mvn-compile找不到符号，即使maven有依赖项

Question

我正试图从这里用连接器jar建立一个Maven项目。但是，使用mvn compile无法找到以下符号：DriverManager、Statement和ResultSet。

我尝试用mvn install:install-file -Dfile=<path-to-file> -DpomFile=<path-to-pomfile>重新安装依赖项，但它返回了一个错误，说它已经安装好了(很可能是因为我之前已经把依赖项放在pom.xml文件中并运行了mvn-compile(

我也尝试过使用Class.forName("com.mysql.jdbc.Driver");，但它并没有解决问题。

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>

下面是一个编译错误的例子。

[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

Answer 1

您使用的DriverManager在源代码中没有导入语句。