Add support for Optimistic Locking using @Version

[roboticscm]

I have an entity bellow:

@Data 
@NoArgsConstructor
@Table
public class Role {
	@Id
	private Long id;
	private String name;
	@Version
	private Long version = 0L;
	public Role(String name) {
		this.name = name;
	}
}

And controller like this:

@RequestMapping("/api/role/save")
public Mono<Role> save(@RequestBody Role role){
	return roleRepo.save(role);
}

When I save a Role without @Version everything is fine
But when I add @Version, it throws exception like this:

java.lang.IllegalArgumentException: Could not obtain required identifier from entity Role(id=null, name=ADMIN, version=0)!
	at org.springframework.data.repository.core.EntityInformation.getRequiredId(EntityInformation.java:65) ~[spring-data-commons-2.2.0.M2.jar:2.2.0.M2]
	at org.springframework.data.r2dbc.repository.support.SimpleR2dbcRepository.save(SimpleR2dbcRepository.java:72) ~[spring-data-r2dbc-1.0.0.M1.jar:1.0.0.M1]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]

Source code demo:
https://github.com/roboticscm/r2dbc-reactive-redis.git

[mp911de]

Please checkout how to format code and logs to keep the issue readable. Thank you.

[mp911de]

Potentially related to #87.

[roboticscm]

Maybe the #87 and #93 are the same. Exceptions occured after I add @Version, the @id works fine.

[mp911de]

Still, we need to sort out two things: The one is a bug that happens when you add @Version. The other issue is optimistic locking support which is not in place yet.

[schauder]

This relates to https://jira.spring.io/browse/DATAJDBC-219

There is even someone working on it already spring-projects/spring-data-relational#124

[vuck3o]

https://github.com/spring-projects/spring-data-jdbc supports optimistic locking since version 2. Is there any information when optimistic locking will also be available for spring data r2dbc?

[RobMaskell]

Same problem, but looks like a different exception, looking forward to this being added

[schauder]

Done.