Android中使用Apache SSH时遭遇java.lang.ClassNotFoundException问题

问题现象 #

在Android应用中通过Java实现SSH连接时，建立连接阶段抛出NoClassDefFoundError，提示无法解析javax.management.ReflectionException类。

异常栈信息 #

FATAL EXCEPTION: main
Process: com.example.atest, PID: 14392
java.lang.NoClassDefFoundError: Failed resolution of: Ljavax/management/ReflectionException;
    at org.apache.sshd.common.util.GenericUtils.peelException(GenericUtils.java:728)
    at org.apache.sshd.common.future.AbstractSshFuture.verifyResult(AbstractSshFuture.java:121)
    at org.apache.sshd.client.future.DefaultConnectFuture.verify(DefaultConnectFuture.java:42)
    at org.apache.sshd.client.future.DefaultConnectFuture.verify(DefaultConnectFuture.java:34)
    at com.example.atest.MainActivity.sshConnect(MainActivity.java:372)
    at com.example.atest.MainActivity.onResults(MainActivity.java:335)
    at android.speech.SpeechRecognizer$InternalRecognitionListener$1.handleMessage(SpeechRecognizer.java:1062)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loopOnce(Looper.java:230)
    at android.os.Looper.loop(Looper.java:319)
    at android.app.ActivityThread.main(ActivityThread.java:8893)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:608)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1103)
Caused by: java.lang.ClassNotFoundException: Didn't find class "javax.management.ReflectionException" on path: DexPathList[[dex file "/data/data/com.example.atest/code_cache/.overlay/base.apk/classes4.dex", dex file "/data/data/com.example.atest/code_cache/.overlay/base.apk/classes5.dex", zip file "/data/app/~~iTqpPkZDjYiDFfzmOJt2nQ==/com.example.atest-uHpPjOVd-8RZr-nUHh2kaw==/base.apk"],nativeLibraryDirectories=[/data/app/~~iTqpPkZDjYiDFfzmOJt2nQ==/com.example.atest-uHpPjOVd-8RZr-nUHh2kaw==/lib/arm64, /data/app/~~iTqpPkZDjYiDFfzmOJt2nQ==/com.example.atest-uHpPjOVd-8RZr-nUHh2kaw==/base.apk!/lib/arm64-v8a, /system/lib64, /system/system_ext/lib64]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:259)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
    at org.apache.sshd.common.util.GenericUtils.peelException(GenericUtils.java:728) 
    at org.apache.sshd.common.future.AbstractSshFuture.verifyResult(AbstractSshFuture.java:121) 
    at org.apache.sshd.client.future.DefaultConnectFuture.verify(DefaultConnectFuture.java:42) 
    at org.apache.sshd.client.future.DefaultConnectFuture.verify(DefaultConnectFuture.java:34) 
    at com.example.atest.MainActivity.sshConnect(MainActivity.java:372) 
    at com.example.atest.MainActivity.onResults(MainActivity.java:335) 
    at android.speech.SpeechRecognizer$InternalRecognitionListener$1.handleMessage(SpeechRecognizer.java:1062) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loopOnce(Looper.java:230) 
    at android.os.Looper.loop(Looper.java:319) 
    at android.app.ActivityThread.main(ActivityThread.java:8893) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:608) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1103) 

当前依赖配置 #

app/build.gradle中的dependencies配置：

dependencies {

    implementation "org.apache.mina:mina-core:3.0.0-M2"

    implementation "org.apache.sshd:sshd-core:2.1.0"

    implementation "org.apache.sshd:sshd-putty:2.1.0"

    implementation "org.apache.sshd:sshd-common:2.1.0"

    implementation "org.slf4j:slf4j-api:1.7.5"

    implementation "org.slf4j:slf4j-simple:1.6.4"
}

SSH连接实现代码 #

public void sshConnect(String username, String password, String host, int port, long defaultTimeoutSeconds, String command) {

        // create a client instance
        try (SshClient client = SshClient.setUpDefaultClient()) {
            client.start();
            Log.d(TAG, "sshConnect(): client.start(): client started");

            // connection and authentication
            try (ClientSession session = client.connect(username, host, port).verify(TimeUnit.SECONDS.toMillis(defaultTimeoutSeconds)).getSession()) {
                Log.d(TAG, "ssh: client.connect()");
                session.addPasswordIdentity(password);
                session.auth().verify(TimeUnit.SECONDS.toMillis(defaultTimeoutSeconds));
                Log.d(TAG, "ssh: connection established");

                // create a channel to communicate
                channel = session.createChannel(Channel.CHANNEL_SHELL);
                Log.d(TAG, "ssh: starting shell");

                ByteArrayOutputStream responseStream = new ByteArrayOutputStream();
                channel.setOut(responseStream);

                // open channel
                channel.open().verify(5, TimeUnit.SECONDS);

                // open channel
                channel.open().verify(5, TimeUnit.SECONDS);
                try (OutputStream pipedIn = channel.getInvertedIn()) {
                    pipedIn.write(command.getBytes());
                    pipedIn.flush();
                }

                // close channel
                channel.waitFor(EnumSet.of(ClientChannelEvent.CLOSED),
                        TimeUnit.SECONDS.toMillis(5));

                // output after converting to string type
                String responseString = responseStream.toString();
                Log.d(TAG, "ssh: responseString == " + responseString);

            } catch (Exception e) {
                Log.d(TAG, "sshConnect(): client.connect(): Exception: " + e.toString());
                e.printStackTrace();
            }
        } catch (Exception e) {
            Log.d(TAG, "sshConnect(): client.start(): Exception: " + e.toString());
            e.printStackTrace();

        }
    }

解决方案 #

原因分析 #

Android SDK并未包含完整的Java EE类库，javax.management相关类属于Java EE范畴，Apache SSHD的部分版本会依赖这些类，导致在Android环境中找不到对应的类文件。

具体修复步骤 #

1. 补充缺失的依赖类库
   添加javax.management相关的API依赖到build.gradle中，直接引入适配的类库：

   implementation "javax.management:javax.management-api:1.3.2"
   

2. 升级Apache SSHD版本并优化依赖
   旧版本的sshd-core（如2.1.0）对Android兼容性较差，建议升级到最新稳定版，同时移除重复依赖（sshd-common已被sshd-core包含，无需单独引入；新版本sshd不再依赖mina-core）：

   dependencies {
       implementation "org.apache.sshd:sshd-core:3.10.0"
       implementation "org.apache.sshd:sshd-putty:3.10.0"
       implementation "org.slf4j:slf4j-api:2.0.9"
       implementation "org.slf4j:slf4j-simple:2.0.9"
       // 移除mina-core和sshd-common依赖
   }
   

3. 启用Java API Desugaring（可选）
   如果上述步骤仍无法解决问题，可在app/build.gradle中启用coreLibraryDesugaring，让Android支持更多Java标准库类：

   android {
       compileOptions {
           coreLibraryDesugaringEnabled true
           sourceCompatibility JavaVersion.VERSION_1_8
           targetCompatibility JavaVersion.VERSION_1_8
       }
   }
   
   dependencies {
       coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.0.4'
   }
   

内容的提问来源于stack exchange，提问作者user1933677