Spring Data JPA ManyToOne and OneToMany - Unable to find entity with ID

I have three tables - role, user, and user_role. This is supposed to be ManyToMany but since I also want to generate id for the user_role, I used OneToMany and ManyToOne.

Here are my entities with relevant fields only:

@Entity
public class Role {
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id;
    @OneToMany(fetch = FetchType.EAGER, mappedBy = "role")
    private Set<UserRole> userRoles;
}

@Entity
public class User {
	@Id
	private String id;
	@OneToMany(fetch = FetchType.EAGER, mappedBy = "user")
	private Set<UserRole> userRoles;
}

@Entity
public class UserRole {
    @Id
    private String id;
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;
    @ManyToOne
    @JoinColumn(name = "role_id")
    private Role role;	
}

Then, this is how I create instances of them and save to the DB:

// Retrieve from DB by ID
Role role = ...;

// ID String is generated from UUID
User user = new User();
user.id("abc");

// ID String is generated from UUID
UserRole userRole = new UserRole();
userRole.setId("xyz");

Set<UserRole> userRoles = Set.of(userRole);

role.setUserRoles(userRoles);
user.setUserRoles(userRoles);

userRole.setUser(user);
userRole.setRole(role);

userRepository.save(user);

The issue that I find it difficult to resolve no matter how I have tried and googled:

2020-09-27 23:41:58.917  WARN 21948 --- [nio-8080-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : Resolved [org.springframework.orm.jpa.JpaObjectRetrievalFailureException: Unable to find com.example.entity.UserRole with id xyz; nested exception is javax.persistence.EntityNotFoundException: Unable to find com.example.entity.UserRole with id xyz]

Please help me. Thanks.

Stern has good point. You are trying to save only user entity, but you don't have any cascade set anywhere. So when you call userRepository.save(user) it is obviously missing role entities. Either save dependent entities before saving user, or better, add cascade above userRoles field in your User class etc.

As mentioned elsewhere you need to se minimum:

@OneToMany(fetch = FetchType.EAGER, mappedBy = "user" , cascade = CascadeType.ALL)
private Set<UserRole> userRoles;

or minimum:

@OneToMany(fetch = FetchType.EAGER, mappedBy = "user" , cascade = 
        CascadeType.PERSIST)
private Set<UserRole> userRoles;

But also if you need to fetch UserRoles by User you need to set:

// for each UserRole in the list.
userRole.setUser(user);

before persisting otherwise list will not be populated.