java - 有没有一种方法，例如使用 @JsonFilter 来仅打印 HashMap 的值？

Question

我希望我的 map 仅在序列化为 JSON 时打印值。类似于此过滤器的内容，用于格式化日期

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "MM/dd/yyyy")
@JsonDeserialize(using = LocalDateDeserializer.class)
@JsonSerialize(using = LocalDateSerializer.class)
LocalDate startDate;

Answer 1

假设您有一个以 Map 作为字段的对象，并且您想要序列化该对象，但您不想使用映射属性的键值对，而是只想打印列表中的值，那么您可以可以有一个用于此转换的自定义 getter:

public class MyTest {

    private Map<String, Object> myMapProperty = new HashMap<>();

    @JsonIgnore
    public Map<String, Object> getMyMapProperty() {
        return myMapProperty;
    }

    public void setMyMapProperty(final Map<String, Object> myMapProperty) {
        this.myMapProperty = myMapProperty;
    }

    @JsonProperty("myMapProperty")
    public List<Object> getMyMapPropertyValues() {
        return myMapProperty.values()
                .stream() // use .map to transform values, e.g. flatten if values are Lists themselves
                .collect(Collectors.toList());
    }

    @Test
    public void test() throws JsonProcessingException {
        final MyTest myObject = new MyTest();
        myObject.getMyMapProperty().put("k1", "value1");
        myObject.getMyMapProperty().put("k2", "value2");

        final String value = new ObjectMapper().writeValueAsString(myObject);
        System.out.println(value);
    }

}