I want to read a JSON file received.
That's the form of the JSON file:
{
"name": "list_name"
"items": [
{
"id": 4
},
{
"id": 3
},
{
"id": 2
},
]
}
I want to parse that JSON that represents a movie list, and the id's of the movies. I want to extract the ids and the name.
#PUT
#Path("/")
#Consumes(MediaType.APPLICATION_JSON)
public Response deleteMoviesFromList2(#Context HttpServletRequest req) Long movieListId) {
Long userId = getLoggedUser(req);
getLoggedUser(req);
final String json = "some JSON string";
final ObjectMapper mapper = new ObjectMapper();
return buildResponse(listMovieService.remove(¿?));
}
I want to extract the ids but I have no clue how to do it.
You can convert json string using ObjectMapper class like this.
ObjectMapper objectMapper = new ObjectMapper();
String carJson =
"{ \"brand\" : \"Mercedes\", \"doors\" : 5 }";
try {
Car car = objectMapper.readValue(carJson, Car.class);
System.out.println("car brand = " + car.getBrand());
System.out.println("car doors = " + car.getDoors());
} catch (IOException e) {
e.printStackTrace();
}
Here you can replace Car class with your custom Movie class and you are done.
If you have a movie class defined, such as:
class Movie {
String id;
//getters
//setters
}
and a Movie list class:
class MovieList {
String name;
List<Movie> items;
//getters
//setters
}
Then you can use an object mapper with an inputStream:
try(InputStream fileStream = new FileInputStream("movielist.json")) {
MovieList list = mapper.readValue(fileStream, MovieList.class);
}
ObjectMapper's readValue has an overloaded version that takes an input stream, and that's the one used above.
Related
I have the following JSON structure:
{
"sets": [
{...},
{
"id": "id",
"html": "<html></html>",
"javascript": "{onError: function (event) {}}",
"css": ".someclass {}",
"translations": {
"en": { "LABEL_1": "Some label text", "HEADER_1": "Some header text" },
"fr": { "LABEL_1": "Some label text", "HEADER_1": "Some header text" }
}
}
]
}
I have an object that represents this JSON for deserialization purpose
#Data //Lombok
#NoArgsConstructor //Lombok
public class Set {
#JsonProperty("screenSetID")
private String screenSetID;
#JsonProperty("html")
private String html;
#JsonProperty("css")
private String css;
#JsonProperty("javascript")
private String javascript;
#JsonProperty("translations")
private String translations;
}
I have the following piece of code to deserialize JSON
private List<Set> parseSetsData(String json) {
ObjectMapper mapper = new ObjectMapper();
try {
return mapper.readValue(json, TypeReference<List<Set>(){});
} catch (IOException e) {
throw new RuntimeException(e);
}
}
How I can parse translations JSON object as it is?
Any Jason object could be mapped to Map<String, Object> and any Json List could be mapped to List<Object>. So you could parse your JSON as follows:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModules(new JavaTimeModule());
objectReader = objectMapper.reader();
Map<String, Object> parsedJson = (Map<String, Object>)objectReader.forType(Map.class).readValue(jsonString)
Note that your JSON is a JSON object and not JSON list, so this example parses it to Map
I'm sure you understand that the that you want is part of on array hats why I had to use a for loop:
ObjectMapper mapper = new ObjectMapper();
JsonNode treeNode = mapper.readTree(json);
treeNode=treeNode.findValue("sets");
for (Iterator<JsonNode> it = treeNode.elements(); it.hasNext(); ) {
JsonNode node = it.next();
String theValueYouWant=node.findValue("translations").textValue();
}
Json I found that when you deserialize your item it should look like the following;
public class En
{
#JsonProperty("LABEL_1")
public String lABEL_1;
#JsonProperty("HEADER_1")
public String hEADER_1;
}
public class Fr
{
#JsonProperty("LABEL_1")
public String lABEL_1;
#JsonProperty("HEADER_1")
public String hEADER_1;
}
public class Translations
{
public En en;
public Fr fr;
}
public class Set
{
public String id;
public String html;
public String javascript;
public String css;
public Translations translations;
}
However, in your class, "translations" is a string, but in a JSON structure, it points to an object.
As input for my Application I might get either a single JsonObject, or a List of them:
input1 = [ { "prop": "val1" }, { "prop": "val2" } ]
input2 = { "prop": "val" }
I can use JsonNode as target type for both inputs
objectMapper.readValue(input1, JsonNode.class);
objectMapper.readValue(input2, JsonNode.class);
And then evaluate whether the root node is a ArrayNode or ObjectNode.
I seek a way to define my custom target type, like a List<MyObject> which has one Element if a JsonObject is provided, or zero to multiple, if a List is provided.
objectMapper.readValue(input, new TypeRef<ArrayList<MyObject>>() {});
however fails for the single object - it can not construc an Array-Type from {.
