我正在开发一个Java库，以便能够读/写Lottie数据（定义为JSON的动画）。我试图用最少的代码和记录来实现这一点，但要为Lottie格式中定义的所有可能的用例实现这一点有点挑战性。我已经能够处理几乎所有的事情，但我仍然需要为关键帧找到一个合适的解决方案。
在下面的单元测试中，应该如何定义Java对象才能解析示例JSON？这在“pureJackson”中可能吗？还是需要一个helper类？我使用的是Jackson 2.14.1。
此时，只有testTimed成功。

public class KeyframeTest {

    private static final ObjectMapper mapper = new ObjectMapper();

    @Test
    void testInteger() throws JsonProcessingException {
        var json = """
                {
                    "k": [
                      128,
                      256
                    ]
                }
                """;

        var animated = mapper.readValue(json, Animated.class);

        assertAll(
                () -> assertEquals(2, animated.keyframes().size()),
                () -> assertTrue(animated.keyframes().get(0) instanceof NumberKeyframe),
                () -> assertEquals(128, animated.keyframes().get(0)),
                () -> JSONAssert.assertEquals(json, mapper.writeValueAsString(animated), false)
        );
    }

    @Test
    void testDouble() throws JsonProcessingException {
        var json = """
                {
                    "k": [
                      5.01,
                      6.02
                    ]
                }
                """;

        var animated = mapper.readValue(json, Animated.class);

        assertAll(
                () -> assertEquals(2, animated.keyframes().size()),
                () -> assertTrue(animated.keyframes().get(0) instanceof NumberKeyframe),
                () -> assertEquals(5.01, animated.keyframes().get(0)),
                () -> JSONAssert.assertEquals(json, mapper.writeValueAsString(animated), false)
        );
    }

    @Test
    void testTimed() throws JsonProcessingException {
        var json = """
                {
                    "k": [
                     {
                       "i": {
                         "x": [
                           0.833
                         ],
                         "y": [
                           0.833
                         ]
                       },
                       "o": {
                         "x": [
                           0.167
                         ],
                         "y": [
                           0.167
                         ]
                       },
                       "t": 60,
                       "s": [
                         1.1,
                         2.2,
                         3.3
                       ]
                     },
                     {
                       "t": 60,
                       "s": [
                         360.0
                       ]
                     }
                   ]
                }
                """;

        var animated = mapper.readValue(json, Animated.class);

        assertAll(
                () -> assertEquals(2, animated.keyframes().size()),
                () -> assertTrue(animated.keyframes().get(0) instanceof TimedKeyframe),
                () -> assertEquals(60, ((TimedKeyframe) animated.keyframes().get(0)).time()),
                () -> JSONAssert.assertEquals(json, mapper.writeValueAsString(animated), false)
        );
    }

    @Test
    void testMixed() throws JsonProcessingException {
        var json = """
                {
                    "k": [
                    100,
                    33.44,
                     {
                       "t": 60,
                       "s": [
                         1.1,
                         2.2,
                         3.3
                       ]
                     }
                   ]
                }
                """;

        var keyFrames = mapper.readValue(json, new TypeReference<List<Keyframe>>() {
        });

        assertAll(
                () -> assertEquals(3, keyFrames.size()),
                () -> assertTrue(keyFrames.get(0) instanceof NumberKeyframe),
                () -> assertTrue(keyFrames.get(1) instanceof NumberKeyframe),
                () -> assertTrue(keyFrames.get(2) instanceof TimedKeyframe),
                () -> JSONAssert.assertEquals(json, mapper.writeValueAsString(keyFrames), false)
        );
    }
}

动画对象

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(Include.NON_NULL)
public record Animated(
        @JsonProperty("a") Integer animated,
        @JsonProperty("k") List<Keyframe> keyframes,
        @JsonProperty("ix") Integer ix,
        @JsonProperty("l") Integer l
) {
}

关键帧对象，基于我前面的问题使用Java记录使用fasterxml将JSON解析为Java记录。Jackson

@JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION)
@JsonSubTypes({
        @JsonSubTypes.Type(TimedKeyframe.class),
        @JsonSubTypes.Type(NumberKeyframe.class)
})
public interface Keyframe {

}

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public record NumberKeyframe(
        BigDecimal value
) implements Keyframe {
}

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public record TimedKeyframe(
        @JsonProperty("t") Integer time, // in frames
        // Use BigDecimal here to be able to handle both Integer and Double
        // https://stackoverflow.com/questions/40885065/jackson-mapper-integer-from-json-parsed-as-double-with-drong-precision
        @JsonProperty("s") List<BigDecimal> values,
        @JsonProperty("i") EasingHandle easingIn,
        @JsonProperty("o") EasingHandle easingOut,
        @JsonProperty("h") Integer holdFrame
) implements Keyframe {
}

这是testDouble的失败消息：

com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Could not resolve subtype of [simple type, class com.lottie4j.core.model.keyframe.Keyframe]: Unexpected input
 at [Source: (String)"{
    "k": [
      5.01,
      6.02
    ]
}
"; line: 3, column: 7] (through reference chain: com.lottie4j.core.model.Animated["k"]->java.util.ArrayList[0])