问题

朋友们，请提供一个解决方案

我已经使用Eclipse IDE在Ubuntu 20.04操作系统中完成了一个使用Java Swing和Maven的项目，并使用了MySql数据库。将项目导出为可运行的JAR文件（启动配置设置为我的主函数类，库处理中所选的单选按钮是将所需库提取到生成的JAR文件中）。

然后，我在Windows 10操作系统中打开了这个可运行的JAR文件。双击后主窗口打开，我只能从主窗口的菜单栏中打开2个窗口，而这两个窗口类没有SQL连接。所有其他窗口都有数据库连接，但无法打开。

在Windows 10中，我安装了MySql Server 8.0.22（使用传统身份验证方法保留MySql 5.x兼容性）和Connector J 8.0.22，我可以使用查询浏览器访问我的数据库。

我在项目中使用的是mysql-connector-java 8.0.22的Maven依赖。我的连接类如下所示。

public class MysqlConnector {
    Connection con = null;

    public static Connection dbConnector() {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306", "sarams", "password");
            return con;
        } catch (Exception e) {
            return null;
        }
    }
}

public class MysqlConnector {
	Connection con=null;
	public static Connection dbConnector() {
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
	        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306","sarams", "password");
	        return con;
	}
		catch (Exception e) {
			return null;
			
		}
			 
		}
}     

答案1

得分: 0

<!-- language: java -->

首先确保您已经安装并将所有驱动程序添加到Maven中
> 使用void的示例

```java
public class MysqlConnector {

    /**
     * 连接到示例数据库
     */
    public static void connect() {
        Connection con = null;
        try {
           // 数据库参数，指明数据库的存储位置，以便访问它
            String url = "jdbc:mysql://localhost:3306/sarams";
            String user = "用户名";
            String password = "密码";
           
            // 创建与数据库的连接
            con = DriverManager.getConnection(url, user, password);
    
            System.out.println("已建立与MySQL的连接。");
    
        } catch (SQLException e) {
            System.out.println(e.getMessage());
        } finally {
            try {
                if (con != null) {
                    con.close();
                }
            } catch (SQLException ex) {
                System.out.println(ex.getMessage());
            }
        }
    }
    
    // 建立连接
    public static void main(String[] args) {
        connect();
    }

使用Connection的示例
<!-- language: java -->

private Connection connect() {
    // MySQL连接字符串
    String url = "jdbc:mysql://localhost:3306/sarams";
    String user = "用户名";
    String password = "密码";
    Connection con = null;
    try {
        con = DriverManager.getConnection(url, user, password);
    } catch (SQLException e) {
        System.out.println(e.getMessage());
    }
    return con;
}

<details>
<summary>英文:</summary>

&lt;!-- language: java --&gt;

First make sure you have all the _drivers installed_ and added to the maven
&gt; Example Using void

public class MysqlConnector {

/**
 * Connect to a sample database
 */
public static void connect() {
    Connection con = null;
    try {
       // db parameters, where the database is being stored, so it could access it
        String url = "jdbc:mysql://localhost:3306","sarams", "password";
       
        // create a connection to the database
        con = DriverManager.getConnection(url);

        System.out.println("Connection to mysql has been established.");

    } catch (SQLException e) {
        System.out.println(e.getMessage());
    } finally {
        try {
            if (con != null) {
                con.close();
            }
        } catch (SQLException ex) {
            System.out.println(ex.getMessage());
        }
    }
}

// establishing connection
public static void main(String[] args) {
    connect();
}

Example Using Connection
<!-- language: java -->

private Connection connect() {
// MySQL connection string
String url = "jdbc:mysql://localhost:3306","sarams", "password";
Connection con = null;
try {
con = DriverManager.getConnection(url);
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return con;
}

</details>



# 答案2
**得分**: 0

问题已解决，只是一个Java冲突。使用JDK 11进行编译，并尝试运行JRE 1.8。移除了JRE并安装了JDK 11，问题得以解决。

<details>
<summary>英文:</summary>

The problem was solved and it was just a java conflict. Compiled using jdk 11 and tried to run JRE 1.8. removed JRE and installed JDK 11 and the problem was solved.


</details>