jni jnienv CallStaticObjectMethod example c c++ java

CallStatic<type>Method Routines - CallStaticObjectMethod
CallStatic<type>MethodA Routines
CallStatic<type>MethodV Routines

NativeType CallStatic<type>Method

(JNIEnv *env, jclass clazz,
jmethodID methodID, ...);

NativeType CallStatic<type>MethodA

(JNIEnv *env, jclass clazz,
jmethodID methodID, jvalue *args);

NativeType CallStatic<type>MethodV

(JNIEnv *env, jclass clazz,
jmethodID methodID, va_list args);

(CallStaticObjectMethod)This family of operations invokes a static method on a Java object, according to the specified method ID. The methodID argument must be obtained by calling GetStaticMethodID().

The method ID must be derived from clazz, not from one of its superclasses.

(CallStaticObjectMethod)

CallStatic<type>Method Routines

Programmers should place all arguments that are to be passed to the method immediately following the methodID argument. TheCallStatic<type>Method routine accepts these arguments and passes them to the Java method that the programmer wishes to invoke. (CallStaticObjectMethod)

CallStatic<type>MethodA Routines

Programmers should place all arguments to the method in an args array of jvalues that immediately follows the methodIDargument. The CallStaticMethodA routine accepts the arguments in this array, and, in turn, passes them to the Java method that the programmer wishes to invoke.

CallStatic<type>MethodV Routines

Programmers should place all arguments to the method in an args argument of type va_list that immediately follows the methodIDargument. The CallStaticMethodV routine accepts the arguments, and, in turn, passes them to the Java method that the programmer wishes to invoke.

The following table describes each of the method calling routines according to their result types. You should replace type inCallStatic<type>Method with the Java type of the method, or one of the actual method calling routine names from the table, and replace NativeType with the corresponding native type for that routine.

Table 4-7a CallStatic<type>Method Calling Routines


CallStatic<type>Method Routine Name	Native Type
`CallStaticVoidMethod()` `CallStaticVoidMethodA()` `CallStaticVoidMethodV()`	void
`CallStaticObjectMethod()` `CallStaticObjectMethodA()` `CallStaticObjectMethodV()`	jobject
`CallStaticBooleanMethod()` `CallStaticBooleanMethodA()` `CallStaticBooleanMethodV()`	jboolean
`CallStaticByteMethod()` `CallStaticByteMethodA()` `CallStaticByteMethodV()`	jbyte
`CallStaticCharMethod()` `CallStaticCharMethodA()` `CallStaticCharMethodV()`	jchar
`CallStaticShortMethod()` `CallStaticShortMethodA()` `CallStaticShortMethodV()`	jshort
`CallStaticIntMethod()` `CallStaticIntMethodA()` `CallStaticIntMethodV()`	jint
`CallStaticLongMethod()` `CallStaticLongMethodA()` `CallStaticLongMethodV()`	jlong
`CallStaticFloatMethod()` `CallStaticFloatMethodA()` `CallStaticFloatMethodV()`	jfloat
`CallStaticDoubleMethod()` `CallStaticDoubleMethodA()` `CallStaticDoubleMethodV()`	jdouble

LINKAGE:

Indices in the JNIEnv interface function table.

Table 4-7b CallStatic<type>Method Calling Routines


CallStatic<type>Method Routine Name	Index
`CallStaticVoidMethod()` `CallStaticVoidMethodA()` `CallStaticVoidMethodV()`	141 143 142
`CallStaticObjectMethod()` `CallStaticObjectMethodA()` `CallStaticObjectMethodV()`	114 116 115
`CallStaticBooleanMethod()` `CallStaticBooleanMethodA()` `CallStaticBooleanMethodV()`	117 119 118
`CallStaticByteMethod()` `CallStaticByteMethodA()` `CallStaticByteMethodV()`	120 122 121
`CallStaticCharMethod()` `CallStaticCharMethodA()` `CallStaticCharMethodV()`	123 125 124
`CallStaticShortMethod()` `CallStaticShortMethodA()` `CallStaticShortMethodV()`	126 128 127
`CallStaticIntMethod()` `CallStaticIntMethodA()` `CallStaticIntMethodV()`	129 131 130
`CallStaticLongMethod()` `CallStaticLongMethodA()` `CallStaticLongMethodV()`	132 134 133
`CallStaticFloatMethod()` `CallStaticFloatMethodA()` `CallStaticFloatMethodV()`	135 137 136
`CallStaticDoubleMethod()` `CallStaticDoubleMethodA()` `CallStaticDoubleMethodV()`	138 140 139

PARAMETERS of CallStaticObjectMethod

env: the JNI interface pointer.

clazz: a Java class object.

methodID: a static method ID.

Additional Parameter for CallStatic<type>Method Routines:

arguments to the static method.

Additional Parameter for CallStatic<type>MethodA Routines:

args: an array of arguments.

Additional Parameter for CallStatic<type>MethodV Routines:

args: a va_list of arguments.

RETURNS:

Returns the result of calling the static Java method.

THROWS:

Exceptions raised during the execution of the Java method.

Example of CallStaticObjectMethod

jmethodID method = env->GetStaticMethodID( cls, "getData", "()[Ljava/lang/String;" );
jarray    data   = (jarray) env->CallStaticObjectMethod( cls, method );

// assumption: the result of getData() is never null
jsize const length = env->GetArrayLength(data);

// assumption: the String[] is always of length > 0
char** args = new char*[ length ];

for( jsize index(0); index < length; ++index )
{
    jstring element = (jstring) env->GetObjectArrayElement( array, index );

    // assumption: there are no null strings in the array
    char  const* nativeString = env->GetStringUTFChars( element, 0 );
    jsize const  nativeLength = strlen(nativeString);

    args[index] = new char[ nativeLength + 1 ];
    strncpy( args[index], nativeString, nativeLength );

    env->ReleaseStringUTFChars( element, nativeString );
}

Example source code bank

Tuesday, April 23, 2013