CommandLine Runner Failed to load - spring

Question

Facing exception null pointer exception the class indicated in error mentioned here
it is saying user is null in override method. Cannot figure out the solution suggest some solution
I have given Error messages and as well every mentioned line for exception in the error message first one is main and second one is override method of addRoleToUser.
#SpringBootApplication
public class UserserviceApplication {
public static void main(String[] args) {
SpringApplication.run(UserserviceApplication.class, args);
}
#Bean
CommandLineRunner run(UserService userService){
return args -> {
userService.saveRole(new Role(null,"ROLE_USER"));
userService.saveRole(new Role(null,"ROLE_MANAGER"));
userService.saveRole(new Role(null,"ROLE_ADMIN"));
userService.saveRole(new Role(null,"ROLE_SUPER_ADMIN"));
userService.saveRole(new Role(null,"ROLE_SUPER_ADMIN_CE"));
userService.saveUser(new AppUser(null,"Ahmad Mujtaba","ahmad","0000",new ArrayList<>()));
userService.saveUser(new AppUser(null,"Hamid Mustafa","hamid","1234",new ArrayList<>()));
userService.saveUser(new AppUser(null,"Areeb Dera","areeb","5678",new ArrayList<>()));
userService.saveUser(new AppUser(null,"Fasih Ahmad","fasih","0000",new ArrayList<>()));
userService.saveUser(new AppUser(null,"Shaheer Zafar","shaheer","1122",new ArrayList<>()));
userService.addRoleToUser("ahmad","ROLE_USER");
userService.addRoleToUser("hamid","ROLE_MANAGER");
userService.addRoleToUser("areeb","ROLE_ADMIN");
userService.addRoleToUser("fasih","ROLE_SUPER_ADMIN");
userService.addRoleToUser("shaheer","ROLE_SUPER_ADMIN_CE");
};
}
#Bean
PasswordEncoder passwordEncoder(){
return new BCryptPasswordEncoder();
}
}
Override method:
#Override
public void addRoleToUser(String userName, String roleName) {
log.info("Adding role {} to user {}",roleName,userName);
AppUser user= userRepo.findByUsername(userName);
Role role=roleRepo.findByName(roleName);
user.getRoles().add(role);
}
Exception Messsage:
java.lang.IllegalStateException: Failed to execute CommandLineRunner
a org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:774)~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:755) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-2.7.2.jar:2.7.2]
at io.getarrays.userservice.UserserviceApplication.main(UserserviceApplication.java:19) ~[classes/:na]
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:577) ~[na:na]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.7.2.jar:2.7.2]
Caused by: java.lang.NullPointerException: Cannot invoke "io.getarrays.userservice.models.AppUser.getRoles()" because "user" is null
at io.getarrays.userservice.service.UserServiceImpl.addRoleToUser(UserServiceImpl.java:65) ~[classes/:na]
at io.getarrays.userservice.service.UserServiceImpl$$FastClassBySpringCGLIB$$cf86a147.invoke(<generated>) ~[classes/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793) ~[spring-aop-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763) ~[spring-aop-5.3.22.jar:5.3.22]
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.22.jar:5.3.22]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.22.jar:5.3.22]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763) ~[spring-aop-5.3.22.jar:5.3.22]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:708) ~[spring-aop-5.3.22.jar:5.3.22]
at io.getarrays.userservice.service.UserServiceImpl$$EnhancerBySpringCGLIB$$51d7b74f.addRoleToUser(<generated>) ~[classes/:na]
at io.getarrays.userservice.UserserviceApplication.lambda$run$0(UserserviceApplication.java:37) ~[classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:771) ~[spring-boot-2.7.2.jar:2.7.2]
... 8 common frames omitted