Java Hibernate:如何使用sql检索预定义对象?
我使用以下sql检索预定义对象Java Hibernate:如何使用sql检索预定义对象?,java,sql,hibernate,Java,Sql,Hibernate,我使用以下sql检索预定义对象 select idpatient, password from Patient where user_name= :username 这是我用来获取患者对象的方法 public Patient getUserNameAndPassword(String username, Session session) { Query query=session.createQuery("select idpatient, password from Pati
select idpatient, password from Patient where user_name= :username
这是我用来获取患者对象的方法
public Patient getUserNameAndPassword(String username, Session session) {
Query query=session.createQuery("select idpatient, password from Patient where user_name= :username");
query.setParameter("username", username);
List list = query.list();
Patient patient=(Patient) list.get(0);
return patient;
}
这是我的Patient对象-Patient.java
public class Patient implements java.io.Serializable {
private Integer idpatient;
private String firstName;
private String lastName;
private String email;
private Date dob;
private String parentEmail;
private String gender;
private String userName;
private String password;
/**
* @return the idpatient
*/
public Integer getIdpatient() {
return idpatient;
}
/**
* @param idpatient the idpatient to set
*/
public void setIdpatient(Integer idpatient) {
this.idpatient = idpatient;
}
/**
* @return the firstName
*/
public String getFirstName() {
return firstName;
}
/**
* @param firstName the firstName to set
*/
public void setFirstName(String firstName) {
this.firstName = firstName;
}
/**
* @return the lastName
*/
public String getLastName() {
return lastName;
}
/**
* @param lastName the lastName to set
*/
public void setLastName(String lastName) {
this.lastName = lastName;
}
/**
* @return the email
*/
public String getEmail() {
return email;
}
/**
* @param email the email to set
*/
public void setEmail(String email) {
this.email = email;
}
/**
* @return the dob
*/
public Date getDob() {
return dob;
}
/**
* @param dob the dob to set
*/
public void setDob(Date dob) {
this.dob = dob;
}
/**
* @return the parentEmail
*/
public String getParentEmail() {
return parentEmail;
}
/**
* @param parentEmail the parentEmail to set
*/
public void setParentEmail(String parentEmail) {
this.parentEmail = parentEmail;
}
/**
* @return the gender
*/
public String getGender() {
return gender;
}
/**
* @param gender the gender to set
*/
public void setGender(String gender) {
this.gender = gender;
}
/**
* @return the userName
*/
public String getUserName() {
return userName;
}
/**
* @param userName the userName to set
*/
public void setUserName(String userName) {
this.userName = userName;
}
/**
* @return the password
*/
public String getPassword() {
return password;
}
/**
* @param password the password to set
*/
public void setPassword(String password) {
this.password = password;
}
}
当我在getUserName和Password方法上方运行时,会生成以下异常
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to beans.Patient
我怎样才能正确地做到这一点?有什么想法吗?试试这个
Query query= session.createQuery("SELECT NEW beans.Patient( idpatient, password) FROM Patient WHERE user_name= :username");
query.setParameter("username", username);
List<Patient> patients = query.list();
Query Query=session.createQuery(“从患者中选择新bean.Patient(idpatient,password),其中user_name=:username”);
query.setParameter(“用户名”,用户名);
List patients=query.List();
这看起来像是一个hibernate实现的构造函数表达式。试试这个
Query query= session.createQuery("SELECT NEW beans.Patient( idpatient, password) FROM Patient WHERE user_name= :username");
query.setParameter("username", username);
List<Patient> patients = query.list();
Query Query=session.createQuery(“从患者中选择新bean.Patient(idpatient,password),其中user_name=:username”);
