I am trying to parse the content of JSON file text.json by using Jackson library.
What I want is to make a java method to get all keys and values of it, but so far in my code I get only the first key and the first value of the JSON file.
The code snippet I used as guidance to make my own Java class is the following:
public void parse(String json) {
JsonFactory factory = new JsonFactory();
ObjectMapper mapper = new ObjectMapper(factory);
JsonNode rootNode = mapper.readTree(json);
Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.fields();
while (fieldsIterator.hasNext()) {
Map.Entry<String,JsonNode> field = fieldsIterator.next();
System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue());
}
}
And my Java class that I created is shown below:
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JacksonStreamExample {
public static void main(String[] args) {
try {
//Create a JsonFactory instance
JsonFactory factory = new JsonFactory();
//Create a JsonParser instance to read from file c:\\text.json
JsonParser jParser = factory.createJsonParser(new File("c:\\text.json"));
/*Create an ObjectMapper instance to provide a pointer
* to root node of the tree after reading the JSON
*/
ObjectMapper mapper = new ObjectMapper(factory);
//Create tree from JSON
JsonNode rootNode = mapper.readTree(jParser);
Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.getFields();
while (fieldsIterator.hasNext()) {
Map.Entry<String,JsonNode> field = fieldsIterator.next();
System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue());
}
jParser.close();
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
My Eclipse output is the following which creates only 1 pair(key-value):
Key: cells Value:[{"type":"basic.Circle","size":{"width":90,"height":54},"position":{"x":-80,"y":200},"angle":0,"id":"cae4c219-c2cd-4a4b-b50c-0f269963ca24","embeds":"","z":1,"wi_name":"START","wi_displayName":"START","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"circle":{"fill":"#000000","width":50,"height":30,"stroke-width":1,"stroke-dasharray":"0"},"text":{"font-size":10,"text":"START","fill":"#ffffff","font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Circle","size":{"width":90,"height":54},"position":{"x":210,"y":200},"angle":0,"id":"d23133e0-e516-4f72-8127-292545d3d479","embeds":"","z":2,"wi_name":"END","wi_displayName":"END","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"circle":{"fill":"#000000","width":50,"height":30,"stroke-width":1,"stroke-dasharray":"0"},"text":{"font-size":10,"text":"END","fill":"#ffffff","font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Rect","position":{"x":-80,"y":370},"size":{"width":90,"height":54},"angle":0,"id":"a53898a5-c018-45c4-bd3f-4ea4d69f58ed","embeds":"","z":3,"wi_name":"ACTIVITY_1","wi_displayName":"ACTIVITY 1","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"rect":{"width":50,"height":30,"rx":2,"ry":2,"stroke-width":1,"stroke-dasharray":"0"},"text":{"text":"Activity","font-size":10,"font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Rect","position":{"x":220,"y":370},"size":{"width":90,"height":54},"angle":0,"id":"e2bd21f2-508d-44b9-9f68-e374d4fa87ea","embeds":"","z":4,"wi_name":"ACTIVITY_2","wi_displayName":"ACTIVITY 2","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"rect":{"width":50,"height":30,"rx":2,"ry":2,"stroke-width":1,"stroke-dasharray":"0"},"text":{"text":"Workitem","font-size":10,"font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"link","source":{"id":"cae4c219-c2cd-4a4b-b50c-0f269963ca24"},"target":{"id":"d23133e0-e516-4f72-8127-292545d3d479"},"router":{"name":"manhattan"},"labels":[{"position":0.5,"attrs":{"text":{"text":"Name"}}}],"id":"60ee7ff7-3a3b-487d-b581-49027e7bebe4","embeds":"","z":5,"attrs":{".marker-source":{"d":"M 10 0 L 0 5 L 10 10 z","transform":"scale(0.001)"},".marker-target":{"d":"M 10 0 L 0 5 L 10 10 z"},".connection":{"stroke":"black"}}},{"type":"link","source":{"id":"a53898a5-c018-45c4-bd3f-4ea4d69f58ed"},"target":{"id":"e2bd21f2-508d-44b9-9f68-e374d4fa87ea"},"router":{"name":"manhattan"},"labels":[{"position":0.5,"attrs":{"text":{"text":"Name"}}}],"id":"cea0d1c2-2c18-4bd7-ba35-d94918c6fc9b","embeds":"","z":6,"attrs":{".marker-source":{"d":"M 10 0 L 0 5 L 10 10 z","transform":"scale(0.001)"},".marker-target":{"d":"M 10 0 L 0 5 L 10 10 z"},".connection":{"stroke":"black"}}}]
