执行JAR时java.lang.ClassNotFoundException：com.mysql.jdbc.Driver [英] java.lang.ClassNotFoundException: com.mysql.jdbc.Driver when executing JAR

问题描述

我正在尝试使用以下代码连接到我的本地MySQL服务器：

I am attempting to connect to my local MySQL server with the following code:

dbURL = "jdbc:mysql://localhost:3306:/" + dbname;
try{
    Class.forName("com.mysql.jdbc.Driver");
    try{
        con = DriverManager.getConnection(dbURL, dbuser, dbpass);
    } catch (SQLException ex){
        System.out.println("ERROR: Could not connection to SQL DB");
        con = null;
    }
} catch (ClassNotFoundException e){
    System.out.println("Error: ");
    e.printStackTrace();
}

然后我得到

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

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

我明白Java不能找到将Java环境连接到MySQL数据库的正确驱动程序。这是在Windows 7系统上编译并移植到Ubuntu 11.04系统。

I understand that Java cannot find the proper driver for connecting the Java environment to the MySQL database. This is being compiled on a Windows 7 system and ported over to an Ubuntu 11.04 system.

我是否有一种特殊的方式可以运行具有特定类路径的Java程序，例如：

Is there a particular way I can run the Java program with a particular classpath such as:

java -cp /usr/share/java/mysql-connector-java.jar program.jar

我试用时没用。

推荐答案

对于JAR， -cp 和 -classpath 参数和％CLASSPATH％环境变量被忽略。相反，必须在JAR自己的 /META-INF/MANIFEST.MF Class-Path 条目中指定类路径。 >文件。它可以是相对于JAR本身的路径。例如。在同一文件夹或 / lib 子文件夹中。

In case of JARs, the -cp and -classpath arguments and the %CLASSPATH% environment variable are ignored. Instead, the classpath has to be specified in the Class-Path entry of JAR's own /META-INF/MANIFEST.MF file. It can be a path relative to the JAR itself. E.g. in the same folder or in a /lib subfolder.

以下示例假设驱动程序位于同一文件夹中作为JAR的文件夹。

The below example assumes the driver to be in the same folder as the JAR.

Class-Path: mysql-connector-java.jar

（确保 MANIFEST.MF 文件末尾有一个空行）

(make sure that the MANIFEST.MF file has a blank line at the end)

• 使用JAR文件 - 基础知识 - 了解MANIFEST.MF


• Eclipse：Package多个项目合并为一个JAR


• Java清单文件的类路径以及它如何确定相对目标

• Using JAR files - The Basics - Understanding the MANIFEST.MF
• Eclipse: Package multiple projects into one JAR
• Java Manifest file's class path and how it determines relative dirs

这篇关于执行JAR时java.lang.ClassNotFoundException：com.mysql.jdbc.Driver的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！