使用 Gson 从 JSON 中删除空集合

问题描述

我想使用 gson 删除具有空集合或空值的属性.

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

我打印 json 并且我有这个:

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":[]}

例如，对于那个 json，我不想拥有 aiAvisos 集合，有一种方法可以从 json 中删除它.我实际上正在处理很多集合，我在这里展示了一个，我真的需要从 json 中删除这些.

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.

我需要这样的东西:

{"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}

我尝试将集合设置为空，我检查了文档，但那里没有任何方法......

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

请提出任何建议.

非常感谢阅读本文的人！

Thanks a lot who read this!

推荐答案

要遵循的步骤:

• 使用
• 迭代地图并从地图中删除null或空ArrayList或Map的条目.
• 使用 Gson#toJson().

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 or Map.
• Form the JSON String back from the final map using Gson#toJson().

注意: 使用 GsonBuilder#setPrettyPrinting() 配置 Gson 以输出适合页面的 Json 以进行漂亮的打印.

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

示例代码:

import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
...

Type type = new TypeToken<Map<String, Object>>() {}.getType();
Map<String, Object> data = new Gson().fromJson(jsonString, type);

for (Iterator<Map.Entry<String, Object>> it = data.entrySet().iterator(); it.hasNext();) {
    Map.Entry<String, Object> entry = it.next();
    if (entry.getValue() == null) {
        it.remove();
    } else if (entry.getValue().getClass().equals(ArrayList.class)) {
        if (((ArrayList<?>) entry.getValue()).size() == 0) {
            it.remove();
        }
    } else if (entry.getValue() instanceof Map){ //removes empty json objects {}
        Map<?, ?> m = (Map<?, ?>)entry.getValue();
        if(m.isEmpty()) {
           it.remove();
        }
    }
}

String json = new GsonBuilder().setPrettyPrinting().create().toJson(data);
System.out.println(json);

输出；

  {
    "idPeriodo": 121.0,
    "codigo": "2014II",
    "activo": false,
    "tipoPeriodo": 1.0,
    "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": 1.0
  }

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