无法使用条件获取列表
Unable to fetch list using criteria
public static List<Image> getList(int userId) {
Session session = HibernateUtil.openSession();
Transaction tx = null;
List<Image> results = null;
try {
tx = session.beginTransaction();
Criteria crit = session.createCriteria(Image.class);
crit.add(Restrictions.eq("userID",new Integer(userId)));
results = crit.list();
tx.commit();
}
catch (HibernateException e) {
System.out.println("Problem in retrieving data from database");
if (tx!=null) tx.rollback();
e.printStackTrace();
} finally {
session.close();
}
return results;
}
图片class
@Entity
@Table(name = "image")
public class Image {
@Id
@Column(name = "userId")
int userID;
@Id
@Column(name = "name")
String name;
@Column(name = "size")
double size;
@Column(name = "preview")
byte[] preview;
public int getUserID() {
return userID;
}
public void setUserID(int userID) {
this.userID = userID;
}
public String getName() {
return name;
}
public Image() {
super();
// TODO Auto-generated constructor stub
}
public Image(int userID, String name, double size, byte[] preview) {
super();
this.userID = userID;
this.name = name;
this.size = size;
this.preview = preview;
}
public void setName(String name) {
this.name = name;
}
public double getSize() {
return size;
}
public void setSize(double size) {
this.size = size;
}
public byte[] getPreview() {
return preview;
}
public void setPreview(byte[] preview) {
this.preview = preview;
}
}
这是我的数据库
图像是一个具有以下属性的实体:用户 ID、名称、大小、预览。
userId + 图片名称为复合主键
我已经获取了所有 userId = 1 的行
当我遍历获得的列表时。我得到 AAdhar(这是数据库中的第一个条目)显示 6 次,而不是每次都显示不同的名称。
我无法找出问题所在。
解决方案:编辑正确的图像Class代码
如前所述创建 ImagePK class
@Entity
@Table(name = "image")
@IdClass(ImagePK.class)
public class Image {
@Id
@Column(name = "userId")
int userID;
@Id
@Column(name = "name")
String name;
@Column(name = "size")
double size;
@Column(name = "preview")
byte[] preview;
……}
我认为您创建复合主键的方式不正确。您可以在休眠中创建复合主键,如下所示 -
public class ImagePK implements Serializable {
protected Integer userID;
protected String name;
public ImagePK() {}
public ImagePK(Integer userID, String name) {
this.userID = userID;
this.name = name;
}
// equals, hashCode
}
在您的 Image
实体中使用 @IdClass
注释 class
@Entity
@Table(name = "image")
@IdClass(ImagePK.class)
public class Image {
}
public static List<Image> getList(int userId) {
Session session = HibernateUtil.openSession();
Transaction tx = null;
List<Image> results = null;
try {
tx = session.beginTransaction();
Criteria crit = session.createCriteria(Image.class);
crit.add(Restrictions.eq("userID",new Integer(userId)));
results = crit.list();
tx.commit();
}
catch (HibernateException e) {
System.out.println("Problem in retrieving data from database");
if (tx!=null) tx.rollback();
e.printStackTrace();
} finally {
session.close();
}
return results;
}
图片class
@Entity
@Table(name = "image")
public class Image {
@Id
@Column(name = "userId")
int userID;
@Id
@Column(name = "name")
String name;
@Column(name = "size")
double size;
@Column(name = "preview")
byte[] preview;
public int getUserID() {
return userID;
}
public void setUserID(int userID) {
this.userID = userID;
}
public String getName() {
return name;
}
public Image() {
super();
// TODO Auto-generated constructor stub
}
public Image(int userID, String name, double size, byte[] preview) {
super();
this.userID = userID;
this.name = name;
this.size = size;
this.preview = preview;
}
public void setName(String name) {
this.name = name;
}
public double getSize() {
return size;
}
public void setSize(double size) {
this.size = size;
}
public byte[] getPreview() {
return preview;
}
public void setPreview(byte[] preview) {
this.preview = preview;
}
}
这是我的数据库
图像是一个具有以下属性的实体:用户 ID、名称、大小、预览。
userId + 图片名称为复合主键 我已经获取了所有 userId = 1 的行 当我遍历获得的列表时。我得到 AAdhar(这是数据库中的第一个条目)显示 6 次,而不是每次都显示不同的名称。 我无法找出问题所在。
解决方案:编辑正确的图像Class代码 如前所述创建 ImagePK class
@Entity
@Table(name = "image")
@IdClass(ImagePK.class)
public class Image {
@Id
@Column(name = "userId")
int userID;
@Id
@Column(name = "name")
String name;
@Column(name = "size")
double size;
@Column(name = "preview")
byte[] preview;
……}
我认为您创建复合主键的方式不正确。您可以在休眠中创建复合主键,如下所示 -
public class ImagePK implements Serializable {
protected Integer userID;
protected String name;
public ImagePK() {}
public ImagePK(Integer userID, String name) {
this.userID = userID;
this.name = name;
}
// equals, hashCode
}
在您的 Image
实体中使用 @IdClass
注释 class
@Entity
@Table(name = "image")
@IdClass(ImagePK.class)
public class Image {
}