使用c3p0報錯

jar包版本：

c3p0-0.9.1.2.jar

mysql-connector-java-5.1.44-bin.jar

問題：使用c3p0創建連接池對象，操作本地數據庫的時候報如下錯誤：

十二月 01, 2017 8:33:16 下午 com.mchange.v2.log.MLog <clinit>
信息: MLog clients using java 1.4+ standard logging.
十二月 01, 2017 8:33:21 下午 com.mchange.v2.c3p0.C3P0Registry banner
信息: Initializing c3p0-0.9.1.2 [built 21-May-2007 15:04:56; debug? true; trace: 10]
十二月 01, 2017 8:33:21 下午 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
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, dataSourceName -> 1hge15z9s50grigjetdko|606d8acf, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hge15z9s50grigjetdko|606d8acf, idleConnectionTestPeriod -> 0, initialPoolSize -> 5, jdbcUrl -> jdbc:mysql://webtest, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
十二月 01, 2017 8:33:41 下午 com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
警告: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@3c7758ee -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
十二月 01, 2017 8:33:41 下午 com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
警告: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@3c7758ee -- APPARENT DEADLOCK!!! Complete Status: 
	Managed Threads: 3
	Active Threads: 3
	Active Tasks: 
		com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@738dab2b (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
		com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@75bb2d9c (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
		com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4234ba1a (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
	Pending Tasks: 
		com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@de86201
		com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@13a25464
Pool thread stack traces:
	Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
		java.lang.Thread.sleep(Native Method)。。。

解決辦法：

網上查的資料，一般這種錯誤都是數據庫連接問題；

所以找到c3p0的配置文件c3p0-config.xml

 <default-config>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
	<property name="jdbcUrl">jdbc:mysql://webtest</property>
	<property name="user">root</property>
	<property name="password">fj123456</property>
	<property name="initialPoolSize">5</property>
	<property name="maxPoolSize">20</property>
  </default-config>

這是按照視頻教程所寫
黃色部分沒寫localhost：3306還有SSL錯誤，所以改成如下：

	<property name="jdbcUrl">jdbc:mysql://localhost:3306/webtest?useUnicode=true&characterEncoding=utf-8&useSSL=false</property>

改完後，文件提示"&"符號要改成"；"  ，但還是報錯，查的大神博客  https://www.cnblogs.com/mstk/p/4281724.html

把上面語句中的"&"改成"&" 後錯誤消失

xml 轉義符

&lt; < 小於號 
&gt; > 大於號 
&amp; & 和 
&apos; ' 單引號 
&quot; " 雙引號