当我在Spring中从服务层返回实体列表时,我不断从Tomcat收到错误500。如果我只是使实体在内存中动态运行,那么我不会收到错误并且它们会返回正常,所以这与事务特别相关。

我的控制器中有以下方法...

@RequestMapping(value = "{examid}", method = RequestMethod.GET)
@ResponseBody
public List<Exam> getExam(@PathVariable String examid, Model model) {
    return examService.getAllExams();
}

调用此方法时,tomcat显示错误500,并且完全没有堆栈跟踪。我什至将其包装在try catch中,并且该stacktrace中没有任何内容。

这项服务只是叫道...
@Service("examService")
public class ExamServiceImpl implements ExamService{

    @Autowired
    private ExamDao examDao;

        @Override
        @Transactional(readOnly = true)
        public List<Exam> getAllExams() {
            return examDao.getAllExams();
        }

而此dao仅返回一个简单的HQL脚本...
@Repository("examDao")
public class ExamDaoImpl implements ExamDao {
@Autowired
    private SessionFactory sessionFactory;

    @Override
    public List<Exam> getAllExams() {
        return sessionFactory.getCurrentSession().createQuery("from Exam")
                .list();
    }

最初,我认为这与延迟加载的实体有关,您可以看到我的实体在下面,它们非常简单
@Entity
@Table(name = "exams")
public class Exam implements Serializable {

    private static final long serialVersionUID = -5109075534794721930L;

    @Id
    @GeneratedValue(generator="system-uuid")
    @GenericGenerator(name="system-uuid", strategy = "uuid")
    @Column(name = "examid", unique = true)
    private String examId;

    @OneToMany(mappedBy = "exam")
    private Set<Question> questions;

    public String getExamId() {
        return examId;
    }

    public void setExamId(String examId) {
        this.examId = examId;
    }

    /**
     * @return the questions
     */
    @JsonManagedReference
    public Set<Question> getQuestions() {
        return questions;
    }

    /**
     * @param questions the questions to set
     */
    public void setQuestions(Set<Question> questions) {
        this.questions = questions;
    }

}

问题实体
@Entity
@Table(name = "questions")
public class Question  implements Serializable  {

    private static final long serialVersionUID = 8804841647267857850L;
    private String questionId;
    private Exam exam;
    private Set<Answer> answers;

    /**
     * @return the answer
     */
    @JsonManagedReference
    @OneToMany(mappedBy = "question")
    public Set<Answer> getAnswers() {
        return answers;
    }

    /**
     * @param answer
     *            the answer to set
     */
    public void setAnswers(Set<Answer> answers) {
        this.answers = answers;
    }

    /**
     * @return the exam
     */
    @JsonBackReference
    @ManyToOne
    @JoinColumn(name = "examid", nullable = false)
    public Exam getExam() {
        return exam;
    }

    /**
     * @param exam
     *            the exam to set
     */
    public void setExam(Exam exam) {
        this.exam = exam;
    }

    /**
     * @return the questionId
     */
    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    @Column(name = "questionid", unique = true)
    public String getQuestionId() {
        return questionId;
    }

    /**
     * @param questionId
     *            the questionId to set
     */
    public void setQuestionId(final String questionId) {
        this.questionId = questionId;
    }
}

回答实体
@Entity
@Table(name = "answers")
public class Answer  implements Serializable {

    private static final long serialVersionUID = -3922870865886851018L;

    @Id
    @GeneratedValue(generator="system-uuid")
    @GenericGenerator(name="system-uuid", strategy = "uuid")
    @Column(name = "answerid", unique = true)
    private String answerId;

    @ManyToOne()
    @JoinColumn(name = "questionid", nullable = false)
    private Question question;

    /**
     * @return the question
     */
    @JsonBackReference
    public Question getQuestion() {
        return question;
    }

    /**
     * @param question the question to set
     */
    public void setQuestion(Question question) {
        this.question = question;
    }

    /**
     * @return the answerId
     */
    public String getAnswerId() {
        return answerId;
    }

    /**
     * @param answerId the answerId to set
     */
    public void setAnswerId(final String answerId) {
        this.answerId = answerId;
    }

}

我正在使用Jackson 2.2.0-现在以下代码可以正常工作,因此无论是联接(最初都是延迟加载但为了调试而删除)肯定都是一个问题。只需从控制器返回以下代码即可正常工作...
        Exam exam = new Exam();
        Question presidentQuestion = new Question();
        presidentQuestion.setExam(exam);
        Question skyQuestion = new Question();
        skyQuestion.setExam(exam);
        Set<Question> questions = new HashSet<>();
        questions.add(skyQuestion);
        questions.add(presidentQuestion);
        exam.setQuestions(questions);
        Answer answer = new Answer();
        answer.setQuestion(skyQuestion);
        Answer answer1 = new Answer();
        answer1.setQuestion(skyQuestion);
        Answer answer2 = new Answer();
        answer2.setQuestion(presidentQuestion);
        Set<Answer> answers1 = new HashSet<>();
        answers1.add(answer2);
        Set<Answer> answers = new HashSet<>();
        answers.add(answer);
        answers.add(answer1);
        presidentQuestion.setAnswers(answers1);
        skyQuestion.setAnswers(answers);
            return Arrays.asList(exam);

Tomcat日志中没有任何内容-如何强制某种堆栈跟踪? Hibernate版本= 4.1.10.Final,Spring版本3.1.4。

最佳答案

进行了一些更改就可以使用…

1)main/resources/log4j.xml应该设置为debug以查看错误:

<logger name="org.springframework.context">
  <level value="debug" />
</logger>

<logger name="org.springframework.web">
  <level value="debug" />
</logger>

<!-- Root Logger -->
<root>
  <priority value="debug" />
  <appender-ref ref="console" />
</root>

我首先错误地编辑了test/resources/log4j.xml。也许您也这样做了?否则,可能是您的IDE造成了麻烦,因为一旦我在log4j.xml上设置了正确的级别,我就会看到终端中的日志记录很好。

最初,我认为错误是因为Chrome在登录后立即要求输入/favicon.ico,而Spring Security拒绝访问。

调试:org.springframework.security.web.util.AntPathRequestMatcher-检查请求是否匹配:“/ favicon.ico”;反对 '/'

调试:org.springframework.security.web.util.AntPathRequestMatcher-检查请求是否匹配:“/ favicon.ico”;针对“/ exam **”

调试:org.springframework.security.web.util.AntPathRequestMatcher-检查请求是否匹配:“/ favicon.ico”;针对“/ exam / **”

调试:org.springframework.security.web.access.intercept.FilterSecurityInterceptor-安全对象:FilterInvocation:URL:/favicon.ico;属性:[denyAll]

调试:org.springframework.security.web.access.intercept.FilterSecurityInterceptor-先前已验证:org.springframework.security.authentication.UsernamePasswordAuthenticationToken@fb77dfdd:主体:org.springframework.security.core.userdetails.User@36ebcb:用户名:user ;密码保护];启用:true; AccountNonExpired:true; certificateNonExpired:true; AccountNonLocked:true;授予的权限:ROLE_ADMIN,ROLE_USER;凭证:[受保护];已验证:true;详细信息:org.springframework.security.web.authentication.WebAuthenticationDetails@0:RemoteIpAddress:0:0:0:0:0:0:0:0:1; SessionId:1qtptnbw65j3g145c9ni63ucw1;授予的权限:ROLE_ADMIN,ROLE_USERDEBUG:org.springframework.security.access.vote.AffirmativeBased-选民:org.springframework.security.web.access.expression.WebExpressionVoter@96f613,返回:-1

调试:org.springframework.security.web.access.ExceptionTranslationFilter-拒绝访问(用户不是匿名用户);委派给AccessDeniedHandlerorg.springframework.security.access.AccessDeniedException:访问被拒绝

我添加了<http pattern="/favicon.ico" security="none" /> security-context.xml 中,以解决此问题,尽管添加该问题后发现它是其他问题。

下一个错误是可怕的“未能延迟初始化集合的集合”,在SO上已涉及了很多次,例如:
  • What is lazy loading in Hibernate?
  • Solve "failed to lazily initialize a collection of role" exception
  • Spring MVC 3.1.2 + Jackson 2: LazyInitializationException when lazily initialize a collection - no session or session was closed-,这可能是您最好看的地方。

  • 调试:org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver-从处理程序[公共java.util.List com.securetest.app.controller.ExamController.getExam(java.lang.String,org.springframework.ui .Model)]: org.springframework.http.converter.HttpMessageNotWritableException:无法编写JSON:无法延迟初始化角色集合:com.securetest.app.entity.Exam.questions ,无法初始化代理-无会话(通过参考链:java.util.ArrayList [0]-> com.securetest.app.entity.Exam [“questions”]);嵌套异常是com.fasterxml.jackson.databind.JsonMappingException:无法延迟初始化角色集合:com.securetest.app.entity.Exam.questions,无法初始化代理-没有会话(通过参考链:java.util。 ArrayList [0]-> com.securetest.app.entity.Exam [“questions”])

    调试:org.springframework.web.servlet.DispatcherServlet-Null ModelAndView返回到DispatcherServlet,名称为“appServlet”:假设HandlerAdapter完成了请求处理

    调试:org.springframework.web.servlet.DispatcherServlet-成功完成请求

    我通过以下方法解决了这种快速的方法:仅手动获取相关数据,同时仍在事务中:
    @Override
    @Transactional(readOnly = true)
    public List<Exam> getAllExams() {
      List<Exam> exams = examDao.getAllExams();
      for (Exam e : exams) {
        for (Question q : e.getQuestions()) {
          q.getAnswers().size();
        }
      }
      return exams;
    }
    

    允许请求成功完成。

    希望能帮助到你!

    10-07 19:37
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