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How to bind native libraries

Some companies(especially game company) uses C/C++ more than java. They uses the native libraries for communication between clients and servers.
They don’t know Java much which nGrinder is built on and want to reuse existing their native asset as much as possible. 
nGrinder has been shipped with JNA which enables java and native libraries(so, jar) binding. Therefore users can use DLL or SO files in their scripts.

The followings describes the step necessary to run so or dlls with nGrinder.

  1. Prepare the DLLs or SOs which defines the simple functions which can be easily bridged to Java.
    Methods with no parameter is pefered. If you want to pass the parameter from nGrinder script to DLLs or SOs, please make the parameter type simple as much as possible like char* or int.
  2. Upload the created DLLs or SOs into lib folder. If you will define the script in the helloworld/TestRunner.groovy, you should upload those native libraries in the helloworld/lib/ folder.
  3. Write the test script using JNA binding. Following show the simple binding between the groovy script and native lib named “dmclient”
    package org.ngrinder;
    // import JNA
    import com.sun.jna.Library
    import com.sun.jna.Native
    import static net.grinder.script.Grinder.grinder
    import net.grinder.plugin.http.HTTPRequest
    import net.grinder.plugin.http.HTTPPluginControl;
    import net.grinder.script.GTest
    import net.grinder.script.Grinder
    import net.grinder.scriptengine.groovy.junit.GrinderRunner
    import net.grinder.scriptengine.groovy.junit.annotation.BeforeProcess
    import net.grinder.scriptengine.groovy.junit.annotation.BeforeThread
    // import static net.grinder.util.GrinderUtils.* // You can use this if you're using nGrinder after 3.2.3
    import org.junit.Before
    import org.junit.BeforeClass
    import org.junit.Test
    import org.junit.runner.RunWith
    import HTTPClient.HTTPResponse
    import HTTPClient.NVPair
    class TestRunner {
        // Define the interface which native library has.
        interface NativeClient extends Library {
            public void connect(  )
        public static GTest test
        public static HTTPRequest request
        public static def nativeClient;
        public static void beforeProcess() {
            // load ' or native_client.dll with interface NativeClient 
            //(File extension(so or dll) is depending on agent's OS)
            nativeClient = Native.loadLibrary( 'native_client', NativeClient);
            test = new GTest(1, "Test1")
        public void beforeThread() {
            // Record the current test instances method "doTest"
            // because the nativeClient instance is not recordable because it's the native method.
            test.record(this, "doTest");
        public void test(){
        public void doTest() {
            // Call the native library's methods.
  4. Then run the test.
    Please be aware that you should run the SOs or DLLs in the machines which contains same library version(e.x. GLIBC) when you developed those.
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