Package tech.ydb.yoj.repository.db.list.token

Class FallbackPageToken

java.lang.Object

tech.ydb.yoj.repository.db.list.token.FallbackPageToken

All Implemented Interfaces:

PageToken

public class FallbackPageToken
extends Object
implements PageToken

Page token which eases migration from one token implementation (fallback) to another (primary). It attempts to decode page token first using primary implementation, and, failing that, using the fallback; and can encode listing results using either fallback or primary, depending on the value of encodeAsPrimary flag.

Changing old token implementation oldImpl to new implementation newImpl should go as follows:

1. Deploy the app using FallbackPageToken(primary=newImpl, fallback=oldImpl, encodeAsPrimary=false) so that all app instances encode listing results using the least common denominator, oldImpl.
2. Deploy the app using FallbackPageToken(primary=newImpl, fallback=oldImpl, encodeAsPrimary=true). Old tokens can still be decoded, but all app instances will encode their listing results using newImpl.
3. Deploy new application version using newImpl only, because no app instances use oldImpl to encode listing results any more.

Field Summary

Fields inherited from interface tech.ydb.yoj.repository.db.list.token.PageToken

EMPTY

Constructor Summary

Constructors

Constructor	Description
FallbackPageToken()

Method Summary

Modifier and Type	Method	Description
<T> ListRequest.Builder<T>	decode(ListRequest.Builder<T> bldr, @NonNull String token)	Decodes page token into listing request. This method must be called only once per page, because it changes the listing request builder's state and is therefore non-idempotent.
<T, R> String	encode(@NonNull GenericListResult<T,R> result)	Encodes information about next search result page.

Methods inherited from class java.lang.Object

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

Constructor Details

FallbackPageToken

public FallbackPageToken()

Method Details

encode

@Nullable
public <T,
R> String encode(@NonNull
 @NonNull GenericListResult<T,R> result)

Description copied from interface: PageToken

Encodes information about next search result page.

Specified by:

encode in interface PageToken

Type Parameters:

T - search request type

R - search result type

Parameters:

result - current search result page

Returns:

next page token or null if this is the last page of results

decode

@NonNull
public <T> ListRequest.Builder<T> decode(@NonNull
 ListRequest.Builder<T> bldr,
 @NonNull
 @NonNull String token)
                                  throws BadListingException.InvalidPageToken

Description copied from interface: PageToken

Decodes page token into listing request.
This method must be called only once per page, because it changes the listing request builder's state and is therefore non-idempotent.

Specified by:

decode in interface PageToken

Type Parameters:

T - search request type

Parameters:

bldr - listing request builder

token - page token

Returns:

listing request builder for to the page encoded by the token

Throws:

BadListingException.InvalidPageToken - page token is invalid