add dynamic JNI load/unload support

Author: s-u

R/jfirst.R

@@ -22,7 +22,7 @@
                     "RgetShortArrayCont", "RgetStringArrayCont", "RidenticalRef", "RgetSimpleClassNames",
                     "RisAssignableFrom", "RpollException", "RsetField", "RthrowException",
                     "javaObjectCache", "initRJavaTools", "newRJavaLookupTable", "useDynamicSymbols",
-                    "RgetJVMstate",
+                    "RgetJVMstate", "RloadJVM", "RunloadJVM",
                      # .External
                     "RcreateObject", "RgetStringValue", "RinitJVM", "RtoString", "RcallMethod",
                      # .C

R/jinit.R

@@ -9,8 +9,41 @@
 .need.init <- function()
     .Call(RJava_needs_init)
 
+.jloadJVM <- function(path, silent=FALSE)
+  .Call(RloadJVM, path.expand(path), silent)
+
+.junloadJVM <- function()
+  .Call(RunloadJVM)
+
+.jfindAndLoadJVM <- function() {
+    home <- Sys.getenv("JAVA_HOME")
+    if (!nzchar(home) || !isTRUE(dir.exists(home))) {
+        ## try java_home first if present
+        if (file.exists("/usr/libexec/java_home")) {
+	    home <- tryCatch(system("/usr/libexec/java_home", intern=TRUE, ignore.stderr=TRUE),
+	                     error=function(...) "")
+	}
+	## otherwise rely on java in PATH
+        if (!nzchar(home) || !isTRUE(dir.exists(home))) {
+	    home <- tryCatch(system(paste("java", "-cp",
+	        shQuote(system.file("java", package="rJava")), "getsp", "java.home"),
+	        intern=TRUE, ignore.stderr=TRUE), error=function(...) "")
+	}
+    }
+    if (!nzchar(home) || !isTRUE(dir.exists(home)))
+        stop("Cannot find Java. Either make sure java executable is on the PATH or set the JAVA_HOME environment variable.")
+    libjvm <- list.files(home, "^libjvm[.]", recursive=TRUE, full.names=TRUE)
+    if (!length(libjvm))
+        stop("Cannot find libjvm in ", home)
+    message("Loading JVM from ", home)
+    .jloadJVM(libjvm)
+}
+
 ## initialization
 .jinit <- function(classpath=NULL, parameters=getOption("java.parameters"), ..., silent=FALSE, force.init=FALSE) {
+  st <- .jvmState()
+  if (st$state == "not-loaded")
+     .jfindAndLoadJVM()
   running.classpath <- character()
   if (!.need.init()) {
     running.classpath <- .jclassPath()

mkdist

@@ -166,6 +166,7 @@ echo "Copy compiled Java classes ..."
 # copy all complied Java classes and sources
 cp src/java/*.class inst/java
 cp src/java/*.java inst/java
+cp tools/getsp* inst/java
 # move RJavaClassLoader into boot area since it will be loaded by the system class loader
 mv inst/java/RJavaClassLoader* inst/java/boot
 # move javadoc directory

