spring - 如何在 Spring IOC 中使用 @Autowired 将值注入 Null 对象？

Question

我刚刚开始研究 Spring Rest 应用程序，目前我正在管理身份验证操作，我想做的是简单地检查输入的电子邮件地址是否已被使用，问题是当它不存在时我不能自动装配 bean用户我得到一个 NullPointerException。

我在 SOF 中发现了类似的问题，但我的代码似乎是正确的，请帮助。

这是我的代码：

项目架构

用户.java：

@Component
@Entity
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="idUser", scope = User.class)
public class User implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long idUser;
    @Column(name = "login", unique = true)
    private String login;
    private String password;
    private String nom;
    private String prenom;
    private String email;
    private long telephone;
    private String statut;
    private int isDeleted;

    @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
    @ManyToOne(fetch = FetchType.LAZY)
    private Role userRole;

    public User(Long idUser, String login, String password, String nom, String prenom, String email,
            long telephone, String statut, int isDeleted, Role userRole) {
        super();
        this.idUser = idUser;
        this.login = login;
        this.password = password;
        this.nom = nom;
        this.prenom = prenom;
        this.email = email;
        this.telephone = telephone;
        this.statut = statut;
        this.isDeleted = isDeleted;
        this.userRole = userRole;
    }

    public User() {
        super();
    }

    public Long getIdUser() {
        return idUser;
    }

    public void setIdUser(Long idUser) {
        this.idUser = idUser;
    }

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getNom() {
        return nom;
    }

    public void setNom(String nom) {
        this.nom = nom;
    }

    public String getPrenom() {
        return prenom;
    }

    public void setPrenom(String prenom) {
        this.prenom = prenom;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public long getTelephone() {
        return telephone;
    }

    public void setTelephone(long telephone) {
        this.telephone = telephone;
    }

    public String getStatut() {
        return statut;
    }

    public void setStatut(String statut) {
        this.statut = statut;
    }

    public int getIsDeleted() {
        return isDeleted;
    }

    public void setIsDeleted(int isDeleted) {
        this.isDeleted = isDeleted;
    }

    public Role getUserRole() {
        return userRole;
    }

    public void setUserRole(Role userRole) {
        this.userRole = userRole;
    }}

用户存储库.java：

@Repository
public interface UserRepository extends JpaRepository<User, Long> {

    User findByLoginLikeAndPasswordLikeAndIsDeletedEquals(String login, String password, int i);

    User findByLoginLike(String login);
    }

用户DTO.java

@Component
public class UserDTO {

    private Long idUser;

    private String login;
    private String password;

    private String role ;

    public UserDTO(Long idUser, String login, String password, String role) {
        super();
        this.idUser = idUser;
        this.login = login;
        this.password = password;
        this.role = role;
    }

    public UserDTO() {
        super();
    }

    public Long getIdUser() {
        return idUser;
    }

    public void setIdUser(Long idUser) {
        this.idUser = idUser;
    }

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    } 

}

用户服务.java：

@Service
public class UserService {


    @Autowired
    private UserDTO userDto;

    @Autowired
    private User user;


    @Autowired
    private UserRepository userRep;

    @Autowired
    private RoleRepository roleRep;




    public boolean addUser(String login, String password, String role) {
        boolean state = false;


        try {
            System.out.println(user.toString());
            user = userRep.findByLoginLike(login);

            if (user == null) {

                user.setPassword(password);
                user.setLogin(login);               
                user.setUserRole(roleRep.findByNomRoleLike(role));
                userRep.save(user);

                state = true;

            } else {
                System.out.println("user already exists");
                state = false;
            }
        } catch (Exception e) {

            e.printStackTrace();
            state = false;
        }

        return state;
    }

用户控制器.java

@RestController
public class UserControler {



    @Autowired
    private User user;

    @Autowired
    private UserRepository userRep;

    @Autowired
    private List<User> allUsers;


    @Autowired
    private UserService userService;

    @Autowired
    private UserDTO userDTO;


    @RequestMapping( value = "/addUser", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    public Boolean addUser(@RequestBody UserDTO u){
        boolean state = false;
        try {
            state = userService.addUser(u.getLogin(), u.getPassword(), "Administrateur");
        } catch (Exception e) {

            e.printStackTrace();
        }

        return state;
    }

堆栈跟踪 ：

Hibernate：选择 users0_.user_role_id_role 作为 user_ro10_1_0_，users0_.id_user 作为 id_user1_1_0_，users0_.id_user 作为 id_user1_1_1_，users0_.email 作为 email2_1_1_，users0_.is_deleted 作为 is_delet3_1_1_，users0_.login 作为 login4_1_1_，users_1_users_nom 作为密码 1_1_1_，users0_1_0 作为。 , users0_.prenom 作为 prenom7_1_1_, users0_.statut 作为 statut8_1_1_, users0_.telephone 作为 telephon9_1_1_, users0_.user_role_id_role 作为 user_ro10_1_1_ 来自用户 users0_ where users0_.user_role_id_role=? 2018-12-20 14:25:58.061 TRACE 6192 --- [nio-8080-exec-5] ohtype.descriptor.sql.BasicBinder：绑定参数1如 [BIGINT] - [3] 2018-12-20 14:26:36.015 WARN 6192 --- [nio-8080-exec-7] .wsmsDefaultHandlerExceptionResolver ：由处理程序执行引起的已解决异常：org.springframework.web.HttpRequestMethodNotSupportedException：不支持请求方法“POST”

java.lang.NullPointerException 在

com.akkaprofil.service.UserService.addUser(UserService.java:63) 在 com.akkaprofil.controller.UserControler.addUser(UserControler.java:46) 在 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 在 sun.reflect。 NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod. java:205) 在 org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) 的 org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)在 org.springframework.web.servlet.mvc.method.annotation。RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:849) 在 org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:760) 在 org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter。处理（AbstractHandlerMethodAdapter.java:85）在 org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) 在 org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) 在 org.springframework .web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872) at javax.servlet.http.HttpServlet.service(HttpServlet.java:661 ) 在 org.springframework.web.servlet。FrameworkServlet.service(FrameworkServlet.java:846) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache .catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) 在 org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain .java:193) 位于 org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) 的 org.springframework.web 的 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)。 filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 在 org.apache.catalina.core。ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) at org .springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain .java:166) 在 org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 在 org.apache.catalina。核。ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) at org .springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain .java:166) 在 org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) 的 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)。身份验证器.AuthenticatorBase。调用（AuthenticatorBase.java:493）在 org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) 在 org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) 在 org.apache .catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) 在 org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) 在 org.apache.coyote.http11.Http11Processor.service(Http11Processor.java :800) 在 org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) 在 org.apache.tomcat.util.net 的 org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)。 NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) 在 org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) 在 java.util。concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java .lang.Thread.run（未知来源）

当我调用 AddUser Request 方法时，触发了此异常，当找不到电子邮件地址时，我找不到未将值设置为用户对象的原因，所有类都用它们的 Stereotypes 进行注释，用户 Bean 是自动装配，我还没有声明一个新的操作员。

您能否澄清此异常背后的原因。谢谢

标签： springdependency-injectionnullpointerexceptionautowired