Question

我有一个servlet，它可以从休息服务或jsp表单发布请求，它将调用内部方法（internalAddPodcast（））将实体添加到数据存储区。

当我从jsp页面点击internalAddPodcast（）时，它工作正常，我可以看到通过在添加后立即查询实体已成功添加实体。但是，当我从rest方法addPodcast（）执行此操作时，datastore.put（）似乎并没有实际添加到数据存储区，因为我尝试在put（）之后立即检索它，并且没有任何东西返回。向下看这个类的底部附近，我把评论“//这个从REST服务添加时是空的:(”这是我希望有一些结果回来的地方，特别是我刚刚放入的实体数据存储。

    package com.aol.sharepodder;

import java.io.IOException;
import java.util.Date;
import java.util.List;
import java.util.logging.Logger;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.Consumes;
import javax.ws.rs.DefaultValue;
import javax.ws.rs.FormParam;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.FetchOptions;
import com.google.appengine.api.datastore.KeyFactory;
import com.google.appengine.api.datastore.PreparedQuery;
import com.google.appengine.api.datastore.Query;
import com.google.appengine.api.users.User;
import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;

@Path("/add/podcast/")
public class AddPodcastServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final Logger log = Logger.getLogger(AddPodcastServlet.class
            .getName());

    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {

        String email = req.getParameter("email");
        String collectionName = req.getParameter("collectionName");
        String podcast_url = req.getParameter("podcast_url");
        String podcast_description = req.getParameter("podcast_description");
        String podcast_title = req.getParameter("podcast_title");

        log.info("--post adding " + collectionName);

        internalAddPodcast(email, collectionName, podcast_url,
                podcast_description, podcast_title);

        resp.sendRedirect("/collection_details.jsp?collectionName="
                + collectionName + "&email=" + email);
    }

    @POST
    @Produces("text/plain")
    @Consumes("application/x-www-form-urlencoded")
    public String addPodcast(
            @DefaultValue("barrand@gmail.com") @FormParam("email") String email,
            @DefaultValue("default") @FormParam("collectionName") String collectionName,
            @DefaultValue("") @FormParam("podcast_url") String podcast_url,
            @DefaultValue("") @FormParam("podcast_description") String podcast_description,
            @DefaultValue("") @FormParam("podcast_title") String podcast_title) {
        try {
            internalAddPodcast(email, collectionName, podcast_url,
                    podcast_description, podcast_title);
            if (podcast_url == "") {
                return "No url supplied";
            }
            return "true";
        } catch (Exception e) {
            return e.getMessage();
        }
    }

    private void internalAddPodcast(String email, String collectionName,
            String podcast_url, String podcast_description, String podcast_title) {
        log.info("--INTERNAL ADD ");
        log.info("--email " + email);
        log.info("--collectionName " + collectionName);
        log.info("--podcast_url " + podcast_url);
        log.info("--podcast_description " + podcast_description);
        log.info("--podcast_title " + podcast_title);

        UserService userService = UserServiceFactory.getUserService();
        User user = userService.getCurrentUser();

        Entity podcast = new Entity("Podcast");
        podcast.setProperty("collectionName", collectionName);
        podcast.setProperty("user", user);
        podcast.setProperty("email", email);
        Date date = new Date();
        podcast.setProperty("date", date);
        podcast.setProperty("podcast_title", podcast_title);
        podcast.setProperty("podcast_description", podcast_description);
        podcast.setProperty("podcast_url", podcast_url);

        DatastoreService datastore = DatastoreServiceFactory
                .getDatastoreService();
        datastore.put(podcast);

        //try to log the podcast that I just got done adding to the datastore
        Query query = new Query("Podcast");
        PreparedQuery pq = datastore.prepare(query);

            //THIS QUERY IS EMPTY WHEN ADDED FROM THE REST SERVICE :(
        for (Entity p : pq.asIterable()) {
            log.info("_loop " + " - " + KeyFactory.keyToString(p.getKey())
                    + " -- " + p.getProperty("podcast_title") + " - "
                    + p.getProperty("podcast_url"));
        }
    }
}

任何想法我做错了，为什么我试图从rest方法添加的实体没有被添加到数据存储中。

我知道在这两种情况下（从jsp帖子或其他服务），当我到达internalAddPodcast（）时，所有方法参数都正确进入。

Answer 1

High Replication数据存储最终是一致的。这意味着大多数查询都不能保证反映刚刚对数据存储区所做的更改 - 包括返回刚刚插入的记录。详细了解此问题以及如何进行强一致性查询here。

Answer 2

啊哈哈！我找到了。我没有记录被抛出的异常。基本上我试图存储一个超过500个字符的字符串属性，它抛出了我需要注意的异常:)所以它永远不会到达datastore.put（）

datastore.put（）没有添加到db？

2 个答案: