JpaRepository 找不到具有 EmbeddedID 的对象

Question

我正在尝试使用 JpaRepository 通过其 ID 从数据库中获取对象并且遇到了一些问题。它是一个带有 EmbeddedId 的实体。

我正在尝试以两种不同的方式获取对象：

1. 使用命名查询 (findById)
2. 使用SowServiceImpl中的方法

尝试使用命名方法获取它时遇到的异常是：

@Override
public SowDocument getById(int i) {
    SowDocument wow = sowRepository.findById(i);
    if (wow == null) {
        System.out.println("NULLLLLLLLLLLLLLLL");
        return null;
    } else {
        return wow;
    }
}

HTTP Status 500 - Request processing failed; nested exception is org.springframework.dao.InvalidDataAccessApiUsageException: Parameter with that position [1] did not exist; nested exception is java.lang.IllegalArgumentException: Parameter with that position [1] did not exist
...
...
at com.sun.proxy.$Proxy791.findById(Unknown Source)
at com.**.pricing.web.services.impl.SowServiceImpl.getById(SowServiceImpl.java:61)
at com.**.pricing.web.controllers.UserController.getSowById(UserController.java:99)

当我尝试使用 EmbeddedId 获取 NullPointerException：

@Override
public SowDocument getById(int i) {
    SowDocumentPK peek = new SowDocumentPK();
    peek.setId(i);

    SowDocument wow = sowRepository.findOne(peek);
    if (wow == null) {
        System.out.println("NULLLLLLLLLLLLLLLL");
        return null;
    } else {
        return wow;
    }
}

这是对象：

@Entity
@Table(name = "SowDocument", uniqueConstraints = {
    @UniqueConstraint(columnNames = {"id"})})
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "SowDocument.findAll", query = "SELECT s FROM SowDocument s"),
    @NamedQuery(name = "SowDocument.findById", query = "SELECT s FROM SowDocument s WHERE s.sowDocumentPK.id = :id"),
    @NamedQuery(name = "SowDocument.findByClientName", query = "SELECT s FROM SowDocument s WHERE s.clientName = :clientName"),
    @NamedQuery(name = "SowDocument.findByCreationDate", query = "SELECT s FROM SowDocument s WHERE s.creationDate = :creationDate"),
    @NamedQuery(name = "SowDocument.findByDocumentCreator", query = "SELECT s FROM SowDocument s WHERE s.sowDocumentPK.documentCreator = :documentCreator"),
    @NamedQuery(name = "SowDocument.findBySowType", query = "SELECT s FROM SowDocument s WHERE s.sowType = :sowType")})
public class SowDocument implements Serializable {

    private static final long serialVersionUID = 1L;
    @EmbeddedId
    protected SowDocumentPK sowDocumentPK;
    @Size(max = 50)
    @Column(name = "clientName", length = 50)
    private String clientName;
    @Size(max = 45)
    @Column(name = "creationDate", length = 45)
    private String creationDate;
    @Lob
    @Column(name = "data")
    private byte[] data;
    @Size(max = 45)
    @Column(name = "sowType", length = 45)
    private String sowType;
    @JoinColumn(name = "documentCreator", referencedColumnName = "id", nullable = false, insertable = false, updatable = false)
    @ManyToOne(optional = false)
    private User user;

    public SowDocument() {
    }

    public SowDocument(SowDocumentPK sowDocumentPK) {
        this.sowDocumentPK = sowDocumentPK;
    }

    public SowDocument(int id, int documentCreator) {
        this.sowDocumentPK = new SowDocumentPK(id, documentCreator);
    }

    public SowDocumentPK getSowDocumentPK() {
        return sowDocumentPK;
    }

    public void setSowDocumentPK(SowDocumentPK sowDocumentPK) {
        this.sowDocumentPK = sowDocumentPK;
    }

    public String getClientName() {
        return clientName;
    }

    public void setClientName(String clientName) {
        this.clientName = clientName;
    }

