我有一串以下
{"pid":{"source":"Doc","name":"pid","value":"8180"},
"cid":{"source":"Doc","name":"cid","value":null},
"fid":{"source":"Doc","name":"fid","value":"ME453REN0004"}}
我需要获取以下字符串
{"pid":"8180",
"cid":null,
"fid":"ME453REN0004"}
如何使用正则表达式?