最新在开发的项目中使用到了Cassandra的udt(user-defined-type)类型, 遇到了不少棘手问题，本文将列举遇到的异常和解决方案。
表结构定义如下
CREATE TYPE cass_stdy.address (addr text,mail text
);
CREATE TABLE cass_stdy.user (id uuid PRIMARY KEY,addr list<frozen<address>>,age int,birthday timestamp,d_addr frozen<address>,name text,score map<text, text>
);
cass_stdy.user表中，addr字段即为本文用到的重点，list<frozen<address>>
Cassandra中，封装类型的UDT类型，必须使用frozen，而frozen的字段将以blob形式存储在硬盘中。
创建非frozen的封装UDT类型提示，非frozen的UDT类型不允许作为集合的内部类型使用：
InvalidRequest: Error from server: code=2200 [Invalid query] message="Non-frozen UDTs are not allowed inside collections: list<address>"
Springboot配置如下：
spring.data.cassandra.keyspace-name=cass_stdy
spring.data.cassandra.contact-points=127.0.0.1
spring.data.cassandra.port=9042
spring.data.cassandra.local-datacenter=datacenter1
@Configuration
@EnableConfigurationProperties(CassandraProperties.class)
@EnableCassandraRepositories
public class SmvcCassandraConfig {@Autowiredprivate CassandraProperties properties;@Beanpublic CqlSession cqlSession() {List<InetSocketAddress> contactPoints = properties.getContactPoints().stream().map(address ->new InetSocketAddress(address, properties.getPort())).collect(Collectors.toList());return CqlSession.builder().withAuthCredentials(properties.getUsername(), properties.getPassword()).withKeyspace(properties.getKeyspaceName()).addContactPoints(contactPoints).withLocalDatacenter(properties.getLocalDatacenter()).build();}
}
User和Address对象定义：
@Table("user")
public class User {@PrimaryKeyColumn(name = "id", type = PrimaryKeyType.PARTITIONED)private UUID id;@Column("name")private String name;@Column("addr")private List<Address> addresses;@Column("age")private Integer age;@Column("birthday")private Timestamp birthday;// getter ... setter ...
}@UserDefinedType("address")
public class Address{@Column("addr")private String addr;@Column("mail")private String mail;// getter ... setter ...
}
Repository代码如下：
@Repository
public interface IUserRepository extends CassandraRepository<User, UUID> {}
此时执行：
@Autowiredprivate IUserRepository userRepository;public User save(User user){return userRepository.save(user);}
查询记录显示， 可以正确保存用户记录。
cqlsh:cass_stdy> SELECT * FROM user;id | addr | age | birthday | d_addr | name | score
--------------------------------------+------------------------------------------------------------------------+------+----------+--------+----------+-------f7702276-694a-47e1-92cf-312db4101353 | [{addr: 'SZ GD CN', mail: 'sz@gd.cn'}, {addr: 'GZ GD CN', mail: null}] | null | null | null | name0000 | null(1 rows)
但是我们使用list<frozen<address>>的目的是为了使用list集合的追加功能，比如，用户要新增一个地址，此时save操作则会将整个addr的值完全覆盖，而如果想要保留原来的地址，就只能先把记录查出来，再由Java来执行list.add操作，然后save把整个值覆盖。这时在IUserRepository中增加一个update方法
@Repository
public interface IUserRepository extends CassandraRepository<User, UUID> {@Query("UPDATE user SET addr = addr + :addrs WHERE id = :id")void updateAddress(List<Address> addrs, UUID id);
}
这样可以在不需要查询原纪录的情况下，直接追加数据，调用updateAddress，出现了异常：
com.datastax.oss.driver.api.core.type.codec.CodecNotFoundException: Codec not found for requested operation: [null <-> com.*******.sbstdy.entity.Address]
com.datastax.oss.driver.api.core.type.codec.CodecNotFoundException: Codec not found for requested operation: [null <-> com.*******.sbstdy.entity.Address]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:639) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:317) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:622) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:287) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.encode(Conversions.java:304) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.encode(Conversions.java:263) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.toMessage(Conversions.java:168) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler.<init>(CqlRequestHandler.java:173) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestAsyncProcessor.process(CqlRequestAsyncProcessor.java:44) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:54) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:30) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.session.DefaultSession.execute(DefaultSession.java:230) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.api.core.cql.SyncCqlSession.execute(SyncCqlSession.java:53) ~[java-driver-core-4.6.1.jar:na]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:293) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:315) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.CassandraTemplate.select(CassandraTemplate.java:340) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]
