Spring + Mongodb with a Null id Issue

Question

I'm working on a academic project with Spring + MongoDB

I have three Document

User.java

@Document
public class User implements UserDetails, Serializable {
private static final long SerialVersionUID = 147147L;

@Id
private String id;

private String username;
private String password;
private String firstname;
private String lastname;

private String email;
private String phone;

private boolean enable = true;
private Set<UserRole> userRoles = new HashSet<>();

...

}

Role.java

@Document
public class Role implements Serializable {
private static final long SerialVersionUID = 456456L;
@Id
private String id;
private String name;
...

}

UserRole.java

@Document(collection = "user_roles")
public class UserRole implements Serializable {
private static final long SerialVersionUID = 789789L;

@Id
private String id;

@DBRef
private User user;

@DBRef
private Role role;

private String name;

...

}

And a UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {
private static final Logger LOG = LoggerFactory.getLogger(UserService.class);

@Autowired
UserRepository userRepository;

@Autowired
RoleRepository roleRepository;

@Autowired
UserRoleRepository userRoleRepository;

@Override
public User createUser(User user, Set<UserRole> userRoles) {
    User localUser = userRepository.findByUsername(user.getUsername());

    if(localUser != null) {
        LOG.info("User with username {} already exist. Nothing will be done. ", user.getUsername());
    } else {
        for (UserRole ur : userRoles) {
            roleRepository.save(ur.getRole());
            //here is the problem: the userrole instance created cannot generate Id
            userRoleRepository.save(ur);
        }

        user.getUserRoles().addAll(userRoles);


        localUser = userRepository.save(user);
    }

    return localUser;
}

}

and the DemoApplication.java

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {
@Autowired
UserService userService;

public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
}

@Override
public void run(String... args) throws Exception {


User user1 = new User();
user1.setFirstname("John");
user1.setLastname("Adams");
user1.setUsername("j");
    user1.setPassword(SecurityUtility.passwordEncoder().encode("p"));
    user1.setEmail("JAdams@gmail.com");
    Set<UserRole> userRoles = new HashSet<>();
    Role role1 = new Role();
    role1.setName("ROLE_USER");
    UserRole userRole1 = new UserRole();
    userRole1.setRole(role1);
    userRole1.setUser(user1);
    userRoles.add(userRole1);

    userService.createUser(user1, userRoles);


    }

and the ExceptionStackTrack

java.lang.IllegalStateException: Failed to execute CommandLineRunner
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:821) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:802) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:341) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1277) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1265) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at com.example.demo.DemoApplication.main(DemoApplication.java:22) [classes/:na]
Caused by: org.springframework.data.mapping.MappingException: Cannot create a reference to an object with a NULL id.
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.createDBRef(MappingMongoConverter.java:936) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writePropertyInternal(MappingMongoConverter.java:554) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeAssociation(MappingMongoConverter.java:517) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeProperties(MappingMongoConverter.java:494) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:481) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:455) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.write(MappingMongoConverter.java:399) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.write(MappingMongoConverter.java:78) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.MongoTemplate.toDocument(MongoTemplate.java:1071) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.MongoTemplate.doSave(MongoTemplate.java:1254) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.core.MongoTemplate.save(MongoTemplate.java:1202) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.save(SimpleMongoRepository.java:82) ~[spring-data-mongodb-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:377) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:641) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:605) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:590) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.0.10.RELEASE.jar:2.0.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at com.sun.proxy.$Proxy73.save(Unknown Source) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:197) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at com.sun.proxy.$Proxy73.save(Unknown Source) ~[na:na]
at com.example.demo.Service.Impl.UserServiceImpl.createUser(UserServiceImpl.java:42) ~[classes/:na]
at com.example.demo.DemoApplication.run(DemoApplication.java:46) [classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:818) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
... 5 common frames omitted

Here I dont't know why roles and users instance can generate automatically but userrole cannot. The console return me an exception that the Id is NULL and cannot be reference.

I'm new for this, and I hope someone could give me an answer.

thanks.

Answer 1

It seems that you are calling userRoleRepository.save(ur) in case when the User with the provided username does not exist in the database and before actually storing this User in it.

I believe you should reorganise your code in a way to store the User first and then store the UserRole with this User set.

In other words (code?), in your UserServiceImpl you could try doing something like this:

@Override
public User createUser(User user, Set<UserRole> userRoles) {
    User localUser = userRepository.findByUsername(user.getUsername());

    if(localUser != null) {
        LOG.info("User with username {} already exist. Nothing will be done. ", user.getUsername());
    } else {
        user.getUserRoles().addAll(userRoles);
        localUser = userRepository.save(user);
        for (UserRole ur : userRoles) {
            roleRepository.save(ur.getRole());
            userRoleRepository.save(ur);
        }
    }

    return localUser;
}

As you can see, I have only reordered the calls - User is stored first, then go the userRoles for this User .