如何修复 c3p0 连接池初始化异常？
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【中文标题】如何修复 c3p0 连接池初始化异常？【英文标题】：How to fix c3p0 connection pool initializing exception? 【发布时间】：2015-08-17 05:47:58 【问题描述】：这是我以前使用 c3p0 创建连接池时发生的异常。
Jun 03, 2015 11:41:29 AM com.mchange.v2.log.MLog
INFO: MLog clients using java 1.4+ standard logging.
Jun 03, 2015 11:41:29 AM com.mchange.v2.c3p0.C3P0Registry
INFO: Initializing c3p0-0.9.5 [built 02-January-2015 13:25:04 -0500; debug? true; trace: 10]
Jun 03, 2015 11:41:29 AM com.mchange.v2.c3p0.management.ActiveManagementCoordinator
WARNING: A C3P0Registry mbean is already registered. This probably means that an application using c3p0 was undeployed, but not all PooledDataSources were closed prior to undeployment. This may lead to resource leaks over time. Please take care to close all PooledDataSources.
Jun 03, 2015 11:41:29 AM com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource
INFO: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1hge136991f2dudczsq8hw|458d8adc, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, extensions -> , factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceUseNamedDriverClass -> false, identityToken -> 1hge136991f2dudczsq8hw|458d8adc, idleConnectionTestPeriod -> 300, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql://localhost:3306/ductoreh_patientdb, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 50, maxStatementsPerConnection -> 0, minPoolSize -> 2, numHelperThreads -> 3, preferredTestQuery -> SELECT 1, privilegeSpawnedThreads -> false, properties -> user=******, password=******, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> true, unreturnedConnectionTimeout -> 0, userOverrides -> , usesTraditionalReflectiveProxies -> false ]
Jun 03, 2015 11:42:02 AM org.apache.catalina.loader.WebappClassLoader loadClass
INFO: Illegal access: this web application instance has been stopped already. Could not load com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1612)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1629)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2161)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Exception in thread "C3P0PooledConnectionPoolManager[identityToken->1hge136991f284clsmmfih|19faec40]-AdminTaskTimer" java.lang.NoClassDefFoundError: com/mchange/v2/resourcepool/BasicResourcePool$AsyncTestIdleResourceTask
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1629)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2161)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Caused by: java.lang.ClassNotFoundException: com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
... 5 more
Jun 03, 2015 11:42:18 AM org.apache.catalina.loader.WebappClassLoader loadClass
INFO: Illegal access: this web application instance has been stopped already. Could not load com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1612)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1629)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2161)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Exception in thread "C3P0PooledConnectionPoolManager[identityToken->1hge136991f28gvv1q0gwo7|753c66d3]-AdminTaskTimer" java.lang.NoClassDefFoundError: com/mchange/v2/resourcepool/BasicResourcePool$AsyncTestIdleResourceTask
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1629)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2161)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Caused by: java.lang.ClassNotFoundException: com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
... 5 more
这些是我用过的类。
-----连接和连接池---
public class DBConnection
private static DBConnection datasource;
private ComboPooledDataSource cpds;
private DBConnection() throws IOException, SQLException, PropertyVetoException
cpds = new ComboPooledDataSource();
cpds.setDriverClass("com.mysql.jdbc.Driver"); //loads the jdbc driver
cpds.setJdbcUrl("jdbc:mysql://localhost:3306/xxxxx");
cpds.setUser("root");
cpds.setPassword("");
// the settings below are optional -- c3p0 can work with defaults
cpds.setMinPoolSize(2);
cpds.setAcquireIncrement(5);
cpds.setMaxPoolSize(20);
cpds.setMaxStatements(50);
cpds.setIdleConnectionTestPeriod(300);
cpds.setTestConnectionOnCheckout(true);
cpds.setPreferredTestQuery("SELECT 1");
public static DBConnection getInstance() throws IOException, SQLException, PropertyVetoException
if (datasource == null)
datasource = new DBConnection();
return datasource;
else
return datasource;
public Connection getConnection() throws SQLException
return this.cpds.getConnection();
----接口-------
public interface DBInterface
public List<UserBean> getUserData();
----豆子-----
public class UserBean
private int idUser;
private String companyName;
private String country;
private String adressLine1;
private String addressLine2;
private String zip;
private String phone;
private String email;
private boolean isTrial;
private Timestamp dateCreated;
private Timestamp lastUpdated;
/**
* @return the idUser
*/
public int getIdUser()
return idUser;
/**
* @param idUser the idUser to set
*/
public void setIdUser(int idUser)
this.idUser = idUser;
/**
* @return the companyName
*/
public String getCompanyName()
return companyName;
/**
* @param companyName the companyName to set
*/
public void setCompanyName(String companyName)
this.companyName = companyName;
/**
* @return the country
*/
public String getCountry()
return country;
/**
* @param country the country to set
*/
public void setCountry(String country)
this.country = country;
/**
* @return the adressLine1
*/
public String getAdressLine1()
return adressLine1;
/**
* @param adressLine1 the adressLine1 to set
*/
public void setAdressLine1(String adressLine1)
this.adressLine1 = adressLine1;
/**
* @return the addressLine2
*/
public String getAddressLine2()
return addressLine2;
/**
* @param addressLine2 the addressLine2 to set
*/
public void setAddressLine2(String addressLine2)
this.addressLine2 = addressLine2;
/**
* @return the zip
*/
public String getZip()
return zip;
/**
* @param zip the zip to set
*/
public void setZip(String zip)
this.zip = zip;
/**
* @return the phone
*/
public String getPhone()
return phone;
/**
* @param phone the phone to set
*/
public void setPhone(String phone)
this.phone = phone;
/**
* @return the email
*/
public String getEmail()
return email;
/**
* @param email the email to set
*/
public void setEmail(String email)
this.email = email;
/**
* @return the isTrial
*/
public boolean isIsTrial()
return isTrial;
/**
* @param isTrial the isTrial to set
*/
public void setIsTrial(boolean isTrial)
this.isTrial = isTrial;
/**
* @return the dateCreated
*/
public Timestamp getDateCreated()
return dateCreated;
/**
* @param dateCreated the dateCreated to set
*/
public void setDateCreated(Timestamp dateCreated)
this.dateCreated = dateCreated;
/**
* @return the lastUpdated
*/
public Timestamp getLastUpdated()
return lastUpdated;
/**
* @param lastUpdated the lastUpdated to set
*/
public void setLastUpdated(Timestamp lastUpdated)
this.lastUpdated = lastUpdated;
---实现类----
public class DBImpl implements DBInterface
public List<UserBean> getUserData()
System.out.println("01");
Statement statement=null;
Connection connection=null;
ResultSet resultSet=null;
List<UserBean> beans=new ArrayList<UserBean>();
System.out.println("02");
try
System.out.println("03");
connection=DBConnection.getInstance().getConnection();
System.out.println("04");
String sql = "select * from user where isTrial=true";
System.out.println("05");
statement=connection.createStatement();
System.out.println("06");
resultSet=statement.executeQuery(sql.toLowerCase());
System.out.println("07");
if(resultSet.isBeforeFirst())
System.out.println("08");
while(resultSet.next())
System.out.println("09");
UserBean bean=new UserBean();
System.out.println("10");
bean.setIdUser(resultSet.getInt("idUser"));
System.out.println(resultSet.getInt("idUser"));
bean.setCompanyName(resultSet.getString("CompanyName"));
System.out.println(resultSet.getString("CompanyName"));
bean.setCountry(resultSet.getString("Country"));
bean.setAdressLine1(resultSet.getString("Address_Line1"));
bean.setAddressLine2(resultSet.getString("Address_Line2"));
bean.setZip(resultSet.getString("Zip"));
bean.setPhone(resultSet.getString("Phone"));
bean.setEmail(resultSet.getString("Email"));
bean.setIsTrial(resultSet.getBoolean("isTrial"));
bean.setDateCreated(resultSet.getTimestamp("DateCreated"));
bean.setLastUpdated(resultSet.getTimestamp("LastUpdated"));
beans.add(bean);
catch (Exception ex)
ex.printStackTrace();
finally
try
if(resultSet!=null)
resultSet.close();
if(statement!=null)
statement.close();
if(connection!=null)
connection.close();
catch(Exception e)
e.printStackTrace();
return beans;
当我运行以下 servlet 时，我遇到了上述异常。
---Servlet---
public class Test01 extends HttpServlet
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try
DBInterface bImpl=new DBImpl();
List<UserBean> userData = bImpl.getUserData();
for(int i=0;i<userData.size();i++)
out.println(userData.get(i).toString());
finally
out.close();
在这里我想知道这个异常是如何产生的，为什么？我可以完成我预期的任务，但这给我带来了错误。而且我是连接池的新手。
【问题讨论】：
你的类路径中有c3po.jar 吗？如果是，哪个版本？
@Jens c3p0-0.9.5.jar
这个 jar 在运行时在你的类路径中吗？
@Jens 是的，我有。
【参考方案1】：
您好，我在我工作的一个应用程序中遇到了同样的异常。以下是我在遇到类似问题时参考的一些有用链接。：
[1]https://forums.hibernate.org/viewtopic.php?t=924835&view=next&sid=abc532479937768dd0fd58e82a1f465f
[2]Getting Exception and application not able to connect with MySqL Database when using connection pooling (c3p0-0.9.1.2) with Hibernate 3.2?
在重新部署类卸载期间，如果您未能关闭 Hibernate 的 sessionFactory，那么您会收到这些 ClassNotFound 错误。 #2 中的答案之一建议您可以添加自定义 ServletContextListener 来处理 contextDestroyed 事件。
【讨论】：
感谢您的帮助，但我没有在这项工作中使用休眠。【参考方案2】：我在一个 Maven 项目中遇到了同样的问题，并且花了两周时间处理它；它在 Eclipse 中有效，但在 Ubuntu Server 中无效。谷歌搜索的所有解决方案均无效。
在我的例子中，解决了将 hibernate-core 和 c3p0 库添加到我的 pom 的问题（该项目已经有了 hibernate-c3p0 库）。
这是我在 pom.xml 添加的代码：
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.2.12.Final</version>
<exclusions>
<exclusion>
<artifactId>jta</artifactId>
<groupId>javax.transaction</groupId>
</exclusion>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
<exclusion>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
</exclusion>
</exclusions>
</dependency>
希望它可以帮助某人！ :)
【讨论】：
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