
myObjStr[x] = obj.toString();
x++;
}
From there, I was able to compare the resulting arrays; Now if only I could figure out how to get rid of pesky angle brackets for nested elements...
What is the preferred method for returning null values in JSON? Is there a different preference for primitives?
For example, if my object on the server has an Integer called "myCount" with no value, the most correct JSON for that value would be:
{}
or
{
"myCount": null
}
or
{
"myCount": 0
}
Same question for Strings - if I have a null string "myString" on the server, is the best JSON:
{}
or
{
"myString": null
}
or
{
"myString": ""
}
or (lord help me)
{
"myString": "null"
}
I like the convention for collections to be represented in the JSON as an empty collection http://jtechies.blogspot.nl/2012/07/item-43-return-empty-arrays-or.html
An empty Array would be represented:
{
"myArray": []
}
EDIT Summary
The 'personal preference' argument seems realistic, but short sighted in that, as a community we will be consuming an ever greater number of disparate services/sources. Conventions for JSON structure would help normalize consumption and reuse of said services. As far as establishing a standard, I would suggest adopting most of the Jackson conventions with a few exceptions:
Objects are preferred over primitives.
Empty collections are preferred over null.
Objects with no value are represented as null.
Primitives return their value.
If you are returning a JSON object with mostly null values, you may have a candidate for refactoring into multiple services.
{
"value1": null,
"value2": null,
"text1": null,
"text2": "hello",
"intValue": 0, //use primitive only if you are absolutely sure the answer is 0
"myList": [],
"myEmptyList": null, //NOT BEST PRACTICE - return [] instead
"boolean1": null, //use primitive only if you are absolutely sure the answer is true/false
"littleboolean": false
}
The above JSON was generated from the following Java class.
package jackson;
import java.util.ArrayList;
import java.util.List;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JacksonApp {
public static class Data {
public Integer value1;
public Integer value2;
public String text1;
public String text2 = "hello";
public int intValue;
public List<Object> myList = new ArrayList<Object>();
public List<Object> myEmptyList;
public Boolean boolean1;
public boolean littleboolean;
}
public static void main(String[] args) throws Exception {
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(new Data()));
}
}
Maven dependency:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.3.0</version>
</dependency>
Let's evaluate the parsing of each:
http://jsfiddle.net/brandonscript/Y2dGv/
var json1 = '{}';
var json2 = '{"myCount": null}';
var json3 = '{"myCount": 0}';
var json4 = '{"myString": ""}';
var json5 = '{"myString": "null"}';
var json6 = '{"myArray": []}';
console.log(JSON.parse(json1)); // {}
console.log(JSON.parse(json2)); // {myCount: null}
console.log(JSON.parse(json3)); // {myCount: 0}
console.log(JSON.parse(json4)); // {myString: ""}
console.log(JSON.parse(json5)); // {myString: "null"}
console.log(JSON.parse(json6)); // {myArray: []}
The tl;dr here:
The fragment in the json2 variable is the way the JSON spec indicates null should be represented. But as always, it depends on what you're doing -- sometimes the "right" way to do it doesn't always work for your situation. Use your judgement and make an informed decision.
JSON1 {}
This returns an empty object. There is no data there, and it's only going to tell you that whatever key you're looking for (be it myCount or something else) is of type undefined.
JSON2 {"myCount": null}
In this case, myCount is actually defined, albeit its value is null. This is not the same as both "not undefined and not null", and if you were testing for one condition or the other, this might succeed whereas JSON1 would fail.
This is the definitive way to represent null per the JSON spec.
JSON3 {"myCount": 0}
In this case, myCount is 0. That's not the same as null, and it's not the same as false. If your conditional statement evaluates myCount > 0, then this might be worthwhile to have. Moreover, if you're running calculations based on the value here, 0 could be useful. If you're trying to test for null however, this is actually not going to work at all.
JSON4 {"myString": ""}
In this case, you're getting an empty string. Again, as with JSON2, it's defined, but it's empty. You could test for if (obj.myString == "") but you could not test for null or undefined.
JSON5 {"myString": "null"}
This is probably going to get you in trouble, because you're setting the string value to null; in this case, obj.myString == "null" however it is not == null.
