我试图使用JpaRepository通过其ID从数据库中获取对象并且遇到一些麻烦。它是一个拥有EmbeddedId的实体。
我试图以两种不同的方式获取对象：
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：
时，我得到一个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;
}
}
这里是SowRepository的代码：
public interface SowRepository extends JpaRepository<SowDocument, Serializable> {
SowDocument findById(int i);
}
这里是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);
}
}
我的猜测是我在某种程度上在SowDocument / SowDocumentPK之间存在错误的映射，或者误解了如何使用JpaRepository。
答案 0 :(得分：1)
我猜你使用的是SpringData JPA。如果这是正确的，请查看CrudRepository接口的超级类型JpaRepostory是如何定义的：
public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> {
...
T findOne(ID id);
...
}
你正在扩展这个界面（顺便说一句，你应该发布实现）：
public interface SowRepository extends JpaRepository<SowDocument, Serializable> {
SowDocument findById(int i);
}
findById(int i)方法在JpaRepository类型层次结构中的接口的 none 中定义，这意味着它是您自己的扩展名。
另一方面，您没有ID为int的实体。您实体的ID类型定义为ShowDocumentPK类型，由两个字段组成。
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);
}
自己实施方法findById()（或使用JpaRepository的官方实现类，即SimpleJpaRepository）。
然后你应该创建一个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);
总之：您的ID不是int类型，findById(int)不是您的情况下实施的方式。
希望这能让您了解如何正确实现它。