gson.toJson 抛出 java.lang.AssertionError: java.lang.NoSuchFieldException: ONLINE

[meijieman]

Gson version

com.google.code.gson:gson:2.8.0

Java / Android version

Android 9+as arctic fox

Used tools

• Maven; version:
• Gradle; version: api 'com.google.code.gson:gson:2.8.0'
• ProGuard (attach the configuration file please); version:
• ...

Description

new Gson().toJsont(object); enter crash.

found into this code

why throw new AssertionError(e); ， not NoSuchFieldException

Expected behavior

not crash!!!

Actual behavior

crashed !!! even add try-catch(Exception e)

Reproduction steps

1. ...
2. ...

Exception stack trace

java.lang.AssertionError: java.lang.NoSuchFieldException: ONLINE
        at com.google.gson.internal.bind.TypeAdapters$EnumTypeAdapter.<init>(TypeAdapters.java:808)
        at com.google.gson.internal.bind.TypeAdapters$30.create(TypeAdapters.java:834)
        at com.google.gson.Gson.getAdapter(Gson.java:423)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:115)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:164)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:100)
        at com.google.gson.Gson.getAdapter(Gson.java:423)
        at com.google.gson.Gson.toJson(Gson.java:661)
        at com.google.gson.Gson.toJson(Gson.java:648)
        at com.google.gson.Gson.toJson(Gson.java:603)
        at com.google.gson.Gson.toJson(Gson.java:583)
        at com.xxx.util.json.JsonUtil.toJson(JsonUtil.java:204)

[meijieman]

use JSON.toJSONString(object) , output is ok

version: 'com.alibaba:fastjson:1.1.70.android'

[meijieman]

i update gson to 'com.google.code.gson:gson:2.8.9'
find not crash, but lost some field.

[Marcono1234]

Could you please verify whether you are using ProGuard? In 2.8.8 an issue with enum constant names and ProGuard usage was fixed (#1495). The AssertionError you are experiencing sounds like that issue.

Most likely obfuscation performed by ProGuard is causing the issues you are seeing. Please either edit your ProGuard config to not obfuscate or shrink your model classes you are using with Gson, or use Gson's @SerializedName annotation to specify the field names, and to not be affected by ProGuard field name obfuscation.

---

Note that I am not a member of this project.

[meijieman]

Could you please verify whether you are using ProGuard? In 2.8.8 an issue with enum constant names and ProGuard usage was fixed (#1495). The AssertionError you are experiencing sounds like that issue.

Most likely obfuscation performed by ProGuard is causing the issues you are seeing. Please either edit your ProGuard config to not obfuscate or shrink your model classes you are using with Gson, or use Gson's @SerializedName annotation to specify the field names, and to not be affected by ProGuard field name obfuscation.

Note that I am not a member of this project.

yes, there have enum constant that using ProGuard, but this model classes in third part jar, so i cannot modify this code.
i saw the #1495 , and update to com.google.code.gson:gson:2.8.9 , it's not crash, but leak some of variable。
still have problem。

[Marcono1234]

It should also be possible to specify ProGuard keep settings for third party libraries, see for example this StackOverflow answer.

However, in general you should be careful when using Gson on third party classes or JDK classes. Gson by default gets private fields of classes, even though the author might not have intended them to be used publicly. This could cause your application to break when the author of the library changes the internal implementation and removes or renames those private fields.
Though, if you only use Gson for an enum class from a third party library, then that is most likely safe because Gson serializes and deserializes the names of the public enum constants.

[meijieman]

It should also be possible to specify ProGuard keep settings for third party libraries, see for example this StackOverflow answer.

However, in general you should be careful when using Gson on third party classes or JDK classes. Gson by default gets private fields of classes, even though the author might not have intended them to be used publicly. This could cause your application to break when the author of the library changes the internal implementation and removes or renames those private fields. Though, if you only use Gson for an enum class from a third party library, then that is most likely safe because Gson serializes and deserializes the names of the public enum constants.

emmm，first the third party library made ProGuard, not my app, so i can do nothing of obfuscation.
then, i just use Gson#toJson for log it's content. is ok if it Obfuscation.
and i thought is a bug for gson leak variable.(i tried use fastjson, and it work ok.)
i hope gson can fix it.

[Marcono1234]

i thought is a bug for gson leak variable.(i tried use fastjson, and it work ok.)

Could you please create a small complete example project which can be used to reproduce this with Gson? (And ideally also showing how it correctly works with Fastjson.) Otherwise it is difficult to find out what is causing this issue.

[meijieman]

i thought is a bug for gson leak variable.(i tried use fastjson, and it work ok.)

Could you please create a small complete example project which can be used to reproduce this with Gson? (And ideally also showing how it correctly works with Fastjson.) Otherwise it is difficult to find out what is causing this issue.

i upload a test project on github. address link: GsonTest
the output log in https://github.com/meijieman/GsonTest/blob/master/REAMDE.md

THX!

[Marcono1234]

Thank you! It looks like the additional JSON properties, such as leftValidDays, mixSuccess or notifyMessage, are obtained by Fastjson from the getter methods of the class (for example getLeftValidDays()), but there are no corresponding fields for them. Gson unfortunately does not support getter methods, it only support fields, see #232.

[meijieman]

i see now. its not a normal model classes.
thanks~

[eamonnmcmanus]

It looks as if the problem here is as described above, namely that Gson currently doesn't support getter methods. Since that's covered by #232, I'm going to close this, but feel free to reopen if needed.