意思是说Codec找不到，我们知道Java的Codec是编解码器，也就是说，Java对象和cql对象的转换过程出现了问题，找不到映射关系，这里就比较奇怪了，save方法执行的时候为啥没有报错，而到了自己手写的cql时就不行了。
这时有两个思路，可以考虑一下:
第一：手动添加编解码器。
第二：从源码上分析save方法为什么可以编解码，而update方法不能，从中找到突破口。
首先，先从第一个思路入手，Cassandra的配置是可以增加编解码器的，也就是下面代码所示的位置：
@Configuration
@EnableConfigurationProperties(CassandraProperties.class)
@EnableCassandraRepositories
public class SmvcCassandraConfig {@Autowiredprivate CassandraProperties properties;@Beanpublic CqlSession cqlSession() {List<InetSocketAddress> contactPoints = properties.getContactPoints().stream().map(address ->new InetSocketAddress(address, properties.getPort())).collect(Collectors.toList());return CqlSession.builder().withAuthCredentials(properties.getUsername(), properties.getPassword()).withKeyspace(properties.getKeyspaceName()).addContactPoints(contactPoints).withLocalDatacenter(properties.getLocalDatacenter()).addTypeCodecs(...) // 增加编解码器配置.build();}
}
这里点进去addTypeCodecs方法看，入参是TypeCodec类型的可变参数，而TypeCodec是一个带JavaType的泛型接口，
public interface TypeCodec<JavaTypeT> {...
这里可以写一个内部类实现类，根据开发工具提示，需要实现的方法如下：
@Beanpublic CqlSession cqlSession() {List<InetSocketAddress> contactPoints = properties.getContactPoints().stream().map(address ->new InetSocketAddress(address, properties.getPort())).collect(Collectors.toList());return CqlSession.builder().withAuthCredentials(properties.getUsername(), properties.getPassword()).withKeyspace(properties.getKeyspaceName()).addContactPoints(contactPoints).withLocalDatacenter(properties.getLocalDatacenter()).addTypeCodecs(new TypeCodec<Address>() {@NonNull@Overridepublic GenericType<Address> getJavaType() { return null; }@NonNull@Overridepublic DataType getCqlType() { return null; }@Nullable@Overridepublic ByteBuffer encode(@Nullable Address value, @NonNull ProtocolVersion protocolVersion) { return null; }@Nullable@Overridepublic Address decode(@Nullable ByteBuffer bytes, @NonNull ProtocolVersion protocolVersion) { return null; }@NonNull@Overridepublic String format(@Nullable Address value) { return null; }@Nullable@Overridepublic Address parse(@Nullable String value) { return null; }}).build();}
看方法的入参出参应该很明了方法里该做什么，当然如果实在不明白的话可以看看TypeCodec的其他实现类，看看其他的实现类都是怎么做的。现将方法补全如下：
@Beanpublic CqlSession cqlSession() {List<InetSocketAddress> contactPoints = properties.getContactPoints().stream().map(address ->new InetSocketAddress(address, properties.getPort())).collect(Collectors.toList());return CqlSession.builder().withAuthCredentials(properties.getUsername(), properties.getPassword()).withKeyspace(properties.getKeyspaceName()).addContactPoints(contactPoints).withLocalDatacenter(properties.getLocalDatacenter()).addTypeCodecs(new TypeCodec<Address>() {@NonNull@Overridepublic GenericType<Address> getJavaType() {return GenericType.of(Address.class);}@NonNull@Overridepublic DataType getCqlType() {return DataTypes.BLOB;}@Nullable@Overridepublic ByteBuffer encode(@Nullable Address value, @NonNull ProtocolVersion protocolVersion) {return ByteBuffer.wrap(new Gson().toJson(value).getBytes());}@Nullable@Overridepublic Address decode(@Nullable ByteBuffer bytes, @NonNull ProtocolVersion protocolVersion) {return new Gson().fromJson(new String(bytes.array()), Address.class);}@NonNull@Overridepublic String format(@Nullable Address value) {return new Gson().toJson(value);}@Nullable@Overridepublic Address parse(@Nullable String value) {return new Gson().fromJson(value, Address.class);}}).build();}
但是实际上，这里存在一个问题，TypeCodec是JavaType和cqlType的映射关系，getCqlType这个方法返回的DataType类型中，有一个工具类DataTypes提供了大部分cqlType，但是唯独缺少了udt类型，所以不论getCqlType方法返回的是什么类型，都会抛出同样的一个异常：
com.datastax.oss.driver.api.core.servererrors.InvalidQueryException: Not enough bytes to read 0th field addr