I was trying to create my own type:
public class MyList extends ArrayList<MyObject> {
public String prop;
#JsonCreator
public MyList(String prop) {
super();
this.prop = prop; // Resp add(new MyObject(prop));
}
public MyList() {}
}
But Jackson refuses to use the JsonCreator for single objects.
Is there any way, I could do that (ideally without a custom serializer, unless that one can be made pretty generic)
Of course, Jackson has an easy solution for that:
DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY to your help!
#EqualsAndHashCode
public class Example {
#JsonProperty public String name
}
#Test
public void experiment() {
ObjectMapper om = new ObjectMapper();
om.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
String list= "[{ \"name\": \"peter\" }]";
String single= "{ \"name\": \"peter\" }";
List<Example> respList = om.readValue(list, new TypeReference<List<Example>>() {});
List<Example> respSingle = om.readValue(single, new TypeReference<List<Example>>() {});
Assert.assertEquals(respList, respSingle)
}
I want to extract a key and its value from json object. I am having a 3 objects in a json with parent child relation, named as
1. Parent,
2. childOne_OfParent and
3. child_OF_childOne.
I want to extract all the value of "userQueryId" from child_OF_childOne and store into a string type variable.
How do I perform this. Thanks in advance.
My Json object is:
{
"createdBy": "****",
"dashboardId": 1,
"childOne_OfParent": [
{
"createdBy": null,
"dashboardSectionId": 1,
"child_OF_childOne": [
{
"createdBy": "XYZ",
"userQueryId": "283"
},
{
"createdBy": "ABC",
"userQueryId": "284"
},
{
"createdBy": "AWS",
"userQueryId": "285"
}
]
}
]
}
You can use the json to create a model java class like this. I used your json to create the class using the site https://codebeautify.org/json-to-java-converter. You can give a classname of your choice in the Class_Name.
public class Class_Name {
private String createdBy;
private float dashboardId;
ArrayList < Object > childOne_OfParent = new ArrayList < Object > ();
// Getter Methods
public String getCreatedBy() {
return createdBy;
}
public float getDashboardId() {
return dashboardId;
}
// Setter Methods
public void setCreatedBy(String createdBy) {
this.createdBy = createdBy;
}
public void setDashboardId(float dashboardId) {
this.dashboardId = dashboardId;
}
}
Then you can use the Jackson to convert your json into a java object and access the data you want. Here jsonString is your json and the objResp is your object.
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
Class_Name objResp = mapper.readerFor(Class_Name.class).readValue(jsonString);
Here is a useful guide for that. https://www.mkyong.com/java/how-to-convert-java-object-to-from-json-jackson/
The tool for these kind of tasks is JsonPath. It has xpath-like search capabilities.
Here is a working example of the given question
public static void main(String[] args) {
String searchQueryIds = "$.childOne_OfParent[*].child_OF_childOne[*].userQueryId";
try (InputStream is = Files.newInputStream(Paths.get("c:/temp/test.json"))) {
List<String> ids = JsonPath.parse(is).read(searchQueryIds);
System.out.println(ids);
} catch (Exception e) {
e.printStackTrace();
}
}
Assuming there is pojo for json and jackson library available. It will return comma separated queryUserIds.
Parent parent = new ObjectMapper().reader(Parent.class).readValue(inputJson);
String userIds = parent.getChildOne_OfParent().get(0).getChild_OF_childOne().stream()
.map(c -> c.getuserQueryId())
.collect(Collectors.joining(","));
I'm trying to parse some JSON data using gson in Java that has the following structure but by looking at examples online, I cannot find anything that does the job.
Would anyone be able to assist?
{
"data":{
"id":[
{
"stuff":{
},
"values":[
[
123,
456
],
[
123,
456
],
[
123,
456
],
],
"otherStuff":"blah"
}
]
}
}
You just need to create a Java class structure that represents the data in your JSON. In order to do that, I suggest you to copy your JSON into this online JSON Viewer and you'll see the structure of your JSON much clearer...
Basically you need these classes (pseudo-code):
class Response
Data data
class Data
List<ID> id
class ID
Stuff stuff
List<List<Integer>> values
String otherStuff
Note that attribute names in your classes must match the names of your JSON fields! You may add more attributes and classes according to your actual JSON structure... Also note that you need getters and setters for all your attributes!
Finally, you just need to parse the JSON into your Java class structure with:
Gson gson = new Gson();
Response response = gson.fromJson(yourJsonString, Response.class);
And that's it! Now you can access all your data within the response object using the getters and setters...
