CODEWITHSUNDEEP
javaarraysjson
Terchila Marian
Terchila Marian

Reputation: 2520

Remove object from JSON array

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);
}

Upvotes: 1

Views: 5632

Answers (3)

LppEdd
LppEdd

Reputation: 21134

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(result)
                     ));

Upvotes: 3

Ryuzaki L
Ryuzaki L

Reputation: 40068

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();
           }
       }

Upvotes: 3

Hemant Patel
Hemant Patel

Reputation: 3260

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.

Upvotes: 1

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