Spring到Java EE的遷移（一）__續

續前節。

我們看到，NetBeans通過自動產生JPA實體為我們節省了大量時間。 “Don’t use wizard code you don’t understand.”———Andrew Hunt and Dave Thomas

咱們看看產生的實體代碼，你自己理解一下。

Listing 1. Examining a Generated Entity

package com.ensode.petclinicjavaee.entity; //imports omitted for brevity @Entity
@Table(name = "owners", catalog = "petclinic", schema = "")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Owner.findAll", query = "SELECT o FROM Owner o"),
    @NamedQuery(name = "Owner.findById",
        query = "SELECT o FROM Owner o WHERE o.id = :id"),
    @NamedQuery(name = "Owner.findByFirstName",
        query = "SELECT o FROM Owner o WHERE o.firstName = :firstName"),
    @NamedQuery(name = "Owner.findByLastName",
        query = "SELECT o FROM Owner o WHERE o.lastName = :lastName"),
    @NamedQuery(name = "Owner.findByAddress",
        query = "SELECT o FROM Owner o WHERE o.address = :address"),
    @NamedQuery(name = "Owner.findByCity",
        query = "SELECT o FROM Owner o WHERE o.city = :city"),
    @NamedQuery(name = "Owner.findByTelephone",
        query = "SELECT o FROM Owner o WHERE o.telephone = :telephone")})public class Owner implements Serializable {    private static final long serialVersionUID = 1L;    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @NotNull
    @Column(name = "id", nullable = false)    private Integer id;    @Size(max = 30)
    @Column(name = "first_name", length = 30)
    private String firstName;    @Size(max = 30)
    @Column(name = "last_name", length = 30)
    private String lastName;    @Size(max = 255)
    @Column(name = "address", length = 255)
    private String address;    @Size(max = 80)
    @Column(name = "city", length = 80)    private String city;    @Size(max = 20)
    @Column(name = "telephone", length = 20)
    private String telephone;    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner")
    private Collection<Pet> petCollection;     public Owner() {    }     public Owner(Integer id) {        this.id = id;    }     //getters and setters omitted for brevity     @Override    public int hashCode() {        int hash = 0;        hash += (id != null ? id.hashCode() : 0);        return hash;    }     @Override    public boolean equals(Object object) {        // TODO: Warning - this method won't work in the case the id        // fields are not set        if (!(object instanceof Owner)) {            return false;        }        Owner other = (Owner) object;        if ((this.id == null && other.id != null) ||              (this.id != null && !this.id.equals(other.id))) {            return false;        }        return true;    }     @Override    public String toString() {        return "com.ensode.petclinicjavaee.entity.Owner[ id=" + id + " ]";    }  }

這些代碼很平淡，很俗，只是標準JavaBean，帶著私人屬性和公開的getter和setter.關鍵是註解。.（對註解的理解請看原文http://www.oracle.com/technetwork/articles/java/springtojavaee-522240.html）

Conclusion

看到了吧，使用JPA和NetBeans開發資料層多簡單，因為NB嚮導幫我們產生了大部分代碼。在後面的第二部分，我們將看到NB幫我們產生其他層。