最近使用了最新版的tomcat9,使用jdbc链接mysql数据库。关闭tomcat过程中出现警告
13-Sep-2017 22:22:54.369 WARNING [main] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [license] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
时间有限没有去追源码,网上的说法:
tomcat6最新版本引入内存溢出检测阻止机制,检测到jdbc在tomcat运行时进行注册,但是当tomcat停止时没有解除注册。
原因是在tomcat停止之前没注销驱动。
网上有的方式是重写org.apache.commons.dbcp.BasicDataSource,这个不推荐。既然是容器级别的事件,那就从事件入手。
@WebListener public class AppContextListener implements ServletContextListener{ public void contextDestroyed(ServletContextEvent event) { try{ while(DriverManager.getDrivers().hasMoreElements()){ DriverManager.deregisterDriver(DriverManager.getDrivers().nextElement()); } }catch(Exception e){ e.printStackTrace(); } } public void contextInitialized(ServletContextEvent event) { ServletContext context = event.getServletContext(); String rootPath = context.getRealPath("/"); System.setProperty("rootPath", rootPath); //logger.info("global setting,rootPath:{}",rootPath); //logger.info("deployed on architecture:{},operation System:{},version:{}", // System.getProperty("os.arch"), System.getProperty("os.name"), // System.getProperty("os.version")); //logger.info("app startup completed...."); } }
Tomcat在停止web应用的时候会调用contextDestroyed方法,加入你的项目,即可在tomcat关闭时注销已经注册的JDBC驱动。
以上代码适用于servlet3.0 web容器,servlet 2.5容器需要在web.xml添加配置文件。
servlet容器2.5用法
public class AppContextListener implements ServletContextListener{ public void contextDestroyed(ServletContextEvent event) { try{ while(DriverManager.getDrivers().hasMoreElements()){ DriverManager.deregisterDriver(DriverManager.getDrivers().nextElement()); } }catch(Exception e){ e.printStackTrace(); } } public void contextInitialized(ServletContextEvent event) { ServletContext context = event.getServletContext(); String rootPath = context.getRealPath("/"); System.setProperty("rootPath", rootPath); //logger.info("global setting,rootPath:{}",rootPath); //logger.info("deployed on architecture:{},operation System:{},version:{}", // System.getProperty("os.arch"), System.getProperty("os.name"), // System.getProperty("os.version")); //logger.info("app startup completed...."); } }
web.xml
<web-app> <listener> <listener-class>com.xxxx.init.AppContextListenerlistener-class> listener> web-app>
至此,问题解决。