padeoe padeoe - 6 months ago 44
JSON Question

Gson deserialize null pointer in released apk

I'm writing an Android app need using gson to deserialize the json string:

{
"reply_code": 001,
"userinfo": {
"username": "002",
"userip": 003
}
}


so I create two classes:

public class ReturnData {
public String reply_code;
public userinfo userinfo;
}

public class userinfo {
public String username;
public String userip;
}


finally, my Java code in MainActivity.java:

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Context context= MainActivity.this;

//Test JSON
String JSON="{\"reply_code\": 001,\"userinfo\": {\"username\": \"002\",\"userip\": 003}}";
Gson gson = new Gson();
ReturnData returnData=gson.fromJson(JSON,ReturnData.class);

if(returnData.reply_code==null)
Toast.makeText(context,"isNULL",Toast.LENGTH_SHORT).show();
else
Toast.makeText(context,"notNULL",Toast.LENGTH_SHORT).show();
}


What made me confused is, when I debug the app,it ran well and output "notNULL".I can see the every attribution of the object has been deserialized properly.
However,when I generated released apk from Android Studio and run apk on phone,it output "isNULL",the json resolution failed´╝ü

Who can tell me what happened?!

PS:build.gradle:

apply plugin: 'com.android.application'
android {
compileSdkVersion 19
buildToolsVersion "19.1"

defaultConfig {
applicationId "com.padeoe.autoconnect"
minSdkVersion 14
targetSdkVersion 21
versionCode 1
versionName "2.1.4"
}
buildTypes {
release {
minifyEnabled true
shrinkResources true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_7
targetCompatibility JavaVersion.VERSION_1_7
}
}

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile files('src/gson-2.3.1.jar')
}

Answer

You have ProGuard enabled in your release build type - minifyEnabled true. It obfuscates the code by changing class/variable names.

You should annotate your class properties, so Gson knows what to look for:

public class ReturnData {
    @SerialiazedName("reply_code")
    public String reply_code;
    @SerialiazedName("userinfo")
    public userinfo userinfo;
}

public class userinfo {
    @SerialiazedName("username")
    public String username;
    @SerialiazedName("userip")
    public String userip;
}

This way Gson won't look at the properties' names, but will look at @SerializedName annotation.