Ebean-功能介绍

Mapping

Ebean使用了和JPA一样的映射，所以你可以使用@Entity, @Table, @Column, @OneToMany等等对你的实体进行注释

@Entity
public class B_Order extends CModel {

    public String uuid = null;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer id;

    @Constraints.Required
    @Version
    public Integer version = 1;

    @ManyToOne
    @Column(nullable = false)
    public B_Customer customer;

    public int status;

    public String shipDate;

    public String orderDate;    

    public int price;
}

Query

1.查询单个结果：

B_Customer customer = Ebean.find(B_Customer.class, 4);

执行的sql为：

select t0.id c0, t0.uuid c1, t0.name c2, t0.version c3 from b_customer t0 where t0.id = 4

2.查询多个结果：

List<B_Customer> customers = Ebean.find(B_Customer.class)
                                .where().like("name", "%a%")
                                .orderBy("name desc") 
                                .findList();

执行的sql为：

select t0.id c0, t0.uuid c1, t0.name c2, t0.version c3 from b_customer t0 where t0.name like '%a%'  order by t0.name desc

3.select() 和 fetch()

你可以使用select（）和fetch（）查询你需要的属性。

List<B_Order> orderList =Ebean.find(B_Order.class).select("id").where().eq("status",B_Order.STATUS_ACTIVE).findList();

执行的sql为：

select t0.id c0 from b_order t0 where t0.status = 1

List<B_Order> orderList =Ebean.find(B_Order.class).select("id")
                            .fetch("customer","name")
                            .where().eq("status",B_Order.STATUS_ACTIVE)
                            .findList();

执行sql为：

select t0.id c0, t1.id c1, t1.name c2 from b_order t0 left outer join b_customer t1 on t1.id = t0.customer_id  where t0.status = 1

4.使用sql查询语言

String q = "find b_order fetch customer where id=:id";
B_Order order = Ebean.createQuery(B_Order.class,q).setParameter("id", 23).findUnique();

执行的sql为：

select t0.id c0, t0.uuid c1, t0.status c2, t0.ship_date c3, t0.order_date c4, t0.version c5, t1.id c6, t1.uuid c7, t1.name c8, t1.version c9 from b_order t0 left outer join b_customer t1 on t1.id = t0.customer_id  where t0.id = 23

等价于：

B_Order order = Ebean.createQuery(B_Order.class).fetch("customer").where().eq("id",23).findUnique();

RawSql

你可以在这种使用例如sum()、count()、max()等功能。

String sql ="select o.id ,o.customer_id, c.name , sum(price) as price from b_order o join b_customer c on o.customer_id = c.id group by customer_id";
RawSql rawSql = RawSqlBuilder.parse(sql)
                    .columnMapping("c.name","customer.name")
                    .columnMapping("o.customer_id","customer.id")
                    .columnMapping("o.id","id")
                    .create();
Query<B_Order> query = Ebean.find(B_Order.class);
List<B_Order> orderList = query.setRawSql(rawSql).findList();

注意：外键一定要查询出来，否则会报Query threw SQLException:Column Index out of range, 0 < 1.错误

Save & Delete

Order order = Ebean.find(Order.class, 12);
order.price = 2;
Ebean.save(order);    

Order order = Ebean.find(Order.class, 12);    
Ebean.delete(order);    

Transactions

注释@Transactional

@Transactional
public void runFirst() throws IOException {
    User u1 = Ebean.find(User.class, 1);
    …
    Customer cust = Ebean.find(Customer.class, 27);
    …
    Ebean.save(cust);
}

注意：函数中的异常不能使用try catch进行抓取，不然事务不起作用。play框架中必须放在最外层Result controller上，不然不起作用。

传统方式

Ebean.beginTransaction();
try {
    ...
    Ebean.save(customer);
    Ebean.save(order);
    Ebean.commitTransaction();
} finally {
    Ebean.endTransaction();
}