在android的JNIHelp.h文件中声明四种可以向JVM抛异常的函数：
int jniThrowException(JNIEnv* env,
const char* className,
const char*
int jniThrowNullPointerException(JNIEnv* env,
char*
int jniThrowIOException(JNIEnv* env,
int errnum)
int jniThrowRuntimeException(JNIEnv* env,
const char*
注意：虽然
const char* className
它是字符串，但是它是要传到中使用，所以它必须和某个类相对应的。
以上4个函数的定义是JNIHelp.c文件中进行的。查看源码你会发现
jniThrowNullPointerException
、
jniThrowRuntimeException
、
jniThrowIOException
其实就是个特殊的jniThrowException。
其实它们是const char*
className
参数分别为"
java/lang/NullPointerException
"、
"java/lang/RuntimeException
"、"
java/IO/IOException
"的jniThrowException。
它们的使用也很简单，具体可以参照下面的示例代码。
另外注意，这里的抛异常函数并不是在抛异常的同时退出当前函数，而是在函数最终返回时，才真正的抛出异常。
示例1
android_database_SQLiteQuery.cpp文件中的native_fill_window函数
static jint
native_fill_window(JNIEnv* env, jobject object, jobject javaWindow,
jint
startPos,
jint
offsetParam)
{
//略
if (statement == NULL) {
LOGE("Invalid statement in fillWindow()");
jniThrowException(env, "java/lang/IllegalStateException",
"Attempting to access a deactivated, closed, or empty cursor");
return
0;
}
// Only do the binding if there is a valid offsetParam. If no binding needs to be done
// offsetParam will be set to 0, an invliad value.
if
(offsetParam > 0) {
// Bind the offset parameter, telling the program which row to start with
err = sqlite3_bind_int(statement, offsetParam, startPos);
if
(err != SQLITE_OK) {
LOGE("Unable to bind offset position, offsetParam = %d", offsetParam);
jniThrowException(env, "java/lang/IllegalArgumentException",
sqlite3_errmsg(GET_HANDLE(env, object)));
return
0;
}
LOG_WINDOW("Bound to startPos %d", startPos);
} else {
LOG_WINDOW("Not binding to startPos %d", startPos);
}
// Get the native window
window = get_window_from_object(env, javaWindow);
if (!window) {
LOGE("Invalid CursorWindow");
jniThrowException(env, "java/lang/IllegalArgumentException","Bad CursorWindow");
return
0;
}
LOG_WINDOW("Window: numRows = %d, size = %d, freeSpace = %d", window->getNumRows(), window->size(), window->freeSpace());
numColumns = sqlite3_column_count(statement);
if (!window->setNumColumns(numColumns)) {
LOGE("Failed to change column count from %d to %d", window->getNumColumns(), numColumns);
jniThrowException(env, "java/lang/IllegalStateException", "numColumns mismatch");
return
0;
}
//略
}
示例2
android_util_EventLog.cpp中的android_util_EventLog_readEvents函数
static void
jintArray tags,
jobject out) {
if (tags == NULL || out == NULL) {
jniThrowException(env, "java/lang/NullPointerException", NULL);
return;
}
int fd = open("/dev/" LOGGER_LOG_EVENTS, O_RDONLY | O_NONBLOCK);
if
jniThrowIOException(env, errno);
return;
}
jsize tagLength = env->GetArrayLength(tags);
jint *tagValues = env->GetIntArrayElements(tags, NULL);
uint8_t buf[LOGGER_ENTRY_MAX_LEN];
struct timeval timeout = {0, 0};
fd_set readset;
FD_ZERO(&readset);
for (;;) {
// Use a short select() to try to avoid problems hanging on read().
// This means we block for 5ms at the end of the log -- oh well.
timeout.tv_usec = 5000;
FD_SET(fd, &readset);
int
if (r == 0) {
break; // no more events
} else if (r < 0 && errno == EINTR) {
continue; // interrupted by signal, try again
} else if (r < 0) {
jniThrowIOException(env, errno); // Will throw on return
break;
}
int len = read(fd, buf, sizeof(buf));
if (len == 0 || (len < 0 && errno == EAGAIN)) {
break; // no more events
} else if (len < 0 && errno == EINTR) {
continue; // interrupted by signal, try again
} else if (len < 0) {
jniThrowIOException(env, errno); // Will throw on return
break;
} else if ((size_t) len < sizeof(logger_entry) + sizeof(int32_t)) {
jniThrowException(env, "java/io/IOException", "Event too short");
break;
}
//略
}
close(fd);
env->ReleaseIntArrayElements(tags, tagValues, 0);
}
