java - 使用fasterxml将json回复解析为对象时出现com.fasterxml.jackson.databind.exc.MismatchedInputException

Question

我正在尝试使用fasterxml将json回复解析为POJO。但问题是 json 回复包含嵌套对象，其中包含反斜杠，因此在通过 ObjectMapper 读取此值时，我收到 com.fasterxml.jackson.databind.exc.MismatchedInputException

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of com.am.api.Message (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"entryType":"Buy","rate":"22000.0","action":"update","offerId":"b96f2da7-55f9-4221-aaa3-8e3ad177567d","market":"BTC-PLN","state":{"market":"BTC-PLN","offerType":"Buy","id":"b96f2da7-55f9-4221-aaa3-8e3ad177567d","currentAmount":"0.0005","lockedAmount":"11.00","rate":"22000.0","startAmount":"0.0005","time":"1535023208260","postOnly":false,"hidden":false,"mode":"limit","receivedAmount":"0"}}') at [Source: (String)"{ "topic":"trading/offers/BTC-PLN", "message":"{\"entryType\":\"Buy\",\"rate\":\"22000.0\",\"action\":\"update\",\"offerId\":\"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\"market\":\"BTC-PLN\",\"state\":{\"market\":\"BTC-PLN\",\"offerType\":\"Buy\",\"id\":\"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\"currentAmount\":\"0.0005\",\"lockedAmount\":\"11.00\",\"rate\":\"22000.0\",\"startAmount\":\"0.0005\",\"time\":\"1535023208260\",\"postOnly\":false,\"hidden\":false,\"mode\":\"limit\",\"receivedAmoun"[truncated 45 chars]; line: 3, column: 13] (through reference chain: com.am.api.WsOrderReply["message"]) at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1329) at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1031) at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:370) at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:314) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1351) at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:170) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:161) at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:519) at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeWithErrorWrapping(BeanDeserializer.java:527) at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeUsingPropertyBased(BeanDeserializer.java:416) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1265) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:325) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2992) at com.am.ReplyMapper.readValue(ReplyMapper.java:154) at com.am.ReplyMapper.mapReplyToCommonExecutionReport(ReplyMapper.java:73) at com.am.ReplyMapper.lambda$apply$1(ReplyMapper.java:54) at java.util.Optional.map(Optional.java:215) at com.am.ReplyMapper.apply(ReplyMapper.java:54) at com.am.ReplyMapperTest.shouldMapUpdateOrderReplyNew(ReplyMapperTest.java:64) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

我不知道如何使用fasterxml解析这个对象？!

我的 POJO 对象模型如下所示:

@EqualsAndHashCode
@ToString
@Getter
@Builder
public class WsOrderReply {

    private final String topic;
    private final Message message;
    private final Long timestamp;

    @JsonCreator
    public WsOrderReply(
            @JsonProperty("topic") String topic,
            @JsonProperty("message") Message message,
            @JsonProperty("timestamp") Long timestamp) {
        this.topic = topic;
        this.message = message;
        this.timestamp = timestamp;
    }
}

@EqualsAndHashCode
@ToString
@Getter
public class Message {

    private final String entryType;
    private final BigDecimal rate;
    private final String action;
    private final String offerId;
    private final String market;
    private final State state;

    @JsonCreator
    public Message(
            @JsonProperty("entryType") String entryType,
            @JsonProperty("rate") BigDecimal rate,
            @JsonProperty("action") String action,
            @JsonProperty("offerId") String offerId,
            @JsonProperty("market") String market,
            @JsonProperty("state") State state) {
        this.entryType = entryType;
        this.rate = rate;
        this.action = action;
        this.offerId = offerId;
        this.market = market;
        this.state = state;
    }
}

@EqualsAndHashCode
@ToString
@Getter
public class State {

    private final String market;
    private final String offerType;
    private final String id;
    private final BigDecimal currentAmount;
    private final BigDecimal lockedAmount;
    private final BigDecimal rate;
    private final BigDecimal startAmount;
    private final String time;
    private final boolean postOnly;
    private final boolean hidden;
    private final String mode;
    private final BigDecimal receivedAmount;

    public State(
            @JsonProperty("market") String market,
            @JsonProperty("offerType") String offerType,
            @JsonProperty("id") String id,
            @JsonProperty("currentAmount") BigDecimal currentAmount,
            @JsonProperty("lockedAmount") BigDecimal lockedAmount,
            @JsonProperty("rate") BigDecimal rate,
            @JsonProperty("startAmount") BigDecimal startAmount,
            @JsonProperty("time") String time,
            @JsonProperty("postOnly") boolean postOnly,
            @JsonProperty("hidden") boolean hidden,
            @JsonProperty("mode") String mode,
            @JsonProperty("receivedAmount") BigDecimal receivedAmount) {
        this.market = market;
        this.offerType = offerType;
        this.id = id;
        this.currentAmount = currentAmount;
        this.lockedAmount = lockedAmount;
        this.rate = rate;
        this.startAmount = startAmount;
        this.time = time;
        this.postOnly = postOnly;
        this.hidden = hidden;
        this.mode = mode;
        this.receivedAmount = receivedAmount;
    }
}

