Question

我想通过使用默认的编解码器注册表（MongoClient.getDefaultCodecRegistry（））和PojoCodecProvider提供的构建器从mongo数据库加载类“DataTable”的实例。我在编解码器提供程序中注册了DataTable类，当records字段为null时，该对象从数据库中正确映射。然而，当records属性包含数据时，我收到错误。此外，我需要将记录字段定义为具有任意属性的对象列表。是否可以为此目的使用默认的PojoCodecProvider？还有其他选择吗？

import com.mongodb.BasicDBList;
import org.bson.types.ObjectId;
import java.util.List;

public class DataTable {

    private ObjectId id;
    private List<String> fields;
    private BasicDBList records;

    public ObjectId getId() {
        return id;
    }
    public void setId(ObjectId id) {
        this.id = id;
    }
    public List<String> getFields() {
        return fields;
    }
    public void setFields(List<String> fields) {
        this.fields = fields;
    }
    public BasicDBList getRecords() {
        return records;
    }
    public void setRecords(BasicDBList records) {
        this.records = records;
    }
}

加载DataTable类的实例时得到的异常如下。

2018-03-21T16:32:04,526 [http-bio-8081-exec-4] ERROR ...service.controllers.BaseController - Failed to decode 'records'. Unable to set value for property 'records' in DataTable
org.bson.codecs.configuration.CodecConfigurationException: Failed to decode 'records'. Unable to set value for property 'records' in DataTable
    at org.bson.codecs.pojo.PojoCodecImpl.decodePropertyModel(PojoCodecImpl.java:192) ~[bson-3.6.3.jar:?]
    at org.bson.codecs.pojo.PojoCodecImpl.decodeProperties(PojoCodecImpl.java:168) ~[bson-3.6.3.jar:?]
    at org.bson.codecs.pojo.PojoCodecImpl.decode(PojoCodecImpl.java:122) ~[bson-3.6.3.jar:?]
    at org.bson.codecs.pojo.PojoCodecImpl.decode(PojoCodecImpl.java:126) ~[bson-3.6.3.jar:?]

当我尝试使用以下代码加载项目

时，我收到此异常

DataTable item = collection.find(eq(new ObjectId(id))).first();

Answer 1

嗯，你可以使用的另一个选择是杰克逊序列化。我觉得这样的事情很适合你

    Document document = collection
            .find(eq(new ObjectId(id)))
            .first();

    String json = document.toJson();
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    DataTable dataTable = mapper.readValue(json, DataTable.class);

请参阅此问题converting Document objects in MongoDB 3 to POJOS以供参考

无法使用mongo db

1 个答案: