在春季使用休眠不起作用创建SQLQuery

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;
}
}

和员工道英普尔.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();
}
}

和员工服务.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>

我在这个代码错误（java.lang.NullPointerException）中出现在行（查询查询= getSession（）.getCurrentSession（）.createSQLQuery（hql）;)我没有发现代码中有什么问题...并且请告诉我会话何时打开和何时关闭，以及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注释的变量，这是表中的主键。

每当使用Hibernate查询语言时，查询应该是 在实体类和变量名称的上下文中编写 类而不是表名和列名