Object[] a = {"123", "abc", "ABC"};

String[] res = new String[a.length];
for(int i=0;i<a.length;i++)
  res[i] = (String)a[i];

------解决方案--------------------
actionContext.getObj("ids") 返回的是object的数组。。。。转成string的 String[] res = new String[actionContext.getObj("ids").length];
for(int i=0;i<actionContext.getObj("ids").length;i++)
 res[i] = (String)actionContext.getObj("ids")[i];



------解决方案--------------------
String s = actionContext.getObj("ids");
String[] ss = s.spilt(",");

就可以了！！