Spring安全注册有效，但登录不可用'；T

我是Spring security的新手，尝试实现注册和登录过程。 我可以使用密码注册新用户，但如果我尝试使用凭据登录，则会出现错误：

org.springframework.security.authentication.InternalAuthenticationServiceException: null
    at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:123) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.dao.AbstractUserDetailsAuthenticationProvider.authenticate(AbstractUserDetailsAuthenticationProvider.java:144) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:199) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:219) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter.attemptAuthentication(UsernamePasswordAuthenticationFilter.java:95) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:212) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:92) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:77) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:358) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:271) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
Caused by: java.lang.NullPointerException: null
    at com.asceocrm.service.UserDetailsServiceImpl.buildUserForAuthentication(UserDetailsServiceImpl.java:45) ~[classes/:na]
    at com.asceocrm.service.UserDetailsServiceImpl.loadUserByUsername(UserDetailsServiceImpl.java:32) ~[classes/:na]
    at com.asceocrm.service.UserDetailsServiceImpl$$FastClassBySpringCGLIB$$e601dc35.invoke(<generated>) ~[classes/:na]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:771) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:367) ~[spring-tx-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:118) ~[spring-tx-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:691) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at com.asceocrm.service.UserDetailsServiceImpl$$EnhancerBySpringCGLIB$$dd1a241.loadUserByUsername(<generated>) ~[classes/:na]
    at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:108) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    ... 51 common frames omitted

2020-09-10 09:37:45.340 DEBUG 20212 --- [nio-8080-exec-5] w.a.UsernamePasswordAuthenticationFilter : Authentication request failed: org.springframework.security.authentication.InternalAuthenticationServiceException

org.springframework.security.authentication.InternalAuthenticationServiceException: null
    at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:123) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.dao.AbstractUserDetailsAuthenticationProvider.authenticate(AbstractUserDetailsAuthenticationProvider.java:144) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:199) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:219) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter.attemptAuthentication(UsernamePasswordAuthenticationFilter.java:95) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:212) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:92) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:77) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:358) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:271) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
    at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
Caused by: java.lang.NullPointerException: null
    at com.asceocrm.service.UserDetailsServiceImpl.buildUserForAuthentication(UserDetailsServiceImpl.java:45) ~[classes/:na]
    at 
    org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:108) ~[spring-security-core-5.3.4.RELEASE.jar:5.3.4.RELEASE]
    ... 51 common frames omitted

Login.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://www.thymeleaf.org">

<head>
    <title>Spring Security Tutorial</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>

<body>
<form th:action="@{/registration}" method="get">
    <button class="btn btn-md btn-warning btn-block" type="Submit">Go To Registration Page</button>
</form>

<div class="container">
    <img th:src="@{/images/login.jpg}" class="img-responsive center-block" width="300" height="300" alt="Logo"/>
    <form th:action="@{/login}" method="POST" class="form-signin">
        <h3 class="form-signin-heading" th:text="Welcome"></h3>
        <br/>

        <input type="text" id="user_name" name="user_name" placeholder="User Name"
               class="form-control"/> <br/>
        <input type="password" th:placeholder="Password"
               id="password" name="password" class="form-control"/> <br/>

        <div align="center" th:if="${param.error}">
            <p style="font-size: 20; color: #FF1C19;">User Name or Password invalid, please verify</p>
        </div>
        <button class="btn btn-lg btn-primary btn-block" name="Submit" value="Login" type="Submit"
                th:text="Login"></button>
    </form>
</div>
</body>
</html>

注册工作正常，注册用户使用用户名和mysql表User中的哈希保存。 我是Spring security的新手，无法调试它或发现错误。有人有主意吗

非常感谢

@Repository
public interface RoleRepository extends JpaRepository<Role, Long>{
        Role findByRoleName(String roleName);
}

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    User findByUsername(String username);
}

@Service
public class UserService {

private UserRepository userRepository;

private RoleRepository roleRepository;

private BCryptPasswordEncoder bCryptPasswordEncoder;

@Autowired
public UserService(UserRepository userRepository,
                    RoleRepository roleRepository,
                    BCryptPasswordEncoder bCryptPasswordEncoder) {
    this.userRepository = userRepository;
    this.roleRepository = roleRepository;
    this.bCryptPasswordEncoder = bCryptPasswordEncoder;
}


public User findUserByUserName(String username) {
    return userRepository.findByUsername(username);
}

public User saveUser(User user) {
    user.setPassword(bCryptPasswordEncoder.encode(user.getPassword()));
    user.setActive(true);
    Role userRole = roleRepository.findByRoleName("ADMIN");
    user.setRoles(new HashSet<Role>(Arrays.asList(userRole)));
    return userRepository.save(user);
}
}

@Service
public class UserDetailsServiceImpl implements UserDetailsService{
    
    @Autowired
    private UserService userService;

