why scala in this case can't use single abstract method? - scala

Question

i use spring boot's RedisTemplate with scala, and i write this code:
redisTemplate1.executePipelined(new RedisCallback[String] {
override def doInRedis(connection: RedisConnection): String = {
MyCode......
null
}
}, redisTemplate1.getValueSerializer)
usually, it's can be wrote like this:
redisTemplate1.executePipelined((connection: RedisConnection) => {
MyCode......
null
}, redisTemplate1.getValueSerializer)
and this style is running well in java:
redisTemplate1.executePipelined((RedisConnection conn) -> {
MyCode......
return null;
}, redisTemplate1.getValueSerializer());
but when i compile in this style with scala, i get an error, so why this happend and how can i use single abstract method in this case?
overloaded method value executePipelined with alternatives:
(x$1: org.springframework.data.redis.core.RedisCallback[_],x$2: org.springframework.data.redis.serializer.RedisSerializer[_])java.util.List[Object] <and>
(x$1: org.springframework.data.redis.core.SessionCallback[_],x$2: org.springframework.data.redis.serializer.RedisSerializer[_])java.util.List[Object]
cannot be applied to (org.springframework.data.redis.connection.RedisConnection => Null, org.springframework.data.redis.serializer.RedisSerializer[?0(in method syncSegmentSrc)])
redisTemplate1.executePipelined((connection: RedisConnection) => {
the executePipelined function source code like this:
#Override
public List<Object> executePipelined(SessionCallback<?> session, #Nullable RedisSerializer<?> resultSerializer) {
Assert.isTrue(initialized, "template not initialized; call afterPropertiesSet() before using it");
Assert.notNull(session, "Callback object must not be null");
RedisConnectionFactory factory = getRequiredConnectionFactory();
// bind connection
RedisConnectionUtils.bindConnection(factory, enableTransactionSupport);
try {
return execute((RedisCallback<List<Object>>) connection -> {
connection.openPipeline();
boolean pipelinedClosed = false;
try {
Object result = executeSession(session);
if (result != null) {
throw new InvalidDataAccessApiUsageException(
"Callback cannot return a non-null value as it gets overwritten by the pipeline");
}
List<Object> closePipeline = connection.closePipeline();
pipelinedClosed = true;
return deserializeMixedResults(closePipeline, resultSerializer, hashKeySerializer, hashValueSerializer);
} finally {
if (!pipelinedClosed) {
connection.closePipeline();
}
}
});
} finally {
RedisConnectionUtils.unbindConnection(factory);
}
}
#Override
public List<Object> executePipelined(RedisCallback<?> action, #Nullable RedisSerializer<?> resultSerializer) {
return execute((RedisCallback<List<Object>>) connection -> {
connection.openPipeline();
boolean pipelinedClosed = false;
try {
Object result = action.doInRedis(connection);
if (result != null) {
throw new InvalidDataAccessApiUsageException(
"Callback cannot return a non-null value as it gets overwritten by the pipeline");
}
List<Object> closePipeline = connection.closePipeline();
pipelinedClosed = true;
return deserializeMixedResults(closePipeline, resultSerializer, hashKeySerializer, hashValueSerializer);
} finally {
if (!pipelinedClosed) {
connection.closePipeline();
}
}
});
}

Answer 1

In cases like this, it should help to specify the type explicitly:
redisTemplate1.executePipelined({ connection =>
YourCode…
}: RedisCallback[String], redisTemplate1.getValueSerializer)
Note the type ascription : RedisCallback[String].