Call DLL function from JAVA

HI!
What's the best way (and simple) to call DLL function from JAVA.
DLL function (developed in C) has two input parameters (string) and return an integer.
Could you help with an example?
Thanks a lot.

Do a google search for 'JNI tutorial' and it will turn up hundreds of examples.

Similar Messages

Calling c function from java!!

hi all,
I want to call c function from java . I have gone through the link http://java.sun.com/docs/books/tutorial/native1.1/stepbystep/index.html for JNI.
According to this link we need to write the native method implementation in such a way that the method signature should exactly match the method signature created in the header file.
My problem is that i have a c application which i cannot modify in any ways i.e., i cannot change its code. But i want to call its function from my java code.
Please suggest me appropriate solution for this. Please let me know whether it can be done using JNI or is there any other method for this.
thanks

This link is amazing since those sources were wrote in 1998 and I started to develop JNative in 2004. I did not found them when I started.
Since JNative can deal with callbacks and probably COM in a near future, I expect to see it living to Dolphin at least.
--Marc (http://jnative.sf.net)

Calling Window's Dll Functions from Java

Hello Audience,
Is there a way to call Win32/64 based Dynamic-Link-Library functions from Java?
Thanks,
GenKabuki

Yes.
In general, if you are trying to call functions in an existing dll, you will have to write a "wrapper" dll that meets the java jni interface requires. There are tools around wich purport to generate these for you. Do a google serach; among other tools, you should turn up JACE.

ORA-00911: invalid character - Calling a function from Java..

Hi to all.. I have an issue when calling an oracle function from Java..
This is my Java code:
final StringBuffer strSql = new StringBuffer();
strSql.append("SELECT GET_TBL('II_2_1_6_5') AS TABLA FROM DUAL;");
st = conexion.createStatement();
rs = st.executeQuery(strSql.toString());
and in the executeQuery a SQLException is throwed:
java.sql.SQLException: ORA-00911: invalid character
I paste the query in TOAD and it works.. :S
anybody knows how can I solve this?

Remove the Semicolon after Dual.
strSql.append("SELECT GET_TBL('II_2_1_6_5') AS TABLA FROM DUAL");
Sushant

Calling OCI functions from Java

Is it possible to call OCI's API functions from Java and create a Lightweight Session ?
Please help me out.

I too would like to know how this can be accomplished. I have
seen several posts that claim it is possible with Oracle91.

ADF: Can i call javascript function from java clsss method in ADF?

Hi,
I want to call javascript function in Java class method, is it possible in ADF? , if yes then how?
or I need to use Java 6 feature directely?
Regards,
Deepak

private void writeJavaScriptToClient(String script)
FacesContext fctx = FacesContext.getCurrentInstance();
ExtendedRenderKitService erks = Service.getRenderKitService(fctx, ExtendedRenderKitService.class);
erks.addScript(fctx, script);
}usage
StringBuilder script = new StringBuilder();
script.append( "var popup = AdfPage.PAGE.findComponentByAbsoluteId('p1');");
script.append("if(popup != null){"); script.append("popup.show();"); script.append("}");
writeJavaScriptToClient(script.toString());Timo

Calling native functions from java w/out DLL

If I invoke a JVM inside my c++ app and try to start up a class that calls a native function, do I still need a DLL for that? Or will it look to my header file and then look to my implementation somewhere in a c++ class?
For example:
WinMain() - Invokes JVM and loads "HelloWorld" java class, then calls its 'main' method.
HelloWorld.java - 'main' method calls "displayHello();" a native function.
HelloWorld.h - defines displayHello native interface
So it looks simply to the cpp implementation of the interface...I tried executing this but it isnt working...is it even possible?

