I have a json file, for example:
{
"A":"-0.4",
"B":"-0.2",
"C":"-0.2",
"D":"X",
"E":"0.2",
"F":"0.2",
"J":"0.3"
}
I want return each element of a list json when I call it via my function.
I did a function to do this:
public JSONObject my_function() {
JSONParser parser = new JSONParser();
List<JSONObject> records = new ArrayList<JSONObject>();
try (FileReader reader = new FileReader("File.json")) {
//Read JSON file
Object obj = parser.parse(reader);
JSONObject docs = (JSONObject) obj;
LOGGER.info("read elements" + docs); // it display all a list of a json file like this: {"A":"-0.4","B":"-0.2","C":"-0.2","D":"X","E":"0.2","F":"0.2","J":"0.3"}
for (int i = 0; i < docs.size(); i++) {
records.add((JSONObject) docs.get(i));
System.out.println((records)); // it return null
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
LOGGER.info("The first element of a list is:" +records.get(0)); // return null
return records.get(0);
How can I change my function to return the value of each element in a json file.
For example, when I call my_function:
my_function.get("A") should display -0.4
Thank you
First you need a Class for mapping
public class Json {
private String a;
private String b;
private String c;
private String d;
private String e;
private String f;
private String j;
//getters and setters
}
Then in your working class
ObjectMapper mapper = new ObjectMapper();
//JSON from file to Object
Json jsn = mapper.readValue(new File("File.json"), Json.class);
then you can use that object in a usual way...
here is the dependency I used
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.6.3</version>
</dependency>
Reference
In Java you can use only class`s methods, as I know.
If you want to get your second element by its first, you should in your class create 2 methods like
class Main {
Map<String, String> records = new HashMap<>();
public JSONObject my_function() {
// your realization where you should insert your pairs into Map.
}
public String get(String firstElement){
return map.getValue(firstElement);
}
}
class someOtherClass {
Main main = new Main();
main .my_function();
main .get("A");
}
Related
private static JSONArray getListOfChildPagesAsJSON(Page page) {
JSONArray pagesArray = new JSONArray();
try {
Iterator<Page> childPages = page.listChildren();
while (childPages.hasNext()) {
Page childPage = childPages.next();
JSONObject pageObject = new JSONObject();
pageObject.put(childPage.getTitle(), childPage.getPath());
pagesArray.put(pageObject);
}
} catch (JSONException e) {
LOG.error(e.getMessage(), e);
}
return pagesArray;
}
So that not only the children of the transferred page put into array, but also the children of the children.
This is a classical case for recursion, like reading directoy tree on filesystem. My suggestion is as follows:
First step: Change the scope of variable JSONArray pagesArray = new JSONArray(); from function to class scope.
public MyClass {
private JSONArray pagesArray = new JSONArray();
...
}
Step two: Change return value to void and the modifier of your function by removing static.
private void getListOfChildPagesAsJSON(Page page) { }
Step three add the missing recusion to your its body.
//JSONArray pagesArray = new JSONArray();
try {
Iterator<Page> childPages = page.listChildren();
while (childPages.hasNext()) {
Page childPage = childPages.next();
JSONObject pageObject = new JSONObject();
pageObject.put(childPage.getTitle(), childPage.getPath());
//Add the created object to your array which is class variable
this.pagesArray.put(pageObject);
//--Check for each single page for child pages again
Iterator<Page> childPagesOfChildpage = childPage.listChildren();
while (childPagesOfChildpage.hasNext()) {
getListOfChildPagesAsJSON(childPagesOfChildpage.next());
}
//--
}
} catch (JSONException e) {
LOG.error(e.getMessage(), e);
}
Note: The check childPage.hasChild() does not work here, because the node jcr:content is a valid child of passed page.
