Exception in thread "pool-2-thread-1" java.lang.NoClassDefFoundError:

其实这个错误情况根本无法给我准确的定位到错误代码。

单例的代码

public class DAOFactory {
		
	//....省略
	
	private static class SingletonHolder {
		//只有在调用的时候才会初始化！而且线程安全。
        static DAOFactory instance = new DAOFactory();
    }  
	
	public static DAOFactory getInstance() {
		return SingletonHolder.instance;
	}
}

期间我加了个ControlDao的一些ibatis的class和module竟然报错误：
Exception in thread "pool-2-thread-1" java.lang.NoClassDefFoundError: Could not initialize class com.xxxx.dao.DAOFactory$SingletonHolder



找啊找，最后我试着改成，不用单例：

public class DAOFactory {
		
	//....省略
	
	public static DAOFactory getInstance() {
		return new DAOFactory():
	}
}

结果就出现了正确的ibatis错误定位了：
java.lang.RuntimeException: Error occurred.  Cause: com.ibatis.common.xml.NodeletException: Error parsing XML.  Cause: java.lang.RuntimeException: Error parsing XPath '/sqlMapConfig/sqlMap'.  Cause: com.ibatis.common.xml.NodeletException: Error parsing XML.  Cause: java.lang.RuntimeException: Error parsing XPath '/sqlMap/insert'.  Cause: com.ibatis.common.beans.ProbeException: There is no READABLE property named 'test' in class 'com.xxx.module.Control'

终于找到原因了，竟然是我的sql语句没写好，改好，再改回原来的单例，运行正常了。

评论

1 楼 rich8w 2010-01-05  

由于把单例的DAOFactory注释掉了

/*错误代码*/
public static DAOFactory getInstance() {
		return new DAOFactory();
		//return SingletonHolder.instance;
	}

产生了意想不到的异常了，我明明已经startTransaction了，可还提示我没started。

com.ibatis.common.jdbc.exception.NestedSQLException: Could not commit transaction.  Cause: com.ibatis.sqlmap.engine.transaction.TransactionException: TransactionManager could not commit.  No transaction is started.
	at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.commitTransaction(SqlMapExecutorDelegate.java:719)
	at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.commitTransaction(SqlMapSessionImpl.java:172)
	at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.commitTransaction(SqlMapClientImpl.java:148)

改回单例就一切OK了。