query.setParameter(“用户名”,用户名);
List patients=query.List();
这看起来像是一个hibernate实现的构造函数表达式。您得到的是java.lang.ClassCastException,因为您正在检索只有两个属性的patient对象,即idpatient,password。但是,Patient类中缺少用于创建此对象的构造函数
Query query=session.createQuery("select idpatient, password from Patient where user_name= :username");
下面的查询检索具有Patient类的两个属性(idpatient,password)的Patient对象
Query query=session.createQuery("select idpatient, password from Patient where user_name= :username");
您需要使用idpatient,password字段在Patient类中创建参数化构造函数
public Patient(Integer idpatient,String password ){
this.idpatient=idpatient;
this.password =password ;
}
现在,您可以使用两个字段检索Patient对象
注意:如果您使用默认构造函数创建对象,还需要创建默认的Patient类构造函数以及参数化构造函数。您得到的是java.lang.ClassCastException,因为您检索的Patient对象只有两个属性,即idpatient,password。但是,Patient类中缺少用于创建此对象的构造函数
Query query=session.createQuery("select idpatient, password from Patient where user_name= :username");
下面的查询检索具有Patient类的两个属性(idpatient,password)的Patient对象
Query query=session.createQuery("select idpatient, password from Patient where user_name= :username");
您需要使用idpatient,password字段在Patient类中创建参数化构造函数
public Patient(Integer idpatient,String password ){
this.idpatient=idpatient;
this.password =password ;
}
现在,您可以使用两个字段检索Patient对象
注意:如果使用默认构造函数创建对象,则还需要创建默认的患者类构造函数以及参数化的构造函数。如果患者类是非托管实体,则可以使用
session.createSQLQuery("SELECT idpatient, password FROM Patient WHERE username=:user_name")
.setParameter("user_name",username)
.setResultTransformer(Transformers.aliasToBean(Patient.class))
详细文件如下:
对于托管实体,可以在Select查询中使用NEW关键字
List<Patient> patients = session.createQuery("SELECT NEW beans.Patient( idpatient, password) FROM Patient WHERE username='" + username + "'").list();
List patients=session.createQuery(“从患者中选择新bean.Patient(idpatient,密码),其中username='”+username+“”)”).List();
请注意,您必须首先定义构造函数
此处的详细文档:如果患者类是非托管实体,则可以使用
session.createSQLQuery("SELECT idpatient, password FROM Patient WHERE username=:user_name")
.setParameter("user_name",username)
.setResultTransformer(Transformers.aliasToBean(Patient.class))
详细文件如下:
对于托管实体,可以在Select查询中使用NEW关键字
List<Patient> patients = session.createQuery("SELECT NEW beans.Patient( idpatient, password) FROM Patient WHERE username='" + username + "'").list();
List patients=session.createQuery(“从患者中选择新bean.Patient(idpatient,密码),其中username='”+username+“”)”).List();
请注意,您必须首先定义构造函数
此处的详细文档:您还可以使用
Hibernate标准来解决此问题
public Patient getUserNameAndPassword(String username, Session session) {
Criteria criteria = session.createCriteria(Patient.class);
criteria.add(Restrictions.eq("username", username));
ProjectionList projectionList = Projections.projectionList();
projectionList.add(Projections.property("idpatient"));
projectionList.add(Projections.property("password"));
criteria.setProjection(projectionList);
criteria.setResultTransformer(new AliasToBeanResultTransformer(Patient.class));
if (!criteria.list().isEmpty()) {
Patient patient = (Patient) list.get(0);
return patient;
} else {
return null;
}
}
您还可以使用Hibernate条件
来解决此问题
public Patient getUserNameAndPassword(String username, Session session) {
Criteria criteria = session.createCriteria(Patient.class);
criteria.add(Restrictions.eq("username", username));
ProjectionList projectionList = Projections.projectionList();
projectionList.add(Projections.property("idpatient"));
projectionList.add(Projections.property("password"));
criteria.setProjection(projectionList);
criteria.setResultTransformer(new AliasToBeanResultTransformer(Patient.class));
if (!criteria.list().isEmpty()) {
Patient patient = (Patient) list.get(0);
return patient;
} else {
return null;
}
}