Can't save "Many"-Entity of #OneToMany with Spring-Boot & Spring-JPA - spring

Question

I'm using Spring Boot and MySQL. I followed this link for setting everything up and I'm able to connect to MySql and read/write data. But there is an 1:n-relationship and I'm not able to save entities of the many side:
#Entity
public class OneSideOfRelationship {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long oneId;
private String someText;
#OneToMany(mappedBy="oneId")
private List<ManySideOfRelationship> manySide;
[Constructor / Getter / Setter]
}
#Entity
public class ManySideOfRelationship {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long manyId;
#ManyToOne(targetEntity=OneSideOfRelationship.class)
#JoinColumn
private long oneId;
private String someMoreText;
[Constructor / Getter / Setter]
}
#Transactional
public interface OneDao extends CrudRepository<OneSideOfRelationship, Long> {}
#Transactional
public interface ManyDao extends CrudRepository<ManySideOfRelationship, Long> {}
If I do this in my controller:
[...]
#Autowired
#private ManySideOfRelationship manyDao;
[...]
ManySideOfRelationship many = new ManySideOfRelationship();
many.setOneId(1L);
many.setSomeMoreText("Text");
manyDao.save(many);
[...]
I got:
org.springframework.orm.jpa.JpaSystemException: could not get a field value by reflection getter of com.package.database.OneSideOfRelationship.oneId; nested exception is org.hibernate.PropertyAccessException: could not get a field value by reflection getter of com.package.database.OneSideOfRelationship.oneId
Out of my application.properties:
spring.datasource.url = jdbc:mysql://myurl:myport/mydatabase
spring.datasource.username = myusername
spring.datasource.password = mypassword
spring.jpa.hibernate.ddl-auto = update
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
And something out of pom.xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
Hope somebody has an idea.

Answer 1

The oneId must be datatype of OneSideOfRelationship not long.
#ManyToOne(targetEntity=OneSideOfRelationship.class)
#JoinColumn
private OneSideOfRelationship oneId;