java - 即使maven具有依赖关系，mvn compile也无法找到符号

我正在尝试使用here中的连接器jar来建立Maven项目。但是，使用mvn compile找不到以下符号：DriverManager，Statement和ResultSet。

我尝试使用mvn install:install-file -Dfile=<path-to-file> -DpomFile=<path-to-pomfile>重新安装依赖项，它返回一个错误消息，表明它已经安装（很可能是因为我已将依赖项放入pom.xml文件中并在之前运行mvn compile）

我也尝试使用Class.forName("com.mysql.jdbc.Driver");，但无法解决问题。

这是我试图用Maven编译的Java类

package Foodmart;

import java.sql.Connection;

public class Foodmart
{
    public static void main(String[] args)
    {

        String url = "";
        String user = "";
        String password = "";

        try
        {
            String query = "SELECT * FROM foodmart";

            Connection conn = DriverManager.getConnection(url, user, password);
            Statement statement = conn.CreateStatement();

            ResultSet results = statement.executeQuery(query);

            while(results.next())
            {
                System.out.println(results.getString(0));
            }
        }
        catch(Exception ex)
        {
            System.out.println("Bummer");
        }
    }
}

和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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.springframework</groupId>
    <artifactId>Foodmart</artifactId>
    <packaging>jar</packaging>
    <version>1.0.0</version>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.21</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                    implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>Foodmart.Foodmart</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

这是编译错误的示例。

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project Foodmart: Compilation failure: Compilation failure:
[ERROR] /projects/challenge/src/main/java/Foodmart/Foodmart.java:[34,31] cannot find symbol
[ERROR] symbol:   variable DriverManager
[ERROR] location: class Foodmart.Foodmart

最佳答案

您在源代码中使用了不带import语句的DriverManager。