使用-cp选项执行时无法加载类 [英] Could not load class when executed with -cp option
问题描述
Java使用-cp选项执行时无法找到类文件,如下所示
Java not able to find the class file when executed with -cp option as below
javac -cp ~/softwares/pig-0.12.0/pig-0.12.0.jar PR.java
编译成功。但是,当我运行上面生成的类时,我收到错误
Compilation is successful. However when I run the above generated class I am getting error
java -cp ~/softwares/pig-0.12.0/pig-0.12.0.jar PR
Error: Could not find or load main class PR
如果我删除-cp我得到低于预期的错误
If I remove the -cp I am getting below error which is expected
java PR
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/pig/PigServer
at PR.runPigScript(PR.java:9)
at PR.main(PR.java:21)
Caused by: java.lang.ClassNotFoundException: org.apache.pig.PigServer
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
... 2 more
你能不能请告诉我可能是失败的原因是Step-2(无法找到或加载主类)。以下是PR.java的代码
Could you please let me what might be reasons for failure is Step-2(Could not find or load main class) . Below is the code of PR.java
import org.apache.pig.ExecType;
import org.apache.pig.PigServer;
import org.apache.pig.backend.executionengine.ExecException;
public class PR {
public void runPigScript(){
try {
PigServer pigServer = new PigServer(ExecType.LOCAL);
pigServer.registerScript("RP.pig");
} catch (Exception ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
}
}
public static void main(String[] args){
PR pr = new PR();
pr.runPigScript();
}
}
来自 https://wiki.apache.org/pig/EmbeddedPig
要运行程序,首先需要使用以下命令对其进行编译:
To run your program, you need to first compile it by using the following command:
javac -cp <path>pig.jar WordCount.java
如果编译成功,则可以运行程序:
If the compilation is successful, you can then run your program:
java -cp <path>pig.jar WordCount
推荐答案
尝试使用:
java -cp ~/softwares/pig-0.12.0/pig-0.12.0.jar;. PR
问题是您还需要加载已编译的PR类。因此,您的类路径需要具有依赖项和编译输出。将当前目录添加到类路径中。
The problem is that you need to load your compiled PR class as well. So your classpath needs to have both dependencies and your compiled output. Add current directory to the classpath.
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