java - 使用 hibernate 的内部联接

我有两个类Task和TaskComponents。 TaskComponents包含一个由Task_ID映射的任务。我试图选择一个加入TaskComponents表的任务。我尝试了许多不同的SQL语句，但是所有这些语句都带有QuerySyntaxException路径。

任务POJO

@Entity
@Table(name = "task")
public class Task implements Serializable {

@Id
@Column(name = "ID")
private int Id;

@Column(name = "Name")
private String name;

@Column(name = "Description")
private String description;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "Site_ID")
private Site site;

public int getId() {
    return Id;
}

public void setId(int Id) {
    this.Id = Id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public Site getSite() {
    return site;
}

public void setSite(Site site) {
    this.site = site;
}


}

TaskComponents POJO

@Entity
@Table(name = "taskcomponents")
public class TaskComponents implements Serializable {

@Id
@Column(name = "ID")
private int Id;

@Column(name = "VersionName")
private String versionName;

@Column(name = "Live", nullable = false)
@Type(type = "org.hibernate.type.NumericBooleanType")
private boolean live;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "Task_ID")
private Task task;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "Group_ID")
private GroupDB group;

public int getId() {
    return Id;
}

public void setId(int Id) {
    this.Id = Id;
}

public String getVersionName() {
    return versionName;
}

public void setVersionName(String versionName) {
    this.versionName = versionName;
}

public boolean isLive() {
    return live;
}

public void setLive(boolean live) {
    this.live = live;
}

public Task getTask() {
    return task;
}

public void setTask(Task task) {
    this.task = task;
}

public GroupDB getGroup() {
    return group;
}

public void setGroup(GroupDB group) {
    this.group = group;
}
}

和我尝试的查询。

Query query = session.createQuery("SELECT t FROM Task t INNER JOIN TaskComponents tc ON t.Id=tc.task.Id");

Query query = session.createQuery("SELECT t FROM Task t INNER JOIN TaskComponents tc ON t=tc.task");

最佳答案

您不应显式地使用ON定义联接，Hibernate将从映射中推断出联接，只需将查询写为

SELECT tc.task FROM TaskComponents tc INNER JOIN tc.task

这是错误消息Path expected for join的后面所指的内容，查询需要从一个实体到另一个实体的属性定义的路径