JSONObject

Introduction

JSONObject represents a key-value object in JSON, enclosed by curly braces, with each key-value pair separated by a comma and the key and value separated by a colon. A JSONObject looks like this:

{
  "key1":"value1",
  "key2":"value2"
}

The key part can be omitted with double quotes, but the value must be enclosed in double quotes if it is a string. If the value is a number or a Boolean value, it does not need to be enclosed in double quotes.

Usage

Creation

JSONObject json1 = JSONUtil.createObj()
  .put("a", "value1")
  .put("b", "value2")
  .put("c", "value3");

JSONUtil.createObj() is a convenience method for quickly creating a new JSONObject. We can also create it directly using the new keyword:

JSONObject json1 = new JSONObject();
...

Conversion

Parsing JSON Strings

String jsonStr = "{\"b\":\"value2\",\"c\":\"value3\",\"a\":\"value1\"}";
// Method 1: Using the utility class to convert
JSONObject jsonObject = JSONUtil.parseObj(jsonStr);
// Method 2: Converting using the new keyword
JSONObject jsonObject2 = new JSONObject(jsonStr);

// Converting a JSONObject to a string (single line)
jsonObject.toString();

// We can also beautify it to display an indented JSON:
jsonObject.toStringPretty();

    
  

Parsing JavaBeans

First, let’s define a Bean:

// Using Lombok for annotations
@Data
public class UserA {
    private String name;
    private String a;
    private Date date;
    private List<Seq> sqs;
}

    
  

Parsing to JSON:

UserA userA = new UserA();
userA.setName("nameTest");
userA.setDate(new Date());
userA.setSqs(CollectionUtil.newArrayList(new Seq(null), new Seq("seq2")));

// false indicates not to skip null values
JSONObject json = JSONUtil.parseObj(userA, false);
Console.log(json.toStringPretty());

    
  

Result:

{
    "date": 1585618492295,
    "a": null,
    "sqs": [
        {
            "seq": null
        },
        {
            "seq": "seq2"
        }
    ],
    "name": "nameTest"
}

    
  

As you can see, the order of the output fields is not consistent with the order of the fields in the Bean. If you want to maintain consistency, you can do:

// The second parameter indicates to keep it ordered 
JSONObject json = JSONUtil.parseObj(userA, false, true);

Result:

{
    "date": 1585618492295,
    "a": null,
    "sqs": [
        {
            "seq": null
        },
        {
            "seq": "seq2"
        }
    ],
    "name": "nameTest"
}

    
  

As you can see, the order of the output fields is inconsistent with the order of the fields in the Bean. To maintain consistency, you can use the following code:

// The second parameter indicates to keep it ordered
JSONObject json = JSONUtil.parseObj(userA, false, true);

Result:

{
    "name": "nameTest",
    "a": null,
    "date": 1585618648523,
    "sqs": [
        {
            "seq": null
        },
        {
            "seq": "seq2"
        }
    ]
}

    
  

By default, Hutool outputs dates as timestamps. If you need to customize the date format, you can call:

json.setDateFormat("yyyy-MM-dd HH:mm:ss");

To get the following result:

{
    "name": "nameTest",
    "a": null,
    "date": "2020-03-31 09:41:29",
    "sqs": [
        {
            "seq": null
        },
        {
            "seq": "seq2"
        }
    ]
}

    
  

JSONUtil JSONArray