我正在编写一个基于 TodoMVC angularjs 的示例项目(http://todomvc.com/ http://todomvc.com/)并使用带有 Google App Engine Cloud Endpoint 的后端 api,当从 App Engine 数据存储区获取待办事项列表时,我得到了一些一致性结果。
Todo 对象使用 objectify 存储在 App Engine 数据存储区中。
Todo 实体的编码如下:
@Entity
public class Todo {
@Id
private Long id;
private String title;
private boolean completed;
private Date lastEdit;
@Index
private Long userId;
public Todo() {
}
public Todo(String title, boolean completed) {
this.title = title;
this.completed = completed;
}
public Todo(Long id, String title, boolean completed) {
this.id = id;
this.title = title;
this.completed = completed;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public boolean isCompleted() {
return completed;
}
public void setCompleted(boolean completed) {
this.completed = completed;
}
public Long getUserId() {
return userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
public Date getLastEdit() {
return lastEdit;
}
public void setLastEdit(Date lastEdit) {
this.lastEdit = lastEdit;
}
@Override
public String toString() {
return "Todo{" +
"id=" + id +
", title='" + title + '\'' +
", completed=" + completed +
", lastEdit=" + lastEdit +
", userId='" + userId + '\'' +
'}';
}
}
将 Todo 保存在数据存储中的操作如下:
@ApiMethod(name = "create", httpMethod = ApiMethod.HttpMethod.POST)
public Todo create(User user, Todo todo) {
logger.info("creating todo : " + todo.toString());
todo.setUserId(new Long(user.getUserId()));
todo.setLastEdit(new Date());
ofy().save().entity(todo).now();
return todo;
}
@ApiMethod(name = "list", httpMethod = ApiMethod.HttpMethod.GET)
public Collection<Todo> getTodos(User user) {
logger.info("user:" + user);
List<Todo> todos = null;
if (user != null) {
todos = ofy().consistency(ReadPolicy.Consistency.STRONG).load().type(Todo.class).filter("userId", new Long(user.getUserId())).list();
}
logger.info("todos:" + todos);
return todos;
}
假设我的列表中有 4 个待办事项,我将它们全部设置为已完成 (completed=true)。
我在数据存储查看器中检查它们的状态:
然后,如果我在几秒钟后请求列表,我将遇到奇怪的一致性问题:
2014-03-08 13:08:43.326
fr.xebia.gae.todo.api.TodoEndpointV2 getTodos: todos:[
Todo{id=5639274879778816, title='vélo', completed=false, lastEdit=Fri Mar 07 23:36:08 UTC 2014, userId='104955400895435072612'},
Todo{id=5676830073815040, title='train', completed=true, lastEdit=Sat Mar 08 12:08:30 UTC 2014, userId='104955400895435072612'},
Todo{id=5717271485874176, title='avion', completed=false, lastEdit=Fri Mar 07 23:36:09 UTC 2014, userId='104955400895435072612'},
Todo{id=5757334940811264, title='voiture', completed=true, lastEdit=Sat Mar 08 12:08:32 UTC 2014, userId='104955400895435072612'}]
正如您所看到的,所有待办事项的完成值均未设置为 true,并且它们的最后编辑日期甚至未更新
2分钟后新请求:
2014-03-08 13:10:20.612
fr.xebia.gae.todo.api.TodoEndpointV2 getTodos: todos:[
Todo{id=5639274879778816, title='vélo', completed=false, lastEdit=Fri Mar 07 23:36:08 UTC 2014, userId='104955400895435072612'},
Todo{id=5676830073815040, title='train', completed=true, lastEdit=Sat Mar 08 12:08:30 UTC 2014, userId='104955400895435072612'},
Todo{id=5717271485874176, title='avion', completed=false, lastEdit=Fri Mar 07 23:36:09 UTC 2014, userId='104955400895435072612'},
Todo{id=5757334940811264, title='voiture', completed=true, lastEdit=Sat Mar 08 12:08:32 UTC 2014, userId='104955400895435072612'}]
17 分钟后又提出新要求,但仍然不是好的价值......
2014-03-08 13:27:07.918
fr.xebia.gae.todo.api.TodoEndpointV2 getTodos: todos:[Todo{id=5639274879778816, title='vélo', completed=false, lastEdit=Fri Mar 07 23:36:08 UTC 2014, userId='104955400895435072612'},
Todo{id=5676830073815040, title='train', completed=true, lastEdit=Sat Mar 08 12:08:30 UTC 2014, userId='104955400895435072612'},
Todo{id=5717271485874176, title='avion', completed=false, lastEdit=Fri Mar 07 23:36:09 UTC 2014, userId='104955400895435072612'},
Todo{id=5757334940811264, title='voiture', completed=true, lastEdit=Sat Mar 08 12:08:32 UTC 2014, userId='104955400895435072612'}]
有人知道为什么使用 Objectify 查询的内容与使用 GAE 数据存储查看器后台查看的内容之间存在如此大的差异吗?
是一致性问题吗?但如果是这样,为什么数据存储查看器没有同样的问题?
我在查询时是否滥用 objectify (如果我在运行过滤器时设置 ofy().consistency(ReadPolicy.Consistency.STRONG) 的事件)?