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To prevent a memory leak, the JDBC Driver has been forcibly unregistered--有關Tomcat自動宕機的解決方案

最近有幾個服務的Tomcat總是無緣無故的宕機,到了不得不解決的地步。
在Stackoverflow上找到比較有用的一篇文章,解決方案如下:
http://stackoverflow.com/questions/3320400/to-prevent-a-memory-leak-the-jdbc-driver-has-been-forcibly-unregistered
有以下幾個解決途徑:
  1. Ignore those warnings. Tomcat is doing its job right. The actual bug is in someone else's code (the JDBC driver in question), not in yours. Be happy that Tomcat did its job properly and wait until the JDBC driver vendor get it fixed so that you can upgrade the driver. On the other hand, you aren't supposed to drop a JDBC driver in webapp's /WEB-INF/lib, but only in server's /lib. If you still keep it in webapp's /WEB-INF/lib, then you should manually register and deregister it using a ServletContextListener.
    忽略警告。把WEB-INF/lib下的mysql驅動文件拷貝到Tomcat/lib下。如果仍然要放在WEB-INF/lib下,需要使用監聽器手動的注冊和注銷。
    下面的文章介紹如何寫監聽器,http://javabeat.net/servletcontextlistener-example/, 當然如果是Servlet3.0, 使用注解方式設置監聽也是可以的。
    下面的代碼是如何注銷。

    Step 1: Register a Listener
    web.xml
    <listener>
        
    <listener-class>com.mysite.MySpecialListener</listener-class>
    </listener>
    Step 
    2: Implement the Listener

    com.mysite.MySpecialListener.java

    public class MySpecialListener extends ApplicationContextListener {

        @Override
        
    public void contextInitialized(ServletContextEvent sce) {
            
    // On Application Startup, please…

            
    // Usually I'll make a singleton in here, set up my pool, etc.
        }

        @Override
        
    public void contextDestroyed(ServletContextEvent sce) {
          
    // This manually deregisters JDBC driver, which prevents Tomcat 7 from complaining about memory leaks wrto this class
            Enumeration<Driver> drivers = DriverManager.getDrivers();
            while (drivers.hasMoreElements()) {
                Driver driver = drivers.nextElement();
                try {
                    DriverManager.deregisterDriver(driver);
                    LOG.log(Level.INFO, String.format("deregistering jdbc driver: %s", driver));
                } catch (SQLException e) {
                    LOG.log(Level.SEVERE, String.format("Error deregistering driver %s", driver), e);
                }

            }
        }

    }
  2. Downgrade to Tomcat 6.0.23 or older so that you will not be bothered with those warnings. But it will silently keep leaking memory. Not sure if that's good to know after all. Those kind of memory leaks are one of the major causes behind OutOfMemoryError issues during Tomcat hotdeployments.
    把Tomcat降級到低版本(6.0.23以下),雖然不會報錯,但是還是存在內存益出的問題,這并不是一個好的解決方案。

  3. Move the JDBC driver to Tomcat's /lib folder and have a connection pooled datasource to manage the driver. Note that Tomcat's builtin DBCP does not deregister drivers properly on close. See also bug DBCP-322 which is closed as WONTFIX. You would rather like to replace DBCP by another connection pool which is doing its job better then DBCP. For exampleHikariCPBoneCP, or perhaps Tomcat JDBC Pool.
    把驅動文件移到Tomcat/lib文件夾下,不用使用DBCP,使用以下的連接池庫,HikariCP, BoneCP,或者Tomcat JDBC Pool.

  4. MAVEN項目

    If you are getting this message from a Maven built war change the scope of the JDBC driver to provided, and put a copy of it in the lib directory. Like this:<dependency>,
    對于MAVEN項目,由于Tomcat中存在mysql驅動文件(1中介紹),這樣在部署時就不會把mysql帶到打包文件里,注意是<scope>provided</scope>。

      <groupId>mysql</groupId>
      
    <artifactId>mysql-connector-java</artifactId>
      
    <version>5.1.18</version>
      
    <!-- put a copy in /usr/share/tomcat7/lib -->
      
    <scope>provided</scope>
    </dependency>
好了,如果您遇到同樣的問題,可以和我溝通,聯系方式見頭部。

posted on 2016-08-03 10:59 草原上的駱駝 閱讀(7641) 評論(0)  編輯  收藏 所屬分類: JAVA基礎知識JAVA框架


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