Question

我正在尝试运行一个使用数据库池的Maven项目并在数据库上做一些事情。实际上我的代码在Eclipse上运行正常，我得到了输出。我的代码如下：

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();
        }
    }

}

所以，我能够得到输出＆＃34; James＆＃34;在控制台上。我还有所需的.jar文件。我已经导入了derby，derbyclient，commons-dbcp2（版本2.1.1）， commons logging（版本1.2），commons-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commons-dbcp2作为依赖项但是当我尝试在终端上运行此代码时（我在mac中工作）我收到以下异常错误：

 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

难道不奇怪，我已经进口了它们吗？有什么问题，我该如何解决？非常感谢提前。

Answer 1

似乎该类不在您的类路径中。导入类并不能保证您在运行时也会在类路径中拥有该类。

线程＆＃34; main＆＃34;中的例外情况java.lang.NoClassDefFoundError：org / apache / commons / dbcp2 / BasicDataSource

1 个答案: