c3p0报空指针异常

Myth丶恋晨 2022-07-24 03:20 245阅读 0赞

</pre>今天建了个登录的小项目, 使用c3p0搭配DBUtil连接数据库,然后使用测试类测试连接数据库的方法可以连接,但是用servlet调用这个方法就报空指针异常.不知道是怎么回事,估计问题很罕见,网上找半天也找不到出错的原因.部分源码是这样的:<pre name="code" class="java">//-------------这是连接数据库的----------------
 public class SimpleModule {
 	private static DataSource ds;
 	
 	static {
 		ds = new ComboPooledDataSource();
 	}
 	
 	public void insertUser(User u) {
 		String createUser = "insert into userinfo values(null,?,?)";
 System.out.println("beforeQueryRunner");
 		QueryRunner qr = new QueryRunner(ds);
 		try {
 			qr.update(createUser, u.getUsername(), u.getPassword());
 		} catch (SQLException e) {
 			e.printStackTrace();
 		}
 	}
 	
 	public User getUser(User u) {
 		String getUser = "select * from userinfo where username=? and password=?";
 System.out.println("beforeqr");
 		QueryRunner qr = new QueryRunner(ds);
 System.out.println(u);
 		User user = null;
 		try {
 			user = qr.query(getUser, new BeanHandler<User>(User.class), u.getUsername(), u.getPassword());
 		} catch (SQLException e) {
 			e.printStackTrace();
 		}
 		return user;
 	}

**在调用query方法时,u无论从测试类还是servlet传过来都是有值的.就是执行query方法这一步出了错,不知道为何.**

//----这是servlet里的调用getUser的方法---------------
 protected void doGet(HttpServletRequest request, HttpServletResponse response) 
 			throws ServletException, IOException {
 		String userName = request.getParameter("username");
 		String password = request.getParameter("password");
 		User u = new User();
 		u.setUsername(userName);
 		u.setPassword(password);
 		
 		SimpleModule sm = new SimpleModule();
 		User user = sm.getUser(u);
 }
 //------这是测试类里的方法------------------
 	@Test
 	public void getUserTest() {
 		User u2 = new User();
 		u2.setUsername("sdf");
 		u2.setPassword("sdf");
 		User user = sm.getUser(u2);
 		if (user != null) {
 			System.out.println(user);
 		} else {
 			System.out.println("null");
 		}
 	}

**其实我认为,我写的方法应该没什么错,就是query方法的错,还有就是可能我懒省事把模型层所有东西都写在了一起所以出错?**

//---------这是报错的信息-------------------
 五月 11, 2016 11:09:32 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 -> y6nvpz9g18hubuj2s97ws|db0359, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> null, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> y6nvpz9g18hubuj2s97ws|db0359, 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 ]
 五月 11, 2016 11:10:02 下午 com.mchange.v2.resourcepool.BasicResourcePool 
 警告: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@1239c31 -- 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
 	at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(JdbcOdbcDriver.java:524)
 	at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(JdbcOdbcDriver.java:493)
 	at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(JdbcOdbcDriver.java:307)
 	at java.sql.DriverManager.getDriver(DriverManager.java:262)
 	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)
 五月 11, 2016 11:10:02 下午 com.mchange.v2.resourcepool.BasicResourcePool 
 警告: Having failed to acquire a resource, com.mchange.v2.resourcepool.BasicResourcePool@7b39a1 is interrupting all Threads waiting on a resource to check out. Will try again in response to new client requests.

**慢慢分析报错信息吧...**

**------------------------更新 16/5/12-----------------------------------------**

**发现问题了, 测试类的c3p0配置是我配置文件里的配置,servlet配置是个莫名其妙的配置,大概是路径不同吧**

Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 2, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> y6nvpz9g18ju4qz18rkmtj|1424bf0, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> y6nvpz9g18ju4qz18rkmtj|1424bf0, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:mysql://localhost:3306/mydata?useUnicode=true&characterEncoding=UTF-8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 30, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]

可是之前就是这样写的却从未报过错,今天用了过滤器和Listener,但是也不应该出这种问题啊,究竟怎么改呢?  
\----------------------更新 16/5/13 21:19--------------------------------------  
解决了:

**出错原因: **

前两天懒省事想着把常用的jar包都放入Tomcat的lib文件夹下,就不用在项目中手动导包--  
错就出在这里,c3p0读取xml配置文件指定是在classes文件夹下,我想把它的包放在Tomcat的lib下在运行时没加载到配置文件,所以才出这种错大哭

# **解决方法:** #

再把c3p0的相关包导入工程就好了...

**总结:还是不能偷懒啊**

**(又改了改文章样式...)**