Question

我试图通过C使用JNI调用java程序。 Java程序基本上是与Hive的JDBC连接。

这是我的代码段

Java程序

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveJdbcClient {
private static String driverName = "org.apache.hive.jdbc.HiveDriver";

  /**
   * @param args
   * @throws SQLException
   */
  public static void main(String[] args) throws SQLException {
    try {
      Class.forName(driverName);
    } catch (ClassNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
      System.exit(1);
    }
    //replace "hive" here with the name of the user the queries should run as
    Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/default", "cloudera", "cloudera");
    //Connection con = DriverManager.getConnection("jdbc:hive2://");    
    Statement stmt = con.createStatement();
    String tableName = "testHiveDriverTable";
    stmt.execute("drop table if exists " + tableName);
    stmt.execute("create table " + tableName + " (key int, value string)");
    String sql = "show tables '" + tableName + "'";
    System.out.println("Running: " + sql);
    ResultSet res = stmt.executeQuery(sql);
    if (res.next()) {
      System.out.println(res.getString(1));
        }

}
}

我的C程序看起来像这样

  #include<stdio.h>
  #include "jni.h"

  int main ( void ) 
  { 
char cpath;
JNIEnv *env;
    JavaVM *jvm;
int res;
jclass cls;
jmethodID mid = NULL;

//JavaVMOption options;
JavaVMOption options [3];
options[0].optionString="-Djava.class.path=desired-classpath";
options[1].optionString = "-verbose:class";
options[2].optionString = "-Xdebug";
JavaVMInitArgs vm_args;
vm_args.version = JNI_VERSION_1_6;
vm_args.options = options;
vm_args.nOptions = 3;


res = JNI_CreateJavaVM (&jvm, (void **)&env, &vm_args);
if(res < 0 || !env)
    printf("\nUnable to Launch JVM\n");
else        
    printf("**JVM launched successfully**\n");


cls = ( * env) -> FindClass(env, "HiveJdbcClient2");
printf("**cls**:\n",cls);
if (cls!=NULL)
    printf("**HiveJdbcClient2 find success**\n");
else
    printf("**Something happend with FindClass\n");

mid = (* env) -> GetStaticMethodID (env,cls, "main", "([Ljava/lang/String;)V");
if (mid!=0)
    {
    printf("**GetStaticMethodID success -test worked**\n");
    (* env) -> CallStaticVoidMethod (env, cls, mid, NULL);
            }

(* jvm) -> DestroyJavaVM (jvm);
return 0;

}

当我只运行java程序时，jdbc连接似乎工作。但是，当通过C程序调用时，执行将在DriverManager.getConnection（）处停止，而不会出现任何错误消息或警告。我检查过hiverserver2正在运行。是否需要像hive-site.xml那样进行其他配置？我使用cloudera CDH virtualbox，因此没有执行任何其他配置。我在这个网站上看到了几个类似的查询和解决方案，但没有任何对我有用....

Answer 1

我通过捕获JNI调用中的异常来解决问题。顺便说一下，问题是缺少我在-D.Java.path中纠正过的类。

没有来自Hive JDBC连接的错误或警告

1 个答案: