我是Java EE编程的初学者。当我尝试将员工保存在数据库中时收到此错误消息：
java.lang.NullPointerException
at ma.lezar.ge.dao.EmployeesDAO.getCurrentSession(EmployeesDAO.java:48)
at ma.lezar.ge.dao.EmployeesDAO.save(EmployeesDAO.java:59)
at ma.lezar.ge.service.ServiceEmployees.save(ServiceEmployees.java:26)
at ma.lezar.ge.bean.InscrirBean.valider(InscrirBean.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:273)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 28 more
这是 employeeDAO.java
package ma.lezar.ge.dao;
import java.util.List;
import java.util.Set;
import ma.lezar.ge.model.Employees;
import org.hibernate.Hibernate;
import org.hibernate.LockOptions;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.Example;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
@Repository("EmployeesDAO")
@Transactional
public class EmployeesDAO implements IEmployeesDAO {
private static final Logger log = LoggerFactory
.getLogger(EmployeesDAO.class);
// property constants
public static final String NOM = "nom";
public static final String NUM = "num";
@Autowired
private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
private Session getCurrentSession() {
return sessionFactory.getCurrentSession();
}
protected void initDao() {
// do nothing
}
public void save(Employees transientInstance) {
//System.out.println(getCurrentSession().toString());
// log.debug("saving Employees instance");
// try {
getCurrentSession().save(transientInstance);
// log.debug("save successful");
// } catch (RuntimeException re) {
// log.error("save failed", re);
// throw re;
// }
}
public void delete(Employees persistentInstance) {
log.debug("deleting Employees instance");
try {
getCurrentSession().delete(persistentInstance);
log.debug("delete successful");
} catch (RuntimeException re) {
log.error("delete failed", re);
throw re;
}
}
public Employees findById(java.lang.Integer id) {
log.debug("getting Employees instance with id: " + id);
try {
Employees instance = (Employees) getCurrentSession().get(
"ma.lezar.ge.model.Employees", id);
return instance;
} catch (RuntimeException re) {
log.error("get failed", re);
throw re;
}
}
public List findAll() {
log.debug("finding all Employees instances");
try {
String queryString = "from Employees";
Query queryObject = getCurrentSession().createQuery(queryString);
return queryObject.list();
} catch (RuntimeException re) {
log.error("find all failed", re);
throw re;
}
}
public static EmployeesDAO getFromApplicationContext(ApplicationContext ctx) {
return (EmployeesDAO) ctx.getBean("EmployeesDAO");
}
}
Employee.java
package ma.lezar.ge.model;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
* Employees entity. @author MyEclipse Persistence Tools
*/
@Entity
@Table(name = "employees", catalog = "gest_emp")
public class Employees implements java.io.Serializable {
// Fields
private Integer id;
private String nom;
private Integer num;
private Set<Compte> comptes = new HashSet<Compte>(0);
// Constructors
/** default constructor */
public Employees() {
}
/** minimal constructor */
public Employees(String nom, Integer num) {
this.nom = nom;
this.num = num;
}
/** full constructor */
public Employees(String nom, Integer num, Set<Compte> comptes) {
this.nom = nom;
this.num = num;
this.comptes = comptes;
}
// Property accessors
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false)
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name = "nom", nullable = false, length = 50)
public String getNom() {
return this.nom;
}
public void setNom(String nom) {
this.nom = nom;
}
@Column(name = "num", nullable = false)
public Integer getNum() {
return this.num;
}
public void setNum(Integer num) {
this.num = num;
}
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "employees")
public Set<Compte> getComptes() {
return this.comptes;
}
public void setComptes(Set<Compte> comptes) {
this.comptes = comptes;
}
}
InscrirBean.java
package ma.lezar.ge.bean;
import java.io.Serializable;
import javax.ejb.EJB;
import org.springframework.beans.factory.annotation.Autowired;
import ma.lezar.ge.dao.EmployeesDAO;
import ma.lezar.ge.model.Employees;
import ma.lezar.ge.service.IServiceEmployees;
import ma.lezar.ge.service.ServiceEmployees;
public class InscrirBean implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
@Autowired
private ServiceEmployees serviceEmployees;
private String nom;
private Integer num;
public String valider()
{
serviceEmployees = new ServiceEmployees();
serviceEmployees.save(new Employees(nom, num));
return "success";
}
public String getNom() {
return nom;
}
public void setNom(String nom) {
this.nom = nom;
}
public Integer getNum() {
return num;
}
public void setNum(Integer num) {
this.num = num;
}
}
ServiceEmployee.java
package ma.lezar.ge.service;
import java.util.List;
import javax.annotation.Resource;
import ma.lezar.ge.dao.EmployeesDAO;
import ma.lezar.ge.dao.IEmployeesDAO;
import ma.lezar.ge.model.Employees;
import org.hibernate.SessionFactory;
import org.springframework.stereotype.Service;
@Service("serviceEmployees")
public class ServiceEmployees implements IServiceEmployees {
@Resource
private EmployeesDAO employeesDao;
public void save(Employees transientInstance) {
employeesDao = new EmployeesDAO();
employeesDao.save(transientInstance);
}
public void delete(Employees persistentInstance) {
employeesDao.delete(persistentInstance);
}
public Employees findById(java.lang.Integer id) {
Employees instance = (Employees) employeesDao.findById(id);
return instance;
}
public List findAll()
{
return employeesDao.findAll();
}
}
HibernateSessionFactory.java
package ma.lezar.ge.util;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
/**
* Configures and provides access to Hibernate sessions, tied to the
* current thread of execution. Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.html }.
*/
public class HibernateSessionFactory {
/**
* Location of hibernate.cfg.xml file.
* Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file.
* The default classpath location of the hibernate config file is
* in the default package. Use #setConfigFile() to update
* the location of the configuration file for the current session.
*/
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
private static org.hibernate.SessionFactory sessionFactory;
private static Configuration configuration = new Configuration();
private static ServiceRegistry serviceRegistry;
static {
try {
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private HibernateSessionFactory() {
}
/**
* Returns the ThreadLocal Session instance. Lazy initialize
* the <code>SessionFactory</code> if needed.
*
* @return Session
* @throws HibernateException
*/
public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}
return session;
}
/**
* Rebuild hibernate session factory
*
*/
public static void rebuildSessionFactory() {
try {
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
/**
* Close the single hibernate session instance.
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
}
}
/**
* return session factory
*
*/
public static org.hibernate.SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
* return hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}
}
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:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd" xmlns:tx="http://www.springframework.org/schema/tx">
<bean id="dataSource"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="url"
value="jdbc:mysql://localhost:3306/gest_emp">
</property>
<property name="username" value="root"></property>
</bean>
<bean id="sessionFactory"
class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
<property name="dataSource">
<ref bean="dataSource" />
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</prop>
</props>
</property>
<property name="annotatedClasses">
<list>
<value>ma.lezar.ge.model.Compte</value>
<value>ma.lezar.ge.model.Employees</value></list>
</property></bean>
<bean id="transactionManager"
class="org.springframework.orm.hibernate4.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<bean id="CompteDAO" class="ma.lezar.ge.dao.CompteDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="EmployeesDAO" class="ma.lezar.ge.dao.EmployeesDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
</beans>
答案 0 :(得分：0)
您自己实例化employeesDao，而不是让Spring管理该类的DI。删除声明
employeesDao = new EmployeesDAO();
ServiceEmployees中的。