Map<String, String> map = new HashMap<String, String>();
map.put("key2", "impl2");
URL url = new URL("p1", "1.2.3.4", 1010, "path1", map);
String echo = ext.yell(url, "haha");
assertEquals("Ext1Impl2-yell", echo);
url = url.addParameter("key1", "impl3"); // 注意: URL是值类型
echo = ext.yell(url, "haha");
assertEquals("Ext1Impl3-yell", echo);