如何忽略变量名但序列化值 - jackson fasterxml

Question

我从代码中得到以下输出：{“list”：[{“x”：“y”}，{“a”：“b”}]}

相反，我希望输出为[{“x”：“y”}，{“a”：“b”}]

代码如下。

public class Test {
List<Map> list = new ArrayList();
public static void main(String [] args){
    Test t = new Test();

    Map m1 = new HashMap();
    m1.put("x","y");
    t.list.add(m1);

    Map m2 = new HashMap();
    m2.put("a","b");
    t.list.add(m2);

    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setSerializationInclusion(Include.NON_EMPTY);
    objectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.NON_PRIVATE);
    Writer writer = new StringWriter();
    try {
        objectMapper.writeValue(writer, t);
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    System.out.println("The json is:\n"+writer.toString());
  }
 }

更新到这个问题 - 再提高一个级别给我：

{ “清单”：[{ “地图”：{ “×”： “Y”， “×1”： “Y1”}}，{ “地图”：{ “A1”： “B1”， “一个”：“B “}}]}

我想要{{“x”：“y”，“x1”：“y1”}，{“a1”：“b1”，“a”：“b”}]

 public class Test {
public class Car{
    Map map = new HashMap();
}
List<Car> list = new ArrayList();
public static void main(String [] args){
    Test t = new Test();

    Test.Car car = t.new Car();
    Map m1 = new HashMap();
    m1.put("x","y");
    m1.put("x1","y1");
    car.map = m1;
    t.list.add(car);

    car = t.new Car();
    Map m2 = new HashMap();
    m2.put("a","b");
    m2.put("a1","b1");
    car.map = m2;
    t.list.add(car);

    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setSerializationInclusion(Include.NON_EMPTY);
    objectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.NON_PRIVATE);
    Writer writer = new StringWriter();
    try {
        objectMapper.writeValue(writer, t);
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    System.out.println("The json is:\n"+writer.toString());
}
 }

Answer 1

您可能想要使用@JsonValue批注，其文档说明：

类似于XmlValue的标记注释，表示带注释的“getter”方法的结果（表示签名必须是getter的结果;非void返回类型，无args）将被用作序列化实例的单个值。 通常，value将是一个简单的标量类型（String或Number），但它可以是任何可序列化的类型（Collection，Map或Bean）。

这是一个有效的例子：

public class Test {
    public static class Car {
        Map map = new HashMap();

        @JsonValue
        public Map getMap() {
            return map;
        }
    }

    List<Car> list = new ArrayList();

    @JsonValue
    public List<Car> getList() {
        return list;
    }

    public static void main(String[] args) throws IOException {
        Test t = new Test();

        Car car = new Car();
        Map m1 = new HashMap();
        m1.put("x", "y");
        m1.put("x1", "y1");
        car.map = m1;
        t.list.add(car);

        car = new Car();
        Map m2 = new HashMap();
        m2.put("a", "b");
        m2.put("a1", "b1");
        car.map = m2;
        t.list.add(car);

        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
        Writer writer = new StringWriter();

        objectMapper.writeValue(writer, t);
        System.out.println("The json is:\n" + writer.toString());
    }
}

Answer 2

我实现了import com.fasterxml.jackson.databind.JsonSerializable; 在Car class上做了以下几点。

  public class Car implements JsonSerializable{
  Map map = new HashMap();
  @Override
    public void serialize(JsonGenerator arg0, SerializerProvider arg1)
        throws IOException, JsonProcessingException {
        arg0.writeObject(map);
    }
  }

这删除了map关键字。 我不能像上面的代码库一样使用JsonValue我不允许在Map上使用getter而JsonValue不适用于非公共字段。 （或者我无法让它工作）