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 = JSONObject.toJSONString(jsonMap);  System.out.println(str);  //輸出結(jié)果:{"a":1,"b":"",d:"wuzhuti.cn"}  從輸出結(jié)果可以看出，null對(duì)應(yīng)的key已經(jīng)被過(guò)濾掉；這明顯不是我們想要的結(jié)果，這時(shí)我們就需要用到fastjson的SerializerFeature序列化屬性也就是這個(gè)方法：JSONObject.toJSONString(Object object, SerializerFeature... features)SerializerFeature有用的一些枚舉值QuoteFieldNames———-輸出key時(shí)是否使用雙引號(hào),默認(rèn)為true WriteMapNullValue——–是否輸出值為null的字段,默認(rèn)為false WriteNullNumberAsZero—-數(shù)值字段如果為null,輸出為0,而非null WriteNullListAsEmpty—–List字段如果為null,輸出為[],而非null WriteNullStringAsEmpty—字符類(lèi)型字段如果為null,輸出為”“,而非null WriteNullBooleanAsFalse–Boolean字段如果為null,輸出為false,而非null現(xiàn)在加上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 = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue);  System.out.println(str);  //輸出結(jié)果:{"a":1,"b":"","c":null,"d":"wuzhuti.cn"}  但是，如果把WriteNullStringAsEmpty也加進(jìn)去，為毛不起作用？！？??？String str = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue，SerializerFeature.WriteNullStringAsEmpty);  System.out.println(str);  //輸出結(jié)果:{"a":1,"b":"","c":null,"d":"wuzhuti.cn"}  目前的解決辦法是加一個(gè)過(guò)濾器private ValueFilter filter = new ValueFilter() {    @Override    public Object process(Object obj, String s, Object v) {    if(v==null)        return "";    return v;    }};JSON.toJSONString(jsonMap, filter)不過(guò)，心里不爽，為毛不起作用??？SerializerFeature.WriteNullStringAsEmptyfastjson github： https://github.com/alibaba/fastjson