src/Rglue.c

@@ -1135,8 +1135,11 @@ REPC SEXP RgetJVMstate(void) {
     const char *st = "unknown";
     switch (rJava_JVM_state) {
     case JVM_STATE_NONE: /* could be detached */
-	st = (existingJVMs() > 0) ? "detached" : "none";
-	break;
+	{
+	    int evm = existingJVMs();
+	    st = (evm == -1) ? "not-loaded" : ((evm > 0) ? "detached" : "none");
+	    break;
+	}
     case JVM_STATE_CREATED:   st = "created"; break;
     case JVM_STATE_ATTACHED:  st = "attached"; break;
     case JVM_STATE_DEAD:      st = "dead"; break;
@@ -1147,3 +1150,31 @@ REPC SEXP RgetJVMstate(void) {
     UNPROTECT(1);
     return res;
 }
+
+REPC SEXP RloadJVM(SEXP sPath, SEXP sSilent) {
+    const char *path;
+    int res, silent = Rf_asInteger(sSilent);
+    if (TYPEOF(sPath) != STRSXP || LENGTH(sPath) != 1)
+	Rf_error("Invalid path to JVM library");
+    /* FIXME: worry about encoding? */
+    path = CHAR(STRING_ELT(sPath, 0));
+    res = djni_load(path);
+    if (silent)
+	return Rf_ScalarInteger(res);
+    switch(res) {
+    case -1: Rf_error("JVM run-time is already loaded");
+    case -2: Rf_error("Cannot load JVM run-time (%s)", djni_last_error() ? djni_last_error() : "unsuccessful");
+    case -3: Rf_error("JVM run-time does not have required entry points");
+    }
+    return Rf_ScalarLogical(1);
+}
+
+REPC SEXP RunloadJVM(void) {
+    int res;
+    if (rJava_JVM_state == JVM_STATE_CREATED ||
+	rJava_JVM_state == JVM_STATE_ATTACHED) {
+	destroyJVM();
+    }
+    res = djni_unload();
+    return Rf_ScalarLogical((res < -1) ? 0 : 1);
+}

src/djni.c

@@ -38,6 +38,8 @@ int djni_load(const char *path) {
 	JNI_GetDefaultJavaVMInitArgs_fn = 0;
 	JNI_CreateJavaVM_fn = 0;
 	JNI_GetCreatedJavaVMs_fn = 0;
+	dlclose(jni_dl);
+	jni_dl = 0;
 	return -3;
     }
     return 0;
@@ -54,6 +56,14 @@ int djni_unload(void) {
     return -1;  
 }
 
+int djni_loaded(void) {
+    return jni_dl ? 1 : 0;
+}
+
+const char* djni_last_error(void) {
+    return last_error;
+}
+
 /* The following are the "normal" JNI API calls which are routed to libjvm JNI API.
    If no JNI was loaded, they return -99 to distinguish it from JNI error codes. */
 

src/djni.h

@@ -9,8 +9,13 @@
 
 #include "jni.h"
 
+/* returned if no run-time is loaded */
+#define JNI_NO_DJNI -99
+
 int djni_load(const char *path);
 int djni_unload(void);
+const char* djni_last_error(void);
+int djni_loaded(void);
 
 jint JNI_GetDefaultJavaVMInitArgs(void *args);
 jint JNI_CreateJavaVM(JavaVM **pvm, void **penv, void *args);

src/init.c

@@ -89,10 +89,12 @@ static void JNICALL exit_hook(int status) {
     exit(status);
 }
 
+/* -1 if no run-time is loaded, otherwise number of active VMs */
 int existingJVMs(void) {
     jsize vms = 0;
     JavaVM *jvms[32];
-    return (JNI_GetCreatedJavaVMs(jvms, 32, &vms) >= 0) ? vms : 0;
+    jint res = JNI_GetCreatedJavaVMs(jvms, 32, &vms);
+    return (res == JNI_NO_DJNI) ? -1 : ((res >= 0) ? vms : 0);
 }
 
 /* in reality WIN64 implies WIN32 but to make sure ... */
@@ -118,7 +120,9 @@ static int initJVM(const char *user_classpath, int opts, char **optv, int hooks,
   if(!user_classpath) user_classpath = "";
 
   vm_args.version = JNI_VERSION_1_2;
-  if(JNI_GetDefaultJavaVMInitArgs(&vm_args) != JNI_OK) {
+  if((res = JNI_GetDefaultJavaVMInitArgs(&vm_args)) != JNI_OK) {
+    if (res == JNI_NO_DJNI) /* DJNI has not loaded a run-time yet */
+      error("No Java run-time is not loaded.");
     error("JNI 1.2 or higher is required");
     return -1;
   }
@@ -193,8 +197,11 @@ static int initJVM(const char *user_classpath, int opts, char **optv, int hooks,
   if (disableGuardPages && (res != 0 || !eenv))
     return -2; /* perhaps this VM does not allow disabling guard pages */
 