    public String getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(String creationDate) {
        this.creationDate = creationDate;
    }

    public byte[] getData() {
        return data;
    }

    public void setData(byte[] data) {
        this.data = data;
    }

    public String getSowType() {
        return sowType;
    }

    public void setSowType(String sowType) {
        this.sowType = sowType;
    }

    public User getUser() {
        return user;
    }

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

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (sowDocumentPK != null ? sowDocumentPK.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof SowDocument)) {
            return false;
        }
        SowDocument other = (SowDocument) object;
        if ((this.sowDocumentPK == null && other.sowDocumentPK != null) || (this.sowDocumentPK != null && !this.sowDocumentPK.equals(other.sowDocumentPK))) {
            return false;
        }
        return true;
    }


}

这是它的嵌入式 ID：

@Embeddable
public class SowDocumentPK implements Serializable {

    @Basic(optional = false)
    @Column(name = "id", nullable = false)
    private int id;
    @Basic(optional = false)
    @NotNull
    @Column(name = "documentCreator", nullable = false)
    private int documentCreator;

    public SowDocumentPK() {
    }

    public SowDocumentPK(int id, int documentCreator) {
        this.id = id;
        this.documentCreator = documentCreator;
    }

    public int getId() {
        return id;
    }

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

    public int getDocumentCreator() {
        return documentCreator;
    }

    public void setDocumentCreator(int documentCreator) {
        this.documentCreator = documentCreator;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (int) id;
        hash += (int) documentCreator;
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof SowDocumentPK)) {
            return false;
        }
        SowDocumentPK other = (SowDocumentPK) object;
        if (this.id != other.id) {
            return false;
        }
        return this.documentCreator == other.documentCreator;
    }


}

这是 SowRepository 的代码：

public interface SowRepository extends JpaRepository<SowDocument, Serializable> {

    SowDocument findById(int i);

}

这是 SowService 的代码：

@Service
public class SowServiceImpl implements SowService {

    @Autowired
    private SowRepository sowRepository;

    @Override
    public void save(SowDocument sow) {
        sowRepository.save(sow);
    }

    @Override
    public Collection<SowDocument> getAll() {
        return sowRepository.findAll();
    }

    @Override
    public SowDocument getById(int i) {
        SowDocumentPK peek = new SowDocumentPK();
        peek.setId(i);
        return sowRepository.findOne(i);
    }


}

我的猜测是我在 SowDocument/SowDocumentPK 之间的映射有误，或者我误解了如何使用 JpaRepository。

Answer 1

我猜你正在使用 SpringData JPA。如果这是正确的，看看CrudRepository是JpaRepostory接口的超类型是如何定义的：

public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> {
     ...
     T findOne(ID id);
     ...
}

你正在扩展这个接口（顺便说一句，你也应该发布实现）：

public interface SowRepository extends JpaRepository<SowDocument, Serializable> {
    SowDocument findById(int i); 
}

findById(int i) 方法在JpaRepository 类型层次结构中的none 接口中定义，这意味着它是您自己的扩展。

另一方面，您没有 ID 类型为 int 的实体。您的实体 ID 的类型定义为由两个字段组成的 ShowDocumentPK 类型。

因此您的存储库定义应如下所示：

public interface SowRepository extends JpaRepository<SowDocument, ShowDocumentPK> {
     SowDocument findById(ShowDocumentPK id); 
}

并自行实现findById()方法（或使用JpaRepository的官方实现类，即SimpleJpaRepository）。

然后您应该创建一个ShowDocumentPK 的实例并将其传递给findById() 方法，例如：

SowDocumentPK peek = new SowDocumentPK();
peek.setId(1);
peek.setDocumentCreator(100);

SowDocument wow = sowRepository.findById(peek);

结论：您的 ID 不是int 类型，findById(int) 不是您的情况下的实现方式。

希望这能让您了解如何正确实现它。