OK, I attempted what you posted by writing the following code... please look at because I get a 'main' not found error. I am trying to execute this from a win32 app...
Callbacks.java:
class Callbacks {
private native void nativeMethod(int depth);
private void callback(int depth) {
    if (depth < 5) {
      System.out.println("In Java, depth = " + depth + ", about to enter C");
      nativeMethod(depth + 1);
      System.out.println("In Java, depth = " + depth + ", back from C");
    } else
      System.out.println("In Java, depth = " + depth + ", limit exceeded");
public static void main(String args[]) {
    Callbacks c = new Callbacks();
    c.nativeMethod(0);
}InvokeJVM.cpp:
#include "InvokeJVM.h"
//Log any windows errors
void InvokeJVM::LogWin32Error(const char * pTitle){
     PCHAR pBuffer;
     LONG lError = GetLastError ( );
     FormatMessage ( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
          NULL,
          lError,
          MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
          (char *)&pBuffer,
          0,
          NULL );
     //LogError ("Win32 error: %s %s\n",pBuffer,pTitle);
     LocalFree ( pBuffer );
//Get a string returned from the windows registry
bool InvokeJVM::GetStringFromRegistry(HKEY key, const char *name, unsigned char *buf, int bufsize){
     DWORD type, size;
     if (RegQueryValueEx(key, name, 0, &type, 0, &size) == 0 && type == REG_SZ && (size < (unsigned int)bufsize)){
          if (RegQueryValueEx(key, name, 0, 0, buf, &size) == 0){
               return true;
     return false;
//Get the path to the runtime environment
bool InvokeJVM::GetPublicJREHome(char *buf, int bufsize){
     HKEY key, subkey;
     char version[MAX_PATH];
     /* Find the current version of the JRE */
     if(RegOpenKeyEx(HKEY_LOCAL_MACHINE, JRE_KEY,0,KEY_READ,&key)!=0){
          //LogError("Error opening registry key '" JRE_KEY "'\n");
          return false;
     if(!GetStringFromRegistry(key,"CurrentVersion",(unsigned char *)version, sizeof(version))){
          //LogError("Failed reading value of registry key:\n\t"JRE_KEY "\\CurrentVersion\n");
          RegCloseKey(key);
          return false;
     if(strcmp(version, DOTRELEASE)!= 0){
          //LogError("Registry key '" JRE_KEY "\\CurrentVersion'\nhas value '%s', but '" DOTRELEASE "' is required.\n", version);
          RegCloseKey(key);
          return false;
     /* Find directory where the current version is installed. */
     if(RegOpenKeyEx(key,version,0,KEY_READ, &subkey)!= 0){
          //LogError("Error opening registry key '"JRE_KEY "\\%s'\n", version);
          RegCloseKey(key);
          return false;
     if(!GetStringFromRegistry(subkey, "JavaHome", (unsigned char *)buf, bufsize)){
          //LogError("Failed reading value of registry key:\n\t"JRE_KEY "\\%s\\JavaHome\n", version);
          RegCloseKey(key);
          RegCloseKey(subkey);
          return false;
     RegCloseKey(key);
     RegCloseKey(subkey);
     return true;
//Native interface call to printf
jint JNICALL _vfprintf_(FILE *fp, const char *format, va_list args){
     //LogError(format,args);
     return 0;
//Native interface call if the VM exited
void JNICALL _exit_(jint code){
     //LogError("VM exited");
     exit(code);
//Native interface call if the VM aborted
void JNICALL _abort_(void){
     //LogError("VM aborted");
     abort();
//Load the Java Virtual Machine
void InvokeJVM::LoadJVM(char* dir){
     HINSTANCE handle;
     JavaVMOption options[5];
     char JREHome[MAX_PATH];
     char JVMPath[MAX_PATH];
     char classpathOption[MAX_PATH];
     char librarypathOption[MAX_PATH];
     if(!GetPublicJREHome(JREHome, MAX_PATH)){
          //LogError("Could not locate JRE");
          abort();
     strcpy(JVMPath,JREHome);
     strcat(JVMPath,"\\jre\\bin\\client\\jvm.dll");
     if ((handle=LoadLibrary(JVMPath))==0) {
          //LogError("Error loading: %s", JVMPath);
          abort();
     CreateJavaVM_t pfnCreateJavaVM=(CreateJavaVM_t)GetProcAddress(handle,"JNI_CreateJavaVM");
     if (pfnCreateJavaVM==0){
          //LogError("Error: can't find JNI interfaces in: %s",JVMPath);
          abort();
     strcpy(classpathOption,"-Djava.class.path=");
     strcat(classpathOption,dir);
     strcat(classpathOption,";");
     strcat(classpathOption,JREHome);
     strcat(classpathOption,"\\lib");
