Java 类路径找不到 MySQL 驱动程序

Question

每当我运行以下代码时：

import com.mysql.jdbc.Driver;

public void insertIntoMysql() {

    // Print out classloader information
    ClassLoader cl = ClassLoader.getSystemClassLoader();
    URL[] urls = ((URLClassLoader) cl).getURLs();
    String urlStr = "";
    for (int i=0; i < urls.length; i++) {
       urlStr += urls[i].getFile() + "\n";
    }
    System.out.println("Classpath:\n" + urlStr);

    // connect to mysql
    Class.forName("com.mysql.jdbc.Driver");
    String myUrl = "jdbc:mysql://localhost:3306/Compass";
    Connection conn = DriverManager.getConnection(myUrl, "root", "newpoint");

    ...
}

我在 Class.forName 行收到 "ClassNotFoundException: com.mysql.jdbc.Driver" 错误。但是，我的类路径打印为：

Classpath: 
... 
/C:/myProjectDir/

我的类路径中有以下 jar“/C:/myProjectDir/mysql-connector-java-5.0.8-bin.jar”。

我已经重新启动了程序，以防类加载器在程序启动时加载所有内容，但我一直收到该错误。

有什么想法吗？

Answer 1

目前看来您的 class 路径上只有您的项目目录，而不是 mysql-connector-java-5.0.8-bin.jar文件本身。

在Java中，class路径中包含的内容规则如下：

For class files in an unnamed package, you include the directory that contains the class files

For class files in a named package, you include the directory that contains the root package, which is the first package in the full package name

For a JAR or zip file that contains class files, you include the name of the zip or JAR file

要获取 mysql 驱动程序，您需要按名称将驱动程序 jar 添加到 class 路径：

Classpath: 
... 
/C:/myProjectDir/
/C:/myProjectDir/mysql-connector-java-5.0.8-bin.jar
...

有关详细信息，请查看 Java tutorial on PATH and CLASSPATH, and the Oracle documentation on Setting the Class Path。

Java 类路径找不到 MySQL 驱动程序

Java classpath cannot find MySQL driver

java

mysql

jdbc