在scala里调用Hibernate JPA

虽然scala里也能直接使用hibernate逆向工程生成的entity文件，但是使用scala可以大大减少代码量。

pojo在java中的定义如下

java 代码

@Entity
@Table(name = "mytable", catalog = "mydb")
public class MyTable implements java.io.Serializable {

    private int id;

    private String title;

    private String summary;

    private Date date;

    private String tags;

    public MyTable () {
    }

    public MyTable (int id, String title, Date date) {
        this.id = id;
        this.title = title;
        this.date = date;
    }

    public MyTable (int id, String title, String summary, Date date,
            String tags) {
        this.id = id;
        this.title = title;
        this.summary = summary;
        this.date = date;
        this.tags = tags;
    }

    @Id
    @Column(name = "id", unique = true, nullable = false)
    public int getId() {
        return this.id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(name = "title", nullable = false, length = 256)
    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Column(name = "summary")
    public String getSummary() {
        return this.summary;
    }

    public void setSummary(String summary) {
        this.summary = summary;
    }

    @Temporal(TemporalType.DATE)
    @Column(name = "date", nullable = false, length = 0)
    public Date getDate() {
        return this.date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    @Column(name = "tags")
    public String getTags() {
        return this.tags;
    }

    public void setTags(String tags) {
        this.tags = tags;
    }

}

Scala由于有内置的BeanProperty支持，上面的代码缩减为下面的，一切setter/getter函数都免了，当然愿意手工加也可以

scala 代码

@Entity
@Table{val name = "mytable", val catalog = "mydb"}
class MyTable extends  java.io.Serializable {

        @Id
        @Column{val name = "id", val unique = true, val nullable = false}
        @BeanProperty
        var id: int = _

        @Column{val name = "title", val nullable = false, val length = 256}
        @BeanProperty
        var title: String = _

        @Column{val name = "summary"}
        @BeanProperty
        var summary: String = _

        @Temporal(TemporalType.DATE)
        @Column{val name = "date", val nullable = false, val length = 0}
        @BeanProperty
        var date: Date = _

        @Column{val name = "tags"}
        @BeanProperty
        var tags: String = _

        def this(id: int, title: String, date: Date) =  {
                this();
                this.id = id;
                this.title = title;
                this.date = date;
        }

        def this(id: int, title: String, summary: String, date: Date,
                        tags: String) = {
               this();
                this.id = id;
                this.title = title;
                this.summary = summary;
                this.date = date;
                this.tags = tags;
        }
}

访问也很简单

scala 代码

val emf = Persistence.createEntityManagerFactory("helloworld")
val em = emf.createEntityManager()
var tests = em.createQuery(
        "from MyTable"
        ).getResultList()

// 这里将java.util.List转换为scala的List，方便处理
val testsList = new scala.collection.jcl.BufferWrapper[MyTable] {
      override def underlying = tests
}

for (test < - testsList) {
      println(test)
      println(test.title)
      println(test.summary)
}