ebean orm框架，其作者認爲hibernate的bean管理會話管理，難以在短時間明白，就自己搞了一套，就成了現在的ebean。ebean被一些開發者這認爲是一把瑞士軍刀，可以看出一些程序員對ebean的高度評價。下面是一些ebean的特點總結
1.簡單易於學習和使用（簡化hibernate，只有一個jar包）
2.使用標準的JPA annotation，即： @@OneToMany等；
3.提供Sessionless API，也就是說沒有merge，flush等方法。（這也是Ebean與Hibernatet等ORM的重要區別之一）；
4.通過Autofetch*進行自動查詢調優；支持級聯保存和刪除。
5.鏈式查詢語言
6.L1、L2 緩存
7.集成Lucene文本搜索。
下面是一段使用ebean的代碼樣例
package models;
import com.avaje.ebean.Ebean;
import com.avaje.ebean.annotation.Formula;
import com.avaje.ebean.annotation.Transactional;
import com.avaje.ebean.cache.ServerCacheManager;
import play.data.validation.Constraints;
import play.db.ebean.Model;
import util.Util;
import javax.persistence.*;
import java.util.List;
/**
* Created by wangjun on 14-3-26.
*/
@Entity // ebean 所用的註解是jpa
//@Table(name = "user")
public class User extends Model {
@Id //@EmbeddedId 複雜id
public Long id; //默認命名約定：first_name maps to firstName
@Constraints.Required
public String username;
//@Column(name = "password")
public String password;
@ManyToOne(cascade = CascadeType.ALL)
//會加載address_id ,但不會加載整個address,這個和hibernate有區別，Ebean的延遲加載對於性能的影響不打，默認EAGER，最好打開
public Address address; //出身地
/*@OneToOne
public User mate;//配偶*/
/* @OneToMany(cascade = CascadeType.PERSIST)
public List<Address> addresses;//曾居住地 會在address端要求user_id 字段，可以用？ManyToMany代替*/
@ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.DETACH)
//cascade = CascadeType.ALL 級聯情況下會自動插入car箇中間表數據,默認不級聯 ，對於一些級聯更新很是有必要
public List<Car> cars;
@Formula(select = "(select count(*) from user_car c where c.user_id = ${ta}.id )")
// 計算擁有車的數量 ${ta} 代表表的別名 ，還可以寫join
public int carSize;
//@Transient
//會滿足上述條件後在調用此方法，全局驗證
public String validate() {
if (username.equals("1")) {
return "Invalid email or password";
}
return null;
}
/* public List<ValidationError> validate() {
if ( username.equals("1")) {
return null;
}
return null;
}
public Map<ValidationError> validate() {
if ( username.equals("1")) {
return null;
}
return null;
}*/
public static Model.Finder<Long, User> find = new Model.Finder(Long.class, User.class);
//============自動抓取測試==start=================
public static User findById(Long id) {
User user = find.byId(id); //不抓取car,LAZY不select address_id
return user;
}
public static User findById(Long id, int loadType) {
User user = find.byId(id); //不抓取car,不抓取address
String name = null;
int size = 0;
if (loadType == 1)
name = user.address.province; //每次都會加載user
else if (loadType == 2)
size = user.cars.size(); //每次都會加載car
Util.report(name);
Util.report(size + "");
return user;
}
//連表查詢測試
public static User findByIdLoadAddress(Long id) {
return find.fetch("address").fetch("cars").where().eq("id", id).findUnique(); // fetch= 生成join查詢 不用fetch延遲加載，且不會生成join查詢；
}
/**
* *
* TxType Descriptions
* TxType Description
* REQUIRED Runs in a Transaction. Will use an existing transaction if it exists, otherwise will create a new Transaction.
* REQUIRES_NEW Runs in a new Transaction. If a current transaction exists it will be suspended.
* MANDATORY Runs in the existing Transaction. If there is no current existing transaction an exception is thrown.
* SUPPORTS Use a transaction if it already exists. If it does not then the method runs without a transaction.
* NOT_SUPPORTS Always runs without a transaction. If one already exists then it is suspended.
* NEVER Always runs without a transaction. If one already exists then it throws an exception.
