(翻译)Spring到Java EE的迁移（一）__续

续前节。

 

我们看到，NetBeans通过自动生成JPA实体为我们节省了大量时间。 “Don’t use wizard code you don’t understand.”———Andrew Hunt and Dave Thomas

 

咱们看看生成的实体代码，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 + " ]";     }   }

这些代码很平淡，很俗，只是标准JavaBean，带着私有属性和公开的getter和setter.关键是注解。.（对注解的理解请看原文http://www.oracle.com/technetwork/articles/java/springtojavaee-522240.html）

 

Conclusion

 

看到了吧，使用JPA和NetBeans开发数据层多简单，因为NB向导帮我们生成了大部分代码。在后面的第二部分，我们将看到NB帮我们生成其他层。