使用fastjson，gson解析null值的时候键保留

public class Test {
    public static void main(String[] args) {
        Gson gson= new GsonBuilder().serializeNulls().create();
        Map < String,Object > jsonMap = new HashMap< String,Object>(); 
        jsonMap.put("a",1); 
        jsonMap.put("b",""); 
        jsonMap.put("c",null); 
        jsonMap.put("d","wuzhuti.cn");
        String str = gson.toJson(jsonMap);
        System.out.println(str);
        
        person peson1 = new person();
        peson1.setAge(1);
        peson1.setName(null);
        System.out.println(gson.toJson(peson1));
    }
    
}
class person{
    private int age;
    private String name;
    public int getAge() {
        return age;
    }
    public void setAge(int agE) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String Name) {
        this.name = name;
    }
    
}

public class FastJsonTest {
    public static void main(String[] args) {
        /*
         * QuoteFieldNames———-输出key时是否使用双引号,默认为true
         * WriteMapNullValue——–是否输出值为null的字段,默认为false
         * WriteNullnumberAsZero—-数值字段@R_874_5330@,输出为0,而非null
         * WriteNullListAsEmpty—–List字段@R_874_5330@,输出为[],而非null
         * WriteNullStringAsEmpty—字符类型字段@R_874_5330@,输出为"",而非null
         * WriteNullBooleanAsfalse–Boolean字段@R_874_5330@,输出为false,而非null
         */
        Map<String,Object> jsonMap = new HashMap<String,Object>();
        jsonMap.put("a",1);
        jsonMap.put("b","");
        jsonMap.put("c",null);
        jsonMap.put("d","json");
 
        String str = JSONObject.toJSONString(jsonMap);
        // 忽略null输出
        System.out.println(str);
 
        String str2 = JSONObject.toJSONString(jsonMap,serializerFeature.WriteMapNullvalue);

        System.out.println(str2);
 
        String json = "{\"fail\":null,\"updatetimestamp\":\"1484096131863\",\"productName\":\"json测试\"}";
        // 忽略null输出
        System.out.println(JSON.parse(json));
        // 
        System.out.println(JSONObject.toJSON(json));
    }
 
}