com.datastax.oss.driver.api.core.servererrors.InvalidQueryException: Not enough bytes to read 0th field addrat com.datastax.oss.driver.api.core.servererrors.InvalidQueryException.copy(InvalidQueryException.java:48) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.util.concurrent.CompletableFutures.getUninterruptibly(CompletableFutures.java:149) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:53) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:30) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.session.DefaultSession.execute(DefaultSession.java:230) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.api.core.cql.SyncCqlSession.execute(SyncCqlSession.java:53) ~[java-driver-core-4.6.1.jar:na]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:293) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:315) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.CassandraTemplate.select(CassandraTemplate.java:340) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.repository.query.CassandraQueryExecution$SingleEntityExecution.execute(CassandraQueryExecution.java:149) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.repository.query.CassandraQueryExecution$ResultProcessingExecution.execute(CassandraQueryExecution.java:239) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.repository.query.AbstractCassandraQuery.execute(AbstractCassandraQuery.java:105) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor$QueryMethodInvoker.invoke(QueryExecutorMethodInterceptor.java:195) ~[spring-data-commons-2.3.0.RELEASE.jar:2.3.0.RELEASE]at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:152) ~[spring-data-commons-2.3.0.RELEASE.jar:2.3.0.RELEASE]at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:130) ~[spring-data-commons-2.3.0.RELEASE.jar:2.3.0.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:80) ~[spring-data-commons-2.3.0.RELEASE.jar:2.3.0.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at com.sun.proxy.$Proxy112.updateAddress(Unknown Source) ~[na:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.2.6.RELEASE.jar:5.2.6.RELEASE]at com.sun.proxy.$Proxy112.updateAddress(Unknown Source) ~[na:na]
没有足够的字节提供给第一个field addr来读取，也就是说编解码器在使用的时候需要从ByteBuffer中把字节码读出来，异常就是没有东西可以读，我一开始一直认为编解码过程的ByteBuffer写错了，实际上是cqlType没有对应上，在错误的位置取值肯定是取不到的。而DataTypes工具类里没有提供udt类型的cqlType，此时似乎已经进入了死胡同。
然而回头再看一下DataType接口的实现类，会发现其实是有一个UserDefinedType的，但是同样是一个接口
再来看看UserDefinedType的实现类，有一个DefaultUserDefinedType，和一个ShallowUserDefinedType，另一个就不看了内部类外部无法访问。
先看看 DefaultUserDefinedType ，
public DefaultUserDefinedType(@NonNull CqlIdentifier keyspace,@NonNull CqlIdentifier name,boolean frozen,List<CqlIdentifier> fieldNames,@NonNull List<DataType> fieldTypes,@NonNull AttachmentPoint attachmentPoint) {Preconditions.checkNotNull(keyspace);Preconditions.checkNotNull(name);Preconditions.checkNotNull(fieldNames);Preconditions.checkNotNull(fieldTypes);Preconditions.checkArgument(fieldNames.size() > 0, "Field names list can't be null or empty");Preconditions.checkArgument(fieldTypes.size() == fieldNames.size(),"There should be the same number of field names and types");this.keyspace = keyspace;this.name = name;this.frozen = frozen;this.fieldNames = ImmutableList.copyOf(fieldNames);this.fieldTypes = ImmutableList.copyOf(fieldTypes);this.index = new IdentifierIndex(this.fieldNames);this.attachmentPoint = attachmentPoint;}
构造器有点复杂，6个入参，再看看 ShallowUserDefinedType:
public ShallowUserDefinedType(CqlIdentifier keyspace, CqlIdentifier name, boolean frozen) {this.keyspace = keyspace;this.name = name;this.frozen = frozen;}
构造器只有3个入参，看起来简单多了，先用 ShallowUserDefinedType 试试，而 CqlIdentifier 提供了2个静态方法用于构造它自己，所以最后getCqlType方法写成如下所示：
@NonNull@Overridepublic DataType getCqlType() {return new ShallowUserDefinedType(CqlIdentifier.fromInternal("cass_stdy"), CqlIdentifier.fromInternal("address"), true);}
再次尝试。还是抛出 com.datastax.oss.driver.api.core.servererrors.InvalidQueryException: Not enough bytes to read 0th field addr 异常。更换为 DefaultUserDefinedType：
