Question

所以这可能是一个愚蠢的问题，但你什么时候注册课程：

ObjectifyService.register( User.class );

目前，我在类似接口的类的构造函数中这样做，我在其他类中使用它来简化数据存储的使用，特别是我的应用程序。但是，我收到了这个错误：

尝试两次注册“用户”

所以，我想我的问题是你在Objectify中注册课程的频率和具体时间是什么？

谢谢！

P.S。这是我的全班：

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Iterator;

import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.persistence.Id;

import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyService;
import com.googlecode.objectify.annotation.Indexed;
import com.googlecode.objectify.annotation.Unindexed;

public class UsersService {

    Objectify ojy;

    public UsersService(){
        ObjectifyService.register( User.class );
        ojy = ObjectifyService.begin();
    }

    public void regUser(String email, String password, String firstName, String lastName){
        //TODO: Check syntax if email
        //TODO: store encrypted password
    }

    public void regUser(String email, String password, String firstName){
        regUser(email, password, firstName, null);
    }

    public void regUser(String email, String password){
        regUser(email, password, "", "");
    }

    public boolean checkFor(Long acc_id){
        User checked_user = ojy.find(User.class, acc_id);
        if(checked_user == null){
            return false;
        }else{
            return true;
        }
    }

    public User getUser(String email, String password) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException{
        String pass_enc = MyUtils.getEncrypted(password);
        Iterable<User> users = ojy.query(User.class).filter("email", email).filter("password", pass_enc);
        Iterator<User> iter = users.iterator();
        if(iter.hasNext()){
            return iter.next();
        }else{
            return null;
        }
    }

}

Answer 1

<强>更新

以下是最佳实践解决方案：

使用您自己的服务，这可以保证在使用Objectify之前注册您的实体，但不一定会影响不访问数据存储区的请求的应用程序启动。

import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyFactory;
import com.googlecode.objectify.ObjectifyService;


public class OfyService {
    static {
        ObjectifyService.register(User.class);
    }

    public static Objectify ofy() {
        return ObjectifyService.begin();//prior to v.4.0 use .begin() , 
                                        //since v.4.0  use ObjectifyService.ofy();
    }

    public static ObjectifyFactory factory() {
        return ObjectifyService.factory();
    }

}

然后像这样使用它：

public User createUser(User pUser) {

    Objectify objectify = OfyService.ofy();
    objectify.put(pUser);

    return pUser;
}

原始答案（更好地使用上面的代码）：

你应该在你的课堂上这样做，只需要放一个这样的静态块：

static{
    ObjectifyService.register( User.class );
}

，请你看一下客体化的最佳实践

http://code.google.com/p/objectify-appengine/wiki/BestPractices

Answer 2

我使用@Entity注释，Reflections库和运行时注册，对我的任何应用程序的启动时间没有重大影响，因为所有信息都是在编译/构建时收集的。

ObjectifyLoaderContextListener.java

package com.vertigrated.servlet;

import com.google.appengine.api.ThreadManager;
import com.googlecode.objectify.ObjectifyFactory;
import com.googlecode.objectify.ObjectifyService;
import com.googlecode.objectify.annotation.Entity;
import org.reflections.Reflections;
import org.reflections.util.ClasspathHelper;
import org.reflections.util.ConfigurationBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * This class processes the classpath for classes with the @Entity or @Subclass annotations from Objectify
 * and registers them with the ObjectifyFactory, it is multi-threaded uses a prebuilt list of classes to process
 * created by the Reflections library at compile time and works very fast!
 */
public class ObjectifyLoaderContextListener implements ServletContextListener
{
    private static final Logger L = LoggerFactory.getLogger(ObjectifyLoaderContextListener.class);

    private final Set<Class<?>> entities;

    public ObjectifyLoaderContextListener()
    {
        this.entities = new HashSet<>();
    }

    @Override
    public void contextInitialized(@Nonnull final ServletContextEvent sce)
    {
        final ConfigurationBuilder cb = new ConfigurationBuilder();
        cb.setUrls(ClasspathHelper.forPackage(""));
        final ExecutorService es = Executors.newCachedThreadPool(ThreadManager.currentRequestThreadFactory());
        cb.setExecutorService(es);
        final Reflections r = new Reflections(cb);
        this.entities.addAll(r.getTypesAnnotatedWith(Entity.class));
        es.shutdown();
        final ObjectifyFactory of = ObjectifyService.factory();
        for (final Class<?> cls : this.entities)
        {
            of.register(cls);
            L.debug("Registered {} with Objectify", cls.getName());
        }
    }

    @Override
    public void contextDestroyed(@Nonnull final ServletContextEvent sce)
    {
        /* this is intentionally empty */
    }
}

Answer 3

基于Danie的回答，如果其他人正在使用依赖注入，我为Spring MVC做了这个并且工作得很完美：

我按如下方式创建了一项服务：

@Service
@Qualifier("objectifyService")
public class OfyService {
    static {
        ObjectifyService.register(GaeUser.class);
    }

    public static Objectify ofy() {
        return ObjectifyService.ofy();
    }

    public static ObjectifyFactory factory() {
        return ObjectifyService.factory();
    }

}

然后，只要我想使用它，我就像这样注入服务：

@Autowired
@Qualifier("objectifyService")
OfyService objectifyService;

然后我就这样使用它：

objectifyService.ofy().save().entity(user).now();

您何时在Objectify中为GAE注册课程？

3 个答案:

ObjectifyLoaderContextListener.java