我再次需要你的帮助，我正在尝试在我的独立java应用程序中集成Hibernate + Spring，但是数据库操作不起作用，但是我注入了通过调试验证的entitymanager，所以我不确定缺少什么我的代码/配置，我通过谷歌搜索做了一些研究，但没有找到解决我的问题的东西。所以我发布了我的代码/配置，以便有人可以帮助我解决这个问题。
实体类：
package com.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "employee")
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "EMP_ID")
private Integer empoyeeId;
@Column(name = "EMP_NAME")
private String employeeName;
public Integer getEmpoyeeId() {
return this.empoyeeId;
}
public void setEmpoyeeId(Integer empoyeeId) {
this.empoyeeId = empoyeeId;
}
public String getEmployeeName() {
return this.employeeName;
}
public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}
}
dao类
package com.dao.impl;
import javax.persistence.EntityManager;
import com.dao.IEmployeeDao;
import com.entity.Employee;
public class EmployeeDao implements IEmployeeDao {
private static final Logger LOGGER =
LogManager.getLogger(EmployeeDao.class);
@PersistenceContext(unitName = "testPU")
private EntityManager em;
@Override
public Employee create(Employee aEmployee) {
return this.em.merge(aEmployee);
}
@Override
public Employee fetchEmployeeById(Integer aEmployeeId) {
return this.em.find(Employee.class, aEmployeeId);
}
}
主要班级：
package com.client;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.dao.IEmployeeDao;
import com.entity.Employee;
public class Client {
private static final Logger LOGGER = LogManager.getLogger(Client.class);
public static void main(String[] args) throws BeansException,
Exception {
ApplicationContext applicationContext = new
ClassPathXmlApplicationContext("applicationcontext.xml");
LOGGER.info("client invoked");
IEmployeeDao employeeDao =
(IEmployeeDao)applicationContext.getBean("employeeDao");
Employee employee = new Employee();
employee.setEmployeeName("Suraj Kumar");
employee = employeeDao.create(employee);
employee =
employeeDao.fetchEmployeeById(employee.getEmpoyeeId());
//getting null pointer here as employee is null
// EntityManagerFactory emf =
Persistence.createEntityManagerFactory("testPU");
// EntityManager em = emf.createEntityManager();
// em.getTransaction().begin();
// EmployeeDao employeeDao = new EmployeeDao();
// employeeDao.setEm(em);
// Employee employee = new Employee();
// employee.setEmployeeName("Suraj Kumar");
// employee = employeeDao.create(employee);
// employee =
employeeDao.fetchEmployeeById(employee.getEmpoyeeId());
// em.getTransaction().commit();
// em.close();
// emf.close();
}
}
使用上面的客户端代码当尝试通过id获取employee时，我得到空指针异常，因为对create的调用返回的员工返回null，断言记录没有持久化。
然而，当我通过评论上面的未注释代码关闭spring并取消注释现在注释的那些，即当我只使用没有spring的hibernate时，一切正常。我在下面提供了配置文件。
的applicationContext.xml：
<?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:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd ">
<import resource="aspects.xml"/>
<bean class="org.springframework.orm.jpa.support.
PersistenceAnnotationBeanPostProcessor"/>
<bean id="myEmf"
class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
<property name="persistenceUnitName" value="testPU"/>
</bean>
<bean id="employeeDao" class="com.dao.impl.EmployeeDao" />
</beans>
的persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="testPU" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.entity.Employee</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name="hibernate.connection.url"
value="jdbc:mysql://localhost:3306/dbname"/>
<property name="hibernate.connection.driver_class"
value="com.mysql.jdbc.Driver"/>
<property name="hibernate.dialect"
value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.connection.username" value="user"/>
<property name="hibernate.connection.password" value="password"/>
<property name="hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>
</persistence>
我也在使用方面，但我还没有发布代码，因为我不确定它是否相关，因为我试图通过关闭方面，即使那时我面临这个问题，只是一个奇怪的事情发生在关闭方面，而不是获取空指针异常我从EntityManager类的find方法中获取另一个异常，这表明在这种情况下dao类的create方法不返回null。
有人可以帮帮我吗？
答案 0 :(得分：1)
您的交易似乎没有被提交。
尝试将@Transactional添加到EmployeeDao类中的方法中，或者更好的是，创建一个Service层来处理事务并注释其方法whit @Transactional