remove null atributes from json with gson

问题

I want to remove attributes that have empty collections or null values using gson.

Aiperiodo periodo = periodoService();
//periodo comes from a service method with a lot of values
Gson gson = new Gson();
String json = gson.toJson(periodo);

I print json and I have this:

{"idPeriodo":121,"codigo":"2014II",
"activo":false,"tipoPeriodo":1,
"fechaInicioPreMatricula":"may 1, 2014",
"fechaFinPreMatricula":"jul 1, 2014",
"fechaInicioMatricula":"jul 15, 2014",
"fechaFinMatricula":"ago 3, 2014",
"fechaInicioClase":"ago 9, 2014",
"fechaFinClase":"dic 14, 2014",
"fechaActa":"ene 15, 2015",
"fechaUltModificacion":"May 28, 2014 12:28:26 PM",
"usuarioModificacion":1,"aiAvisos":[],
"aiAlumnoCarreraConvalidacionCursos":[],
"aiAlumnoMatriculas":[],"aiMallaCurriculars":[],
"aiAlumnoCarreraEstados":[],"aiAdmisionGrupos":[],
"aiMatriculaCronogramaCabeceras":[],
"aiAlumnoCarreraConvalidacions":[],
"aiHorarioHorases":[],"aiAsistencias":[],
"aiAlumnoPreMatriculas":[],
"aiAlumnoMatriculaCursoNotaDetalles":[],
"aiOfertaAcademicas":[],"aiTarifarios":[]}

For example for that json I don't want to have the collection aiAvisos, there is a way to delete this from the json. I'm working with a lot of collections actually here I show one, I really need remove these from the json.

I need something like this:

{"idPeriodo":121,"codigo":"2014II",
"activo":false,"tipoPeriodo":1,
"fechaInicioPreMatricula":"may 1, 2014",
"fechaFinPreMatricula":"jul 1, 2014",
"fechaInicioMatricula":"jul 15, 2014",
"fechaFinMatricula":"ago 3, 2014",
"fechaInicioClase":"ago 9, 2014",
"fechaFinClase":"dic 14, 2014",
"fechaActa":"ene 15, 2015",
"fechaUltModificacion":"May 28, 2014 12:28:26 PM",
"usuarioModificacion":1}

I tried setting the collections to null, I check the documentation and there's no method there neither...

Please any suggestions. Yeah I update the json I had posted some minutes ago.

Thanks a lot who read this!

回答1:

Steps to follow:

Convert the JSON String into Map<String,Object> using Gson#fromJson()
Iterate the map and remove the entry from the map which are null or empty ArrayList.
Form the JSON String back from the final map using Gson#toJson().

Note : Use GsonBuilder#setPrettyPrinting() that configures Gson to output Json that fits in a page for pretty printing.

Find the sample code here Remove empty collections from a JSON with Gson

来源：https://stackoverflow.com/questions/23918580/remove-null-atributes-from-json-with-gson

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