How to parse raw values from JSON array items with Jackson?

user_2774914 0
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Using Jackson deserialization it would be great to have an option
to deserialize JSON array of items (of any nature: object, number, string) to a Java array of String.

I see that @JsonRawValue allows to have similar functionality for nested fields.
Is it possible to implement the same for "top level" objects?

void test(){
    var payload = """ [
          {"a": 1, "b": "hello"},
          {"a": 2, "b": "bye"},
          "something"
    ]
    """;

    // What else is required to get the effect of @JsonRawValue ?

    String[] rawItems = new ObjectMapper().readValue(payload, String[].class);

    assertEquals("""{"a": 1, "b": "hello"}""", rawItems[0]);
    assertEquals("""{"a": 2, "b": "bye"}""", rawItems[1]);
    assertEquals("\"something\"", rawItems[2]);
}
json-deserialization deserialization jackson json java
1 Answers

You can convert the payload to com.fasterxml.jackson.databind.node.ArrayNode and then iterate through elements (JsonNode in this case) and add them to a List<String> (which you can then convert to String[] if you want).

One thing to be aware of - the formatting will not be as you expect. JsonNode has two methods - toString() which deletes all the white space and toPrettyString which adds whitespaces and newlines to the final String

        String payload = """ 
        [
          {"a": 1, "b": "hello"},
          {"a": 2, "b": "bye"},
          "something"
        ]
        """;
        ArrayNode items = new ObjectMapper().readValue(payload, ArrayNode.class);

        List<String> rawItemsList = new ArrayList<>();

        for (JsonNode jsonNode : items) {
            rawItemsList.add(jsonNode.toString());
        }

        // You can just keep using the rawItemsList, but I've converted it to array since the question mentioned it
        String[] rawItemsArr = rawItemsList.toArray(new String[0]);

        assertEquals("""
                {"a":1,"b":"hello"}""", rawItemsArr[0]);
        assertEquals("""
                {"a":2,"b":"bye"}""", rawItemsArr[1]);
        assertEquals("\"something\"", rawItemsArr[2]);
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