-  if (res != 0)
-      error("Cannot create Java virtual machine (JNI_CreateJavaVM returned %ld)", (long int) res);
+  if (res != 0) {
+      if (rJava_JVM_state != JVM_STATE_NONE)
+	  Rf_warning("Attempt to re-create a second JVM in a process - most known Java implementations do not support it.");
+      Rf_error("Cannot create Java virtual machine (JNI_CreateJavaVM returned %d)", (int) res);
+  }
   if (!eenv)
     error("Cannot obtain JVM environment");
 
@@ -760,21 +767,31 @@ static SEXP RinitJVM_jsw(SEXP par) {
 /** RinitJVM(classpath)
     initializes JVM with the specified class path */
 REP SEXP RinitJVM(SEXP par) {
-
+    if (!djni_loaded())
+	Rf_error("No Java run-time is loaded.");
 #ifndef JVM_STACK_WORKAROUND
-  return RinitJVM_real(par, 0);
+    return RinitJVM_real(par, 0);
 #else
-  return RinitJVM_jsw(par);
+    return RinitJVM_jsw(par);
 #endif
 }
 
-REP void doneJVM(void) {
-  (*jvm)->DestroyJavaVM(jvm);
-  jvm = 0;
-  eenv = 0;
-  rJava_JVM_state = JVM_STATE_DESTROYED;
+/* detaches (if only attached) or destroys (if created) JVM */
+HIDE void destroyJVM(void) {
+    if (!jvm)
+	return;
+    if (rJava_JVM_state == JVM_STATE_CREATED ||
+	rJava_JVM_state == JVM_STATE_ATTACHED) {
+	(*jvm)->DetachCurrentThread(jvm);
+	if (rJava_JVM_state == JVM_STATE_CREATED)
+	    (*jvm)->DestroyJavaVM(jvm);
+	jvm = 0;
+	eenv = 0;
+	rJava_JVM_state = (rJava_JVM_state == JVM_STATE_CREATED) ? JVM_STATE_DESTROYED : JVM_STATE_DETACHED;
+    }
 }
 
+
 /**
  * Initializes the cached values of classes and methods used internally
  * These classes and methods are the ones that are in rJava (RJavaTools, ...)

src/rJava.h

@@ -1,7 +1,7 @@
 #ifndef __RJAVA_H__
 #define __RJAVA_H__
 
-#define RJAVA_VER 0x01000b /* rJava v1.0-11 */
+#define RJAVA_VER 0x010010 /* rJava v1.1-0 */
 
 /* important changes between versions:
    3.0  - adds compiler
@@ -19,7 +19,7 @@
    0.2  - uses S4 classes
    0.1  - first public release */
 
-#include <jni.h>
+#include "djni.h"
 #include <R.h>
 #include <Rinternals.h>
 #include <Rversion.h>
@@ -140,7 +140,8 @@ extern int rJava_initialized;
 #define JVM_STATE_CREATED   1  /* JVM was created by us */
 #define JVM_STATE_ATTACHED  2  /* we attached to another JVM */
 #define JVM_STATE_DEAD      4  /* set when Java exit handler was called */
-#define JVM_STATE_DESTROYED 8  /* JVM was destroyed */
+#define JVM_STATE_DETACHED  8  /* detached from existing JVM */
+#define JVM_STATE_DESTROYED 9  /* JVM was destroyed */
 
 extern int rJava_JVM_state;
 
@@ -168,6 +169,7 @@ extern jmethodID mid_RJavaImport_lookup ;
 extern jmethodID mid_RJavaImport_exists ;
 
 HIDE void init_rJava(void);
+HIDE void destroyJVM(void);
 
 /* in otables.c */
 // turn this for debugging in otables.c