Cassandra CodecNotFoundException：找不到请求的操作的编解码器 [英] Cassandra CodecNotFoundException: Codec not found for requested operation

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

A将Enum实例序列化为CQL varchars的编解码器，它们表示Enum.name（）返回的程序名称
。

A codec that serializes Enum instances as CQL varchars representing their programmatic names as returned by Enum.name().

EnumOrdinalCodec

一个编解码器，将Enum实例序列化为CQL int，表示由Enum返回的
序数值。 ordinal（）。

A codec that serializes Enum instances as CQL ints representing their ordinal values as returned by Enum.ordinal().

链接到 Javadoc

这篇关于Cassandra CodecNotFoundException：找不到请求的操作的编解码器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！