JNI exception catching and handling

• Case 1:
• Case 2
• Is three

JNI exception capture and handling, common 3 cases:

• Native layer code fails and native consumes error messages
• Java layer code error, resulting in native layer call error
• Native layer code problem, calling Java layer code error

Case 1:

Native layer code fails and native consumes error messages

Native layer code:

extern "C"
JNIEXPORT void JNICALL
Java_com_example_jni_activity_ExceptionActivity_nativeException1(JNIEnv *env, jobject thiz) {

    jclass j_class = env->GetObjectClass(thiz);

    // This line of code will report an error!!
    jfieldID j_id = env->GetFieldID(j_class, "name"."Ljava/lang/String;");
    / / TODO a way
    // Determine whether an exception has occurred
    jthrowable j_thr = env->ExceptionOccurred();
    if (j_thr) {
        LOGE("Exception detected");
        // Clear the exceptionenv->ExceptionClear(); }}Copy the code

Auxiliary graph:



If the name attribute is not found now,name is reported as an error.

env->ExceptionOccurred();
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JNI code can be detected if the error is reported, then clear the error:

 env->ExceptionClear();
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Case 2

extern "C"
JNIEXPORT void JNICALL
Java_com_example_jni_activity_ExceptionActivity_nativeException2(JNIEnv *env, jobject thiz) {
    jclass j_class = env->GetObjectClass(thiz);
    // This line of code will report an error!!
    jfieldID j_id = env->GetFieldID(j_class, "name"."Ljava/lang/String;");

    / / TODO a way
    // Determine whether an exception has occurred
    jthrowable j_thr = env->ExceptionOccurred();
    // Non-zero true
    if (j_thr) {
        LOGE("Exception detected");
        // Clear the exception
        env->ExceptionClear();

        // The parameter is the exception package name path
        jclass null_class = env->FindClass("java/lang/NullPointerException");

        env->ThrowNew(null_class, "NullPointerException!!"); }}Copy the code

// The parameter is the exception package name path
jclass null_class = env->FindClass("java/lang/NullPointerException");

env->ThrowNew(null_class, "NullPointerException!!");
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Is three

Native layer code problem, calling Java layer code error

Native layer code:

/ / TODO three ways
extern "C"
JNIEXPORT void JNICALL
Java_com_example_jni_activity_ExceptionActivity_nativeException3(JNIEnv *env, jobject thiz) {
    jclass j_class = env->GetObjectClass(thiz);

    jmethodID j_id = env->GetStaticMethodID(j_class, "showExpetcion"."()V");
    // Call the exception method of the Java layer
    env->CallStaticVoidMethod(j_class, j_id);

    // Check to see if it crashes.
    if (env->ExceptionCheck()) {
        // Description error information is displayed
        env->ExceptionDescribe();
        // Clear the crash informationenv->ExceptionClear(); }}Copy the code

Auxiliary graph:

You can mask the Java layer error exception message

The complete code