     strcat(classpathOption,";");
     strcat(classpathOption,JREHome);
     strcat(classpathOption,"\\lib\\comm.jar");
     strcpy(librarypathOption,"-Djava.library.path=");
     strcat(librarypathOption,JREHome);
     strcat(librarypathOption,"\\lib");
     OutputDebugString("classpath option=");
     OutputDebugString(classpathOption);
     OutputDebugString("\n");
     OutputDebugString("librarypath option=");
     OutputDebugString(librarypathOption);
     OutputDebugString("\n");
     options[0].optionString=classpathOption;
     options[1].optionString=librarypathOption;
     options[2].optionString="vfprintf";
     options[2].extraInfo=_vfprintf_;
     options[3].optionString="exit";
     options[3].extraInfo=_exit_;
     options[4].optionString="abort";
     options[4].extraInfo=_abort_;
     vmArgs.version = JNI_VERSION_1_2;
     vmArgs.nOptions = 5;
     vmArgs.options = options;
     vmArgs.ignoreUnrecognized = false;
     if(pfnCreateJavaVM(&jvm,(void**)&env, &vmArgs) != 0){
          //LogError("Could not create VM");
          abort();
}Winmain.cpp:
#define WIN32_MEAN_AND_LEAN
#define WIN32_EXTRA_LEAN
#include <windows.h>
#include "oglwindow.h"          // the OpenGL window class
#include "vector.h"
#include "engine.h"               // the engine's main class
#include "BrimstoneEngine.h"
#include "InvokeJVM.h"
JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld(JNIEnv *, jobject){
    MessageBox(NULL, "Hello From Java!", "Error", MB_OK);
    return;
JNIEXPORT void JNICALL Java_Callbacks_nativeMethod(JNIEnv *env, jobject obj, jint depth){
jclass cls = env->GetObjectClass(obj);
jmethodID mid = env->GetMethodID(cls, "callback", "(I)V");
if (mid == 0) {
    return;
printf("In C, depth = %d, about to enter Java\n", depth);
env->CallVoidMethod(obj, mid, depth);
printf("In C, depth = %d, back from Java\n", depth);
JNINativeMethod methods[] = {"nativeMethod","()V", Java_Callbacks_nativeMethod};
WINAPI WinMain(HINSTANCE hInst, HINSTANCE, LPSTR, int nCmdShow){
     InvokeJVM javaVirtualMachine;
     int loopRet;
     javaVirtualMachine.running = false;
     CoInitialize(NULL);
     if (!COGLWindow::RegisterWindow(hInst)){
          MessageBox(NULL, "Failed to register window class", "Error", MB_OK);
          return -1;
     BrimstoneEngine *engine = NULL;
     try{
          char path[MAX_PATH];
          char drive[MAX_PATH];
          char file[MAX_PATH];
          char dir[MAX_PATH];
          char ext[MAX_PATH];
          jclass cls, cls1;
          jmethodID mid;
          jobjectArray args;
          jint err;
          _splitpath(path,drive,dir,file,ext);
          javaVirtualMachine.LoadJVM(dir);
          if(javaVirtualMachine.env == NULL){
               MessageBox(NULL, "Could not load VM", "Error", MB_OK);
               abort();
          if(GetModuleFileName(NULL, path, MAX_PATH) == 0){
               javaVirtualMachine.LogWin32Error("Getting module filename");
               abort();
          cls = javaVirtualMachine.env->FindClass("Callbacks");
          if(cls == NULL){
               MessageBox(NULL, "Could not find class %s (or its superclass)", "Error", MB_OK);
               exit(-1);
          err = javaVirtualMachine.env->RegisterNatives(cls, methods, 1 );
          mid = javaVirtualMachine.env->GetMethodID(cls, "main", "([Ljava/lang/String;)V");
          if(mid == NULL){
               MessageBox(NULL, "Could not find method 'main'", "Error", MB_OK);
               exit(-1);
          args = javaVirtualMachine.env->NewObjectArray(2-2, javaVirtualMachine.env->FindClass("java/lang/String"), NULL);
          if(args==NULL){
               MessageBox(NULL, "Could not create args array", "Error", MB_OK);
          for(int arg=0; arg < 2;arg++)     {
               javaVirtualMachine.env->SetObjectArrayElement(args, arg, javaVirtualMachine.env->NewStringUTF(argv[arg+2]));
          javaVirtualMachine.env->CallStaticVoidMethod(cls,mid,args);
          javaVirtualMachine.jvm->DestroyJavaVM();
          engine = new BrimstoneEngine("OpenGL Game", FALSE, 800, 600, 16);
          loopRet = engine->EnterMessageLoop();
          delete engine;
          return loopRet;
     catch(char *sz)
          MessageBox(NULL, sz, 0, 0);
          delete engine;
     CoUninitialize();
     return -1;
}any help is always appreciated

