Hibernate 休眠加载选定列
我有一张桌子: 具有以下列的用户:{id,name,address} 我想使用hibernate仅从该表中选择id。但我不想将HQL用于本机SQL查询。我想使用Criteria对象。有办法吗 谢谢Hibernate 休眠加载选定列,hibernate,Hibernate,我有一张桌子: 具有以下列的用户:{id,name,address} 我想使用hibernate仅从该表中选择id。但我不想将HQL用于本机SQL查询。我想使用Criteria对象。有办法吗 谢谢 肖恩·阮是的。您必须使用投影: Criteria c = session.createCriteria(User.class, "u"); c.setProjection(Projections.property("u.id")); return c.list(); // the list of al
肖恩·阮是的。您必须使用投影:
Criteria c = session.createCriteria(User.class, "u");
c.setProjection(Projections.property("u.id"));
return c.list(); // the list of all the user IDs
但是HQL对于这种查询更具可读性和直观性。条件对于动态生成的查询或在多个查询中重用部分查询非常有用:
return session.createQuery("select u.id from User u").list();
对。您必须使用投影:
Criteria c = session.createCriteria(User.class, "u");
c.setProjection(Projections.property("u.id"));
return c.list(); // the list of all the user IDs
但是HQL对于这种查询更具可读性和直观性。条件对于动态生成的查询或在多个查询中重用部分查询非常有用:
return session.createQuery("select u.id from User u").list();
可以将ResultTransformer应用于本机SQL查询,从而允许它返回非托管实体 作为一个例子,假设我们有如下的entdemetail实体
@Entity
@Table(name = "demodetail")
public class EntDemodetail {
Integer id;
String description;
Integer demoid;
EntDemo demo;
@Id
@GeneratedValue
@Column(name = "id_detail", unique = true, nullable = false)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name="detaildesc")
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Column(name="demoid")
public Integer getDemoid() {
return demoid;
}
public void setDemoid(Integer demoid) {
this.demoid = demoid;
}
@OneToOne()
@JoinColumn(name="demoid")
public EntDemo getDemo() {
return demo;
}
public void setDemo(EntDemo demo) {
this.demo = demo;
}
}
/* Method to READ some columns of an entity with native sql */
public void nativesqlwithresulttransformer( ){
Session session = HibernateUtilMysql.getSessionFactory().openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
String sql = "SELECT id_detail as id FROM demodetail d"; //
SQLQuery query = session.createSQLQuery(sql);
List results = query.setResultTransformer(Transformers.aliasToBean(EntDemodetail.class)).list();
for (Iterator iterator =
results.iterator(); iterator.hasNext();){
EntDemodetail entdemodetail = (EntDemodetail) iterator.next();
System.out.print("Id: " + entdemodetail.getId());
//System.out.print("Desc: " + entdemodetail.getDescription());
}
tx.commit();
}catch (HibernateException e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
}
您可以阅读此实体的某些列,如下所示
@Entity
@Table(name = "demodetail")
public class EntDemodetail {
Integer id;
String description;
Integer demoid;
EntDemo demo;
@Id
@GeneratedValue
@Column(name = "id_detail", unique = true, nullable = false)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name="detaildesc")
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Column(name="demoid")
public Integer getDemoid() {
return demoid;
}
public void setDemoid(Integer demoid) {
this.demoid = demoid;
}
@OneToOne()
@JoinColumn(name="demoid")
public EntDemo getDemo() {
return demo;
}
public void setDemo(EntDemo demo) {
this.demo = demo;
}
}
/* Method to READ some columns of an entity with native sql */
public void nativesqlwithresulttransformer( ){
Session session = HibernateUtilMysql.getSessionFactory().openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
String sql = "SELECT id_detail as id FROM demodetail d"; //
SQLQuery query = session.createSQLQuery(sql);
List results = query.setResultTransformer(Transformers.aliasToBean(EntDemodetail.class)).list();
for (Iterator iterator =
results.iterator(); iterator.hasNext();){
EntDemodetail entdemodetail = (EntDemodetail) iterator.next();
System.out.print("Id: " + entdemodetail.getId());
//System.out.print("Desc: " + entdemodetail.getDescription());
}
tx.commit();
}catch (HibernateException e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
}
有关更多信息,请参见可以将ResultTransformer应用于本机SQL查询,从而允许它返回非托管实体 作为一个例子,假设我们有如下的entdemetail实体
@Entity
@Table(name = "demodetail")
public class EntDemodetail {
Integer id;
String description;
Integer demoid;
EntDemo demo;
@Id
@GeneratedValue
@Column(name = "id_detail", unique = true, nullable = false)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name="detaildesc")
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Column(name="demoid")
public Integer getDemoid() {
return demoid;
}
public void setDemoid(Integer demoid) {
this.demoid = demoid;
}
@OneToOne()
@JoinColumn(name="demoid")
public EntDemo getDemo() {
return demo;
}
public void setDemo(EntDemo demo) {
this.demo = demo;
}
}
/* Method to READ some columns of an entity with native sql */
public void nativesqlwithresulttransformer( ){
Session session = HibernateUtilMysql.getSessionFactory().openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
String sql = "SELECT id_detail as id FROM demodetail d"; //
SQLQuery query = session.createSQLQuery(sql);
List results = query.setResultTransformer(Transformers.aliasToBean(EntDemodetail.class)).list();
for (Iterator iterator =
results.iterator(); iterator.hasNext();){
EntDemodetail entdemodetail = (EntDemodetail) iterator.next();
System.out.print("Id: " + entdemodetail.getId());
//System.out.print("Desc: " + entdemodetail.getDescription());
}
tx.commit();
}catch (HibernateException e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
}
您可以阅读此实体的某些列,如下所示
@Entity
@Table(name = "demodetail")
public class EntDemodetail {
Integer id;
String description;
Integer demoid;
EntDemo demo;
@Id
@GeneratedValue
@Column(name = "id_detail", unique = true, nullable = false)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name="detaildesc")
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Column(name="demoid")
public Integer getDemoid() {
return demoid;
}
public void setDemoid(Integer demoid) {
this.demoid = demoid;
}
@OneToOne()
@JoinColumn(name="demoid")
public EntDemo getDemo() {
return demo;
}
public void setDemo(EntDemo demo) {
this.demo = demo;
}
}
/* Method to READ some columns of an entity with native sql */
public void nativesqlwithresulttransformer( ){
Session session = HibernateUtilMysql.getSessionFactory().openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
String sql = "SELECT id_detail as id FROM demodetail d"; //
SQLQuery query = session.createSQLQuery(sql);
List results = query.setResultTransformer(Transformers.aliasToBean(EntDemodetail.class)).list();
for (Iterator iterator =
results.iterator(); iterator.hasNext();){
EntDemodetail entdemodetail = (EntDemodetail) iterator.next();
System.out.print("Id: " + entdemodetail.getId());
//System.out.print("Desc: " + entdemodetail.getDescription());
}
tx.commit();
}catch (HibernateException e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
}
有关更多信息,请参见,或者使用c.setProjection(Projections.id());或者使用c.setProjection(Projections.id());