fastjson解析字符串，字段按字符串中顺序排列

fastjson在把字符串解析成Json对象时，可以通过指定Feature.OrderedField来使Json对象中的元素按字符串中的顺序排列。

但在把字符串解析成JsonArray时好像没有这样的参数可以设置。

在查看源码后发现JSONArray.parseArray内部调用了new JSONObject(lexer.isEnabled(Feature.OrderedField))

public final boolean isEnabled(Feature feature) {
        return isEnabled(feature.mask);
    }
 
    public final boolean isEnabled(int feature) {
        return (this.features & feature) != 0;
    }

这里的this.features实际就是JSON.DEFAULT_PARSER_FEATURE

废话少说，上代码：

public static void main(String[] args) {
        String str = "{\"b\":321,\"a\":123}";
        JSONObject json = JSONObject.parseObject(str);
        System.out.println(json);//结果为：{"a":123,"b":321}
         
        JSONObject json2 = JSONObject.parseObject(str, Feature.OrderedField);
        System.out.println(json2);//结果为：{"b":321,"a":123}
         
        String arrStr = "[{\"b\":321,\"a\":123}]";
        JSONArray array = JSONArray.parseArray(arrStr);
        System.out.println(array);//结果为：[{"a":123,"b":321}]
         
        int temp = JSON.DEFAULT_PARSER_FEATURE;
        JSON.DEFAULT_PARSER_FEATURE = Feature.config(JSON.DEFAULT_PARSER_FEATURE, Feature.OrderedField, true);
        JSONArray array2 = JSONArray.parseArray(arrStr);
        JSON.DEFAULT_PARSER_FEATURE = temp;
        System.out.println(array2);//结果为：[{"b":321,"a":123}]
    }