How to parse string value JSON

[youngfreeFJS]

how to parse this JSON?
want to print 3 and 4,
but found :

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of cases.apis.lyrebird.response.TestJackson$DemoBean$C (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"d": "3", "e": "4"}')

my code：

public class TestJackson {
    private ObjectMapper jackson = new ObjectMapper();

    private static String testDataStr = "{" +
        "\"a\": \"1\", " +
        "\"b\": \"2\", " +
        "\"c\": \"{\\\"d\\\": \\\"3\\\", \\\"e\\\": \\\"4\\\"}\"}";

    @Data
    public static class DemoBean {
        private String a;
        private String b;
        private C c;

        @Data
        public static class C {
            private String d;
            private String e;
        }
    }

    @Test
    public void testTrans() throws JsonProcessingException {
        DemoBean demo = jackson.readValue(testDataStr, DemoBean.class);
        System.out.println(demo.getC().getD());
        System.out.println(demo.getC().getE());
    }
}

[pjfanning]

I'm guessing @Data is a lombok annotation. If so, try adding more Lombok annotations so that more Java methods are autogenerated, making it easier for Jackson to find a way to set the values. @AllArgsConstructor would be the first one I would try.