使用Jackson将许多对象转换为JSON

Question

我有JSON，具有不同级别的字段，因此我想转换为具有一个级别的字段的单个JSON，例如：

{
  "prop1":"value1",
  "prob2":"value2",
  "prop3": {
     "prop4":"value4",
     "prop5":"value5"
  }
  ... many level fields
}

结果

{
  "prop1":"value1",
  "prop2":"value2",
  "prop4":"value4",
  "prop5":"value5"
  .......
}

我正在使用带有批注的Jackson
@JsonProperty("field")，我对第一级字段没有问题，但是我不知道如何在JSON内部访问字段，例如prop4和prop5。

Answer 1

JsonUnwrapped是要使用的注释，它甚至适用于多层嵌套。例如：

@RunWith(JUnit4.class)
public class Sample {

    @Test
    public void testName() throws Exception {
        SampleClass sample = new SampleClass("value1", "value2", new SubClass("value4", "value5", new SubSubClass("value7")));
        new ObjectMapper().writeValue(System.out, sample);
    }

    @JsonAutoDetect(fieldVisibility=Visibility.ANY)
    public static class SampleClass {
        private String prop1;
        private String prop2;
        @JsonUnwrapped
        private SubClass prop3;

        public SampleClass(String prop1, String prop2, SubClass prop3) {
            this.prop1 = prop1;
            this.prop2 = prop2;
            this.prop3 = prop3;
        }
    }
    @JsonAutoDetect(fieldVisibility=Visibility.ANY)
    public static class SubClass {
        private String prop4;
        private String prop5;
        @JsonUnwrapped
        private SubSubClass prop6;
        public SubClass(String prop4, String prop5, SubSubClass prop6) {
            this.prop4 = prop4;
            this.prop5 = prop5;
            this.prop6 = prop6;
        }

    }
    @JsonAutoDetect(fieldVisibility=Visibility.ANY)
    public static class SubSubClass{
        private String prop7;

        public SubSubClass(String prop7) {
            this.prop7 = prop7;
        }
    }
}

会产生

{"prop1":"value1","prop2":"value2","prop4":"value4","prop5":"value5","prop7":"value7"}