Unless the function calls for xalan have C bindings on them, the answer is no, I think. For example, if something like the following exists, then you can call some_xalan_function() from within Objective C. Otherwise, you will have to provide a C wrapper on top of xalan.
/* xalan_header_file.h */
#ifdef __cplusplus
extern "C" {
#endif
extern void some_xalan_function(...);
#ifdef __cplusplus
}
#endif