    @Override
    @Transactional
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        User user = userService.findUserByUserName(username);
        List<GrantedAuthority> authorities = getUserAuthority(user.getRoles());
        return buildUserForAuthentication(user, authorities);
    }

    private List<GrantedAuthority> getUserAuthority(Set<Role> userRoles) {
        Set<GrantedAuthority> roles = new HashSet<GrantedAuthority>();
        for (Role role : userRoles) {
            roles.add(new SimpleGrantedAuthority(role.getRoleName()));
        }
        List<GrantedAuthority> grantedAuthorities = new ArrayList<>(roles);
        return grantedAuthorities;
    }

    private UserDetails buildUserForAuthentication(User user, List<GrantedAuthority> authorities) {
        return new org.springframework.security.core.userdetails.User(user.getUsername(), user.getPassword(), user.getActive(),
                true, true, true, authorities);
    }
}

@Controller
public class LoginController {

    @Autowired
    private UserService userService;

    @RequestMapping(value={"/", "/login"}, method = RequestMethod.GET)
    public ModelAndView login(){
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("login");
        return modelAndView;
    }


    @RequestMapping(value="/registration", method = RequestMethod.GET)
    public ModelAndView registration(){
        ModelAndView modelAndView = new ModelAndView();
        User user = new User();
        modelAndView.addObject("user", user);
        modelAndView.setViewName("registration");
        return modelAndView;
    }

    @RequestMapping(value = "/registration", method = RequestMethod.POST)
    public ModelAndView createNewUser(@Validated User user, BindingResult bindingResult) {
        ModelAndView modelAndView = new ModelAndView();
        User userExists = userService.findUserByUserName(user.getUsername());
        if (userExists != null) {
            bindingResult
                    .rejectValue("userName", "error.user",
                            "There is already a user registered with the user name provided");
        }
        if (bindingResult.hasErrors()) {
            modelAndView.setViewName("registration");
        } else {
            userService.saveUser(user);
            modelAndView.addObject("successMessage", "User has been registered successfully");
            modelAndView.addObject("user", new User());
            modelAndView.setViewName("registration");

        }
        return modelAndView;
    }

    @RequestMapping(value="/admin/home", method = RequestMethod.GET)
    public ModelAndView home(){
        ModelAndView modelAndView = new ModelAndView();
        Authentication auth = SecurityContextHolder.getContext().getAuthentication();
        User user = userService.findUserByUserName(auth.getName());
        modelAndView.addObject("userName", "Welcome " + user.getUsername());
        modelAndView.addObject("adminMessage","Content Available Only for Users with Admin Role");
        modelAndView.setViewName("admin/home");
        return modelAndView;
    }


}

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://www.thymeleaf.org">

<head>
    <title>Spring Security Tutorial</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>

<body>
<form th:action="@{/registration}" method="get">
    <button class="btn btn-md btn-warning btn-block" type="Submit">Go To Registration Page</button>
</form>

<div class="container">
    <img th:src="@{/images/login.jpg}" class="img-responsive center-block" width="300" height="300" alt="Logo"/>
    <form th:action="@{/login}" method="POST" class="form-signin">
        <h3 class="form-signin-heading" th:text="Welcome"></h3>
        <br/>

        <input type="text" id="user_name" name="user_name" placeholder="User Name"
               class="form-control"/> <br/>
        <input type="password" th:placeholder="Password"
               id="password" name="password" class="form-control"/> <br/>

        <div align="center" th:if="${param.error}">
            <p style="font-size: 20; color: #FF1C19;">User Name or Password invalid, please verify</p>
        </div>
        <button class="btn btn-lg btn-primary btn-block" name="Submit" value="Login" type="Submit"
                th:text="Login"></button>
    </form>
</div>
</body>
</html>

@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private BCryptPasswordEncoder bCryptPasswordEncoder;

    @Autowired
    private UserDetailsServiceImpl userDetailsServiceImpl;

    @Bean
    public BCryptPasswordEncoder passwordEncoder() {
        BCryptPasswordEncoder bCryptPasswordEncoder = new BCryptPasswordEncoder();
        return bCryptPasswordEncoder; }

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
                auth
                    .userDetailsService(userDetailsServiceImpl)
                    .passwordEncoder(bCryptPasswordEncoder);
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {

        http.
                authorizeRequests()
                .antMatchers("/").permitAll()
                .antMatchers("/login").permitAll()
                .antMatchers("/registration").permitAll()
                .antMatchers("/admin/**").hasAuthority("ADMIN").anyRequest()
                .authenticated().and().csrf().disable().formLogin()
                .loginPage("/login").failureUrl("/login?error=true")
                .defaultSuccessUrl("/admin/home")
                .usernameParameter("user_name")
                .passwordParameter("password")
                .and().logout()
                .logoutRequestMatcher(new AntPathRequestMatcher("/logout"))
                .logoutSuccessUrl("/login").and().exceptionHandling()
                .accessDeniedPage("/access-denied");
    }

    @Override
    public void configure(WebSecurity web) throws Exception {
        web
                .ignoring()
                .antMatchers("/resources/**", "/static/**", "/css/**", "/js/**", "/images/**");
    }

}