Call C function from Java

Hi
How do I call a C function from a java applet. Any ideas.
Thanks
Jay

How do I call a C function from a java applet.
You're going to run into problems here even after you figure out all the JNI details. Loading a shared object from an applet violates the security model - you will have to sign the applet. In addition, to be cross-platform (I'm using linux now), you will have to provide multiple dll/so - one for each architecture...

How to call a function from Java to JSP

Hello,
I have a question about using tags.
I have a java file,which has a function. Now I want to call this function into my JSP page.
I'm using JSP 1.2 and TOMCAT 4.1 with Java2 SDK.
I search through the web and find a method to do this.Bu it requires JSP 2.0
But I try that in my machine(using JSP 1.2).It gives an error:
Did you know what is the error? Or is there any method to call a function into my JSP page?
Please, help me to solve this.
Here are my codes(part of them)
UserPassword.java file
package data;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class UserPassword
     public static String verify(String username,String password){
          // some codes
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
     "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>simple</short-name>
<uri>http://jakarta.apache.org/tomcat/HRM/WEB-INF/lib</uri>
<description>
     A tab library for the login
</description>
<function>
        <description>verify username and password</description>
        <name>verify</name>
        <function-class>data.UserPassword</function-class>
        <function-signature>String verify(java.lang.String,java.lang.String)
        </function-signature>
</function>
</taglib>I put this file into the webapps/HRM/WEB-INF/lib folder
Here is my JSP file.
<%@ page language="java" %>
<%@ page import="data.UserPassword" %>
<%@ page session="true" %>
<%@ taglib prefix="login" uri="/WEB-INF/lib/LoginVerify.tld" %>
<jsp:useBean id="useraccount" class="data.UserPassword"/>
<jsp:setProperty name="useraccount" property="*"/>
<%
String status = UserPassword.verify(String username,String password);
String nextPage = "MainForm.jsp";
if(status.equals("InvalidU")) nextPage ="InvalidUserName.jsp";
if(status.equals("InvalidP")) nextPage ="InvalidPassword.jsp";
if(status.equals("main")) nextPage ="MainForm.jsp";
%>
<jsp:forward page="<%=nextPage%>"/>
Here is the error:
org.apache.jasper.JasperException: XML parsing error on file /WEB-INF/lib/LoginVerify.tld: (line 18, col -1): Element "taglib" does not allow "function" here.
     at org.apache.jasper.xmlparser.ParserUtils.parseXMLDocument(ParserUtils.java:189)
     at org.apache.jasper.compiler.TagLibraryInfoImpl.parseTLD(TagLibraryInfoImpl.java:247)
     at org.apache.jasper.compiler.TagLibraryInfoImpl.(TagLibraryInfoImpl.java:183)
     at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:354)
     at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:381)Please, help me to solve this trouble.
Thanks.

Yes. As serlank showed, you can just call the function easily in scriptlet tags
However the whole point of a tag library is to avoid the use of scriptlets.
Seeing as you can't use functions, is just to do it as a standard tag.
ie in your jsp
<login:verify name="<%= userName %>" password = "<%= password %>" resultVar = "status"/>
<c:choose>
<c:when test="${status == 'InvalidU'}">
    <c:set var="nextPage" value="InvalidUserName.jsp"/>
</c:when>
<c:when test="${status == 'InvalidP'}">
    <c:set var="nextPage" value="InvalidPassword.jsp"/>
</c:when>
</c:choose>In your case, this tag in the tld would possibly look something like this.
You would then have to write a tag handler class that would call the function you want.
<tag>
<name>verify</name>
<tagclass>com.tags.login.Verify</tagclass>
<teiclass>com.tags.login.VerifyTEI</teiclass> (if required)
<bodycontent>JSP</bodycontent>
// name attribute
<attribute>
      <name>name</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
// password attribute
    <attribute>
      <name>password</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
// result variable to return a response from the tag.
<variable>
    <name-from-attribute >resultVar</name-from-attribute >
    <variable-class>java.lang.String</variable-class>
    <declare>true</declare>
    <scope>AT_END</scope>
</variable>
</tag>Hope this helps some, and doesn't confuse too much :-)
Cheers,
evnafets

Call peoplesoft function from java code

Can we call the peoplesoft decrypt function from within java code ?

Hi Sumit,
For getting the connection, I would use something like:
import com.sap.mw.jco.JCO;
public class R3Connector {
     private JCO.Client jcoclient = null;
     public R3Connector () {
               super();
     public JCO.Client getClient() {
          if (jcoclient == null) {
               /* get connection from Pool */
               jcoclient = JCO.getClient (POOL_NAME);
          return jcoclient;
     public void releaseClient() {
          if (jcoclient != null) {
               JCO.releaseClient(jcoclient);
and of course you will have to define your POOL property somewhere (portalapp.xml presumably)
Hope this helps!

