java无法连接到jdbc

Question

我正在尝试使用 JDBC 通过 Java 建立与 MySQL 数据库的连接。

但是当我尝试这样做时，我遇到了一些错误。 我确定问题不是因为 MySQL 服务器设置错误，因为我尝试连接 MySQL Workbench，并且这有效。

我使用这段 Java 代码来设置 de JDBC 连接:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;


public class SQLConnection {

    public static SQLConnection instance = new SQLConnection();
    public static String URL = "jdbc:mysql://localhost:3306/canbusdata";
    public static String USER= "root";
    public static String PSW = "root";

    public SQLConnection()
    {
    }

    public static Connection getConnection() {
        System.out.println("-------- MySQL JDBC Connection ------------\n");

        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            System.out.println("Where is your MySQL JDBC Driver?");
            e.printStackTrace();

        }
        System.out.println("MySQL JDBC Driver Registered!");
        Connection connection = null;

        try {
            connection = DriverManager.getConnection(URL,USER,PSW);

        } catch (SQLException e) {
            System.out.println("Connection Failed! Check output console: \n");
            e.printStackTrace();

        }

        return connection;
    }
}

但是我得到这个错误:

-------- MySQL JDBC Connection ------------

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
Where is your MySQL JDBC Driver?
MySQL JDBC Driver Registered!
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
Connection Failed! Check output console: 

    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:190)
    at SQLConnection.getConnection(SQLConnection.java:21)
    at Start.ProcessData(Start.java:109)
    at Start.main(Start.java:21)
java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/canbusdata
    at java.sql.DriverManager.getConnection(DriverManager.java:596)
    at java.sql.DriverManager.getConnection(DriverManager.java:215)
    at SQLConnection.getConnection(SQLConnection.java:31)
    at Start.ProcessData(Start.java:109)
    at Start.main(Start.java:21)
Exception in thread "main" java.lang.NullPointerException
    at Start.ProcessData(Start.java:110)
    at Start.main(Start.java:21)
Java Result: 1

Answer 1

看起来您还没有在项目中配置 JDBC 驱动程序。确保在运行它之前将它添加到类路径中(通过命令行或基于 IDE)。