线程“主”java.lang.NoClassDefFoundError异常：org/apache/commons/dbcp2/BasicDataSource

问题描述：

我想运行一个Maven项目，它使用数据库池和数据库上做一些东西。其实我的代码在Eclipse上正常工作，我得到的输出。我的代码如下：线程“主”java.lang.NoClassDefFoundError异常：org/apache/commons/dbcp2/BasicDataSource

package pack; 

import org.apache.commons.dbcp2.BasicDataSource; 

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

public class App { 

    private final String CONNECTION_URL = "jdbc:derby:memory:test;create=true"; 

    private BasicDataSource ds; 

    //private Connection classicalWay() throws SQLException { 
    // return DriverManager.getConnection(CONNECTION_URL); 
    //} 

    public static void main(String[] args) { 
     final App app = new App(); 
     app.process(); 
    } 

    private Connection poolWay() throws SQLException { 
     if (ds == null) { 
      ds = new BasicDataSource(); 
      ds.setUrl(CONNECTION_URL); 
      ds.setMaxTotal(10); 
     } 
     return ds.getConnection(); 
    } 

    private Connection getConnection() throws SQLException { 
     return poolWay(); 
     //return classicalWay(); 
    } 

    private void createTable(final Statement stmt) throws SQLException { 
     stmt.execute("CREATE TABLE CUSTOMER (NAME VARCHAR(10))"); 
    } 

    private void insertRecord(final Statement stmt) throws SQLException { 
     stmt.execute("INSERT INTO CUSTOMER (NAME) VALUES ('James')"); 
    } 

    private void selectTable(Statement stmt) throws SQLException { 
     final ResultSet rs = stmt.executeQuery("SELECT * FROM CUSTOMER"); 
     while (rs.next()) 
      System.out.println(rs.getString(1)); 
    } 

    public void process() { 
     try { 
      final Connection con = getConnection(); 
      try { 
       final Statement stmt = con.createStatement(); 
       try { 
        createTable(stmt); 
        insertRecord(stmt); 
        selectTable(stmt); 
       } finally { 
        stmt.close(); 
       } 
      } finally { 
       con.close(); 
      } 
     } catch (SQLException e) { 
      e.printStackTrace(); 
     } 
    } 

}

因此，我能够在控制台上获得输出“James”。另外我有所需的.jar文件。我已经导入德比，derbyclient，公地dbcp2（版本2.1.1），公共记录（1.2版），公地POOL2，（版本2.4.2）和我的pom.xml如下：

  <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>oguzbayral.trial.dummy</groupId> 
       <artifactId>Dummy-Project</artifactId> 
       <version>1.0-SNAPSHOT</version> 
       <packaging>jar</packaging> 

       <name>Dummy-Project</name> 
       <url>http://maven.apache.org</url> 

       <properties> 
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> 
       </properties> 

       <dependencies> 

        <dependency> 
         <groupId>junit</groupId> 
         <artifactId>junit</artifactId> 
         <version>3.8.2</version> 
         <scope>test</scope> 
        </dependency> 

        <dependency> 
         <grenter code here`oupId>org.apache.commons</groupId> 
         <artifactId>commons-dbcp2</artifactId> 
         <version>2.1</version> 
        </dependency> 

       </dependencies> 
       <build> 
        <plugins> 
         <plugin> 
          <groupId>org.codehaus.mojo</groupId> 
          <artifactId>exec-maven-plugin</artifactId> 
          <version>1.5.0</version> 
          <configuration> 
           <mainClass>list.Trial</mainClass> 
          </configuration> 
         </plugin> 
        </plugins> 
       </build> 
      </project>

所以，我还添加了公地dbcp2作为依赖但是当我尝试运行终端代码（我在Mac上工作）我得到下面的异常错误：

Oguz-Bayral:Dummy-Project OguzBayral$ java -cp target/Dummy-Project-1.0-SNAPSHOT.jar oguzbayral.trial.dummy.Apply 
       Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/dbcp2/BasicDataSource 
        at oguzbayral.trial.dummy.Apply.poolWay(Apply.java:19) 
        at oguzbayral.trial.dummy.Apply.getConnection(Apply.java:27) 
        at oguzbayral.trial.dummy.Apply.process(Apply.java:47) 
        at oguzbayral.trial.dummy.Apply.main(Apply.java:67) 
       Caused by: java.lang.ClassNotFoundException: org.apache.commons.dbcp2.BasicDataSource 
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381) 
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424) 
        at `enter code here`sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) 
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357) 
        ... 4 more

是不是很奇怪，我已经输入了他们？有什么问题，我该如何解决它？提前致谢。

在终端中运行它时，必须将所有依赖项的jar包添加到classpath中，而不仅仅是程序本身的JAR。 – Jesper

@Jesper我试过了，但没有奏效。我已经将Junit 3.8.1 jar添加到我的类路径中，并且我确信其他jar文件的版本完全匹配。现在我有junit 3.8.1，commons-pool2 2.4.2，commons-dbcp2 2.1.1和commons logging 1.2在maven依赖关系中，我也将它们放在引用库中。另外我还有一些其他的.jar文件，比如derby.jar，derbyLocale_esjar或者derbyclient.jar等。再次感谢！ – 88yomc

要明确：您必须将它们全部添加到命令行中作为'-cp'选项的参数：'java -cp target/Dummy-Project-1.0-SNAPSHOT.jar：thislib.jar：thatlib.jar：anotherlib .jar ...' – Jesper

答

似乎这个类不在你的类路径中。导入一个类并不能保证在运行时你的类路径中也有这个类。

线程“主”java.lang.NoClassDefFoundError异常：org/apache/commons/dbcp2/BasicDataSource

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