2

I am trying to run an example of JRI and being unsuccessful, here is a link to the example. http://blog.comsysto.com/2013/07/10/java-r-integration-with-jri-for-on-demand-predictions/

import org.rosuda.JRI.Rengine;
import org.rosuda.JRI.REXP;

public class HelloRWorld {
   Rengine rengine; // initialized in constructor or autowired

   public void helloRWorld() {
      rengine.eval(String.format("greeting <- '%s'", "Hello R World"));
      REXP result = rengine.eval("greeting");
      System.out.println("Greeting from R: "+result.asString());
   }
}

This is the error the console gives me.

Exception in thread "main" java.lang.NullPointerException
    at org.roulette.games.HelloRWorld.helloRWorld(HelloRWorld.java:10)
    at org.roulette.games.HelloRWorld.main(HelloRWorld.java:17)

As far as I know I have the external JRI 2014-10-19 jar attached to the project correctly. I have R 3.1.2 installed and I have the rJava 0.9-6 package installed.

Line 10 is "rengine.eval(String.format("greeting <- '%s'", "Hello R World"));".

And Line 17 is "hello.helloRWorld();".

Please Let me know if you have an idea as to why it's throwing these exceptions.... :)

4

3 回答 3

1

试试这个：是有效的：

package stackoverflow;

import org.rosuda.JRI.REXP;
import org.rosuda.JRI.Rengine;
/**
 *
 * @author yschellekens
 */
public class StackOverflow {  

   public static void main(String[] args) throws Exception {
    String[] Rargs = {"--vanilla"};
     Rengine rengine = new Rengine(  Rargs, false, null);
     rengine.eval("greeting <- '%Hello R World'");
      REXP result = rengine.eval("greeting");
      System.out.println("Greeting from R: "+result.asString());
   }
}

请注意，您有几个错误，包括不包括主类，以及没有创建正确的构造函数。

于 2015-02-04T12:16:22.933 回答
1

连接 Java 和 R 有两种不同的方法。

如果你想使用JRI-Djava.library.path ，你必须使用指向包含 JRI 库的文件夹的 JVM 参数来启动你的 java 程序。

例如：

$JAVA_HOME/bin/java  -Djava.library.path=/app/vendor/R/lib/R/library/rJava/jri/ -jar target/myapp.jar

如果找不到 JRI 安装目录，请尝试查找 JRI SO 库：

find / -name "libjri.*"

此外，请确保您已在您的环境中创建了 R_HOME 和 LD_LIBRARY_PATH：

  • R_HOME：指向您的本地 R 安装（Ej：/Library/Frameworks/R.framework/Resources）
  • LD_LIBRARY_PATH：指向 R lib 目录以及 JRI 目录（EJ：$LD_LIBRARY_PATH:/app/vendor/R/lib/R/lib:/app/vendor/R/lib/R/bin）

这是一个例子：

@Test
public void testMeanFunction() {

    // just making sure we have the right version of everything
    if (!Rengine.versionCheck()) {
        System.err.println("** Version mismatch - Java files don't match library version.");
        fail(String.format("Invalid versions. Rengine must have the same version of native library. Rengine version: %d. RNI library version: %d", Rengine.getVersion(), Rengine.rniGetVersion()));
    }

    // Enables debug traces
    Rengine.DEBUG = 1;

    System.out.println("Creating Rengine (with arguments)");
    // 1) we pass the arguments from the command line
    // 2) we won't use the main loop at first, we'll start it later
    // (that's the "false" as second argument)
    // 3) no callback class will be used
    engine = REngine.engineForClass("org.rosuda.REngine.JRI.JRIEngine", new String[] { "--no-save" }, null, false);
    System.out.println("Rengine created...");

    engine.parseAndEval("rVector=c(1,2,3,4,5)");
    REXP result = engine.parseAndEval("meanVal=mean(rVector)");
    // generic vectors are RVector to accomodate names
    assertThat(result.asDouble()).isEqualTo(3.0);
}

另一方面，如果你想使用Rserve，你需要在一个单独的进程中启动 Rserve ，然后从你的 java 进程中创建一个 RConnection 。

例如：

        if(LOGGER.isInfoEnabled()) {
            LOGGER.info("Starting RServe process...");
        }
        ProcessBuilder builder = new ProcessBuilder("/bin/sh", "-c", String.format("echo 'library(Rserve);Rserve(FALSE,args=\"--no-save --slave --RS-conf %s\")'|%s --no-save --slave", rserveConf, rexe));
        builder.inheritIO();
        Process rProcess = builder.start();

        if(LOGGER.isInfoEnabled()) {
            LOGGER.info("Waiting for Rserve to start...");
        }
        int execCodeResult = rProcess.waitFor();

        if(execCodeResult != SUCCESS_CODE) {
            LOGGER.error(String.format("Unexpected error code starting RServe: %d", execCodeResult));
        } else {
            LOGGER.error("RServe started successfully");
        }

        if(LOGGER.isInfoEnabled()) {
            LOGGER.info("Opening connection to RServe daemon....");
        }
        REngine engine = new RConnection();
        if(LOGGER.isInfoEnabled()) {
            LOGGER.info(String.format("Obtaining R server version: %d", ((RConnection)engine).getServerVersion()));
        }
        //Perform some engine.parseAndEval("....");

rserveConf是 Rserv conf 文件的路径，而rexe是 R 可执行文件的完整路径。

例如，在我的 MacOS 计算机中，我可以启动 Rserve 执行此行：

/bin/sh -c "echo 'library(Rserve);Rserve(FALSE,args=\"--slave --RS-conf /Users/me/Documents/test/rserve.conf\")'|/Library/Frameworks/R.framework/Versions/3.2/Resources/bin/exec/R --no-save --slave"

此命令输出如下内容：

Starting Rserve:
  /Library/Frameworks/R.framework/Resources/bin/R CMD /Library/Frameworks/R.framework/Versions/3.2/Resources/library/Rserve/libs//Rserve --slave 

Rserv started in daemon mode.

确保在启动 Rserve 时指定“--slave”参数。

如果您想查看更多示例，我的 github 中有一个使用两种方法 JRI 和 RServe 的演示项目：

https://github.com/jfcorugedo/RJavaServer

于 2015-10-02T11:55:22.023 回答
0

您应该使用以下命令导出 LD_LIBRARY_PATH

export LD_LIBRARY_PATH=/usr/lib/jvm/jre/lib/amd64:/usr/lib/jvm/jre/lib/amd64/default

并从 R 内部执行

install.packages("rJava")

这肯定会让您的 REngine 从您的 java 应用程序中成功运行

于 2016-10-06T08:52:03.300 回答