I need to load the data to the elasticsearch index. I am using BULK API of elasticsearch to load the JSONs to index.
private String FOLDER_PATH = "src/main/resources/allJsons";
private String index = "test1";
private static final String TYPE = "test_type";
#Autowired
private RestHighLevelClient restHighLevelClient;
public String loadBulkData() throws IOException {
BulkRequest bulkRequest = new BulkRequest();
AtomicInteger counter = new AtomicInteger();
try (Stream<Path> filePathStream = Files.walk(Paths.get(FOLDER_PATH))) {
filePathStream.forEach(filePath -> {
if (Files.isRegularFile(filePath)) {
counter.getAndIncrement();
try {
String content = Files.readString(filePath);
JSONObject jsonObject1 = new JSONObject(content);
HashMap yourHashMap1 = new Gson().fromJson(jsonObject1.toString(), HashMap.class);
IndexRequest indexRequest = new IndexRequest(index, TYPE).source(yourHashMap1);
bulkRequest.add(indexRequest);
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
try {
restHighLevelClient.bulk(bulkRequest, RequestOptions.DEFAULT);
} catch (IOException e) {
e.printStackTrace();
}
return "Bulk data loaded to index " + index + "";
}
}
I have multiple JSONs based on the following format
[
{
"Nutrient" : "Calories",
"Amount" : " 289.00",
"Unit" : " kcal"
}, {
"Nutrient" : "Fat",
"Amount" : " 17.35",
"Unit" : " g"
}
]
While running the code it gives me error ,
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.json.JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1]
I think the data is in JSONArray and for the code, we need JSONObject. Anyone could please guide to how to do this
You can do bulk insertion by passing hashmap of your json objects to Elasticsearch Bulk API.
You can create Hashmap by parsing your JSON file through JSONParser.
Here is the code for the same :
Code :
Integer id= 1;
//You need to call this method for inserting bulk documents which
// internally calls `createBulkRequest` and `parseObjectList` methods.
//This method uses JSONParser to parse your file and convert into JSONArray.
public String insertBulkDocuments() throws Exception {
Object obj = new JSONParser().parse(new FileReader(<path-of-file>));
JSONArray objList= (JSONArray) obj;
BulkRequest request = createBulkRequest(objList);
BulkResponse bulkresp=restHighLevelClient.bulk(request, RequestOptions.DEFAULT);
return bulkresp.status().toString();
}
// Each JSONArray element that was obtained through first method
//is parsed individually through Gson and converted into you defined Object.
//This object is then converted to Map and passed to IndexRequest object.
private BulkRequest createBulkRequest(JSONArray objList) {
BulkRequest request = new BulkRequest();
objList.forEach( obj -> parseObjectList((JSONObject) obj, request,id++));
return request;
}
private void parseObjectList(JSONObject obj, BulkRequest request, int id) {
Gson gson = new GsonBuilder().create();
NutrientDocument doc = gson.fromJson(obj.toJSONString(), NutrientDocument .class);
Map<String, Object> documentMapper = objectMapper.convertValue(doc, Map.class);
IndexRequest indexRequest = new IndexRequest(<your-index-name>).id(Integer.toString(id)).source(documentMapper);
request.add(indexRequest);
}
You need to create Custom object which has same feilds as your json . I have created NutrientDocument for testing which has same fields as your JSON and this I am using in parseObjectList method.
public class NutrientDocument {
private String Nutrient;
private Float Amount;
private String Unit;
public String getNutrient() {
return Nutrient;
}
public void setNutrient(String nutrient) {
Nutrient = nutrient;
}
public Float getAmount() {
return Amount;
}
public void setAmount(Float amount) {
Amount = amount;
}
public String getUnit() {
return Unit;
}
public void setUnit(String unit) {
Unit = unit;
}
}
NOTE :
For each document elasticserach generates unique id .
For creating our own id value instead of Elasticsearch autogenerated value, we are using id variable. But, if you want to go with Elasticsearch autogenerated number , you can create IndexRequest object as below in parseObjectList method and remove id variable wherever we are passing.
IndexRequest indexRequest = new IndexRequest().source(documentMapper);
I want to store the json array sent by php code in java array in android. My php code is working perfectly fine but in the app I get name: as the output. I want to display the names in the texview for checking purpose. Also I want to work with the namesby accessing them one by one.
Php code:
echo json_encode(array("result"=>$result));
Java code:
public class Salary {
public static final String DATA_URL1 = "http://********.com/name.php?salary=";
public static final String KEY_name = "name";
public static final String JSON_ARRAY1 = "result";
}
This is a method of my Name.java
private void showJSON(String response) {
String name = "";
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray result = jsonObject.getJSONArray(Salary.JSON_ARRAY1);
for (int i = 0; i < result.length(); i++) {
JSONObject collegeData = result.getJSONObject(i);
name = collegeData.getString(Salary.KEY_name);
}
} catch (JSONException e) {
e.printStackTrace();
}
textViewResult1.setText("Name:\t" + name);
}
Use GSON Library
ArrayList<Salary> salaryArrayList = new ArrayList<>();
try {
salaryArrayList = new Gson().fromJson(response, new TypeToken<Salary>() {}.getType());
} catch (JsonSyntaxException e) {
e.printStackTrace();
}
Then use salaryArrayList to get values.
Download GSON jar from this link
I want to extract JSON structure (only keyNames structure) by preserving the hierarchy (parent child relationship); I don't want values from the JSON yet.
I am new to Java and have been tying to achieve this using Jackson , but with no success.
Any direction on this will be much appreciated.
I created a static inner class for you by using JSONObject (http://www.json.org/javadoc/org/json/JSONObject.html)
public static class KeyNode {
private String name;
private ArrayList<KeyNode> children;
public KeyNode(String name) {
this.name = name;
this.children = new ArrayList<KeyNode>();
}
public void addChild(KeyNode child) {
this.children.add(child);
}
public static void parseJsonToKeys(KeyNode node, JSONObject json) throws JSONException {
Iterator<?> keys = json.keys();
while (keys.hasNext()) {
String name = (String) keys.next();
KeyNode child = new KeyNode(name);
node.addChild(child);
if (json.optJSONObject(name) != null) {
parseJsonToKeys(child, json.getJSONObject(name));
} else if (json.optJSONArray(name) != null) {
JSONArray array = json.getJSONArray(name);
for (int i = 0; i < array.length(); i++) {
try {
array.getJSONObject(i);
parseJsonToKeys(child, json.getJSONObject(name));
} catch (JSONException e) {
// this is ok
}
}
}
}
}
public static void exampleCodeUsage() {
try {
JSONObject json = new JSONObject("your json");
KeyNode keyHierarchy = new KeyNode("root");
parseJsonToKeys(keyHierarchy, json);
} catch (JSONException e) {
// your json is not formatted correctly
}
}
}
JSONParser parser = parser;
Object obj = parser.parse(new FileReader(FileName.Json));
JSONObject jobj = (JSONObject) obj;
obj.keys()
The method will give you the list of all keys in JSONObject
i have a problem how to cast JSONObject or String to integer..
I send data once as a JSONObject
#GET
#Produces(MediaType.APPLICATION_JSON)
public JSONObject sayJSONHello() {
JSONArray numbers = new JSONArray();
numbers.put(1);
numbers.put(2);
numbers.put(3);
numbers.put(4);
JSONObject result = new JSONObject();
try {
result.put("numbers", numbers);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
And one as a String
#Path("/test")
public class Hello {
#GET
#Produces(MediaType.APPLICATION_JSON)
public String sayJSONHello() {
String myString =null;
try
{
myString = new JSONObject().put("data", "1 2 4").toString();
}
catch (JSONException e)
{
e.printStackTrace();
}
return myString;
}
Then, i have problem how to receive this data as a Int.
I tried like this (Client):
Syste m.out.println(service.path("rest").path("hello").accept(MediaType.APPLICATION_JSON).get(String.class));
System.out.println(service.path("rest").path("test").accept(MediaType.APPLICATION_JSON).get(String.class));
String k = service.path("rest").path("test").accept(MediaType.APPLICATION_JSON).get(String.class);
// ERROR int temp = Integer.parseInt(k);
Could anyone advise how to deal with it ?
Your variable k is storing the whole JSON. You would need to parse the JSON object first and then pull out the specific integer (I assume in the array?) that you want.