Exam 1z0-898 topic 1 question 26 discussion

Actual exam question from Oracle's 1z0-898

Question #: 26
Topic #: 1

The department entity has a unidirectional OneToMany relationship to the employee entity. The developer wants to model this relationship as a java.util.map such that the key of map is true employee name. The primary key of the Employees entity is empId, an integer.
Which of the following is correct?

A. @OneToMany (targetEntity = Employee.class) @MapKeyClass (string.class) map employees;
B. @OneToMany @mapKey (name = "name") map < integer, Employee> Employees;
C. @OneToMany @MapKeyJoinColumn (name = "name") map <String, Employee> employees;
D. @OneToMany @mapsId (name = "name") map <String, Employee> employees;

Show Suggested Answer

Suggested Answer: B 🗳️
Annotation Type MapKey specifies the map key for associations of type java.util.Map when the map key is itself the primary key or a persistent field or property of the entity that is the value of the map.
Example:
@Entity
public class Department {
...
@OneToMany(mappedBy="department")
@MapKey(name="name")
public Map<String, Employee> getEmployees() {... }
...
}
@Entity
public class Employee {
@Id public Integer getEmpId() { ... }
...
@ManyToOne
@JoinColumn(name="dept_id")
public Department getDepartment() { ... }
...
}

Reference: javax.persistence, Annotation Type MapKey

by [deleted] at April 4, 2025, 2:49 p.m.

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