Question

我想为我的测试项目使用dao和服务层但由于某种原因我得到了java.lang.NullPointerException：null。

这是工作示例：

UserController：

public class UserController {

    @Autowired
    private UserRepository repo;

    @RequestMapping(value = "/register",method = RequestMethod.POST)
    public User addUser(@RequestBody User user) {

        return repo.saveAndFlush(user);
    }}

UserRepository：

public interface UserRepository extends JpaRepository<User,String> {

    // Optional<User> findOneByLogin(String login);

}

但我将其替换为：我使用以下教程作为指南Hibernate JPA DAO Example

userDAO的

public class UserDao implements UserDaoInterface <User,Integer> {

    private Session currentSession;

    private Transaction currentTransaction;

    public org.hibernate.Session openCurrentSession() {
        currentSession = getSessionFactory().openSession();
        return currentSession;
    }

    public org.hibernate.Session openCurrentSessionwithTransaction() {
        currentSession = getSessionFactory().openSession();
        currentTransaction = currentSession.beginTransaction();
        return currentSession;
    }

    public void closeCurrentSession() {
        currentSession.close();
    }

    public void closeCurrentSessionwithTransaction() {
        currentTransaction.commit();
        currentSession.close();
    }

    private static SessionFactory getSessionFactory() {
        Configuration configuration = new Configuration().configure();
        StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()
                .applySettings(configuration.getProperties());
        SessionFactory sessionFactory = configuration.buildSessionFactory(builder.build());
        return sessionFactory;
    }

    public Session getCurrentSession() {
        return currentSession;
    }

    public void setCurrentSession(Session currentSession) {
        this.currentSession = currentSession;
    }

    public Transaction getCurrentTransaction() {
        return currentTransaction;
    }

    public void setCurrentTransaction(Transaction currentTransaction) {
        this.currentTransaction = currentTransaction;
    }

    public UserDao() {

    }

    @Override
    public void create(User user) {
        getCurrentSession().save(user);
    }

会话是否会返回null？为什么以及如何解决这个问题？

UserService

public class UserService {

    private static UserDao userDao;

    public UserService (){

        userDao = new UserDao();

    }

    public void save (User user){

        userDao.openCurrentSessionwithTransaction();
        userDao.create(user);
        userDao.closeCurrentSessionwithTransaction();


    }

}

最后 UserController的

public class UserController {

    private UserService userService;

    @RequestMapping(value = "/register",method = RequestMethod.POST)
    public void addUser(@RequestBody User user) {

        userService.save(user);

    }}

我不知道这是否与此有关，但我也在错误日志

中得到了这个

at demo.security.SecurityConfiguration$1.doFilterInternal(SecurityConfiguration.java:119)

公共类SecurityConfiguration扩展了WebSecurityConfigurerAdapter {

//For more information check spring documentation
private Filter csrfHeaderFilter() {
    return new OncePerRequestFilter() {
        @Override
        protected void doFilterInternal(HttpServletRequest request,
                                        HttpServletResponse response, FilterChain filterChain)
                throws ServletException, IOException {
            CsrfToken csrf = (CsrfToken) request.getAttribute(CsrfToken.class
                    .getName());
            if (csrf != null) {
                Cookie cookie = WebUtils.getCookie(request, "XSRF-TOKEN");
                String token = csrf.getToken();
                if (cookie == null || token != null
                        && !token.equals(cookie.getValue())) {
                    cookie = new Cookie("XSRF-TOKEN", token);
                    cookie.setPath("/");
                    response.addCookie(cookie);
                }
            }
            filterChain.doFilter(request, response); // this is line 119
        }
    };
}}

application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/login5
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driverClassName=com.mysql.jdbc.Driver

#Hibernate Configuration:
hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
hibernate.show_sql=true
entitymanager.packages.to.scan=com.spr.model

**编辑**

所以我做了АнатолійВакалюк建议的内容添加了@Repository和@Service注释，因此Spring可以管理它。

但现在我得到以下错误：

org.hibernate.HibernateException: /hibernate.cfg.xml not found

我正在使用spring boot我是否需要使用xml配置。

Answer 1

你得到一个NullPointeException，因为你的UserDao不是由Spring上下文管理的。你必须使用@Repository注释你的DAO，之后你可以在服务中注入/自动装载它：

@Autowire
private UserDao userDao;

同样的事情是你的服务。你必须用@Service注释它并在你的控制器中自动装配它。

此外，如果您配置了JPA，则需要使用EntityManager而不是Hibernate Session

修改

如果要自定义Spring Data存储库，可以使用自定义方法声明自己的接口：

public interface CustomRepository { //custom methods here }

并为其提供实施：

public class CustomRepositoryImpl implements CustomRepository { @PersistenceContext private EntityManager entityManager; //custom methods implementation }

之后只需使用自定义界面扩展您的存储库：

public interface SomeRepository extends JpaRepository<Entity, Integer>, CustomRepository { //you have both spring data and custom methods here

}

有关详细信息，请参阅此文章。 Customize spring data repositories

Hibernate Dao服务而不是repository.JpaRepository

1 个答案: