通过一对一关联连接spring data jpa表

Question

我试图通过使用spring data JPA一对一关联来连接两个表并显示其结果。下面我要添加我的模型和存储库类,我的第一个模型类用户是,

@Entity
@Table(name = "users")

public class Users implements Serializable{

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;

@Column(name = "username")
public String username;

@Column(name = "password")
public String password;

@Column(name = "privid")
public Integer privid;

@OneToOne()
@JoinColumn(name="join_privillage")
private Privillages priviJoin;


public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public Integer getPrivid() {
    return privid;
}

public void setPrivid(Integer privid) {
    this.privid = privid;
}

public Privillages getPriviJoin() {
    return priviJoin;
}

public void setPriviJoin(Privillages priviJoin) {
    this.priviJoin = priviJoin;
}



protected Users() {
}

public Users(String username, String password, Integer privid) {
    this.username = username;
    this.password = password;
    this.privid = privid;
}
@Override
public String toString() {
    return String.format("Users[id=%d, username='%s', password='%s']", id, 
username, password);
}
}

而我需要加入的下一个模型类是：

@Entity
@Table(name = "privillages")
public class Privillages implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public  Integer id;

@Column(name = "privid")
public Integer privid;

@Column(name = "privi_name")
public String privi_name;

@OneToOne(fetch=FetchType.LAZY, mappedBy="priviJoin")
public Users user;


public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getPrivid() {
    return privid;
}

public void setPrivid(Integer privid) {
    this.privid = privid;
}

public String getPrivi_name() {
    return privi_name;
}

public void setPrivi_name(String privi_name) {
    this.privi_name = privi_name;
}

public Users getUser() {
    return user;
}

public void setUser(Users user) {
    this.user = user;
}

public Privillages() {
}

public Privillages(Integer privid, String privi_name ) {
    this.privid = privid;
    this.privi_name = privi_name;

}
}

public interface UsersRepository extends CrudRepository<Users, Integer> {

@Query("SELECT u.username FROM Users u inner join p.privi_name FROM 
Privillages p")
List<Users> findByUsername();
}

“意外标记：来自第1行附近的第74列[SELECT u.username FROM com.central.model.users u inner join p.privi_name FROM com.central.model.privillages p]”。

而且

“对方法public abstract java.util.List com.central.Repository.UsersRepository.FindByUserName（）！的查询验证失败。”

Answer 1

• 您在查询中使用了一个投影，但期望得到一个整个实体。
• 而且您的连接方式错误，使用了数据库列名而不是映射的字段名。
• 您正在使用两次FROM..

如果您希望获得整个实体,并且用户已获得特权,请尝试：

@Query("SELECT u FROM Users u inner join fetch u.priviJoin")

更新

@Query("SELECT u.username,p.privi_name FROM Users u inner join u.priviJoin p")
List<Object[]> findByUsername();

在这种情况下，您也不需要fetch。