Question

我编写了一个自定义序列化程序和反序列化程序，用于读取kafka上的json字符串。

Json Serializer和Deserializer如下所示

package com.kafka.api.serdes;

import java.util.Map;

import org.apache.kafka.common.errors.SerializationException;
import org.apache.kafka.common.serialization.Serializer;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonSerializer<T> implements Serializer<T> {

    private ObjectMapper om = new ObjectMapper();

    @Override
    public void close() {
        // TODO Auto-generated method stub

    }

    @Override
    public void configure(Map<String, ?> config, boolean isKey) {
        // TODO Auto-generated method stub

    }

    @Override
    public byte[] serialize(String topic, T data) {
        // TODO Auto-generated method stub
        try {
            return om.writeValueAsBytes(data);
        } catch (JsonProcessingException e) {
            throw new SerializationException();
        }
    }

}

package com.kafka.api.serdes;

import java.util.Map;

import org.apache.kafka.common.errors.SerializationException;
import org.apache.kafka.common.serialization.Deserializer;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonDeserializer<T> implements Deserializer<T> {

    private ObjectMapper om = new ObjectMapper();
    private Class<T> type;

    /*
     * Default constructor needed by kafka
     */
    public JsonDeserializer() {

    }

    public JsonDeserializer(Class<T> type) {
        this.type = type;
    }

    @Override
    public void close() {
        // TODO Auto-generated method stub

    }

    @SuppressWarnings("unchecked")
    @Override
    public void configure(Map<String, ?> map, boolean arg1) {
        if (type == null) {
            type = (Class<T>) map.get("type");
        }

    }

    @Override
    public T deserialize(String undefined, byte[] bytes) {
        if (bytes == null || bytes.length == 0) {
            return null;
        }

        try {
            String s = new String(bytes);
            System.out.println("The erreneous string is " + s + " "
                    + "The length is " + s.length());
            System.out.println("The type is " + type);
            return (T) om.readValue(bytes, type);
        } catch (Exception e) {
            throw new SerializationException(e);
        }
    }

    protected Class<T> getType() {
        return type;
    }

}

json数据如下所示

dgerssam0，f1d0d29a-f067-45a1-b753-e3d1e8e3d32f，Guinea，Developer III

madamou1，cf8c06c7-bff1-47ce-944f-0f1975aa5e73，葡萄牙，PhysicalAssistant

对应的pojo

package com.kafka.api.models;

public class Person {

    private String name;
    private String personalID;
    private String country;
    private String occupation;

    public Person(){

    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPersonalID() {
        return personalID;
    }
    public void setPersonalID(String personalID) {
        this.personalID = personalID;
    }
    public String getCountry() {
        return country;
    }
    public void setCountry(String country) {
        this.country = country;
    }
    public String getOccupation() {
        return occupation;
    }
    public void setOccupation(String occupation) {
        this.occupation = occupation;
    }

    @Override
    public String toString(){
        return "{" + " "+"Name :" + " " + name
                   + " "+"ID :" + " " + personalID
                   + " "+"Country :" + " " + country
                   + " "+"Occupation :" + " " + occupation
                   +
                "}";
    }
}

但在反序列化json期间，我面临一个奇怪的问题

Caused by: org.apache.kafka.common.errors.SerializationException: com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'hello': was expecting ('true', 'false' or 'null')
 at [Source: [B@1685c6d8; line: 1, column: 11]
Caused by: com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'hello': was expecting ('true', 'false' or 'null')
 at [Source: [B@1685c6d8; line: 1, column: 11]
    at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1702)
    at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:558)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._reportInvalidToken(UTF8StreamJsonParser.java:3524)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._handleUnexpectedValue(UTF8StreamJsonParser.java:2686)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._nextTokenNotInObject(UTF8StreamJsonParser.java:878)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:772)
    at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3834)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3783)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2929)
    at com.kafka.api.serdes.JsonDeserializer.deserialize(JsonDeserializer.java:52)
    at org.apache.kafka.common.serialization.ExtendedDeserializer$Wrapper.deserialize(ExtendedDeserializer.java:65)
    at org.apache.kafka.common.serialization.ExtendedDeserializer$Wrapper.deserialize(ExtendedDeserializer.java:55)
    at org.apache.kafka.streams.processor.internals.SourceNode.deserializeValue(SourceNode.java:56)
    at org.apache.kafka.streams.processor.internals.SourceNodeRecordDeserializer.deserialize(SourceNodeRecordDeserializer.java:44)
    at org.apache.kafka.streams.processor.internals.RecordQueue.addRawRecords(RecordQueue.java:84)
    at org.apache.kafka.streams.processor.internals.PartitionGroup.addRawRecords(PartitionGroup.java:117)
    at org.apache.kafka.streams.processor.internals.StreamTask.addRecords(StreamTask.java:483)
    at org.apache.kafka.streams.processor.internals.StreamThread.addRecordsToTasks(StreamThread.java:604)
    at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:512)
    at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
    at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)

我发现奇怪的原因是stacktace说该类期望一个布尔值，但我的daya和我的POJO都没有布尔数据。我检查了互联网但没有找到答案，我无法理解代码出错的地方。

Answer 1

在使POJO类可序列化并向类中添加jackson注释后，问题得以解决。

{{1}}

反序列化时杰克逊api无法识别的令牌问题

1 个答案: