序列化LinkedHashMap，有序輸出Json字符串

LinkedHashMap本身是有序的，使用JDK自帶的序列化代碼或者fastJson代碼序列化后，字符串並非按照插入順序輸出

Map<String,String> linkedMap=new LinkedHashMap<String,String>();
linked2.put("b","2");
linked2.put("a","1");
linked2.put("c","3");
String jsonStr=JSON.toJSONString(linkedMap);
輸出jsonStr為{"a":"1","b":"2","c":"3"}
解決辦法：
使用Gson(com.google.gson)序列化

Map<String,String> linkedMap=new LinkedHashMap<String,String>();
linked2.put("b","2");
linked2.put("a","1");
linked2.put("c","3");
Gson gson = new GsonBuilder().enableComplexMapKeySerialization().create();
String jsonStr=gson.toJson(linked2);
System.out.println(jsonStr);
輸出jsonStr為{"b":"2","a":"1","c":"3"}