org.hibernate.MappingException：无法确定types：java.util.List，在表：College，for列：

现在，我正在学习hibernate，并开始在我的项目中使用它。 这是一个CRUD应用程序。 我用所有的crud操作hibernate。 它适用于所有的人。 但是，一对多和多对一，我厌倦了尝试。 最后它给了我下面的错误。

org.hibernate.MappingException: Could not determine type for: java.util.List, at table: College, for columns: [org.hibernate.mapping.Column(students)]

然后我再次通过这个video教程 。 一开始我对我来说很简单。 但是，我不能让它工作。 现在也是这样说

org.hibernate.MappingException: Could not determine type for: java.util.List, at table: College, for columns: [org.hibernate.mapping.Column(students)]

我在互联网上跑了一些search，有人告诉它在Hibernate的一个错误 ，有人说，通过添加@GenereatedValue这个错误将被清除。 但是，nothings为我工作，

我希望我会得到一些修复！

谢谢！

在这里我的代码：

College.java

 @Entity public class College { @Id @GeneratedValue(strategy=GenerationType.AUTO) private int collegeId; private String collegeName; private List<Student> students; @OneToMany(targetEntity=Student.class, mappedBy="college", fetch=FetchType.EAGER) public List<Student> getStudents() { return students; } public void setStudents(List<Student> students) { this.students = students; }//Other gettters & setters omitted 

Student.java

 @Entity public class Student { @Id @GeneratedValue(strategy=GenerationType.AUTO) private int studentId; private String studentName; private College college; @ManyToOne @JoinColumn(name="collegeId") public College getCollege() { return college; } public void setCollege(College college) { this.college = college; }//Other gettters & setters omitted 

Main.java：

 public class Main { private static org.hibernate.SessionFactory sessionFactory; public static SessionFactory getSessionFactory() { if (sessionFactory == null) { initSessionFactory(); } return sessionFactory; } private static synchronized void initSessionFactory() { sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); } public static Session getSession() { return getSessionFactory().openSession(); } public static void main (String[] args) { Session session = getSession(); Transaction transaction = session.beginTransaction(); College college = new College(); college.setCollegeName("Dr.MCET"); Student student1 = new Student(); student1.setStudentName("Peter"); Student student2 = new Student(); student2.setStudentName("John"); student1.setCollege(college); student2.setCollege(college); session.save(student1); session.save(student2); transaction.commit(); } } 

安慰：

  Exception in thread "main" org.hibernate.MappingException: Could not determine type for: java.util.List, at table: College, for columns: [org.hibernate.mapping.Column(students)] at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:306) at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:290) at org.hibernate.mapping.Property.isValid(Property.java:217) at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:463) at org.hibernate.mapping.RootClass.validate(RootClass.java:235) at org.hibernate.cfg.Configuration.validate(Configuration.java:1330) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1833) at test.hibernate.Main.initSessionFactory(Main.java:22) at test.hibernate.Main.getSessionFactory(Main.java:16) at test.hibernate.Main.getSession(Main.java:27) at test.hibernate.Main.main(Main.java:43) 

XML：

 <?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> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/dummy</property> <property name="connection.username">root</property> <property name="connection.password">1234</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">1</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- Enable Hibernate's automatic session context management --> <property name="current_session_context_class">thread</property> <!-- Disable the second-level cache --> <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.auto">update</property> <mapping class="test.hibernate.Student" /> <mapping class="test.hibernate.College" /> </session-factory> 

Answer 1

您正在使用字段访问策略 （由@Id注释确定）。 把每个字段上面的JPA相关注释，而不是getter属性

 @OneToMany(targetEntity=Student.class, mappedBy="college", fetch=FetchType.EAGER) private List<Student> students; 

Answer 2

将@ElementCollection添加到List字段解决了这个问题：

  @Column @ElementCollection(targetClass=Integer.class) private List<Integer> countries; 

Answer 3

访问策略问题

作为JPA提供者，Hibernate可以反省实体属性（实例字段）或访问者（实例属性）。 默认情况下， @Id注释的位置提供了默认的访问策略。 当放置在一个领域，hibernate将承担基于现场的访问。 放置在标识符getter上，Hibernate将使用基于属性的访问。

基于现场的访问

当使用基于字段的访问时，添加其他实体级别的方法是非常灵活的，因为Hibernate不会考虑持久化状态的那些部分

 @Entity public class Simple { @Id private Integer id; @OneToMany(targetEntity=Student.class, mappedBy="college", fetch=FetchType.EAGER) private List<Student> students; //getter +setter } 

基于财产的访问

当使用基于属性的访问时，Hibernate使用访问器读取和写入实体状态

 @Entity public class Simple { private Integer id; private List<Student> students; @Id public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } @OneToMany(targetEntity=Student.class, mappedBy="college", fetch=FetchType.EAGER) public List<Student> getStudents() { return students; } public void setStudents(List<Student> students) { this.students = students; } } 

但是，您不能同时使用基于字段和基于属性的访问。 它会显示像你这样的错误

更多的想法按照这个

Answer 4

 @Access(AccessType.PROPERTY) @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name="userId") public User getUser() { return user; } 

我有同样的问题，我解决了通过添加@Access(AccessType.PROPERTY)

Answer 5

别担心！ 发生此问题是因为注释。 我面临着类似的问题。

这是正确的代码：

 package onetomanymapping; import java.util.List; import javax.persistence.*; @Entity public class College { private int collegeId; private String collegeName; private List<Student> students; @OneToMany(targetEntity = Student.class, mappedBy = "college", cascade = CascadeType.ALL, fetch = FetchType.EAGER) public List<Student> getStudents() { return students; } public void setStudents(List<Student> students) { this.students = students; } @Id @GeneratedValue public int getCollegeId() { return collegeId; } public void setCollegeId(int collegeId) { this.collegeId = collegeId; } public String getCollegeName() { return collegeName; } public void setCollegeName(String collegeName) { this.collegeName = collegeName; } 

}