优化Hibernate多对多关联：使用自定义连接实体避免额外中间表

@Embeddable
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class AlarmListId implements Serializable {
    private Integer alarmId;
    private String listId;
}

import jakarta.persistence.Embeddable;
import jakarta.persistence.ManyToOne;
import static jakarta.persistence.FetchType.LAZY; // 确保导入FetchType
import lombok.*;

import java.io.Serializable;

@Embeddable
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class AlarmListId implements Serializable {

    // 明确声明对Alarm实体的引用
    @ManyToOne(optional = false, fetch = LAZY)
    private Alarm alarm;

    // 明确声明对AlarmList实体的引用
    @ManyToOne(optional = false, fetch = LAZY)
    private AlarmList list; // 注意这里命名为'list'以避免与Java关键字冲突

    // ！！！重要：对于复合主键，必须正确实现hashCode()和equals()方法
    // Lombok的@EqualsAndHashCode通常足够，但请务必验证其语义是否符合业务需求
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        AlarmListId that = (AlarmListId) o;
        return alarm.equals(that.alarm) && list.equals(that.list);
    }

    @Override
    public int hashCode() {
        return java.util.Objects.hash(alarm, list);
    }
}

import jakarta.persistence.*;
import lombok.*;
import java.util.List;

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "alarm")
public class Alarm {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Integer alarmId;

    @Column(unique = true)
    String name;
    // ... 其他属性 ...

    // 指明此关系由ListAlarmJoinTable中的id.alarm字段映射
    @OneToMany(orphanRemoval = true, cascade = {CascadeType.REMOVE, CascadeType.MERGE}, mappedBy = "id.alarm")
    private List<ListAlarmJoinTable> alarmLists;

    // ... toString() 方法 ...
}

import jakarta.persistence.*;
import lombok.*;
import java.util.List;

@Entity
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@ToString
@Table(name = "alarm_list")
public class AlarmList {

    @Id
    private String name;

    // ... ListSequenceJoinTable 关联 (与本问题无关，保持不变) ...
    @OneToMany(orphanRemoval = true, cascade = {CascadeType.REMOVE, CascadeType.MERGE})
    private List<ListSequenceJoinTable> alarmSequences;

    // 指明此关系由ListAlarmJoinTable中的id.list字段映射
    @OneToMany(orphanRemoval = true, cascade = {CascadeType.REMOVE, CascadeType.MERGE}, mappedBy = "id.list")
    private List<ListAlarmJoinTable> alarms;

}

import jakarta.persistence.*;
import lombok.*;

@Entity
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@Table(name = "list_alarms_join_table")
public class ListAlarmJoinTable {

    @EmbeddedId
    private AlarmListId id; // 使用修改后的AlarmListId
    private int position;

}