Question

我正在研究一个测试项目来学习hibernate，不幸的是我收到了这个错误并查看了其他类似的错误，但是关注它们并没有解决我的问题。我仍然收到此错误。

有人可以检查出了什么问题，我真的很想知道我的错误是什么。

我的模型类：

@Entity
@Table(name="survey")
public class Survey implements java.io.Serializable{

    /**
    * 
    */
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "survey_id")
private Long _id;

@OneToMany(fetch = FetchType.LAZY, mappedBy = "survey")
private List<Question> _questions ;

@Column(name="name")
private String _name;

public Survey() {
    super();
}

public Survey(Long id, List<Question> questions, String name) {
    super();
    _id = id;
    _questions = questions;
    _name = name;

    Assert.notNull(_id, "_id cannot be null");
    Assert.notNull(_questions, "_questions cannot be null");
    Assert.notNull(_name, "_name cannot be null");
}

public Long getId() {
    return _id;
}

public void setId(Long id) {
    _id = id;
}


public List<Question> getQuestions() {
    return _questions;
}

public void setQuestions(List<Question> questions) {
    _questions = questions;
}


public String getName() {
    return _name;
}

public void setName(String name) {
    _name = name;
}

@Override
public String toString() {
    return "Survey [_id=" + _id + ", _questions=" + _questions + ", _name="
            + _name + "]";
}

}

这是第二个模型类：

@Entity
@Table(name="question")
public class Question implements java.io.Serializable{

/**
 * 
 */
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "id")
private Long _id;

@Column(name = "label")
private String _label;

@Column(name="type")
private QuestionType _type;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name="survey_id")
private Survey _survey;

public Question() {
}

public Question(final Long id, final String label, final QuestionType type, final Survey survey,final Long surveyId) {
    _id = id;
    _label = label;
    _type = type;
    _survey = survey;

    Assert.notNull(_id, "_id cannot be null");
    Assert.notNull(_label, "_label cannot be null");
    Assert.notNull(_type, "_type cannot be null");
    Assert.notNull(_survey, "_survey cannot be null");
}

public Long getId() {
    return _id;
}

public void setId(Long id) {
    _id = id;
}


public String getLabel() {
    return _label;
}

public void setLabel(String label) {
    _label = label;
}


public QuestionType getType() {
    return _type;
}

public void setType(QuestionType type) {
    _type = type;
}

public Survey getSurvey() {
    return _survey;
}

public void setSurvey(Survey survey) {
    _survey = survey;
}

@Override
public String toString() {
    return "Question [_id=" + _id + ", _label=" + _label + ", _type="
            + _type + "]";
}

}

这是我的主要内容：

public class Application {

public static void main(String[] args) {


    System.out.println("Hibernate one to many (Annotation)");
    Session session = HibernateUtil.getSessionFactory().openSession();

    session.beginTransaction();
    Survey survey = new Survey();
    survey.setName("Ice Cream final");
    session.save(survey);

    Question question1 = new Question();
    question1.setLabel("Whats your favorite Ice Cream");
    question1.setType(QuestionType.TEXT);
    question1.setSurvey(survey);
    survey.getQuestions().add(question1);
    session.save(question1);
    session.getTransaction().commit();
    System.out.println("Done");

}

这是我的hibernate util类：

public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory（）;

private static SessionFactory buildSessionFactory() {
    try {
        // Create the SessionFactory from hibernate.cfg.xml
        return new AnnotationConfiguration().configure().buildSessionFactory();
    } catch (Throwable ex) {
        // Make sure you log the exception, as it might be swallowed
        System.err.println("Initial SessionFactory creation failed." + ex);
        throw new ExceptionInInitializerError(ex);
    }
}

public static SessionFactory getSessionFactory() {
    return sessionFactory;
}

public static void shutdown() {
    // Close caches and connection pools
    getSessionFactory().close();
}

}

这是我的配置文件：

<?xml version="1.0" encoding="UTF-8"?>
      <!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/survey</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password"></property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="show_sql">true</property>
    <mapping class="xxxxx.Survey" />
    <mapping class="xxxxx.Question" />
</session-factory>

错误：

Initial SessionFactory creation failed.org.hibernate.AnnotationException: mappedBy reference an     unknown target entity property: xxxx.model.Question.Survey in xxxx.model.Survey._questions
Exception in thread "main" java.lang.ExceptionInInitializerError
at xxxx.util.HibernateUtil.buildSessionFactory(HibernateUtil.java:16)
at xxxx.util.HibernateUtil.<clinit>(HibernateUtil.java:7)
at xxxx.Application.main(Application.java:25)
Caused by: org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: xxxx.model.Question.SurveyModel in xxxx.model.Survey._questions
at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:655)
at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:619)
at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:66)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1221)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:383)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1377)
at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:954)
at xxxx.util.HibernateUtil.buildSessionFactory(HibernateUtil.java:12)
... 2 more

Answer 1

@OneToMany(fetch = FetchType.LAZY, mappedBy = "survey")
private List<Question> _questions ;

所以你要告诉Hibernate：去查看Question.survey字段，了解这种关联是如何映射的。

问题中是否有一个名为survey的字段？不，没有。该字段名为_survey。

请请，让您的代码可读，让您的生活更轻松，并尊重Java命名约定。变量不以下划线开头。你真的不希望你的应用的每个JPQL / HQL查询到处都有下划线。

Answer 2

映射必须是子类的getter名称。

@OneToMany(fetch = FetchType.LAZY, mappedBy = "survey")
private List<Question> _questions ;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name="survey_id")
private Survey survey;

Answer 3

在问题实体类中，您必须对Survey类中的mappedBy中使用的字段使用相同的名称。所以：

@OneToMany(fetch = FetchType.LAZY, mappedBy = "survey")
private List<Question> _questions ;

@JoinColumn(name="survey_id")
private Survey survey;

mappedBy引用一个未知的目标实体属性 - hibernate错误maven注释

3 个答案: