春天使用Hibernate的createSQLQuery不起作用

Question

employee.java

package pckg;


import java.util.*;
import javax.persistence.Entity;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
@Table( name = "employee")
public class Employee {

public void Employee(int empid,String empName,String empPassword, boolean isPermanent){
    this.empid=empid;
    this.empName=empName;
    this.empPassword=empPassword;
    this.isPermanent=isPermanent;
}

@Id
private int empid;
private String empName;
private String empPassword;
private boolean isPermanent;

@Transient
public String getEmpPassword() {
    return empPassword;
}
public void setEmpPassword(String empPassword) {
    this.empPassword = empPassword;
}

@Basic
public boolean isPermanent() {
    return isPermanent;
}
public void setPermanent(boolean isPermanent) {
    this.isPermanent = isPermanent;
}


@Id
@Column(name = "Empid")
public int getEmpid() {
    return empid;
}
public void setEmpid(int empid) {
    this.empid = empid;
}
public String getEmpName() {
    return empName;
}
public void setEmpName(String empName) {
    this.empName = empName;
}

}

和employeeDaoImpl.java

package pckg.dao;
import java.util.*;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.annotations.NamedQuery;
import org.hibernate.cfg.Configuration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;

import pckg.Employee;
import pckg.dao.*;


@Repository 
public class EmployeeDaoImpl {

@Autowired
private SessionFactory sessionFactory;

public SessionFactory getSessionFactory() {
    return sessionFactory;
}

public void setSessionFactory(SessionFactory sessionFactory) {
    this.sessionFactory = sessionFactory;
}

private Employee employee;
private int empid;

public Employee getEmployee(int empid) {
    return (Employee)getSessionFactory().getCurrentSession().get(Employee.class,  empid);
}


public void add(Employee employee) {
    getSessionFactory().getCurrentSession().save(employee);
}

public void delete(int empid) {
    getSessionFactory().getCurrentSession().delete(getEmployee(empid));
}

public void edit(Employee employee) {
    getSessionFactory().getCurrentSession().update(employee);
}

public int getAllEmployee(){
    String hql = "select count(e) from Employee e";
    ;
    System.out.println("hello");
    Query query = getSessionFactory().openSession().createQuery(hql);
    System.out.println("hello");
    return ((Long) query.uniqueResult()).intValue();
}
}

和employeeServiceImpl.java

package pckg.service;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import pckg.Employee;
import pckg.dao.EmployeeDaoImpl;


@Service
public class EmployeeServiceImpl  {

@Autowired
private EmployeeDaoImpl employeeDao;

@Transactional
public void add(Employee employee) {
    employeeDao.add(employee);
}

@Transactional
public void delete(int empid) {
    employeeDao.delete(empid);

}

@Transactional
public void edit(Employee employee) {
    employeeDao.edit(employee);

}

@Transactional
public Employee getEmployee(int empid) {
    return employeeDao.getEmployee(empid);
}

@Transactional
public int getAllEmployee() {
    return employeeDao.getAllEmployee();
}
public static void main(String arg[]){
ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");
EmployeeDaoImpl dao = (EmployeeDaoImpl)  ctx.getBean("EmployeeDaoImpl",EmployeeDaoImpl.class);
System.out.println(dao.getAllEmployee());
}
}

和spring.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:context="http://www.springframework.org/schema/context"
   xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<bean id="dataSource"  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/employee_record"/>
<property name="username" value="root"/>
<property name="password" value=""/>
<!-- <property name="maxActive" value="5"/>  -->

</bean>



<bean id ="sessionFactory"    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
 <property name="dataSource" ref="dataSource"/>
<property name="packagesToScan" value="pckg"/>
<property name="hibernateProperties">
<props>
    <prop key="dialect">org.hibernate.dialect.MySQLDialect</prop>
</props>
</property>
</bean>
<bean name="EmployeeDaoImpl" class="pckg.dao.EmployeeDaoImpl"></bean>

</beans>

我是这个春天的初学者，冬眠。 在此代码中错误（java.lang.NullPointerException）出现在行中（查询查询= getSession（）。getCurrentSession（）。createSQLQuery（hql）;）我没有在代码中遇到什么问题...并且请告诉我何时会话打开，何时关闭，如何在其中执行搜索和插入查询。

Answer 1

您的查询应该是

String hql = "SELECT count(e.id) FROM Employee e";

假设Employee是您的实体类，其中id是带有@Id批注的变量，这是表中的主键。

无论何时使用Hibernate查询语言，查询都应在实体类和上下文中的变量名而不是表名和列名的上下文中编写