学习Ajax过程中出现错误，怎么改正，错误原因是什么

ColmHisa 2018-03-13 04:43:53

三月 13, 2018 4:36:11 下午 com.mchange.v2.log.MLog 

信息: MLog clients using java 1.4+ standard logging.

三月 13, 2018 4:36:11 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]

三月 13, 2018 4:36:11 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 -> ajaxApp, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> oracle.jdbc.driver.OracleDriver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> 1b60boj9u8gojhz18pj3d1|1fca5b31, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:oracle:thin:@localhost:1521:orcl, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 30, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 100, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 10, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]

三月 13, 2018 4:36:12 下午 org.apache.jasper.compiler.TldLocationsCache tldScanJar

信息: At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.

java.lang.reflect.InvocationTargetException

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:498)

	at ajax.xx.com.servlets.EmployeeServlet.doGet(EmployeeServlet.java:28)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)

	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)

	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)

	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)

	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)

	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)

	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)

	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)

	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)

	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)

	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)

	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)

	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

	at java.lang.Thread.run(Thread.java:745)

Caused by: java.lang.NumberFormatException: null

	at java.lang.Integer.parseInt(Integer.java:542)

	at java.lang.Integer.parseInt(Integer.java:615)

	at ajax.xx.com.servlets.EmployeeServlet.listDepartments(EmployeeServlet.java:46)

	... 27 more

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