Remove object from JSON array

Question

I have an JSON array who looks like this:

[ {
  "name" : "1",
  "date" : "30/03 19:36:20"
}, {
  "name" : "12",
  "date" : "30/03 19:36:21"
}, {
  "name" : "123",
  "date" : "30/03 19:36:22"
}, {
  "name" : "1234",
  "date" : "30/03 19:36:23"
}, {
  "name" : "12345",
  "date" : "30/03 19:36:25"
} ]

How could I possibly delete one object by its name in java, like let's suppose I wanna delete the 1

 {
  "name" : "1",
  "date" : "30/03 19:36:20"
},

How could I possibly delete just those lines, because my code at the moment deletes all entries from the file

public static void deleteSavefile() throws IOException {
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode jsonNode = objectMapper.readTree(new File("savefiles.json"));
    for (JsonNode node : jsonNode) {
        ((ObjectNode)node).remove("name");
        ((ObjectNode)node).remove("date");
    }
    objectMapper.writeValue(new File("savefiles.json"), jsonNode);
}

What progress have you made till now? What approach are you following to parse and operate on this json? — Durlabh Sharma
– Durlabh Sharma, Commented Mar 30, 2019 at 19:41

Ryuzaki L · Accepted Answer · 2019-03-30 20:03:41Z

3

If jsonNode is an Array of Objects then jsonNode.elements() returns Iterator<JsonNode>, by using if condition check the node with name equals 1 then delete the entire node

 JsonNode jsonNode = objectMapper.readTree(new File("savefiles.json"));
Iterator<JsonNode> nodes = jsonNode.elements()
 while(nodes.hasNext()) {
     if(nodes.next().get("name").textValue().equals("1")){
           nodes.remove();
           }
       }

edited Mar 30, 2019 at 20:03

answered Mar 30, 2019 at 19:47

Ryuzaki L

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3 Comments

Terchila Marian Over a year ago

Your code works except that it doesn't delete the brackets at the end of execution, [{},{"name":"12","date":"30/03 19:36:21"},{"name":"123","date":"30/03 19:36:22"},{"name":"1234","date":"30/03 19:36:23"},{"name":"12345","date":"30/03 19:36:25"}]

Terchila Marian Over a year ago

I've tried but still cannot get rid of the empty brackets

Ryuzaki L Over a year ago

check the updated code @TerchilăMarian that should work

seby · Accepted Answer · 2025-05-25 18:04:15Z

If you want to remove an element from the ArrayNode, just

final JsonNode json = objectMapper.readTree(new File("savefiles.json"));

if (json.isArray()) {
    for (final Iterator<JsonNode> i = json.elements(); i.hasNext(); ) {
        final JsonNode jsonNode = i.next();

        if ("1".equals(jsonNode.get("name").asText())) {
            i.remove();
        }
    }
}

This will not create a new instance. The original TreeNode (which is an ArrayNode) is maintained.
Note also the .asText() while comparing.

A Stream version is

final ArrayNode filtered =
        StreamSupport.stream(json.spliterator(), false)
                     .filter(e -> !"1".equals(e.get("name").asText()))
                     .collect(Collector.of(
                             objectMapper::createArrayNode,
                             (array, element) -> array.add(element),
                             (result, toMerge) -> result.addAll(toMerge)
                     ));

Hemant Patel · Accepted Answer · 2019-03-30 19:59:57Z

Read the json in the list, iterate on the list, find the element and remove it.

ObjectMapper objectMapper = new ObjectMapper();
// read in a list
List<Map<String, String>> jsonList = objectMapper.readValue(new File("savefiles.json"), new TypeReference<List<Map<String, String>>>(){});

// remove object with name "1"
jsonList = jsonList.stream().filter(e -> !"1".equals(e.get("name"))).collect(Collectors.toList());

You can simplify more by defining a bean class with two field name and date then instead of List<Map<String, String> you can use List<BeanClass>.

// read in a list
List<BeanClass> jsonList = objectMapper.readValue(new File("savefiles.json"), new TypeReference<List<BeanClass>>(){});

// remove object with name "1"
jsonList = jsonList.stream().filter(e -> !"1".equals(e.getName())).collect(Collectors.toList());

Wrote code directly here, there might be some typo.

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