classNotFound在eclipse中在Tomcat上使用JDBC进行MYSQL时出现异常 [英] classNotFound Exception when using JDBC for MYSQL on Tomcat in eclipse

问题描述

这似乎是一个常见问题，但我找不到有效的解决方案。我已经浏览了几十个帖子并且一直在和我的老师一起工作。
我正在尝试使用JDBC连接到MYSQL。我也在使用tomcat服务器并运行xubuntu 12.04。我得到了ClassNotFound异常。

我已经尝试了放在/ tomact / lib和/ usr / share / java中的JDBC mysql-connector-java.jar驱动程序在每个实例中手动构建路径。我也尝试通过部署程序集添加路径。我尝试过使用EXPORT CLASSPATH。没有任何效果。我不能让这个例外停止被抛出。有没有人可以尝试其他解决方案？

我的代码：

  public static Connection getConnection（）{
 if（connection！= null）{
 return connection; 
} else {
 try {
 Class.forName（com.mysql.jdbc.Driver）。newInstance（）; 
 String dbURL =jdbc：mysql：//144.91.20.136：3306 / jewelryInventoryGallison; 
 String username =javaee; 
 String password =mills2012; 
 
 connection = DriverManager.getConnection（dbURL，username，password）; 
返回连接; 
} catch（Exception ex）{
 ex.printStackTrace（）; 
返回null; 
} 
} 
} 
  

测试类：

  public static void main（String [] args）throws Exception {
 Connection conn = DatabaseUtils.getConnection（）; 
语句st = conn.createStatement（）; 
 ResultSet rs = st.executeQuery（SELECT * FROM Inventory）; 
 while（rs.next（））{
 System.out.println（rs.getString（name））; 
} 
 
} 
  

和跟踪：

在$ java $。$。 ：366）
at java.net.URLClassLoader $ 1.run（URLClassLoader.java:355）
at java.security.AccessController.doPrivileged（Native Method）
at java.net.URLClassLoader。 findClass（URLClassLoader.java:354）
at java.lang.ClassLoader.loadClass（ClassLoader.java:423）
at sun.misc.Launcher $ AppClassLoader.loadClass（Launcher.java:308）
at java.lang.ClassLoader.loadClass（ClassLoader.java:356）
at java.lang.Class.forName0（Native Method）
at java.lang.Class.forName（Class.java: 186）utils.DatabaseUtils.getConnection（DatabaseUtils.java:19）
at utils.DatabaseUtils.main（DatabaseUtils.java:34）

线程main中的异常java.lang.NullPointerException
at utils.DatabaseUtils.main（DatabaseUtils.java:35）

你的非常感谢帮助！

解决方案

java.lang.ClassNotFoundException：com.mysql.jdbc。驱动程序

您缺少 MySQL 驱动程序库。因为，您使用 Mysql 数据库，请确保已包含 mysql-connector-java 。

 < dependency> 
< groupId> mysql< / groupId> 
< artifactId> mysql-connector-java< / artifactId> 
< version> 8.0.8-dmr< / version> 
< / dependency> 
  

This seems to be a common problem, but I could not find a working solution. I've looked through dozens of thread and have been working with my teacher. I am trying to connect to MYSQL using JDBC. I'm also using a tomcat server and running xubuntu 12.04. I am getting ClassNotFound exception.

I've tried the JDBC mysql-connector-java.jar driver placed in both /tomact/lib and /usr/share/java and have manually built paths in each instance. I've also tried adding paths through deploy assembly. I've tried using EXPORT CLASSPATH. Nothing has worked. I cannot get this exception to stop being thrown. Does anyone have other solutions I can try?

my code:

public static Connection getConnection() {
    if(connection!=null){
        return connection;
    }else{
        try{
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            String dbURL = "jdbc:mysql://144.91.20.136:3306/jewelryInventoryGallison";
            String username = "javaee";
            String password = "mills2012";

            connection = DriverManager.getConnection(dbURL, username, password);
            return connection;
        } catch (Exception ex) {
            ex.printStackTrace();
            return null;
        }
    }
}

test class:

public static void main(String[] args) throws Exception{ 
      Connection conn = DatabaseUtils.getConnection();
      Statement st = conn.createStatement();
      ResultSet rs = st.executeQuery("SELECT * FROM Inventory");
      while(rs.next()) {
       System.out.println(rs.getString("name"));
      }

 }

and trace:

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:186)
at utils.DatabaseUtils.getConnection(DatabaseUtils.java:19)
at utils.DatabaseUtils.main(DatabaseUtils.java:34)

Exception in thread "main" java.lang.NullPointerException at utils.DatabaseUtils.main(DatabaseUtils.java:35)

your help will be greatly appreciated!

解决方案

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

You missing MySQL driver library. Since, you are using Mysql database, make sure you have included mysql-connector-java.

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.8-dmr</version>
</dependency>

这篇关于classNotFound在eclipse中在Tomcat上使用JDBC进行MYSQL时出现异常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！