error log:

com.google.gson.JsonSyntaxException: 2017-08-03 20:04:21
        at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:74)
        at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:59)
        at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:41)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
        at com.google.gson.Gson.fromJson(Gson.java:887)
        at com.google.gson.Gson.fromJson(Gson.java:852)
        at com.google.gson.Gson.fromJson(Gson.java:801)
        at com.google.gson.Gson.fromJson(Gson.java:773)

code:

 Gson gson = new Gson();
 String dataAsJson = "{\"planTime\":\"2017-08-03 17:28:45\"}";
 A a = gson.fromJson(dataAsJson, A.class);

fix:

 Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd HH:mm:ss").create();
 String dataAsJson = "{\"planTime\":\"2017-08-03 17:28:45\"}";
 A a = gson.fromJson(dataAsJson, A.class);