我收到的原始 json 消息:

{ "topic":"交易/报价/BTC-PLN", "message":"{\"entryType\":\"Buy\",\"rate\":\"22000.0\",\"action\":\"update\",\"offerId\":\"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\"市场\":\"BTC-PLN\",\"状态\":{\"市场\":\"BTC-PLN\",\"offerType\":\"购买\",\"id\":\"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\"当前金额\":\"0.0005\",\"锁定金额\":\"11.00\",\"费率\":\"22000.0\",\"startAmount\":\"0.0005\",\"时间\":\"1535023208260\",\"postOnly\":false,\"隐藏\":false,\"模式\":\"限制\",\"收到金额\":\"0\"}}", “时间戳”:1535023208264}

我的 JUnit 测试:

public class ReplyMapperTest {

    private static ObjectMapper objectMapper;

    private MessageFactory msgFactory = new quickfix.fix42.MessageFactory();

    private TypeSelector fixMsgBuilder = FixMessageBuilder
            .usingFactory(msgFactory::create)
            .withBeginString(FixVersions.BEGINSTRING_FIX42);

    private ReplyMapper replyMapper = new ReplyMapper(objectMapper, fixMsgBuilder);

    @BeforeClass
    public static void beforeClass() {
        objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

    }

    @Test
    public void shouldMapUpdateOrderReplyNew() throws FieldNotFound, IOException {
        String json = IOUtils.toString(this.getClass().getResourceAsStream("/json/UpdateOrderReplyNew.json"), StandardCharsets.UTF_8);

        //When
        List<Message> result = replyMapper.apply(json);

        //Then
        assertThat(result.get(0).getHeader().getString(MsgType.FIELD), is(Heartbeat.MSGTYPE));
    }

也许有人也遇到了和我一样的问题。如何解决这个问题？

Answer 1

即使未转义，您使用的 JSON 也不正确因此它将整个对象视为一个字符串。使用正确的转义 json 可以解决问题，我已经更正了 JSON，让您现在看看它是否有效

{\r\n\t\"topic\": \"trading\/offers\/BTC-PLN\",\r\n\t\"message\": {\r\n\t\t\"entryType\": \"Buy\",\r\n\t\t\"rate\": \"22000.0\",\r\n\t\t\"action\": \"update\",\r\n\t\t\"offerId\": \"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\r\n\t\t\"market\": \"BTC-PLN\",\r\n\t\t\"state\": {\r\n\t\t\t\"market\": \"BTC-PLN\",\r\n\t\t\t\"offerType\": \"Buy\",\r\n\t\t\t\"id\": \"b96f2da7-55f9-4221-aaa3-8e3ad177567d\",\r\n\t\t\t\"currentAmount\": \"0.0005\",\r\n\t\t\t\"lockedAmount\": \"11.00\",\r\n\t\t\t\"rate\": \"22000.0\",\r\n\t\t\t\"startAmount\": \"0.0005\",\r\n\t\t\t\"time\": \"1535023208260\",\r\n\t\t\t\"postOnly\": false,\r\n\t\t\t\"hidden\": false,\r\n\t\t\t\"mode\": \"limit\",\r\n\t\t\t\"receivedAmount\": \"0\"\r\n\t\t}\r\n\t},\r\n\t\"timestamp\": 1535023208264\r\n}

如果 Json 无法更改，则需要在构造函数中以 String 值的形式获取消息，然后使用对象映射器将其显式转换为对象

public class WsOrderReply {

        private final String topic;
        private final Message message;
        private final Long timestamp;
        ObjectMapper mapper = new ObjectMapper();

        @JsonCreator
        public WsOrderReply(
                @JsonProperty("topic") String topic,
                @JsonProperty("message") String messageString,
                @JsonProperty("timestamp") Long timestamp) {
            this.topic = topic;
            this.message = mapper.readValue(messageString, Message.class);;
            this.timestamp = timestamp;
        }
    }

另一个不需要更改模型类的解决方案是从服务器获取 JSON，然后在本地将其更改为第一种方法中提到的格式