Druid 1.1.24 在控制台打印"discard long time none received connection. , jdbcUrl : jdbc:mysql://...."错误日志

Druid 1.1.24 在控制台打印"discard long time none received connection. , jdbcUrl : jdbc:mysql://..."错误日志

参考资料

• https://q.cnblogs.com/q/133036/
• https://blog.csdn.net/weixin_41613567/article/details/83148800

报错原因

1. 我使用的是mysql 数据库,驱动包使用的是mysql-connector-java-8.0.27.jar
2. druid 使用的是 druid-1.1.24.jar
3. 经过每个包的翻看,在 com.alibaba.druid.pool.vendor 包下查到这个MySqlValidConnectionChecker类 ,根据类名猜测出这个是 MySQL 数据连接校验类.
4. MySqlValidConnectionChecker 源码如下:

点击查看代码

public class MySqlValidConnectionChecker extends ValidConnectionCheckerAdapter implements ValidConnectionChecker, Serializable {

    public static final int DEFAULT_VALIDATION_QUERY_TIMEOUT = 1;
    public static final String DEFAULT_VALIDATION_QUERY = "SELECT 1";

    private static final long serialVersionUID = 1L;
    private static final Log  LOG              = LogFactory.getLog(MySqlValidConnectionChecker.class);

    private Class<?> clazz;
    private Method   ping;
    private boolean  usePingMethod = false;

    public MySqlValidConnectionChecker(){
        try {
            clazz = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
            if (clazz == null) {
                clazz = Utils.loadClass("com.mysql.cj.jdbc.ConnectionImpl");
            }

            if (clazz != null) {
                ping = clazz.getMethod("pingInternal", boolean.class, int.class);
            }

            if (ping != null) {
                usePingMethod = true;
            }
        } catch (Exception e) {
            LOG.warn("Cannot resolve com.mysql.jdbc.Connection.ping method.  Will use 'SELECT 1' instead.", e);
        }

        configFromProperties(System.getProperties());
    }

    @Override
    public void configFromProperties(Properties properties) {
        String property = properties.getProperty("druid.mysql.usePingMethod");
        if ("true".equals(property)) {
            setUsePingMethod(true);
        } else if ("false".equals(property)) {
            setUsePingMethod(false);
        }
    }

    public boolean isUsePingMethod() {
        return usePingMethod;
    }

    public void setUsePingMethod(boolean usePingMethod) {
        this.usePingMethod = usePingMethod;
    }

    public boolean isValidConnection(Connection conn, String validateQuery, int validationQueryTimeout) throws Exception {
        if (conn.isClosed()) {
            return false;
        }

        if (usePingMethod) {
            if (conn instanceof DruidPooledConnection) {
                conn = ((DruidPooledConnection) conn).getConnection();
            }

            if (conn instanceof ConnectionProxy) {
                conn = ((ConnectionProxy) conn).getRawObject();
            }

            if (clazz.isAssignableFrom(conn.getClass())) {
                if (validationQueryTimeout <= 0) {
                    validationQueryTimeout = DEFAULT_VALIDATION_QUERY_TIMEOUT;
                }

                try {
                    ping.invoke(conn, true, validationQueryTimeout * 1000);
                } catch (InvocationTargetException e) {
                    Throwable cause = e.getCause();
                    if (cause instanceof SQLException) {
                        throw (SQLException) cause;
                    }
                    throw e;
                }
                return true;
            }
        }

        String query = validateQuery;
        if (validateQuery == null || validateQuery.isEmpty()) {
            query = DEFAULT_VALIDATION_QUERY;
        }

        Statement stmt = null;
        ResultSet rs = null;
        try {
            stmt = conn.createStatement();
            if (validationQueryTimeout > 0) {
                stmt.setQueryTimeout(validationQueryTimeout);
            }
            rs = stmt.executeQuery(query);
            return true;
        } finally {
            JdbcUtils.close(rs);
            JdbcUtils.close(stmt);
        }

    }

}

5. 根据源码中 isValidConnection(Connection conn, String validateQuery, int validationQueryTimeout) 方法,有个判断 :

// 如果使用 ping 方法,则会反射调用 ping 方法验证数据库连接是否有效,而不执行 validateQuery 验证.
if (usePingMethod) {
            if (conn instanceof DruidPooledConnection) {
                conn = ((DruidPooledConnection) conn).getConnection();
            }

            if (conn instanceof ConnectionProxy) {
                conn = ((ConnectionProxy) conn).getRawObject();
            }

            if (clazz.isAssignableFrom(conn.getClass())) {
                if (validationQueryTimeout <= 0) {
                    validationQueryTimeout = DEFAULT_VALIDATION_QUERY_TIMEOUT;
                }

                try {
                    ping.invoke(conn, true, validationQueryTimeout * 1000);
                } catch (InvocationTargetException e) {
                    Throwable cause = e.getCause();
                    if (cause instanceof SQLException) {
                        throw (SQLException) cause;
                    }
                    throw e;
                }
                return true;
            }
        }

那么 usePingMethod 是怎么来的?
查看构造器方法:

public MySqlValidConnectionChecker(){
        try {
		   //  先加载的驱动类    
            clazz = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
            if (clazz == null) {
                clazz = Utils.loadClass("com.mysql.cj.jdbc.ConnectionImpl");
            }
            // 反射获取驱动类的 pingInternal 方法
            if (clazz != null) {
                ping = clazz.getMethod("pingInternal", boolean.class, int.class);
            }
           // 若驱动类的 pingInternal 方法如果存在则 usePingMethod = true 
            if (ping != null) {
                usePingMethod = true;
            }
        } catch (Exception e) {
            LOG.warn("Cannot resolve com.mysql.jdbc.Connection.ping method.  Will use 'SELECT 1' instead.", e);
        }
        // 从系统配置文件配置属性,
        configFromProperties(System.getProperties());
    }
	@Override
    public void configFromProperties(Properties properties) {
	   // 从系统属性(JVM启动参数)中获取'druid.mysql.usePingMethod'属性 覆盖 usePingMethod 的值
        String property = properties.getProperty("druid.mysql.usePingMethod");
        if ("true".equals(property)) {
            setUsePingMethod(true);
        } else if ("false".equals(property)) {
            setUsePingMethod(false);
        }
    }

以上可以得出结论, 通过配置JVM启动参数"druid.mysql.usePingMethod=false" 告知 Druid 停止使用 usePingMethod 方法验证数据库连接,转而使用 validateQuery 验证.

解决方法

1. JVM启动参数添加如下配置

-Ddruid.mysql.usePingMethod=false