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copied!<p>My code starts in Java, invokes C++, which then invokes Java back again for things like finding, getting, and setting field values.</p> <p>In case someone looking for a C++ approach finds this page, I'll plough on with this:</p> <p>What I'm now doing is wrapping my JNI method bodies up with a C++ try/catch block,</p> <pre><code>JNIEXPORT void JNICALL Java_com_pany_jni_JNIClass_something(JNIEnv* env, jobject self) { try { ... do JNI stuff // return something; if not void. } catch (PendingException e) // (Should be &e perhaps?) { /* any necessary clean-up */ } } </code></pre> <p>where PendingException is declared trivially:</p> <pre><code>class PendingException {}; </code></pre> <p>and I'm invoking the following method after invoking any JNI from C++, so if the Java exception status indicates an error, I'll bail immediately and let the normal Java exception handling add the (Native method) line to the stack trace, while giving the C++ the opportunity to clean up while unwinding:</p> <pre><code>PendingException PENDING_JNI_EXCEPTION; void throwIfPendingException(JNIEnv* env) { if (env->ExceptionCheck()) { throw PENDING_JNI_EXCEPTION; } } </code></pre> <p>My Java stack trace looks like this for a failed env->GetFieldId() call:</p> <pre><code>java.lang.NoSuchFieldError: no field with name='opaque' signature='J' in class Lcom/pany/jni/JniClass; at com.pany.jni.JniClass.construct(Native Method) at com.pany.jni.JniClass.doThing(JniClass.java:169) at com.pany.jni.JniClass.access$1(JniClass.java:151) at com.pany.jni.JniClass$2.onClick(JniClass.java:129) at android.view.View.performClick(View.java:4084) </code></pre> <p>and pretty similar if I call up to a Java method that throws:</p> <pre><code> java.lang.RuntimeException: YouSuck at com.pany.jni.JniClass.fail(JniClass.java:35) at com.pany.jni.JniClass.getVersion(Native Method) at com.pany.jni.JniClass.doThing(JniClass.java:172) </code></pre> <p>I can't talk to wrapping the Java exception within another Java exception from within C++, which I think is part of your question - I've not found the need to do that - but if I did, I'd either do it with a Java-level wrapper around the native methods, or just extend my exception-throwing methods to take a jthrowable and replace the env->ThrowNew() call with something ugly: it's unfortunate Sun didn't provide a version of ThrowNew that took a jthrowable.</p> <pre><code>void impendNewJniException(JNIEnv* env, const char *classNameNotSignature, const char *message) { jclass jClass = env->FindClass(classNameNotSignature); throwIfPendingException(env); env->ThrowNew(jClass, message); } void throwNewJniException(JNIEnv* env, const char* classNameNotSignature, const char* message) { impendNewJniException(env, classNameNotSignature, message); throwIfPendingException(env); } </code></pre> <p>I wouldn't consider caching (exception) class constructor references because exceptions aren't supposed to be a usual control flow mechanism, so it shouldn't matter if they're slow. I imagine look-up isn't terribly slow anyway, since Java presumably does its own caching for that sort of thing.</p>

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