(通译)Spring到Java EE的迁移（一）_续

续前节。

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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

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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）

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Conclusion

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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。?

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