Cassandra CodecNotFoundException：找不到请求的操作的编解码器

问题描述

我有一个枚举字段，我想映射到cassandra中的列

I have an enum field that i want to map to a column in cassandra

public enum MyEnum {
    Aa,
    Bb,
    Cc,
}

我是怎么注册的

CodecRegistry myCodecRegistry = new CodecRegistry();
             myCodecRegistry.register(new EnumOrdinalCodec<MyEnum>(MyEnum.class));

            cluster = Cluster.builder().addContactPoint(cassandraHosts).withPort(cassandraPort).withCodecRegistry(myCodecRegistry).build();

我能够连接到cassandra很好。这是模型类的摘要

i am able to connect to cassandra just fine. Here is a snippet of the model class

public class MyModel
{
    @PartitionKey
    @Column(name="id")
    private String id;

    @ClusteringColumn
    @Column(name="name")
    private String name = "";

    @Column(name="enum")
    private MyEnum enum;

    public MyModel(String i, String n)
    {
        id=i;
        name=n
        enum=MyEnum.Aa;
    }
}

这是我使用CQL创建表的方式

and here is how i created the table using CQL

CREATE TABLE IF NOT EXISTS
tab
    (
        name varchar ,
        id varchar,
        enum varchar,
        PRIMARY KEY ((id), name));

最后，我有我的映射代码

finally, i have my mapping code

    manager = new MappingManager(session);
    mapper = manager.mapper(MyModel.class);
    accessor = manager.createAccessor(MyAccessor.class);

这是 MyAccessor

@Accessor
public interface MyAccessor{

    @Query("SELECT * FROM case WHERE id=? and name=? ALLOW FILTERING;")
    MyModel readByIdAndName(String id,String name);
}

所以当我尝试执行时

MyModel m = new MyModel("asdasf","qw");
mapper.save(m);

我得到

com.datastax.driver.core.exceptions.CodecNotFoundException: Codec not found for requested operation: [varchar <-> my.pack.MyEnum]
    at com.datastax.driver.core.exceptions.CodecNotFoundException.copy(CodecNotFoundException.java:56)
    at com.datastax.driver.core.exceptions.CodecNotFoundException.copy(CodecNotFoundException.java:25)
    at com.datastax.driver.mapping.DriverThrowables.propagateCause(DriverThrowables.java:41)
    at com.datastax.driver.mapping.Mapper.save(Mapper.java:289)

我在做什么错了？

推荐答案

EnumOrdinalCodec仅用于在int<-> Enum之间进行映射。由于您的Enum是基于字符串的，因此请改用 EnumNameCodec 类。这两个编解码器类的Javadoc如下。希望对您有所帮助。

EnumOrdinalCodec is used to map between int <-> Enum only. As your Enum is based on string, so please use EnumNameCodec class instead. Javadoc for these two codec classes are as per below. Hope it helps.

EnumNameCodec

EnumOrdinalCodec

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