How to create JSON dynamically in java?

Question

I have a CustomerEntiy with getter and setter the sample customerEntity is

customerEntity =
{
  "customerNumber": "1234",
  "firstName": "Test",
  "email": "[email protected]",
  "id": "1",
  "middleName": "doe",
  "phone": "11111"
}

I have java class Attributes of JsonProperty with getter and Setters as below

Attributes = 
{
"name": "string"
"value": "string"
}

I have a list which will contains random elements from CustomerEntiy for example:

List<String> stringlist = { "firstName" , "phone"}

I have created an List of type Attributes

List<Attributes> Attributeslist = new ArrayList<>();

I want to create Attributelist of all the elements in stringlist for Example here it would be:

Attributeslist =[
{
"name": "firstName"
"value": "Test"
},
{
"name": "phone"
"value": "11111"
}
]

For this i have written the code as below but what to pass in previewattributes.setValue(); because that value would depends on what is mystring in below for loop. In this example it would be previewattributes.setValue(customerEntity.getFirstName()); and previewattributes.setValue(customerEntity.getPhone()); for different iteration but how do i code it??

for (String mystring : stringlist) {
    Attributes previewattributes;
    previewattributes = new Attributes();
    previewattributes.setName(mystring);
    previewattributes.setValue(value here would be of customerentity);
    Attributeslist.add(previewattributes);
}

CustomerEntity:

@Entity
@Table(name = "Customer_tbl")
public class CustomerEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long rowId;


    @Column(name = "customer_number")
    private String customerNumber;

    public String getCustomerNumber() {
        return customerNumber;
    }

    public void setCustomerNumber(String customerNumber) {
        this.customerNumber = customerNumber;
    }
}

Depends on what data structure you use to store your customerentities.? You didn't mention that. — jschnasse
– jschnasse, Commented Oct 16, 2020 at 8:42
use reflection, get all fields and iterate with each fields. — Himeshgiri gosvami
– Himeshgiri gosvami, Commented Oct 16, 2020 at 8:54

Mahesh · Accepted Answer · 2020-10-16 10:58:46Z

1

You can make use reflection in Java. Even more simple way is to store the customerEntity in HashMap and fetch from it.

HashMap<String,String> m=new HashMap<>();
m.put("customerNumber", customerEntity.getCustomerNumber());
m.put("firstName", customerEntity.getFirstName());
m.put("email", customerEntity.getEmail());
m.put("id", customerEntity.getId());
m.put("middleName", customerEntity.getMiddleName());
m.put("phone", customerEntity.getPhone());

And inside for loop:

previewattributes.setValue(m.get(attribute));

answered Oct 16, 2020 at 10:58

Mahesh

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1 Comment

yatharth meena Over a year ago

Storing as hashmap worked but how can i use reflection?

Amit Kumar Lal · Accepted Answer · 2020-10-16 11:30:35Z

If I understood u correctly u have an Array of Customer Json in which u want some attribute separated , check below code

public static void main(String[] args)  {

    String jsonArray = "[\r\n" + 
            "   {\r\n" + 
            "      \"customerNumber\":\"1234\",\r\n" + 
            "      \"firstName\":\"Test\",\r\n" + 
            "      \"email\":\"[email protected]\",\r\n" + 
            "      \"id\":\"1\",\r\n" + 
            "      \"middleName\":\"doe\",\r\n" + 
            "      \"phone\":\"11111\"\r\n" + 
            "   },\r\n" + 
            "   {\r\n" + 
            "      \"customerNumber\":\"1235\",\r\n" + 
            "      \"firstName\":\"Test2\",\r\n" + 
            "      \"email\":\"[email protected]\",\r\n" + 
            "      \"id\":\"2\",\r\n" + 
            "      \"middleName\":\"doe2\",\r\n" + 
            "      \"phone\":\"2222\"\r\n" + 
            "   }\r\n" + 
            "]";
    
    List<String> requiredKeys = Arrays.asList("firstName" , "phone");
    JSONArray array = new JSONArray(jsonArray);
    Iterator iterator = array.iterator();
    
    JSONArray outputArray = new JSONArray(); 
    while(iterator.hasNext()) {
        JSONObject jsonObject = (JSONObject)iterator.next();
        Iterator<String> keys = jsonObject.keys();
        while(keys.hasNext()) {
            String key = keys.next();
            if(requiredKeys.contains(key)) {
                JSONObject attribute = new JSONObject();
                attribute.put("name", key);
                attribute.put("value", jsonObject.get(key));
                outputArray.put(attribute);
            }
        }
    }
    
    System.out.println(outputArray);
}

}

output

[
   {
      "name":"firstName",
      "value":"Test"
   },
   {
      "name":"phone",
      "value":"11111"
   },
   {
      "name":"firstName",
      "value":"Test2"
   },
   {
      "name":"phone",
      "value":"2222"
   }
]

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