@NonNull@Overridepublic DataType getCqlType() {// return new ShallowUserDefinedType(CqlIdentifier.fromInternal("cass_stdy"), CqlIdentifier.fromInternal("address"), true);return new DefaultUserDefinedType(CqlIdentifier.fromInternal("cass_stdy"), CqlIdentifier.fromInternal("address"), true,Lists.newArrayList(CqlIdentifier.fromInternal("addr"), CqlIdentifier.fromInternal("mail")),Lists.newArrayList(DataTypes.TEXT, DataTypes.TEXT));}
再次尝试。还是抛出 com.datastax.oss.driver.api.core.servererrors.InvalidQueryException: Not enough bytes to read 0th field addr 异常。
看起来这条路走不通，更换第二种思路再来看。
从源码上分析save方法为什么可以编解码，而update方法不能，从中找到突破口。
首先把配置还原，去掉addTypeCodec，重现save方法可以，update不行的场景，然后分析一下堆栈信息：
com.datastax.oss.driver.api.core.type.codec.CodecNotFoundException: Codec not found for requested operation: [null <-> com.*******.sbstdy.entity.Address]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:639) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:317) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:622) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:287) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.encode(Conversions.java:304) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.encode(Conversions.java:263) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.Conversions.toMessage(Conversions.java:168) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler.<init>(CqlRequestHandler.java:173) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestAsyncProcessor.process(CqlRequestAsyncProcessor.java:44) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:54) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.cql.CqlRequestSyncProcessor.process(CqlRequestSyncProcessor.java:30) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.session.DefaultSession.execute(DefaultSession.java:230) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.api.core.cql.SyncCqlSession.execute(SyncCqlSession.java:53) ~[java-driver-core-4.6.1.jar:na]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:293) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.cql.CqlTemplate.query(CqlTemplate.java:315) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]at org.springframework.data.cassandra.core.CassandraTemplate.select(CassandraTemplate.java:340) ~[spring-data-cassandra-3.0.0.RELEASE.jar:3.0.0.RELEASE]
先来看倒数第二行堆栈对应源码：
com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]
@NonNullprotected TypeCodec<?> createCodec(@Nullable DataType cqlType, @Nullable GenericType<?> javaType, boolean isJavaCovariant) {LOG.trace("[{}] Cache miss, creating codec", logPrefix);// Either type can be null, but not both.if (javaType == null) {assert cqlType != null;return createCodec(cqlType);} else if (cqlType == null) {return createCodec(javaType, isJavaCovariant);} else { // Both non-nullTypeToken<?> token = javaType.__getToken();if (cqlType instanceof ListType && List.class.isAssignableFrom(token.getRawType())) {DataType elementCqlType = ((ListType) cqlType).getElementType();TypeCodec<Object> elementCodec;if (token.getType() instanceof ParameterizedType) {Type[] typeArguments = ((ParameterizedType) token.getType()).getActualTypeArguments();GenericType<?> elementJavaType = GenericType.of(typeArguments[0]);elementCodec = uncheckedCast(codecFor(elementCqlType, elementJavaType, isJavaCovariant));} else {elementCodec = codecFor(elementCqlType);}return TypeCodecs.listOf(elementCodec);} else if (cqlType instanceof SetType && Set.class.isAssignableFrom(token.getRawType())) {DataType elementCqlType = ((SetType) cqlType).getElementType();TypeCodec<Object> elementCodec;if (token.getType() instanceof ParameterizedType) {Type[] typeArguments = ((ParameterizedType) token.getType()).getActualTypeArguments();GenericType<?> elementJavaType = GenericType.of(typeArguments[0]);elementCodec = uncheckedCast(codecFor(elementCqlType, elementJavaType, isJavaCovariant));} else {elementCodec = codecFor(elementCqlType);}return TypeCodecs.setOf(elementCodec);} else if (cqlType instanceof MapType && Map.class.isAssignableFrom(token.getRawType())) {DataType keyCqlType = ((MapType) cqlType).getKeyType();DataType valueCqlType = ((MapType) cqlType).getValueType();TypeCodec<Object> keyCodec;TypeCodec<Object> valueCodec;if (token.getType() instanceof ParameterizedType) {Type[] typeArguments = ((ParameterizedType) token.getType()).getActualTypeArguments();GenericType<?