Question

使用netflix astyanax驱动程序的简单Cassandra客户端应用程序是在Eclipse中构建的。这是pom.xml文件：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>CCL1</groupId>
  <artifactId>CCL10</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>CassandraCL1</name>
  <description>Cassandra Client 1</description>

    <dependencies>
        <dependency>
            <groupId>com.netflix.astyanax</groupId>
            <artifactId>astyanax</artifactId>
            <version>1.56.44</version>
        </dependency>
     </dependencies>      

</project>

从Eclipse启动时，该应用程序正常运行。但是当jar文件被复制到外部机器时，它无法启动，但出现以下异常：

ubuntu@ip-172-31-31-41:~/tmp$ java -cp ./CCL10-0.0.1-SNAPSHOT.jar AppCCL1
Exception in thread "main" java.lang.NoClassDefFoundError: com/netflix/astyanax/connectionpool/exceptions/ConnectionException
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
        at java.lang.Class.getMethod0(Unknown Source)
        at java.lang.Class.getMethod(Unknown Source)
        at sun.launcher.LauncherHelper.getMainMethod(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
Caused by: java.lang.ClassNotFoundException: com.netflix.astyanax.connectionpool.exceptions.ConnectionException
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 6 more

外部机器是亚马逊t1.micro Ubuntu-12实例。唯一安装的软件是Oracle的Java Runtime Environment 1.7。看起来缺少一些依赖，但我甚至看不到缺少的类的名称。

为什么Maven无法在jar中插入一些依赖？如何排除故障并解决此类问题？

Answer 1

事实证明，Maven不包含jar中的所有依赖项。（我假设Maven自动执行此操作）。包括jar中的所有依赖关系在这里解释：

How can I create an executable JAR with dependencies using Maven?

所以我通过在我的xml文件中添加以下片段解决了这个问题：

<build>
  <plugins>
<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <mainClass>AppCCL1</mainClass>
      </manifest>
    </archive>
    <descriptorRefs>
      <descriptorRef>jar-with-dependencies</descriptorRef>
    </descriptorRefs>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id> <!-- this is used for inheritance merges -->
      <phase>package</phase> <!-- bind to the packaging phase -->
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
    </plugin>
  </plugins>
</build>

ClassLoader中的异常在构建环境之外执行jar

1 个答案: