io.lettuce.core

Class HashImport<K>

java.lang.Object

io.lettuce.core.HashImport<K>

Type Parameters:

K - Key type, matching the field-name type of the connection's codec.

All Implemented Interfaces:

AutoCloseable

@Experimental
public class HashImport<K>
extends Object
implements AutoCloseable

Reusable set of field names shared by many hashes, imported with the HIMPORT command family.

Create a fieldset once and pass it to every himportSet call that writes those fields, supplying only the values. The field names themselves are declared to the server on first use and re-declared transparently across reconnects, pooled connections, and new cluster nodes, so no prepare step is ever issued by the caller.

Use of(String...) for String-keyed connections, or of(Function, Object...) to derive the fieldset name for another key type. Field names must be non-empty and free of duplicates.

A fieldset is safe to share across threads and connections. Close it when the import is finished to release its server-side state; a fieldset that is never closed holds that state until the connections it was used on are closed. Imports already issued when close() is called still complete, so try-with-resources is safe with the synchronous, asynchronous, and reactive APIs alike.

 try (HashImport<String> fieldset = HashImport.of("name", "email")) {
     redis.himportSet("user:1", fieldset, "alice", "alice@example.com");
     redis.himportSet("user:2", fieldset, "bob", "bob@example.com");
 }
 

Since:

7.7

Author:

Aleksandar Todorov

Method Summary

Modifier and Type	Method and Description
void	close() Discard this fieldset, releasing its server-side state on every connection it was used on.
K[]	fields() Return the field names, in the order values are supplied to himportSet.
K	name() Return the generated name identifying this fieldset on the server.
static <K> HashImport<K>	of(Function<Long,K> idCodec, K... fields) Create a fieldset for a key type other than String, naming it by applying idCodec to a generated sequence number.
static HashImport<String>	of(String... fields) Create a fieldset for String-keyed connections.
int	size() Return the number of fields, which is the number of values every himportSet call must supply.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

of

public static HashImport<String> of(String... fields)

Create a fieldset for String-keyed connections. The fieldset name is generated and unique per instance.

Parameters:

fields - the field names, in the order values are supplied to himportSet; must not be null, empty, or contain null or duplicate elements.

Returns:

a new fieldset over fields.

Throws:

IllegalArgumentException - if fields is null, empty, or contains null or duplicate elements.

Since:

7.7

of

@SafeVarargs
public static <K> HashImport<K> of(Function<Long,K> idCodec,
                                                K... fields)

Create a fieldset for a key type other than String, naming it by applying idCodec to a generated sequence number.

idCodec must map distinct sequence numbers to distinct names: two live fieldsets sharing a name also share their server-side state, and closing either releases it for both.

Type Parameters:

K - Key type.

Parameters:

idCodec - maps a generated sequence number to a fieldset name, must not be null and must produce a distinct name per invocation.

fields - the field names, in the order values are supplied to himportSet; must not be null, empty, or contain null or duplicate elements.

Returns:

a new fieldset over fields.

Throws:

IllegalArgumentException - if idCodec is null or returns null, or if fields is null, empty, or contains null or duplicate elements.

Since:

7.7

name

public K name()

Return the generated name identifying this fieldset on the server.

Returns:

the fieldset name, never null.

Since:

7.7

fields

public K[] fields()

Return the field names, in the order values are supplied to himportSet.

Returns:

a copy of the field names; modifying it does not affect this fieldset.

Since:

7.7

size

public int size()

Return the number of fields, which is the number of values every himportSet call must supply.

Returns:

the number of fields, always greater than zero.

Since:

7.7

close

public void close()

Discard this fieldset, releasing its server-side state on every connection it was used on.

Further imports are rejected from the moment this returns: a subsequent himportSet fails with an IllegalStateException. Imports already issued are not cancelled and still complete, so this may return before the state has actually been released.

Release is best-effort and does not report failures. The state is released in any case when a connection closes, so closing a fieldset is not required for correctness — but on long-lived and pooled connections an unclosed fieldset holds its state for the life of those connections. Calling this more than once has no further effect.

Specified by:

close in interface AutoCloseable

Since:

7.7

toString

public String toString()

Overrides:

toString in class Object