I just need to make a method to put this code inside to get all key-value pairs:
//Create a JsonFactory instance
JsonFactory factory = new JsonFactory();
//Create a JsonParser instance to read from file c:\\text.json
JsonParser jParser = factory.createJsonParser(new File("c:\\text.json"));
/*Create an ObjectMapper instance to provide a pointer
*to root node of the tree after reading the JSON
*/
ObjectMapper mapper = new ObjectMapper(factory);
//Create tree from JSON
JsonNode rootNode = mapper.readTree(jParser);
Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.getFields();
while (fieldsIterator.hasNext()) {
Map.Entry<String,JsonNode> field = fieldsIterator.next();
System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue());
}
How will I do it please?
You should use Jackson2 instead of Jackson1. As the error message specifies, Jackson1's JsonNode indeed does not have this fields() method, while Jackson2's version does.
In Jackson1, you would have to do something like this:
Iterator<String> fieldNameIterator = rootNode.getFieldNames();
while (fieldNameIterator.hasNext()) {
String fieldName = fieldNameIterator.next();
JsonNode fieldValue = rootNode.getFieldValue(fieldName);
System.out.println("Key: " + fieldName + "\tValue:" + fieldValue);
}
I solved my problem by changing JSON library.
I used json-simple-1.1.1
My final code that worked is the following:
package jsontoxml;
import java.io.*;
import org.json.simple.parser.JSONParser;
import org.json.simple.*;
import java.util.*;
public class JacksonStreamExample {
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader("text.json"));
JSONObject jsonObject = (JSONObject) obj;
JSONArray cells = (JSONArray) jsonObject.get("cells");
Iterator<JSONObject> iterator = cells.iterator();
while(iterator.hasNext()){
System.out.println(iterator.next());
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Now that you have modified the question and json, here is the solution you're looking for:
public static void main(String[] args) {
try {
Map source = (new ObjectMapper()).readValue(new File(
"C:\\json.txt"), Map.class);
Map<String, Object> result = new LinkedHashMap<>();
buildFlattenedMap(result, source, null);
for (String s : result.keySet()) {
System.out.println(s);
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static void buildFlattenedMap(Map<String, Object> result,
Map<String, Object> source, String path) {
for (Map.Entry<String, Object> entry : source.entrySet()) {
String key = entry.getKey();
if (hasText(path)) {
if (key.charAt(0) == '[') {
key = StringUtils.join(path, key);
} else {
key = StringUtils.join(path, '.', key);
}
}
Object value = entry.getValue();
if (value instanceof String) {
result.put(key, value);
} else if (value instanceof Map) {
// Need a compound key
#SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>) value;
buildFlattenedMap(result, map, key);
} else if (value instanceof Collection) {
// Need a compound key
#SuppressWarnings("unchecked")
Collection<Object> collection = (Collection<Object>) value;
int count = 0;
for (Object object : collection) {
buildFlattenedMap(result, Collections.singletonMap("["
+ (count++) + "]", object), key);
}
} else {
result.put(key, value == null ? StringUtils.EMPTY : value);
}
}
}
private static boolean hasText(CharSequence str) {
if (StringUtils.isEmpty(str)) {
return false;
}
int strLen = str.length();
for (int i = 0; i < strLen; i++) {
if (!Character.isWhitespace(str.charAt(i))) {
return true;
}
}
return false;
}
FYI, buildFlattenedMap method is actually from spring framework which I had used recently for processing a similar stuff.
https://github.com/spring-projects/spring-framework/blob/master/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java
I want to map below Json data to java object of List<Map<String, String>> type.
Sample Json:
{
{
a:b,
c:d
},
{
e:f,
g:h,
i:j
},
{
h:k
}
}
Here a:b represents key-value pair. So a:b and c:d will be mapped to first map of the list and so on.
one way to do this is by building JSON tree and access each node and store the pair into the map.
Is there a better way to do this (cleaner approach)?
Here is the code to read a List<Map<String, String>> using the Jackson library, with your example data as input:
public class JsonTest {
public static void main(String[] args) throws Exception {
final String json
= "[\n"
+ " {\n"
+ " \"a\":\"b\",\n"
+ " \"c\":\"d\"\n"
+ " },\n"
+ " {\n"
+ " \"e\":\"f\",\n"
+ " \"g\":\"h\",\n"
+ " \"i\":\"j\"\n"
+ " },\n"
+ " {\n"
+ " \"h\":\"k\"\n"
+ " }\n"
+ "]"; // [{a:b,c:d},{e:f,g:h,i:j},{h:k}]
ObjectMapper mapper = new ObjectMapper();
TypeFactory factory = TypeFactory.defaultInstance();
List<Map<String, String>> list = mapper.readValue(json,factory
.constructCollectionType(List.class, factory
.constructMapType(Map.class, String.class, String.class)));
System.out.println(list.toString());
}
}
Note: I had to fix your outermost braces from {} to [], which is the correct JSON list syntax.
You can use Jackson to achieve this task through below example code
public class JacksonExample {
public static void main(String[] args) {
ObjectMapper mapper = new ObjectMapper();
try {
// Convert JSON string from file to Object
User user = mapper.readValue(new File("C:\\user.json"), User.class);
System.out.println(user);
// Convert JSON string to Object
String jsonInString = "{\"age\":33,\"messages\":[\"msg 1\",\"msg 2\"],\"name\":\"xyz\"}";
User user1 = mapper.readValue(jsonInString, User.class);
System.out.println(user1);
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
First I made few changes to your json to make it valid
{
"key":
[{
"a": "b",
"c": "d"
},
{
"e": "f",
"g": "h",
"i": "j"
},
{
"h": "k"
}]
}
Please find the below code that I have tried out :
ObjectMapper mapper = new ObjectMapper();
ObjectNode objectNode1 = mapper.createObjectNode();
Map<String, Object> i = mapper.readValue(new File("J:/temp/sample.json"), Map.class);
System.out.println(i.get("key"));
System.out.println(i.values());
Output :
//For System.out.println(i.get("key"));
[{a=b, c=d}, {e=f, g=h, i=j}, {h=k}]
//For System.out.println(i.values());
[[{a=b, c=d}, {e=f, g=h, i=j}, {h=k}]]
If the above approach helps you, Make a right decision based on your needs either i.get("key") or i.values()
Just use gson library to Json to object and object to Json
import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
Object to Json
Gson gson = new Gson();
Student obj=new Student();
String jsonInString = gson.toJson(obj);
Json To Object
Student obj = gson.fromJson(jsonInString, Student.class);
I am facing a problem , sometimes Json response returns an array of objects , sometimes object itself , how we can handle dynamically in the response class.
In the current eg :results sometimes gets an array of objects
"\"results\": " +
"[{" +
and sometimes object itself
"\"results\": " +
"{" +
Eg:
How we can handle this ?
Gson gson = new Gson();
SearchResponse response=new SearchResponse();
response= gson.fromJson("{" +
"\"completed_in\": 0.047," +
"\"max_id\": 291771567376039936," +
"\"max_id_str\": \"291771567376039936\"," +
"\"next_page\": \"?page=2&max_id=291771567376039936&q=javacodegeeks\"," +
"\"page\": 1," +
"\"query\": \"javacodegeeks\"," +
"\"refresh_url\": \"?since_id=291771567376039936&q=javacodegeeks\"," +
"\"results\": " +
"{" +
"\"created_at\": \"Thu, 17 Jan 2013 04:58:57 +0000\"," +
"\"from_user\": \"hkokko\"," +
"\"from_user_id\": 24726686," +
"\"from_user_id_str\": \"24726686\"," +
" \"from_user_name\": \"Hannu Kokko\"," +
" \"geo\": null," +
"\"id\": 291771567376039936," +
"\"id_str\": \"291771567376039936\"," +
"\"iso_language_code\": \"en\"," +
" \"metadata\": {" +
"\"result_type\": \"recent\"}," +
"\"profile_image_url\": \"hjh\"," +
"\"profile_image_url_https\": \"kkj\"," +
"\"source\": \"<a href="hj;\"," +
"\"text\": \"Continuous Deployment: Are You Afraid It Might Work? jh\"," +
"\"to_user\": null," +
"\"to_user_id\": 0," +
"\"to_user_id_str\": \"0\"," +
"\"to_user_name\": null" +
" }," +
"\"results_per_page\": 15," +
"\"since_id\": 0," +
"\"since_id_str\": \"0\"" +
"}", SearchResponse.class);
System.out.println(response.toString());
Kindly assist...
Can anyone give any suggestions by using different jars to achieve this?
i found a solution for this ,i felt to share this..The code will automatically convert ..if excepted response is arraylist in response class....then if object is coming in response then add to arraylist else if arraylist it will take the same list.
we need hook change the response bfore it calls fromJson.
public class ArrayAdapter<T> extends TypeAdapter<List<T>> {
private Class<T> adapterclass;
public ArrayAdapter(Class<T> adapterclass) {
this.adapterclass = adapterclass;
}
public List<T> read(JsonReader reader) throws IOException {
List<T> list = new ArrayList<T>();
Gson gson = new Gson();
if (reader.peek() == JsonToken.BEGIN_OBJECT) {
T inning = (T) gson.fromJson(reader, adapterclass);
list.add(inning);
} else if (reader.peek() == JsonToken.BEGIN_ARRAY) {
reader.beginArray();
while (reader.hasNext()) {
T inning = (T) gson.fromJson(reader, adapterclass);
list.add(inning);
}
reader.endArray();
} else {
reader.skipValue();
}
return list;
}
public void write(JsonWriter writer, List<T> value) throws IOException {
}
}
public class ArrayAdapterFactory implements TypeAdapterFactory {
#SuppressWarnings({ "unchecked" })
#Override
public <T> TypeAdapter<T> create(final Gson gson, final TypeToken<T> type) {
ArrayAdapter typeAdapter = null;
try {
if (type.getRawType() == List.class)
{
typeAdapter = new ArrayAdapter(
(Class) ((ParameterizedType) type.getType())
.getActualTypeArguments()[0]);
}
} catch (Exception e) {
e.printStackTrace();
}
return typeAdapter;
}
then just call
Gson gson = new GsonBuilder().registerTypeAdapterFactory(new ArrayAdapterFactory()).create();
SearchResponse response;
esponse= gson.fromJson("your json string", SearchResponse.class)
You would need to write a custom deserializer that checks the type of results in the JSON then acts accordingly.
Your POJO will contain an array for results and if your incoming JSON only has a single object you'll need to fix that. One way is to modify the JSON then deserialize it:
class SearchResponseDeserializer implements JsonDeserializer<SearchResponse> {
public SearchResponse deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
throws JsonParseException {
if (json.getAsJsonObject().get("results").isJsonObject()) {
//modify JSON: change results to be an array
// ...
}
return new Gson().fromJson(json, SearchResults.class);
}
}
Or, fix the server, of course. It should always be returning an array to avoid this issue.