Calling oracle Function from java

first of all ... i don't know english very vell and sorry about it ..... then ...
i've created table in oracle :
create table STUDENT
ID NUMBER,
NAME VARCHAR2(50),
SURNAME VARCHAR2(50),
AGE NUMBER
and than i've wrote function like that :
create or replace function sf_SearchStudent
nID in number
return MyPackage.CursorType is
Result MyPackage.CursorType;
begin
open Result for select * from STUDENT where ID=nID;
return Result;
end sf_SearchStudent;
and it's working fine but in java i wrote code like that :
CallableStatement callst = conn.prepareCall("{?=call sf_SearchStudent(?,?,?,?)}");
callst.registerOutParameter(1, OracleTypes.CURSOR);
callst.setInt(1,id);
callst.setString(2,name);
callst.setString(3,surname);
callst.setInt(4,age);
callst.executeUpdate(); ------->>>>> ERROR Occur
ResultSet res = ((OracleCallableStatement)callst).getCursor(1);
while (res.next())
System.out.println(res.getInt("ID"));
System.out.println(res.getString("NAME"));
System.out.println(res.getString("SURNAME"));
System.out.println(res.getInt("AGE"));
but here is an error and i don't know why :( ....... please help me ..... F!
error type :
java.sql.SQLException: Missing IN or OUT parameter at index:: 5

no it's not a problem ........ I so already tried, but a mistake all the same was. After that I a little bit simplified.
ok consequently i did oracle procedure like that :
create or replace function sf_SearchStudent
nID in number
return MyPackage.CursorType is
wCursor MyPackage.CursorType;
begin
open wCursor for Wselect;
return wCursor;
end sf_SearchStudent;
and the java source code looks like that :
CallableStatement callst = conn.prepareCall("{?=call sf_SearchStudent(?,?,?,?)}");
callst.registerOutParameter(1, OracleTypes.CURSOR);
callst.setString(1, name);
callst.executeUpdate(); ------------------>>>>>>>>>> HERE IS AN ERROR ------------<<<<<<<<<<<<
ResultSet res = ( (OracleCallableStatement) callst).getCursor(4);
while (res.next())
System.out.println(res.getInt("ID"));
System.out.println(res.getString("NAME"));
System.out.println(res.getString("SURNAME"));
System.out.println(res.getInt("AGE"));
error type :
java.sql.SQLException: Missing IN or OUT parameter at index:: 3

Calling c functions from java

i need to call from my java program to c functions that get
c structs as a parameters in their prototype.
as you probablly know java is not working with structs (classes only), so my question is how can i do it , i mean call the c functions that gets structs as parameters form java????

1. Define java objects that hold the same data as the structs.
2. Write C code that can take the java objects as parameters, call their methods to retrieve the data, and create C structs.
3. Call the C routines that use the structs.

Calling JavaScript functions from Java

Hi,
I am trying to call the javascript function alert("text message") from a section of Java code.
I want to do something like below....
if (balh blah blah...){
isFound = false;
alert("Record already exists");
Dose anyone know how to do this?

If your Java code is in a JSP page or a Servlet, then yes, but not exactly...
Since the Java portion of a JSP / Servlet is executed on the server side, there is no way to instantaneously pop up something to the user per se - the code is executed on the server before the output is transmitted to the browser.
What you could do, however, is to have a JavaScript function defined in your page which would perform the alert:
<script language="JavaScript">
function userAlert(message){
    alert(message);
</script>Then, on the jsp/servlet side, you could perform your if/else check:
String bodyTag = "<body>";
String userMessage = null;
if (balh blah blah...){
   isFound = false;
   userMessage = "Record already exists";
   bodyTage = "<body onLoad=\"userAlert('" + userMessage + "')>\"";
}This way, as soon as the browser loads the page, it alerts the user with your message.
Hope this helped,
-Scott

Calling OCI function from Java

I am looking for a sample code in Java wherein OCI is used to create a Lightweight Session.
Thanks

This link is amazing since those sources were wrote in 1998 and I started to develop JNative in 2004. I did not found them when I started.
Since JNative can deal with callbacks and probably COM in a near future, I expect to see it living to Dolphin at least.
--Marc (http://jnative.sf.net)

Calling c functions in java

How do I call c functions from java?

See http://java.sun.com/docs/books/tutorial/native1.1/index.html

Call DLL function from JAVA

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