JSON6 {"myArray": []}
This will tell you that your array myArray exists, but it's empty. This is useful if you're trying to perform a count or evaluation on myArray. For instance, say you wanted to evaluate the number of photos a user posted - you could do myArray.length and it would return 0: defined, but no photos posted.
null is not zero. It is not a value, per se: it is a value outside the domain of the variable indicating missing or unknown data.
There is only one way to represent null in JSON. Per the specs (RFC 4627 and json.org):
2.1. Values
A JSON value MUST be an object, array, number, or string, or one of
the following three literal names:
false null true
There is only one way to represent null; that is with null.
console.log(null === null); // true
console.log(null === true); // false
console.log(null === false); // false
console.log(null === 'null'); // false
console.log(null === "null"); // false
console.log(null === ""); // false
console.log(null === []); // false
console.log(null === 0); // false
That is to say; if any of the clients that consume your JSON representation use the === operator; it could be a problem for them.
no value
If you want to convey that you have an object whose attribute myCount has no value:
{ "myCount": null }
no attribute / missing attribute
What if you to convey that you have an object with no attributes:
{}
Client code will try to access myCount and get undefined; it's not there.
empty collection
What if you to convey that you have an object with an attribute myCount that is an empty list:
{ "myCount": [] }
I would use null to show that there is no value for that particular key. For example, use null to represent that "number of devices in your household connects to internet" is unknown.
On the other hand, use {} if that particular key is not applicable. For example, you should not show a count, even if null, to the question "number of cars that has active internet connection" is asked to someone who does not own any cars.
I would avoid defaulting any value unless that default makes sense. While you may decide to use null to represent no value, certainly never use "null" to do so.
I would pick "default" for data type of variable (null for strings/objects, 0 for numbers), but indeed check what code that will consume the object expects. Don't forget there there is sometimes distinction between null/default vs. "not present".
Check out null object pattern - sometimes it is better to pass some special object instead of null (i.e. [] array instead of null for arrays or "" for strings).
According to the JSON spec, the outermost container does not have to be a dictionary (or 'object') as implied in most of the comments above. It can also be a list or a bare value (i.e. string, number, boolean or null). If you want to represent a null value in JSON, the entire JSON string (excluding the quotes containing the JSON string) is simply null. No braces, no brackets, no quotes. You could specify a dictionary containing a key with a null value ({"key1":null}), or a list with a null value ([null]), but these are not null values themselves - they are proper dictionaries and lists. Similarly, an empty dictionary ({}) or an empty list ([]) are perfectly fine, but aren't null either.
In Python:
>>> print json.loads('{"key1":null}')
{u'key1': None}
>>> print json.loads('[null]')
[None]
>>> print json.loads('[]')
[]
>>> print json.loads('{}')
{}
>>> print json.loads('null')
None
This is a personal and situational choice. The important thing to remember is that the empty string and the number zero are conceptually distinct from null.
In the case of a count you probably always want some valid number (unless the count is unknown or undefined), but in the case of strings, who knows? The empty string could mean something in your application. Or maybe it doesn't. That's up to you to decide.
'null' is best for practical use
FWIW, using PHP as an example, PHP interprets empty sets as entries made by PHP...
// This loop will iterate one item with the value 'the car'
$empty_json = '["the car"]';
$some_json_array = json_decode($empty_json);
foreach ($some_json_array as $i) {
echo "PHP sees one item";
}
output: PHP sees the car
// This loop will iterate one item, but with no values
$empty_json = '[""]';
$some_json_array = json_decode($empty_json);
foreach ($some_json_array as $i) {
echo "PHP sees: $i";
}
output: PHP sees
// This loop will iterate nothing because PHP's `json_decode()` function knew it was `null`
$empty_json = 'null';
$some_json_array = json_decode($empty_json);
foreach ($some_json_array as $i) {
echo "PHP sees one item";
}
output: (nothing, foreach will not loop)
I have a JSON response form HTTP request.
"AdditionalData": {
"default" : "checked",
"example" : "empty"
}
This specific response would ideally be interoperated as a dictionary type (Key value pair). But when I auto-detect the return type of the JSON, FB 4.6 makes it of type Object. This does not work for me. For some reason the AdditionalData object in the model that I'm mapping is always null. What data type can I manually set this response to?
I don't know if you can force the result of a complex grouping to be anything but an Object when it gets returned. Once it arrives you could convert it into an ArrayCollection (of Objects or other ArrayCollections) though.