尽管添加了驱动程序的JAR文件，JDBC程序中的ClassNotFoundException [英] ClassNotFoundException in JDBC program despite of adding driver's JAR file

问题描述

我正在用Java编写一个简单的程序，用来演示使用JDBC在MySQL表中插入数据.但是程序在注册驱动程序时会生成ClassNotFoundException.

  import java.sql.*;公开课测试{公共静态void main(String [] args){尝试 {Class.forName("com.mysql.jdbc.Driver")；}catch(ClassNotFoundException e){System.out.println("ClassNotFoundException:" + e.getMessage())；}}} 

我已经在同一目录中添加了驱动程序JAR文件.

要编译程序:

  javac -cp.:〜/Programs/D/friends/assignment/driver.jar;"test.java 

要执行程序，请执行以下操作:

  java -cp.:〜/Programs/D/friends/assignment/driver.jar;"测试 

O/p:

  ClassNotFoundException:com.mysql.jdbc.Driver 

解决方案

注意:该问题是由driver.jar末尾的; 引起的，但不是使用完全限定的路径.

基于Windows的操作系统使用; 分隔符，而基于Unix的操作系统使用:分隔符.

解决方案:

1. 首先编译代码: javac test.java (运行此命令)

2. 运行不带分号的代码: java -cp.:<完全限定路径>/driver.jar测试

样本输出:

  anish @ Anishs-MacBook-Pro〜％javac Test.javaanish @ Anishs-MacBook-Pro〜％java -cp.:/Users/anish/driver.jar测试加载类"com.mysql.jdbc.Driver".不推荐使用.新的驱动程序类为"com.mysql.cj.jdbc.Driver".通过SPI自动注册驱动程序，通常不需要手动加载驱动程序类. 

注意::我正在使用 mysql-connector-8.0.15.jar .如果使用相同或更大的版本，则在不赞成使用该类的情况下，从 com.mysql.jdbc.Driver 更改为 com.mysql.cj.jdbc.Driver ./p>

I am writing a simple program in Java using to demonstrate insertion of data in MySQL table using JDBC. But the program is generating ClassNotFoundException while registering driver.

import java.sql.*;

public class test {
    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        }
        catch(ClassNotFoundException e) {
            System.out.println("ClassNotFoundException: "+e.getMessage());
        }
    }    
}

I have added the driver JAR file in the same directory.

To compile the program:

javac -cp ".:~/Programs/D/friends/assignment/driver.jar;" test.java

To execute the program:

java -cp ".:~/Programs/D/friends/assignment/driver.jar;" test

O/p:

ClassNotFoundException: com.mysql.jdbc.Driver

解决方案

Note: The issue is caused by ; at the end of the driver.jar and also not using fully qualified path.

Windows based OS uses ; separator whereas Unix-based OS uses : separator.

Solution :

1. First compile the code : javac test.java (Run this command)

2. Run the code without semi-colon : java -cp .:<fully-qualified-path>/driver.jar test

Sample output :

anish@Anishs-MacBook-Pro ~ % javac Test.java
anish@Anishs-MacBook-Pro ~ % java -cp .:/Users/anish/driver.jar Test  
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

Note : I'm using mysql-connector-8.0.15.jar. If you are using the same or greater, then change from com.mysql.jdbc.Driver to com.mysql.cj.jdbc.Driver as that class is deprecated.

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