Eclipse、JSF、Java 中的 crud 实现

Question

我有一个类（车辆），我实现了CRUD操作。删除作品，更新作品，只是创建不起作用。我可以放什么来代替这个创建代码？附言：我使用Eclipse这是FormMasini.java我从Vehicule.java日期中获取，它将以JSF形式显示。错误出现在这一行：this.vehicul = new Vehicul（）;

package vehiculeFeaa;
import java.util.List;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.TableGenerator;
@Entity
@Table(name = "VEHICUL")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "VEHICUL_TYPE")
public abstract class Vehicul {
    @TableGenerator(name = "VEHICUL_GEN", table = "ID_GEN", pkColumnName = "GEN_NUME", valueColumnName = "GEN_VALOARE", allocationSize = 1)
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE, generator = "VEHICUL_GEN")
    private int idVehicul;
    private String producator;
    public int getIdVehicul() {
        return idVehicul;
    }
    public void setIdVehicul(int idVehicul) {
        this.idVehicul = idVehicul;
    }
    public String getProducator() {
        return producator;
    }
    public void setProducator(String producator) {
        this.producator = producator;
    }
    public boolean isEmpty() {
        // TODO Auto-generated method stub
        return false;
    }
    public List<Vehicul> get(int i) {
        // TODO Auto-generated method stub
        return null;
    }
}    

package masinifeaa;
import java.util.ArrayList;
import java.util.List;
import javax.faces.event.ActionEvent;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import vehiculeFeaa.Vehicul;
public class FormMasini {
    private Vehicul vehicul;
    private List<Vehicul>vehicule=new ArrayList<Vehicul>();
    public Vehicul getVehicul() {
        return vehicul;
    }
    public void setVehicul(Vehicul vehicul) {
        this.vehicul = vehicul;
    }
    public List<Vehicul> getVehicule() {
        return vehicule;
    }
    public void setVehicule(List<Vehicul> vehicule) {
        this.vehicule = vehicule;
    }
    private EntityManager em;
    @SuppressWarnings("unchecked")
    public FormMasini() {
        EntityManagerFactory emf=
                Persistence.createEntityManagerFactory("FirmeJPA");
        em=emf.createEntityManager();
        this.vehicule= em.createQuery("SELECT v FROM Vehicul v")
                .getResultList();
        if(!this.vehicule.isEmpty())
            vehicul=this.vehicule.get(0);
    }
    public void backVehicul(ActionEvent evt) {
    Integer idxCurent = this.vehicule.indexOf(vehicul);
    if(idxCurent > 0)
        this.vehicul=this.vehicule.get(idxCurent-1);
    }
    public void nextVehicul(ActionEvent evt) {
        Integer idxCurent = this.vehicule.indexOf(vehicul);
        if((idxCurent + 1) < this.vehicule.size())
             this.vehicul=this.vehicule.get(idxCurent + 1);
    }
    //Implementez actiunile CRUD
    public void deleteVehicul(ActionEvent evt) {
        this.vehicule.remove(this.vehicul);
        if(this.em.contains(this.vehicul)) {
            this.em.getTransaction().begin();
            this.em.remove(this.vehicul);
            this.em.getTransaction().commit();
    }
        if(!this.vehicule.isEmpty())
            this.vehicul=this.vehicule.get(0);
        else
            this.vehicul=null;
    }
    public void saveVehicul(ActionEvent evt) {
        this.em.getTransaction().begin();
        this.em.persist(this.vehicul);
        this.em.getTransaction().commit();
    }
    public void abandonVehicul(ActionEvent evt) {
        if(this.em.contains(this.vehicul))
            this.em.refresh(this.vehicul);
    }
        public void createVehicul(ActionEvent evt) {
                this.vehicul = new Vehicul();
                this.vehicul.setidVehicul(999);
                this.vehicul.setNume("New car");
                this.vehicule.add(this.vehicul);
}

Answer 1

与 JSF 或其他内容无关。你只是不能实例化一个抽象类，这是基本的Java。