java.lang.NoClassDefFoundError：解析失败：Lretrofit2/Retrofit$Builder；

Question

I'm working on writing very simple Retrofit2 based Instrumented tests in Android (connectedTestAndroid task).

My tests fail however due to the above short error message.

Here's an example of the code I'm using:

package com.example.app.android;

import okhttp3.ResponseBody;
import okhttp3.OkHttpClient;

import java.util.concurrent.TimeUnit;
import java.io.IOException;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import android.util.Log;

public class Retrofit2Requests extends BasicRequest
{
  private Call<ResponseBody> call;
  private OkHttpClient _client;
  private String _baseUrl;
  private Retrofit2Adapter _adapter;
  private static final String LOG_TAG = "RetroFit2Requests";

  public Retrofit2Requests (String baseUrl) throws Exception
  {
    _client = new OkHttpClient
      .Builder()
      .connectTimeout(TIME_SOCKET_TIMEOUT, TimeUnit.MILLISECONDS)
      .readTimeout(TIME_CONNECTION_TIMEOUT, TimeUnit.MILLISECONDS)
      .build();
    _adapter = (Retrofit2Adapter) new Retrofit.Builder()
      .client(_client)
      .baseUrl(baseUrl)
      .build()
      .create(Retrofit2Adapter.class);
    _baseUrl = baseUrl;
  }

  public void getResponse(String data) throws IOException
  {
    Call<ResponseBody> call = _adapter.getDelayResponse(50, data);
    call.enqueue(getCallback());
  }

  private Callback getCallback()
  {
    return new Callback<ResponseBody>()
    {
      @Override
      public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response)
      {
        ResponseBody responseBody = (ResponseBody) response.body();

        Log.d(LOG_TAG, "ResponseBody: " + responseBody.toString());
      }

      @Override
      public void onFailure(Call<ResponseBody> call, Throwable t)
      {
        Log.e(LOG_TAG, "An exception occured fetchign response...", t);
      }
    };
  }
}

The goal of this code is not to test any business logic or anything special in my app. All it is supposed to do is attempt a request and that's it.

Here's also my Gradle dependencies. Based on the output of ./gradlew :app:dependencies also cleared me off any potential issues regarding different versions of retrofit in the same place. The app does not use obfuscation or minification as it, again, is only supposed to do a network request.

dependencies {    
    compile 'org.apache.httpcomponents:httpclient-android:4.3.5.1'
    compile 'com.mcxiaoke.volley:library:1.0.19'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'org.apache.commons:commons-lang3:3.7'
    compile 'com.squareup.retrofit2:retrofit:2.4.0'
    compile 'com.android.support:multidex:1.0.1'

    androidTestCompile 'org.hamcrest:hamcrest-library:1.3'
    androidTestCompile 'com.android.support.test:runner:0.5'
    androidTestCompile 'junit:junit:4.12'
}

If you're curious, yes, I'm doing the same thing with multiple network libraries. Their existence unless creating this builds NoClassDefFoundException should not matter. Previously, I also explicitly depended on OkHttp directly but since retrofit2 depends on it I skipped that dependency, naturally.

Here's the defaultConfig for my android application:

defaultConfig {
  applicationId 'com.example.app.android'
  minSdkVersion 16
  targetSdkVersion 24
  testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        
  multiDexEnabled true

  dexOptions {
    preDexLibraries true
    javaMaxHeapSize '6g'
    incremental true
  }
}

I was able, by decompiling the debug APK, to see that retrofit2/Retrofit.class wasn't available. This is confusing, as from my understanding Dex'ing shouldn't affect it.

Any ideas what could be the source of this issue and resolve in this context?

Answer 1

NoClassDefFoundError error means no definition of the class could be found. It is different from NoClassFoundException .

• NoClassDefFoundError : JVM can find the class but can't load it success.(something wrong when init the class)

• NoClassFoundException : JVM can not find the class in the classpath.

NoClassDefFoundError always happens during class init. I suggest you clean the project and check the init process of Lretrofit2/Retrofit$Builder

Hope this post can help you Java understand NoClassDefFoundError

Answer 2

For my case, I just clean and rebuild project and this made me this issues solved. this exception arises when you change any class name but the compiler still keeps the previous class name in cache and in runtime compiler can not find previously stored class name as you changed the name later.

Answer 3

Add this to your app`s build.gradle, inside android {...}:

compileOptions {
    sourceCompatibility 1.8
    targetCompatibility 1.8
}

Then clean and rebuild your project. It worked for me.

Answer 4

The issue was solved in Retrofit 2.8.1 just upgrade retrofit dependency to 2.8.1 if it's below that.

From retrofit changelog :

Version 2.8.1 (2020-03-25) Fix: Do not access MethodHandles. Lookup on Android API 24 and 25. The class is only available on Android API 26 and higher.