title: 500 Internal Server Error on one of my cloud endpoint methods when deployed
body: <p>All of my Cloud Endpoints methods work locally, and all but one work when the app is deployed. Here is the method:</p>
  
  <pre><code>@ApiMethod(name = "listUrl", path ="article/urls", httpMethod = HttpMethod.GET)
  public String[] listUrl() {
      List&lt;Article&gt; articles = getArticleList();
      String[] urlArray = new String[articles.size()];
      int i = 0;
      for (Article article : articles)
          urlArray[i++] = article.getUrl(); 
      return urlArray;
  }
  </code></pre>
  
  <p>I know that the three accepted return types are "a POJO, an array or a Collection." But I thought that perhaps the <code>String[]</code> was causing the error, so tried returning a collection of <code>String</code>s instead. </p>
  
  <pre><code>@ApiMethod(name = "listUrl", path ="article/urls", httpMethod = HttpMethod.GET)
  public CollectionResponse&lt;String&gt;/*String[]*/ listUrl() {
      List&lt;Article&gt; articles = getArticleList();
      List&lt;String&gt; urls = new ArrayList&lt;String&gt;();
      //String[] urlArray = new String[articles.size()];
      //int i = 0;
      for (Article article : articles)
          urls.add(article.getUrl());
          //urlArray[i++] = article.getUrl(); 
      return /*urlArray*/ CollectionResponse.&lt;String&gt; builder().setItems(urls).build();
  }
  </code></pre>
  
  <p>But to no avail. I continue to get "500 Internal Server Error."</p>
  
  <p><img src="https://i.stack.imgur.com/Qisz0.jpg" alt="500: Internal Server Error">The most bizarre part is that when I look at the logs in the admin console, it states that the request went through fine:</p>
  
  <pre><code>2013-09-22 22:08:00.715 /_ah/spi/com.example.hiserver.ArticleEndpoint.listUrl 200 55ms 0kb Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:23.0) Gecko/20100101 Firefox/23.0
  
  xx.xxx.xx.xxx(my IP) - - [22/Sep/2013:22:08:00 -0700] "POST /_ah/spi/com.example.hiserver.ArticleEndpoint.listUrl HTTP/1.1" 200 129 - "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:23.0) Gecko/20100101 Firefox/23.0" "hylyt-it.appspot.com" ms=56 cpu_ms=21 cpm_usd=0.000014 app_engine_release=1.8.4 instance=00c61b117cdf561948b997f4ec6be2ca72c139d1
  </code></pre>