Why Does Hibernate Throw a \'Could Not Determine Type for java.util.List\' Error in One-To-Many Relationships?

Hibernate Error: Could Not Determine Type for java.util.List

Problem:

When attempting to use Hibernate for CRUD operations involving One-To-Many and Many-To-One relationships, the following error is encountered:

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

Entity Classes:

<code class="java">@Entity
public class College {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int collegeId;
    private String collegeName;

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

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int studentId;
    private String studentName;

    @ManyToOne
    @JoinColumn(name = "collegeId")
    private College college;
}</code>

Additional Details:

• The error suggests that Hibernate cannot determine the type of the students field in the College class.
• The use of field access strategy is indicated by the annotations placed directly on the fields.
• The @OneToMany annotation uses the mappedBy attribute, which implies that the relationship is managed by the college field in the Student class.
• The XML configuration file provided sets up the Hibernate session factory and specifies the relevant properties.

Solution:

The issue arises because Hibernate cannot determine the type of the students field due to the use of field access strategy. To resolve this, the JPA annotations should be placed directly above each field instead of the getter properties.

<code class="java">@Entity
public class College {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int collegeId;
    private String collegeName;

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

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