Note some of my own low-level mistakes, if it helps, it’s an honor
Recently, I followed the school to learn dynamic javaweb, and the following error occurred when I used c3p0. It probably means that the connection timed out. I searched a lot, and they all said that it was a problem with the c3p0 configuration file. Finally, I found that it was related to the mysql version, which was reduced from 8 to 5.5, and the database was successfully found. content
The content of the error is as follows
June 26, 2022 2:09:15 PM com.mchange.v2.log.MLog <clinit>
Info: MLog clients using java 1.4 + standard logging.
June 26, 2022 2:09:16 pm com.mchange.v2.c3p0.C3P0Registry banner
INFO: Initializing c3p0-0.9.1.2 [built 21-May-2007 15:04:56; debug? true; trace: 10]
June 26, 2022 2:09:16 PM com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
Information: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout - > 30000, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1hge0ytap180hwervupaz4|2dda6444, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver , factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hge0ytap180hwervupaz4|2dda6444, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:mysql://localhost:3306/myshop?useSSL=true & amp;characterEncoding =UTF-8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 30, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 100, maxStatements -> 0, maxStatementsPerConnection -> 0, minPool Size -> 10, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin - > false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
June 26, 2022 2:09:36 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
Warning: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@8988e90 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
June 26, 2022 2:09:36 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
Warning: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@8988e90 -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 3
Active Threads: 3
Active Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@47626bc8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@bc281ba (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@766f29c8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@73259d00
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@274d9487
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@389d1e85
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@37334137
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@6821174c
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@23034f63
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@733a14b0
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
java.lang.Thread.sleep(Native Method)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
java.lang.Thread.sleep(Native Method)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
java.lang.Thread.sleep(Native Method)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
null
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
at org.apache.commons.dbutils.AbstractQueryRunner.prepareConnection(AbstractQueryRunner.java:156)
at org.apache.commons.dbutils.QueryRunner.query(QueryRunner.java:285)
at com.zpr.dao.impl.UserDaoImpl.selectUserByUname(UserDaoImpl.java:24)
at com.zpr.test.UserDaoTest.main(UserDaoTest.java:12)
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@67f89fa3 -- timeout at awaitAvailable()
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317)
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
... 5 more