> keyJavaType = GenericType.of(typeArguments[0]);GenericType<?> valueJavaType = GenericType.of(typeArguments[1]);keyCodec = uncheckedCast(codecFor(keyCqlType, keyJavaType, isJavaCovariant));valueCodec = uncheckedCast(codecFor(valueCqlType, valueJavaType, isJavaCovariant));} else {keyCodec = codecFor(keyCqlType);valueCodec = codecFor(valueCqlType);}return TypeCodecs.mapOf(keyCodec, valueCodec);} else if (cqlType instanceof TupleType&& TupleValue.class.isAssignableFrom(token.getRawType())) {return TypeCodecs.tupleOf((TupleType) cqlType);} else if (cqlType instanceof UserDefinedType&& UdtValue.class.isAssignableFrom(token.getRawType())) {return TypeCodecs.udtOf((UserDefinedType) cqlType);} else if (cqlType instanceof CustomType&& ByteBuffer.class.isAssignableFrom(token.getRawType())) {return TypeCodecs.custom(cqlType);}throw new CodecNotFoundException(cqlType, javaType);}}
首先，这个方法有3个入参，核心的前面2个，cqlType和javaType。刚才我说了，TypeCodec的关键是对象转换编解码，而此时抛出异常的位置在 else if (cqlType == null) 这个分支上，说明入参 cqlType 的值是空的，说明 Address 需要一个对应的 cqlType 来映射，而刚刚我们尝试了在配置中增加Codec的方式，似乎是行不通的，这个时候需要另辟蹊径来处理这个问题，再往下看代码，我们应该是想让代码往下面这个分支上走
else if (cqlType instanceof UserDefinedType&& UdtValue.class.isAssignableFrom(token.getRawType())) {return TypeCodecs.udtOf((UserDefinedType) cqlType);}
所以我们要解决的应该是 cqlType 为空的问题，继续往前跟踪堆栈信息，看看是从哪里开始找cqlType对应关系的。
跟踪发现关键在于：
com.datastax.oss.driver.api.core.type.codec.CodecNotFoundException: Codec not found for requested operation: [null <-> com.*******.sbstdy.entity.Address]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:639) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:317) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:622) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.createCodec(CachingCodecRegistry.java:558) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:95) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry$1.load(DefaultCodecRegistry.java:92) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2276) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2154) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$Segment.get(LocalCache.java:2044) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.get(LocalCache.java:3951) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache.getOrLoad(LocalCache.java:3973) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4957) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.shaded.guava.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4963) ~[java-driver-shaded-guava-25.1-jre.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.DefaultCodecRegistry.getCachedCodec(DefaultCodecRegistry.java:117) ~[java-driver-core-4.6.1.jar:na]at com.datastax.oss.driver.internal.core.type.codec.registry.CachingCodecRegistry.codecFor(CachingCodecRegistry.java:287) ~[java-driver-core-4.6.1.jar:na]
最下面这一行对应的代码位置：
@NonNull@Overridepublic <JavaTypeT> TypeCodec<JavaTypeT> codecFor(@NonNull JavaTypeT value) {// 此处省略无关代码DataType cqlType = inferCqlTypeFromValue(value);GenericType<?> javaType = inspectType(value, cqlType);LOG.trace("[{}] Continuing based on inferred CQL type {} and Java type {}",logPrefix,cqlType,javaType);return uncheckedCast(getCachedCodec(cqlType, javaType, true));}
这个时候 cqlType 是从 DataType cqlType = inferCqlTypeFromValue(value); 方法来的，而且debug可以发现这个value是有值的
所以跟进方法里看：
@Nullableprotected DataType inferCqlTypeFromValue(@NonNull Object value) {if (value instanceof List) {List<?> list = (List<?>) value;if (list.isEmpty()) {return CQL_TYPE_FOR_EMPTY_LISTS;}Object firstElement = list.get(0);if (firstElement == null) {throw new IllegalArgumentException("Can't infer list codec because the first element is null "+ "(note that CQL does not allow null values in collections)");}DataType elementType = inferCqlTypeFromValue(firstElement);if (elementType == null) {return null;}return DataTypes.listOf(elementType);} else if (value instanceof Set) {Set<?> set = (Set<?