使用 Jackson 将 JSON 字符串解析为数组

Question

I get the following JSON response:

[
{
    "name": "Assets",
    "id": "assets---0020",
    "elements": [
        {
            "name": "user generates an token",
            "steps": [
            {
                "name": "I have generated a common access token",
                "result": {
                    "duration": 1124800,
                    "status": "passed"
                }                    
            }
            ]
        },
        {
            "name": "user generates an token",
            "steps": [
            { 
                "name": "I have generated a common access token",
                "result": {
                    "duration": 1124800,
                    "status": "passed"
                }                    
            }
            ]
        },
        {
            "name": "User clicks on dropdown",
            "steps": [
            {
                "name": "User clicks on dropdown and selects option and api response printed",
                "result": {
                    "duration": 1124800,
                    "status": "failed"
                }
            }
            ]
        }
    ]    
}
]

I want below output:

Name: Assets
Total - 3
No Of Success - 2
No Of Failed - 1

I've been trying to parse it automatically with Jackson with little/no success. I am able to display:

Name: Assets 

below is code for my main Java class:

package JsonToJava.test;

import java.io.File;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;


public class JsontoJava
{

    public static void main( String[] args ) throws JsonMappingException, JsonProcessingException
    {        
       ObjectMapper mapper = new ObjectMapper();

       try {            
      
          Data[] dataObj  = mapper.readValue(new File("data/sample_array_data.json"), Data[].class);
       
      
          for (Data data: dataObj) {
           
             System.out.println("Track Name--->"+data.getName());
            
             System.out.println("Printing Elements--->"+data.getElements());
            
             System.out.println("------------------------");
          }
        } catch (JsonMappingException e) {
          e.printStackTrace();
        }catch (JsonProcessingException e) {
          e.printStackTrace();
        }catch (IOException e) {
          e.printStackTrace();
      } 
   }
}

But not getting how to loop elements & get desired data from it. Anyone know what is the solution? Please help.

Answer 1

Click this link jsonschema2pojo and paste your JSON code. Type the name of your file and package and select both the radio buttons JSON and jackson 2.x . Click preview and copy the code displayed in the modal window.

Screenshot

Answer 2

So you have a list of JSON objects ( in the question this list contains only one element) and you have defined Data class that can map this single json object, right?

In this case this question is actually about how to parse a list of object with jackson:

Here is an answer:

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

...
String str = "...";
List<Data> dataList = objectMapper.readValue(str, new TypeReference<List<Data>>(){});

Answer 3

Do this Data[] datas = mapper.readValue(new File("sample_json_file.json"), Data[].class); then loop through.