Objectify是GAE Java的一個lightware IoC framework
透過Objectify可以達到與Spring相似的IoC功能
下面是操作Objectify的一些過程：
Step1: Download Objectify library
本文下載的是objectify 3.1版本的
Step2: Create Entity class
Objectify是針對Entity Object來進行資料的存取動作，因此需要先建立Car的Entity類別
package com.mitac.objectify;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Car {
@Id
String idx; // Can be Long, long, or String
String name;
public Car(String idx, String name) {
this.idx = idx;
this.name = name;
}
}
Step3: Create service middleware
建立static class的middleware來作為呼叫Objectify的中介
package com.mitac.objectify;
import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyFactory;
import com.googlecode.objectify.ObjectifyService;
public class OfyService {
static {
factory().register(Car.class);
//... etc
}
public static Objectify ofy() {
return ObjectifyService.begin();
}
public static ObjectifyFactory factory() {
return ObjectifyService.factory();
}
}
Step4: Using middleware to put data
package com.mitac.objectify;
import static com.mitac.objectify.OfyService.ofy;
import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@SuppressWarnings("serial")
public class GaeObjectifyServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
ofy().put(new Car("audi", "audi a3"));
Car car = ofy().get(Car.class, "audi");
resp.setContentType("text/plain");
resp.getWriter().println("Hello, world ==> " + car.name );
}
}
Other: Query example
查詢的方式跟Low Level API差不多，範例如下：
Query<Car> query = ofy().query(Car.class);
query.filter("name = ", "audi a3").order("name");
List<Car> cars = query.list();
Iterator iter = cars.iterator();
while(iter.hasNext()) {
Car c = (Car) iter.next();
out.println("Hello, world ==> " + c.name );
}
參考文獻：
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