jni jnienv SetLongField example c c++ java

Set<type>Field Routines - SetLongField

void Set<type>Field(JNIEnv *env, jobject obj, jfieldID fieldID, NativeType value);

This family of accessor routines sets the value of an instance (nonstatic) field of an object. The field to access is specified by a field ID obtained by calling GetFieldID(). (SetLongField)

The following table describes the Set<type>Field routine name and value type. You should replace type in Set<type>Field with the Java type of the field, or use one of the actual routine names from the table, and replace NativeType with the corresponding native type for that routine.

Table 4-2a Set<type>Field Family of Accessor Routines

Set<type>Field Routine	Native Type
SetObjectField()	jobject
SetBooleanField()	jboolean
SetByteField()	jbyte
SetCharField()	jchar
SetShortField()	jshort
SetIntField()	jint
SetLongField()	jlong
SetFloatField()	jfloat
SetDoubleField()	jdouble

LINKAGE:

Indices in the JNIEnv interface function table.

Table 4-2b Set<type>Field Family of Accessor Routines

Set<type>Field Routine	Index
SetObjectField()	104
SetBooleanField()	105
SetByteField()	106
SetCharField()	107
SetShortField()	108
SetIntField()	109
SetLongField()	110
SetFloatField()	111
SetDoubleField()	112

PARAMETERS:

env: the JNI interface pointer.

obj: a Java object (must not be NULL).

fieldID: a valid field ID.

value: the new value of the field.

Example - SetLongField

public abstract class CPointer {
     protected long peer;
     public native void copyIn(int bOff, int[] buf,
                               int off,int len);
     public native void copyOut(...);
     ...
 }

FID_CPointer_peer is the precomputed field ID for CPointer.peer

 JNIEXPORT void JNICALL

 Java_CMalloc_free(JNIEnv *env, jobject self)
 {
     long peer = env->GetLongField(self, FID_CPointer_peer);
     if (peer == 0) {
         return; /* not an error, freed previously */
     }
     free((void *)peer);
     peer = 0;
     env->SetLongField(self, FID_CPointer_peer, peer);
 }