For example, in order to access the first value 456, you'll need to do:
int value = response.getData().getId().get(0).getValues().get(0).get(1);
Depending on what you are trying to do. You could just setup a POJO heirarchy that matches your json as seen here (Preferred method). Or, you could provide a custom deserializer. I only dealt with the id data as I assumed it was the tricky implementation in question. Just step through the json using the gson types, and build up the data you are trying to represent. The Data and Id classes are just pojos composed of and reflecting the properties in the original json string.
public class MyDeserializer implements JsonDeserializer<Data>
{
#Override
public Data deserialize(JsonElement je, Type type, JsonDeserializationContext jdc) throws JsonParseException
{
final Gson gson = new Gson();
final JsonObject obj = je.getAsJsonObject(); //our original full json string
final JsonElement dataElement = obj.get("data");
final JsonElement idElement = dataElement.getAsJsonObject().get("id");
final JsonArray idArray = idElement.getAsJsonArray();
final List<Id> parsedData = new ArrayList<>();
for (Object object : idArray)
{
final JsonObject jsonObject = (JsonObject) object;
//can pass this into constructor of Id or through a setter
final JsonObject stuff = jsonObject.get("stuff").getAsJsonObject();
final JsonArray valuesArray = jsonObject.getAsJsonArray("values");
final Id id = new Id();
for (Object value : valuesArray)
{
final JsonArray nestedArray = (JsonArray)value;
final Integer[] nest = gson.fromJson(nestedArray, Integer[].class);
id.addNestedValues(nest);
}
parsedData.add(id);
}
return new Data(parsedData);
}
}
Test:
#Test
public void testMethod1()
{
final String values = "[[123, 456], [987, 654]]";
final String id = "[ {stuff: { }, values: " + values + ", otherstuff: 'stuff2' }]";
final String jsonString = "{data: {id:" + id + "}}";
System.out.println(jsonString);
final Gson gson = new GsonBuilder().registerTypeAdapter(Data.class, new MyDeserializer()).create();
System.out.println(gson.fromJson(jsonString, Data.class));
}
Result:
Data{ids=[Id {nestedList=[[123, 456], [987, 654]]}]}
POJO:
public class Data
{
private List<Id> ids;
public Data(List<Id> ids)
{
this.ids = ids;
}
#Override
public String toString()
{
return "Data{" + "ids=" + ids + '}';
}
}
public class Id
{
private List<Integer[]> nestedList;
public Id()
{
nestedList = new ArrayList<>();
}
public void addNestedValues(final Integer[] values)
{
nestedList.add(values);
}
#Override
public String toString()
{
final List<String> formattedOutput = new ArrayList();
for (Integer[] integers : nestedList)
{
formattedOutput.add(Arrays.asList(integers).toString());
}
return "Id {" + "nestedList=" + formattedOutput + '}';
}
}
I have the followed snipets of Json String:
{
"networks": {
"tech11": {
"id": "1",
"name": "IDEN"
},
"tech12": {
"id": "2",
"name": "EVDO_B"
}
}
}
I use some methods to convert this String to Object:
private static Gson mGson = new Gson();
...
public static WebObjectResponse convertJsonToObject(String jsonString) {
WebObjectResponse webObjectResponse = null;
if(jsonString != null && jsonString.length() > 1){
webObjectResponse = mGson.fromJson(jsonString, WebObjectResponse.class);
}
return webObjectResponse;
}
Where WebObjectResponse is class that should represent above mentioned String.
Its not complicated if I get static fields.
But in my case the values have different names: tech11, tech12 ....
I can use #SerializedName but its works in specific cases like convert "class" to "class_".
As you see networks Object defined as list of tech Objects but with different post-fix.
public class WebObjectResponse{
private DataInfoList networks = null;
}
This is static implementation, i defined 2 values tech11 and tech12 but next response might be techXX
public class DataInfoList {
private DataInfo tech11 = null;
private DataInfo tech12 = null;
}
public class DataInfo {
private String id = null;
private String name = null;
}
What is the good way to convert current Json String to Object where list of elements are Objects too and have different names?
Thank you.
Use a Map!
I would do the following
public class WebObjectResponse {
private Map<String, DataInfo> networks;
}
public class DataInfo {
private String id = null;
private String name = null;
}
// later
Gson gson = new Gson();
String json = "{\"networks\": {\"tech11\": { \"id\": \"1\",\"name\": \"IDEN\" }, \"tech12\": { \"id\": \"2\", \"name\": \"EVDO_B\" } }}";
WebObjectResponse response = gson.fromJson(json, WebObjectResponse .class);
For each object in json networks, a new entry will be added to the Map field of your class WebObjectResponse. You then reference them by techXX or iterate through the keyset.
Assuming a structure like this
{
"networks": {
"tech11": {
"id": "1",
"name": "IDEN"
},
"tech12": {
"id": "2",
"name": "EVDO_B"
},
"tech13": {
"id": "3",
"name": "WOHOO"
}, ...
}
}
We would need your class structure for more details.
As far as I am aware, I think you will need to have some mappings defined somewhere (I used xml's) and then try to match json with one of the mappings to create objects.
Google gson is good. I did it in Jackson
Also, converting objects should be trivial. But since you might have variable fields like tech11 and tech12 , you might want to store the "network" value as a string and then extract fields out of it when required.
Hope I could help.
Edit : Sotirious nails it.
Please use this link for converting SON Response to Java POJO class
http://www.jsonschema2pojo.org/