How to allow a User only access their own data in Spring Boot / Spring Security?

In any @Controller, @RestController annotated bean you can use Principal directly as a method argument.

    @RequestMapping("/users/{user_id}")
    public String getUserInfo(@PathVariable("user_id") Long userId, Principal principal){
        // test if userId is current principal or principal is an ADMIN
        ....
    }

If you don't want the security checks in your Controllers you could use Spring EL expressions. You probably already use some build-in expressions like hasRole([role]).

And you can write your own expressions.

1. Create a bean

    @Component("userSecurity")
    public class UserSecurity {
         public boolean hasUserId(Authentication authentication, Long userId) {
            // do your check(s) here
        }
    }

2. Use your expression

    http
     .authorizeRequests()
     .antMatchers("/user/{userId}/**")
          .access("@userSecurity.hasUserId(authentication,#userId)")
        ...

The nice thing is that you can also combine expressions like:

    hasRole('admin') or @userSecurity.hasUserId(authentication,#userId)

You can also use @PreAuthorize on the service interface. If you have a custom userdetails object then you can do it easily. In one of my projects I did it like this:

@PreAuthorize(value = "hasAuthority('ADMIN')"
        + "or authentication.principal.equals(#post.member) ")
void deletePost(Post post);

BTW this is in a service interface. You have to make sure to add the right annotations to get preauthorize to work.

You should first choose your security strategy, What you need names "Row Filtering", one of Authorization Concepts of 3A( Authentication, Authorization,Audit ) Concepts.

If you want to implement comprehensive solution, take a look at :

https://docs.spring.io/spring-security/site/docs/3.0.x/reference/domain-acls.html

Spring ACL completely covers concepts like "Row Filtering", "White-Black List", "Role Base Authorization", "ACL Inheritance", "Role Voter", ....

Otherwise you should save the owner per business case you want to be secured and filter them in your Service Layer.