*
* @param type
*/
@Transactional// 打開事務，或通過beginTr.... endTr.. 或TxRunnable
public void saveUser(int type) {
Util.report("=============saveUser==start===============================");
if (type == 0) { //不級聯情況保存
this.address.save(); // 保存用戶前將用戶輸入的出生地也保存到數據庫
this.save(); // 保存用戶數據
this.saveManyToManyAssociations("cars"); //保存中間表
} else if (type == 1) { //如果設置級聯car
this.save(); // 會級聯插入car和中間表數據
}
Util.report("===============saveUser===end============================");
}
public void deleteUser(Long id) {
Ebean.delete(User.class, id);
}
/**
* *********************other test*********************
* public void updateUser() {
* this.update();
* }
* <p/>
* //批量操作
* public void deleteUser(List<User> users) {
* Ebean.delete(users);//批量刪除
* Ebean.save(users);//批量保存
* }
* <p/>
* public void deleteUser() {
* this.delete();
* }
* ***************
*/
//L1 測試 事務級緩存或持久化上下文緩存
public static User find() {
Ebean.beginTransaction();
Car car1 = Car.find.byId(Long.valueOf(7));
Car car2 = Car.find.byId(Long.valueOf(8));
User user = User.findById(Long.valueOf(45));
if (user.cars.get(0).id == 7) { // 查到的ｃａｒ實例屬於同一個實例
Util.report((user.cars.get(0) == car1) + "");
} else if (user.cars.get(0).id == 8) {
Util.report((user.cars.get(0) == car2) + "");
}
Ebean.endTransaction();
return user;
}
//L2 測試 bean cache and query cache
public static Address findAddress() {//手動指定使用緩存，同時設置爲只讀，可以在model使用註解指定緩存策略，如果有修改緩存的bean，會自動維持緩存
Address address_ = Ebean.find(Address.class).setUseCache(true).setReadOnly(true).setId(56).findUnique();
List<Address> addressList = Ebean.find(Address.class).setUseQueryCache(true).setReadOnly(true).findList();
Util.report(addressList.size() + "");
return address_;
}
// 測試 不用cache 查詢10000次
public static Car findCar() {
Car car = null;
for (int i = 0; i < 100000; i++) {
Car car_ = Ebean.find(Car.class, 1);
Util.report((car == car_) + "");
car = car_;
}
return car;
}
// 測試 不用cache 查詢10000次
public static Car findCar2() {
Car car = null;
for (int i = 0; i < 10000; i++) { // 只查1次
Car car_ = Ebean.getReference(Car.class, 1); // getReference 只會加載創建存在id屬性的bean，不會查詢數據庫，當得到這個bean，用id外的其它屬性就會引發查詢
Util.report((car == car_) + "");
car = car_;
}
return car;
}
//L1 測試 查詢10000次
public static Address findAddressInL1() { // 只查1次
// Address address_ = Ebean.find(Address.class, "56");
Address address = null;
Ebean.beginTransaction();
for (int i = 0; i < 10000; i++) {
Address address_ = Ebean.find(Address.class, 56);
Util.report((address == address_) + "");
address = address_;
}
Ebean.endTransaction();
return address;
}
//L2 測試 查詢10000次
public static Address findAddressInL2() {
Address address = null;
for (int i = 0; i < 10000; i++) { // 查了數據庫
Address address_ = Ebean.find(Address.class, 56);
// Address address_ = Ebean.find(Address.class).setUseCache(true).setReadOnly(true).setId(56).findUnique();
Util.report((address == address_) + "");
address = address_;
}
return address;
}
//L2 測試 查詢10000次
public static Address findAddressInL22() {
Address address = null;
for (int i = 0; i < 10000; i++) { // 測試查了數據庫
// Address address_ = Ebean.getReference(Address.class,56);
Address address_ = Ebean.find(Address.class).setUseCache(true).setReadOnly(true).setId(56).findUnique();
Util.report((address == address_) + "");
address = address_;
}
return address;
}
//L2 測試 抓取Address10000次 當第一次查詢的時候會查詢address，之後會從緩存取
public static Address findAddressInL222() {
Address address = null;
for (int i = 0; i < 10000; i++) { // 測試查了數據庫
User user = User.findById(Long.valueOf(41));
Address address_ = user.address; // 數據從緩存內得到
Util.report((address == address_) + (address == null ? null : address.province));
address = address_;
}
return address;
}
/**
* **
* Handling External Modification (
* via stored procedures etc
* )
* When you save/delete beans via Ebean.save() and Ebean.delete() etc Ebean will
* automatically maintain its cache (removing cached beans and cached queries as
* appropriate). However, you may often find yourself modifying the database outside of
* Ebean.
* For example, you could be using other frameworks, your own JDBC code, stored
* procedures, batch systems etc. When you do so (and you are using Ebean caching) then
* you can inform Ebean so that it invalidates appropriate parts of its cache.
*/
public void test() {
boolean inserts = true;
boolean updates = true;
boolean deletes = false;
// inform Ebean that some rows have been inserted and updated on address table Ebean will maintain the appropriate caches.
Ebean.externalModification("address", inserts, updates, deletes);
// clearAll() caches via the ServerCacheManager ...
ServerCacheManager serverCacheManager = Ebean.getServerCacheManager();
// Clear all the caches on the default/primary EbeanServer
serverCacheManager.clearAll();
// clear both the bean and query cache for Country beans ...
serverCacheManager.clear(Address.class);
// Warm the cache of Country beans
Ebean.runCacheWarming(Address.class);
}
@Override
public String toString() {
String result = "";
if (address == null)
result.concat("address:null");
else
result.concat("address:").concat(address.province).concat("-").concat(address.town);
return result;
}
}
