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开始第一个JNI程序

In the previous article, Divide by Zero. A comparison between Java and C, we concluded that C++ programs will crash when it meets a DivideByZero Exception. Even with a handler, it will crash anyway.

Conclustion: Java and C++ are in the same process.

A comparison of DivideByZero(c++ and Java)

.java file:class CatchThrow{ private native void doit() throws IllegalArgumentException; private void callback() throws NullPointerException{ throw new NullPointerException("CathThrow.callback

.c file#include #include #include "InstanceMethodCall.h"JNIEXPORT void JNICALL Java_InstanceMethodCall_nativeMethod (JNIEnv *env, jobject obj){ jclass cls = (*env)->GetObjectClass(env,obj);

Method 1. Caching at the Point of Usestatic jmethodID cid = NULL;if (cid == NULL){ cid = (*env)->GetMethodID(env,stringClass,"","([C)V"); if (cid == NULL){ return NULL; }}Method 2

Call static method.jclass cls = *(env)->GetObjectClass(env,obj);jmethodID mid = (*env)->GetStaticMethodID(env, cls, "callback", "()V";(*env)->CallStaticVoidMethod(env, cls, mid);Attention:

Command line :javap -s -p Method_Call_NameJava method:class MethodDescriptor { MethodDescriptor(); private native java.lang.String getLine(java.lang.String); private native int GetLine(i

class FieldDescriptors{ int intvalue; double doublevalue; float floatvalue; String stringvalue = new String(); int intarrayvalue[] = new int[5]; MyClass myclassvalue = new MyClass();}How

class StaticFieldAccess{ private static int si; private native void accessField(); public static void main(String args[]){ StaticFieldAccess c = new StaticFieldAccess(); StaticFieldAccess.si =

.java File:class InstanceFieldAccess{ private String s; private native void accessField(); public static void main(String args[]){ InstanceFieldAccess c = new InstanceFieldAccess(); c.s =

.java fileclass ObjectArrayTest{ private static native int[][] initInt2DArray(int size); public static void main(String[] args){ int[][] i2arr = initInt2DArray(3); for (int i=0;i<3;i++){ fo

.java fileclass IntArray{ private native int sumArray(int arr[]); public static void main(String[] args){ IntArray p = new IntArray(); int arr[] = new int[10]; for ( int i=0; i<10;i++) ar

.c file:#include #include #include #include #include "Prompt.h"JNIEXPORT jstring JNICALL Java_Prompt_getLine (JNIEnv *env, jobject this, jstring prompt){ char buf[128]; const jbyte *str;

•The JNI interface pointer(JNIEnv) isvalid only in the current thread.•Should another thread need to access theJava VM, it must first call AttachCurrentThread() toattach itself to the VM and obt