【发布时间】：2016-08-22 18:23:20
【问题描述】：
以下警告的原因是什么。
WARNING: The web application [TI] 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.
Apr 28, 2016 11:03:25 AM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
WARNING: The web application [TI] appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.Object.wait(Object.java:503)
java.util.TimerThread.mainLoop(Timer.java:526)
java.util.TimerThread.run(Timer.java:505)
每当我更改我的代码并tomcat 重新启动时就会发生这种情况。
我正在创建 mysql 连接，我认为我正在正确关闭它。
这是我的代码。
@RequestMapping(value = "/file/md5", method = RequestMethod.POST)
public ResponseEntity<?> md5Status(@RequestParam(required = true) String filename) {
Connection con = SqlUtility.getMysqlConnection(host, port, database,username, password);
SqlUtility.closeDbInstances(SqlUtility.mysqlConnection);
SqlUtility.closeDbInstances(con);
return new ResponseEntity<>(HttpStatus.CONFLICT);
}
这是实用程序代码。
public static Connection mysqlConnection = null;
private static PreparedStatement preparedStatement = null;
private static ResultSet resultSet = null;
public static Connection getMysqlConnection(String host, int port, String database, String username,
String password) {
MysqlDataSource mds = null;
try {
if (mysqlConnection == null || mysqlConnection.isClosed()) {
if (database != null && host != null) {
while (mds == null) {
System.out.println("In Loop");
mds = new MysqlDataSource();
mds.setServerName(host);
mds.setPortNumber(port);
mds.setDatabaseName(database);
mds.setUser(username);
mds.setPassword(password);
try {
mysqlConnection = mds.getConnection();
} catch (CommunicationsException e) {
System.out.format(
"Error occurred while trying to get connection with database [%s]. Are your database host [%s] and port [%s] correct? %n%s%n",
database, host, port, e);
mds = null;
// Had to handle for retrying again and again
// This is because your mysql is bind on localhost change it in my.cfg
}
}
} else {
System.out.format(
"Error occurred while trying to get connection with database [%s] with username [%s] and password [%s].\n [ATTN] Make sure your DB adapter properties file contains all required attributes. %n",
database, username, password);
}
}
} catch (SQLException e) {
System.out.format(
"Error occurred while trying to get connection at host [%s] with database [%s] with username [%s] and password [%s] %n%s%n",
host, database, username, password, e);
// It might be because of the database privileges which must be grant to access
} catch (RuntimeException e) {
System.out.format("Error occurred while trying to get [%s] Connection %n%s%n", database, e);
}
if (mysqlConnection != null)
System.out.format("[%S] Connection Successfully Created%n", database);
return mysqlConnection;
}
public static void closeDbInstances(Connection con) {
System.out.println("Trying to close Database Connection...");
if (con != null && preparedStatement != null && resultSet != null) {
try {
resultSet.close();
preparedStatement.close();
con.close();
System.out.println("Database Connection Closed");
} catch (SQLException e) {
System.out.println("Error occurred while trying to close Database connection " + e);
}
}
}
【问题讨论】：
-
你的tomcat库中有mysql连接器jar吗？
-
没有必要吗？
-
是的，在 tomcat lib 中添加连接器 jar，然后尝试，让我知道。
-
不，它不会仍然给我同样的警告。
-
我不认为这是一个 jar 缺失问题，因为在这种情况下，异常可能是
ClassNotFound品种。