fastjson null 值处理

import java.util.HashMap;
import java.util.Map;

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;

public class Test2 {

/**
* @param args
*/
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—-数值字段如果为null,输出为0,而非null
WriteNullListAsEmpty—–List字段如果为null,输出为[],而非null
WriteNullStringAsEmpty—字符类型字段如果为null,输出为”“,而非null
WriteNullBooleanAsFalse–Boolean字段如果为null,输出为false,而非null
*/

Map < String , Object > jsonMap = new HashMap< String , Object>();
jsonMap.put("xyw",1);
jsonMap.put("123","");
jsonMap.put("xuyw",null);
jsonMap.put("xywa","css");

String str = JSONObject.toJSONString(jsonMap);
System.out.println(str);

String str2 = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue);
System.out.println(str2);
}

}

{"123":"","xyw":1,"xywa":"css"}
{"123":"","xuyw":null,"xyw":1,"xywa":"css"}

指定序列化字段
SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Map.class, "code","name");
JSON.toJSONString(list,filter)