Question

我是Spring领域的新手，在这个时候我正在研究如何将它与Hibernate集成以创建我的DAO对象，但我发现 DELETE 操作有些困难......

所以我有一个人员表，我创建了这个实现我的DAO对象的具体类：

package org.andrea.myexample.HibernateOnSpring.dao;

import java.util.List;

import org.andrea.myexample.HibernateOnSpring.entity.Person;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.transaction.annotation.Transactional;

public class PersonDAOImpl implements PersonDAO {

private SessionFactory sessionFactory;

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

// Metodo che inserisce un nuovo record nella tabella person
@Transactional(readOnly = false)
public void addPerson(Person p) {
    Session session = sessionFactory.openSession();
    session.save(p);
    session.close();
}

/*
 * Metodo che recupera un record, rappresentante una persona, avente uno
 * specifico id dalla tabella.
 * 
 * @param L'id univoco della persona
 */

public Person getById(int id) {
    Session session = sessionFactory.openSession();
    try {
        return (Person) session.get(Person.class, id);
    } finally {
        session.close();
    }
}

/*
 * Metodo che recupera la lista di tutti le persone rappresentanti dalle
 * righe della tabella person
 */
@SuppressWarnings("unchecked")
public List<Person> getPersonsList() {

    Session session = sessionFactory.openSession();
    try {

        Criteria criteria = session.createCriteria(Person.class);
        return criteria.list();

    } finally {
        session.close();
    }

}

/*
 * Metodo che elimina dalla tabella person la riga avente uno specifico id
 * 
 * @param l'id della persona da eliminare dalla tabella person
 */
public void delete(int id) {

    Session session = sessionFactory.openSession();
    try {
        Person personToDelete = getById(id);
        session.delete(personToDelete);

    } finally {
        session.close();
    }

}

}

然后我创建了一个主类来测试我的DAO如何工作我可以将新对象插入到dable中，获取单个对象或表中所有对象的列表，但是我发现从表中删除对象时遇到问题。

这是我的测试类：

package org.andrea.myexample.HibernateOnSpring;

import java.util.List;

import org.andrea.myexample.HibernateOnSpring.dao.PersonDAO;
import org.andrea.myexample.HibernateOnSpring.dao.PersonDAOImpl;
import org.andrea.myexample.HibernateOnSpring.entity.Person;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App {

public static void main( String[] args ){

    ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
    System.out.println("Contesto recuperato: " + context);

    Person persona1 = new Person();

    persona1.setFirstname("Pippo");
    persona1.setLastname("Blabla");
    //persona1.setPid(1);

    System.out.println("Creato persona1: " + persona1);

    PersonDAO dao = (PersonDAO) context.getBean("personDAOImpl");

    System.out.println("Creato dao object: " + dao);

    dao.addPerson(persona1);

    System.out.println("persona1 salvata nel database");

    Person personaEstratta = dao.getById(persona1.getPid());

    System.out.println("Persona con id: " + personaEstratta.getPid() + " estratta dal DB");
    System.out.println("Dati persona estratta:");
    System.out.println("Nome: " + personaEstratta.getFirstname());
    System.out.println("Cognome: " + personaEstratta.getLastname());

    System.out.println("");

    // STAMPA LA LISTA DELLE PERSONE NELLA TABELL person:
    List<Person> listaPersone = dao.getPersonsList();
    System.out.println("Lista delle persone recuperata: " + listaPersone );

    // MOSTRA I DATI DI TUTTE LE PERSONE NELLA LISTA:
    for(int i=0; i<listaPersone.size(); i++){
        Person currentPerson = listaPersone.get(i);
        System.out.println("id: " + currentPerson.getPid()
                            + " nome: " + currentPerson.getFirstname()
                            + " cognome: " + currentPerson.getLastname());  
    }

    // ELIMINAZIONE DI UNA PERSONA DALLA TABELLA person:
    System.out.println("");
    System.out.println("ELIMINAZIONE DI UNA PERSONA DALLA TABELLA person:");


    // ELIMINA TUTTI I RECORD DALLA TABELLA persone:
    for(int i=0; i<listaPersone.size(); i++){
        dao.delete(listaPersone.get(i).getPid());
        System.out.println("Persona con id: " + i + " eliminata");
    }

    listaPersone = dao.getPersonsList();    // Lista vuota

    // MOSTRA I DATI DI TUTTE LE PERSONE NELLA LISTA:
    for(int i=0; i<listaPersone.size(); i++){
        Person currentPerson = listaPersone.get(i);
        System.out.println("id: " + currentPerson.getPid()
                                  + " nome: " + currentPerson.getFirstname()
                                  + " cognome: " + currentPerson.getLastname());    
    }

}
}

在本课程的最后，我试图删除执行一个循环的所有表记录，只执行：

dao.delete(listaPersone.get(i).getPid());

但它不起作用，在我的表中所有记录仍然保持不变......

为什么呢？我的代码有什么问题？（我也不例外......）

这是我的Person类代码：

package org.andrea.myexample.HibernateOnSpring.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="person")
public class Person {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int pid;

private String firstname;

private String lastname;

public int getPid() {
    return pid;
}

public void setPid(int pid) {
    this.pid = pid;
}

public String getFirstname() {
    return firstname;
}

public void setFirstname(String firstname) {
    this.firstname = firstname;
}

public String getLastname() {
    return lastname;
}

public void setLastname(String lastname) {
    this.lastname = lastname;
}
}

Answer 1

我已经解决了这个问题：

@Override
public void deleteData(int id) {
    log.info("delete by id = "+id);
    Transaction tx=null;

    //open a session and begin the transaction with the database
    Session session = null;


    try {
        session = getSession();
        tx = session.beginTransaction();
        Person person = getPerson(id);
        session.delete(person);            
        tx.commit();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {

        if (!tx.wasCommitted()) {
           tx.rollback();
        }//not much doing but a good practice
        session.flush(); //this is where I think things will start working.
        session.close();
    }
}

Answer 2

你的删除方法看起来怎么样？它是否包含@Transaction 这是一个例子：

@Transaction
public int deleteUser(String userName) {
    try {

    //open a session and begin the transaction with the database
    sessionFactory = HibernateUtil.getSessionFactory();
    Session session = sessionFactory.openSession();
    session.beginTransaction();

    //query the database
    Query query =  session.createQuery("delete from Users u where u.userName ='" +    userName +"'");
    int result = query.executeUpdate();
    session.close();

    return result;
}

确认您在返回身份之前关闭会话

Answer 3

从你的代码看起来似乎保存工作但删除不是。我假设会话与事务同步（在事务完成之前刷新会话）。在@Transactional方法上放置delete应该有效。

Answer 4

我没有在删除方法上看到@Transactional？你有一个

吗？

Spring + Hibernate：我无法从表中删除记录

4 个答案: