java - Maven java.lang.ClassNotFoundException : com. mysql.jdbc.Driver

Question

我是java新手，我使用maven创建了我的项目。我有一个如下所示的 pom.xml 文件

<?xml version="1.0" encoding="UTF-8"?>

<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>com.swingy.app</groupId>
  <artifactId>swingy</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>swingy</name>
  <!-- FIXME change it to the project's website -->
  <url>http://maven.apache.org</url>
  <packaging>jar</packaging>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>com.oracle</groupId>
      <artifactId>ojdbc14</artifactId>
      <version>10.2.0.2.0</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.36</version>
    </dependency>
  </dependencies>
</project>

我的主 java 程序看起来大致/简单如下

package com.swingy.app;

import java.sql.*;

public class App {
    static Connection conn = null;
    static PreparedStatement pStatement = null;

    public static void main(String[] args) {

        makeJDBCConnection();

    }

    private static void makeJDBCConnection() {

        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return;
        }

        try {
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/", "root", "Pass");
            if (conn != null) {
                System.out.println("Connection Successful! Enjoy. Now it's time to push data");
            } else {
                System.out.println("Failed to make connection!");
            }
        } catch (SQLException e) {
            System.out.println("MySQL Connection Failed!");
            e.printStackTrace();
            return;
        }

    }
}

这可以使用mvn clean package正确编译，然后当我尝试使用java -jar target/swingy-1.0-SNAPSHOT.jar运行时，我收到此错误

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

我到处寻找答案，大多数文章建议我“添加.jar文件”到我的类路径中，但我不知道这可能意味着什么，因为我尝试过的所有事情都像下载.jar文件到项目路径，还是没有。我正在使用 vscode，这是我的项目树结构

.
├── pom.xml
├── src
│   ├── main
│   │   └── java
│   │       └── com
│   │           └── swingy
│   │               ├── app
│   │               │   ├── App.java
│   │               │   └── Main.java
│   │               ├── controls
│   │               ├── models
│   │               │   └── Player.java
│   │               └── views
│   │                   └── Colors.java
│   └── test
│       └── java
│           └── com
│               └── swingy
│                   └── app
│                       └── AppTest.java
└── target
    ├── classes
    ...

Answer 1

您需要在最终的 jar 中添加依赖项，这可以通过 Maven 使用以下插件来完成:

<build>
<plugins>
  <plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <executions>
      <execution>
        <phase>package</phase>
        <goals>
          <goal>single</goal>
        </goals>
      </execution>
    </executions>
    <configuration>
      <descriptorRefs>
        <descriptorRef>jar-with-dependencies</descriptorRef>
      </descriptorRefs>
      <archive>
        <manifest>
          <mainClass>com.swingy.app.App</mainClass>
        </manifest>
      </archive>
    </configuration>
  </plugin>
</plugins>

要运行您的项目，您可以使用以下命令:

java -jar target/swingy-1.0-SNAPSHOT-jar-with-dependencies.jar

我希望它对你有用:)