当我从Spring的服务层返回实体列表时，我不断从Tomcat收到错误500。如果我只是在内存中实时制作实体，我就不会收到错误并且它们返回正常，所以这是专门针对事务做的事情。
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会显示错误500并且根本没有堆栈跟踪。我甚至把它包裹在try catch中，并且堆栈跟踪中没有任何内容。
这项服务只是召唤道......
@Service("examService")
public class ExamServiceImpl implements ExamService{
@Autowired
private ExamDao examDao;
@Override
@Transactional(readOnly = true)
public List<Exam> getAllExams() {
return examDao.getAllExams();
}
这个dao只返回一个简单的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，我认为这与懒惰加载的实体有关，我的实体在下面，你可以看到，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 - 现在下面的代码工作正常，所以它肯定是连接的一些问题（最初是延迟加载但是为了调试而删除）。只需从控制器返回以下代码就可以了......
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 - 我如何强制进行某种堆栈跟踪？ Hibernate版本= 4.1.10.Final，Spring版本3.1.4。
答案 0 :(得分：6)
使用了一些更改......
1）main/resources/log4j.xml应设置为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。也许你做了同样的事情？否则，您的IDE可能会受到影响，因为只要我在log4j.xml上设置了正确的级别，我就会看到终端中的日志记录就好了。
最初我认为错误是因为Chrome在登录后立即要求/favicon.ico并且Spring Security拒绝访问。
DEBUG：org.springframework.security.web.util.AntPathRequestMatcher - 检查请求的匹配：'/ favicon.ico';反对'/'
DEBUG：org.springframework.security.web.util.AntPathRequestMatcher - 检查请求的匹配：'/ favicon.ico';反对'/ exam **'
DEBUG：org.springframework.security.web.util.AntPathRequestMatcher - 检查请求的匹配：'/ favicon.ico';反对'/ exam / **'
DEBUG：org.springframework.security.web.access.intercept.FilterSecurityInterceptor - 安全对象：FilterInvocation：URL：/favicon.ico;属性：[denyAll]
DEBUG：org.springframework.security.web.access.intercept.FilterSecurityInterceptor - 以前经过身份验证：org.springframework.security.authentication.UsernamePasswordAuthenticationToken@fb77dfdd：校长：org.springframework.security.core.userdetails.User@36ebcb：用户名：user;密码保护];启用：true; AccountNonExpired：true; credentialsNonExpired：true; AccountNonLocked：true;授权机构：ROLE_ADMIN，ROLE_USER;证书：[保护];认证：真实;详细信息：org.springframework.security.web.authentication.WebAuthenticationDetails@0：RemoteIpAddress：0：0：0：0：0：0：0：1; SessionId：1qtptnbw65j3g145c9ni63ucw1;授权机构：ROLE_ADMIN，ROLE_USERDEBUG：org.springframework.security.access.vote.AffirmativeBased - Voter：org.springframework.security.web.access.expression.WebExpressionVoter@96f613，返回：-1
DEBUG：org.springframework.security.web.access.ExceptionTranslationFilter - 拒绝访问（用户不是匿名的）;委托给AccessDeniedHandlerorg.springframework.security.access.AccessDeniedException：访问被拒绝
我已将<http pattern="/favicon.ico" security="none" />添加到 security-context.xml 以删除此问题，但在添加该问题后结果显示为其他内容。
下一个错误是可怕的“懒得初始化一个集合”，已经多次覆盖SO，例如：
DEBUG：org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver - 解析来自handler [public java.util.List com.securetest.app.controller.ExamController.getExam（java.lang.String，org。）的异常。 springframework.ui.Model）]： org.springframework.http.converter.HttpMessageNotWritableException：无法编写JSON：懒得初始化角色集合：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] - ＆gt; com.securetest.app.entity.Exam [“questions”]）;嵌套异常是com.fasterxml.jackson.databind.JsonMappingException：懒得初始化一个角色集合：com.securetest.app.entity.Exam.questions，无法初始化代理 - 没有Session（通过引用链：java.util。 ArrayList的[0] - ＆GT; com.securetest.app.entity.Exam [ “问题”]）
DEBUG：org.springframework.web.servlet.DispatcherServlet - Null ModelAndView返回DispatcherServlet，名称为'appServlet'：假设HandlerAdapter已完成请求处理
DEBUG：org.springframework.web.servlet.DispatcherServlet - 已成功完成请求
我解决了这个问题，只需手动获取相关数据，同时仍在交易中：
@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。
希望它有所帮助！