Java Hibernate：投影多对多关系的特定列

我需要一些关于Hibernate投影和标准API的帮助。当我在两个实体（具有双向多对多映射）中包含字段时，我只从根实体获得结果

我定义了一名

员工

@Entity
@Table(name="EMPLOYEE")
public class Employee {

    @Id
    @Column(name="EMPLOYEE_ID")
    @GeneratedValue
    private Long employeeId;

    @Column(name="FIRSTNAME")
    private String firstname;

    @Column(name="LASTNAME")
    private String lastname;

    @ManyToMany(fetch = FetchType.EAGER , cascade = {CascadeType.ALL})
    @JoinTable(name="EMPLOYEE_MEETING",
            joinColumns={@JoinColumn(name="EMPLOYEE_ID")},
            inverseJoinColumns={@JoinColumn(name="MEETING_ID")})
    private Set<Meeting> meetings = new HashSet<Meeting>();

    public Employee() {
    }

    public Employee(String firstname, String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }
...

他们的

schema

createtableemployee(
员工id序列号，
firstname VARCHAR（50）NULL默认为NULL，
lastname VARCHAR（50）NULL默认为NULL，
主键（员工id）
);
创建表会议(
会议编号：，
subject VARCHAR（50）不为空，
会议日期不为空，
主键（会议id）
);
创建员工会议表(
员工id BIGINT不为空，
会议id BIGINT不为空，
主键（员工id、会议id），
约束FK_员工外键（员工id）引用员工（员工id），
约束FK会议外键（会议id）引用会议（会议id）
);

我想得到一份具有会议属性的员工的扁平列表

没有where子句

Meeting meeting1 = new Meeting("Quaterly Status meeting");
Meeting meeting2 = new Meeting("Weekly Status meeting");
Meeting meeting3 = new Meeting("daily Status meeting");

Employee employee1 = new Employee("Gingerly", "Brint");
Employee employee2 = new Employee("Mary", "Kate");

employee1.getMeetings().add(meeting1);
employee1.getMeetings().add(meeting2);
employee2.getMeetings().add(meeting1);
employee2.getMeetings().add(meeting3);

meeting1.getEmployees().add(employee1);
meeting1.getEmployees().add(employee2);
meeting2.getEmployees().add(employee1);
meeting3.getEmployees().add(employee2);

session.save(employee1);
session.save(employee2);

Criteria criteria = session.createCriteria(Employee.class, "e");
criteria.setFetchMode("e.meetings", FetchMode.JOIN);
criteria = criteria.createAlias("e.meetings", "m", JoinType.LEFT_OUTER_JOIN);
final ProjectionList projections = Projections.projectionList()
        .add(Projections.property("e.firstname"))
        .add(Projections.property("m.subject"))
        ;
criteria.setProjection(projections);
final List<Object> list = criteria.list();

当我指定投影时，我只得到Employee表的列的结果。下面的查询示例

选择
此名为y0，m1。主题为y1_
从…起
雇员本_
左外连接
员工会议3在本次会议上。员工ID=会议3。员工ID
左外连接
在会议3上召开m1会议。会议ID=m1会议ID；

即使SQL查询包含关于主题的投影，我也没有得到这样的结果

您需要完整的源代码

任何帮助都将不胜感激

谢谢

Meeting meeting1 = new Meeting("Quaterly Status meeting");
Meeting meeting2 = new Meeting("Weekly Status meeting");
Meeting meeting3 = new Meeting("daily Status meeting");

Employee employee1 = new Employee("Gingerly", "Brint");
Employee employee2 = new Employee("Mary", "Kate");

employee1.getMeetings().add(meeting1);
employee1.getMeetings().add(meeting2);
employee2.getMeetings().add(meeting1);
employee2.getMeetings().add(meeting3);

meeting1.getEmployees().add(employee1);
meeting1.getEmployees().add(employee2);
meeting2.getEmployees().add(employee1);
meeting3.getEmployees().add(employee2);

session.save(employee1);
session.save(employee2);

Criteria criteria = session.createCriteria(Employee.class, "e");
criteria.setFetchMode("e.meetings", FetchMode.JOIN);
criteria = criteria.createAlias("e.meetings", "m", JoinType.LEFT_OUTER_JOIN);
final ProjectionList projections = Projections.projectionList()
        .add(Projections.property("e.firstname"))
        .add(Projections.property("m.subject"))
        ;
criteria.setProjection(projections);
final List<Object> list = criteria.list();