Spring + Hibernate：我无法从表中删除记录 [英] Spring + Hibernate: I can't delete a record from a table

问题描述

我在Spring领域非常新，现在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 操作遇到了一些困难......

I am quite new in Spring field and in this time I am studying how integrate it with Hibernate to create my DAO object but I am finding some difficulties with the DELETE operation...

所以我有一个人表，我创建了这个实现我的DAO对象的具体类：

So I have a person table and I have create this concrete class that implement my DAO object:

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
我没有任何问题要将新对象插入到表中，以获取表中所有对象的单个对象或列表，但我正在查找问题从表中删除一个对象。

Then I have create a main class to test how my DAO work I have no problem to insert a new object into the dable, to get a single object or a list of all object in the table but I am finding problem to delete an object from the table.

这是我的测试类：

This is my test class:

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());    
    }

}
}

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

但它不起作用，在我的表格中，所有记录仍保持不变...

But it don't work and in my table all the record still remain the same...

为什么？我的代码有什么问题？ （我没有例外...）

Why? What is wrong in my code? (I have not exception...)

这是我的Person类代码：

This is my Person class code:

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;
}
}

推荐答案

I已经解决了这样的问题：

I have solved this problem like that:

@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();
    }
}

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