>) value;if (set.isEmpty()) {return CQL_TYPE_FOR_EMPTY_SETS;}Object firstElement = set.iterator().next();if (firstElement == null) {throw new IllegalArgumentException("Can't infer set codec because the first element is null "+ "(note that CQL does not allow null values in collections)");}DataType elementType = inferCqlTypeFromValue(firstElement);if (elementType == null) {return null;}return DataTypes.setOf(elementType);} else if (value instanceof Map) {Map<?, ?> map = (Map<?, ?>) value;if (map.isEmpty()) {return CQL_TYPE_FOR_EMPTY_MAPS;}Entry<?, ?> firstEntry = map.entrySet().iterator().next();Object firstKey = firstEntry.getKey();Object firstValue = firstEntry.getValue();if (firstKey == null || firstValue == null) {throw new IllegalArgumentException("Can't infer map codec because the first key and/or value is null "+ "(note that CQL does not allow null values in collections)");}DataType keyType = inferCqlTypeFromValue(firstKey);DataType valueType = inferCqlTypeFromValue(firstValue);if (keyType == null || valueType == null) {return null;}return DataTypes.mapOf(keyType, valueType);}Class<?> javaClass = value.getClass();if (ByteBuffer.class.isAssignableFrom(javaClass)) {return DataTypes.BLOB;} else if (String.class.equals(javaClass)) {return DataTypes.TEXT;} else if (Long.class.equals(javaClass)) {return DataTypes.BIGINT;} else if (Boolean.class.equals(javaClass)) {return DataTypes.BOOLEAN;} else if (BigDecimal.class.equals(javaClass)) {return DataTypes.DECIMAL;} else if (Double.class.equals(javaClass)) {return DataTypes.DOUBLE;} else if (Float.class.equals(javaClass)) {return DataTypes.FLOAT;} else if (Integer.class.equals(javaClass)) {return DataTypes.INT;} else if (Instant.class.equals(javaClass)) {return DataTypes.TIMESTAMP;} else if (UUID.class.equals(javaClass)) {return DataTypes.UUID;} else if (BigInteger.class.equals(javaClass)) {return DataTypes.VARINT;} else if (InetAddress.class.isAssignableFrom(javaClass)) {return DataTypes.INET;} else if (LocalDate.class.equals(javaClass)) {return DataTypes.DATE;} else if (LocalTime.class.equals(javaClass)) {return DataTypes.TIME;} else if (Short.class.equals(javaClass)) {return DataTypes.SMALLINT;} else if (Byte.class.equals(javaClass)) {return DataTypes.TINYINT;} else if (CqlDuration.class.equals(javaClass)) {return DataTypes.DURATION;} else if (UdtValue.class.isAssignableFrom(javaClass)) {return ((UdtValue) value).getType();} else if (TupleValue.class.isAssignableFrom(javaClass)) {return ((TupleValue) value).getType();}// This might mean that the java type is a custom type with a custom codec,// so don't throw CodecNotFoundException just yet.return null;}
这个方法很长，但是意义很明了，一个长 if-else 代码块，根据JavaType的类型进行强制类型转换，找到关键，倒数第二个分支：
else if (UdtValue.class.isAssignableFrom(javaClass)) {return ((UdtValue) value).getType();}
这里才是我们想要让代码走的分支，但是实际上，我们定义的Java对象是不满足条件的，我们的 Address 对象没有显式声明继承任何父类或实现任何接口，所以这时候给出的方案是，让Address实现UdtValue接口，或继承UdtValue的实现类。UdtValue只有一个实现类 DefaultUdtValue
所以把Address做一下改造：
@UserDefinedType("address")
public class Address extends DefaultUdtValue{@Column("addr")private String addr;@Column("mail")private String mail;public Address() {super(new DefaultUserDefinedType(CqlIdentifier.fromInternal("cass_stdy"), CqlIdentifier.fromInternal("address"), true,Lists.newArrayList(CqlIdentifier.fromInternal("addr"), CqlIdentifier.fromInternal("mail")),Lists.newArrayList(DataTypes.TEXT, DataTypes.TEXT)));}// getter ... setter ...
}
因为 DefaultUdtValue 的默认构造器入参需要 UserDefinedType 所以把之前用在配置添加 TypeCodec 的代码移过来。
完成之后再次启动工程，执行save和update，结果成功了，并没有报错，查询数据库：
cqlsh:cass_stdy> SELECT * FROM user;id | addr | age | birthday | d_addr | name | score
--------------------------------------+----------------------------------------------------------------------------------------------------------+------+----------+--------+----------+-------dbde2592-9275-4494-b525-ee84a8263b44 | [{addr: null, mail: null}, {addr: null, mail: null}] | null | null | null | name0000 | nullf7702276-694a-47e1-92cf-312db4101353 | [{addr: null, mail: null}, {addr: null, mail: null}, {addr: null, mail: null}, {addr: null, mail: null}] | null | null | null | name0000 | null(2 rows)
情况好像有点不对劲，怎么addr里的值都是null呢。