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Jack9

•Created by Jack9 on 11/14/2024 in #java-help

Jackson Mapper - String[] conversion possible?

This should be trivial, but I cannot figure out how to do it. In looking at custom annotations and additional registered serializers, I must be missing something.

import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.impl.StringArraySerializer;

public class ExampleDto {
    @JsonSerialize(using = StringArraySerializer.class)
    public String[] field;
}

public class ExampleDtoTest {
    @Test
    public void testConvertToMap() {
        HashMap<String, Object> expectedMap = new HashMap<>() {{
            put("field", (new String[]{"1","2","3"}));
        }};

        ExampleDto exampleDto = new ExampleDto();
        exampleDto.field = new String[]{"1","2","3"};

        ObjectMapper mapper = new ObjectMapper();
        HashMap result = mapper.convertValue(exampleDto, HashMap.class);
        assertEquals(String[].class, result.get("field").getClass()); // fails
    }
}

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