【JDBC】使用c3p0数据库连接池的各种报错警告

使用c3p0数据库连接池的各种报错警告

使用c3p0数据库连接池的时候，先导入了三个jar包在lib 文件夹中，

c3p0-0.9.5.2.jar
mchange-commons-java-0.2.3.4.jar
mysql-connector-java-8.0.13.jar

注意下载的 c3p0 jar包要与mchange-commons-java jar包和mysql-connector-java jar包以及你的mysql版本一致，不一致会报错

然后写c3p0-config.xml配置文件

<c3p0-config><!-- 使用默认的配置读取连接池对象 ，也就是不传参的情况下获取DataSource,使用默认的配置--><default-config><!--  连接参数 --><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost:3306/db3?useSSL=false</property><property name="user">root</property><property name="password">root</property><!-- 连接池参数 --><!--初始化申请的连接数量--><property name="initialPoolSize">5</property><!--最大的连接数量--><property name="maxPoolSize">10</property><!--超时时间--><property name="checkoutTimeout">3000</property></default-config><named-config name="otherc3p0"><!--  连接参数，传参使用这个 --><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost:3306/db3?useSSL=false</property><property name="user">root</property><property name="password">root</property><!-- 连接池参数 --><property name="initialPoolSize">5</property><property name="maxPoolSize">8</property><property name="checkoutTimeout">1000</property></named-config>
</c3p0-config>

在此处要注意版本的不同的差异，如果时mysql 5.x 则在配置文件中
写 <property name="jdbcUrl">jdbc:mysql://localhost:3306/database?useSSL=false</property>
如果是mysql 8之后，<property name="jdbcUrl">jdbc:mysql://localhost:3306/database?useSSL=false&serverTimezone=UTC</property>

如果你这里配置的不对会报错如下

警告: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@2200d7 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception:
java.sql.SQLException: The server time zone value '???ú±ê×??±??' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89)at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63)at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:73)at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:76)at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175)at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220)at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206)at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:203)at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138)at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125)at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44)at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870)at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)
Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '???ú±ê×??±??' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.at sun.reflect.GeneratedConstructorAccessor5.newInstance(Unknown Source)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)at java.lang.reflect.Constructor.newInstance(Constructor.java:423)at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:85)at com.mysql.cj.util.TimeUtil.getCanonicalTimezone(TimeUtil.java:132)at com.mysql.cj.protocol.a.NativeProtocol.configureTimezone(NativeProtocol.java:2234)at com.mysql.cj.protocol.a.NativeProtocol.initServerSession(NativeProtocol.java:2258)at com.mysql.cj.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:1319)at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:966)at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825)... 12 more

然后运行发现报错信息

一月 28, 2021 7:23:24 下午 com.mchange.v2.c3p0.C3P0Registry
信息: Initializing c3p0-0.9.5.2 [built 08-December-2015 22:06:04 -0800; debug? true; trace: 10]
一月 28, 2021 7:23:24 下午 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource
信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1hgeb5tafk6ijyw11flv6q|5387f9e0, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> null, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> 1hgeb5tafk6ijyw11flv6q|5387f9e0, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> null, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]
一月 28, 2021 7:23:54 下午 com.mchange.v2.resourcepool.BasicResourcePool
警告: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@6a2fe339 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception:
java.lang.NullPointerExceptionat com.mysql.fabric.jdbc.FabricMySQLDriver.parseFabricURL(FabricMySQLDriver.java:97)at com.mysql.fabric.jdbc.FabricMySQLDriver.acceptsURL(FabricMySQLDriver.java:93)at java.sql.DriverManager.getDriver(DriverManager.java:299)at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:285)at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:161)at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:161)at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:147)at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:202)at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138)at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125)at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44)at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870)at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)

注意其中的关键报错信息点

警告: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@6a2fe339 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: java.lang.NullPointerException
一般此处报错空指针异常就是我们配置文件位置错误了，xml文件必须放在src文件夹根目录下，前面不能包裹住各种文件夹或包。因为主程序找配置文件是在src根目录下面去找.
（事实上我的文件就在src目录下，但还是报错了这个信息，于是我复制了c3p0-config.xml配置文件将其放在了项目下，也就是说src文件上一级文件的目录下，然后没有报错信息了，我估计是我的project strcture中设置路径有问题，如果你也遇到了和我一样的问题可以这样试一下)

写一个测试代码看看

package src.cn.itcast.datasource.c3p0;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
/*** c3p0的演示*/
public class C3P0Demo1 {public static void main(String[] args) throws SQLException {//1.创建数据库连接池对象DataSource ds=new ComboPooledDataSource();//2.获取连接对象Connection conn = ds.getConnection();//3.打印System.out.println(conn);}
}

运行成功（上面红色的不是报错是日志信息不用在意。）

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