java.sql.SQLException:无法从基础数据库获取连接

Question

我正在使用Hibernate,MySQL连接有效但我得到以下内容.如何查看与其连接的连接字符串的更多详细信息？

ERROR SchemaUpdate - could not get database metadata
java.sql.SQLException: Connections could not be acquired from the underlying database!
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:78)
        at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:51)
        at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:168)
        at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:356)
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1341)
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
        ... 10 more
ERROR SchemaUpdate - could not complete schema update
java.sql.SQLException: Connections could not be acquired from the underlying database!
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:78)
        at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:51)
        at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:168)
        at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:356)
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1341)
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
        ... 10 more

ERROR JDBCExceptionReporter - Connections could not be acquired from the underlying database!
org.hibernate.exception.GenericJDBCException: Cannot open connection
        at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:126)
        at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:114)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
        at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
        at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
        at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142)
        at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85)
        at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1354)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:342)
        at com.sun.proxy.$Proxy0.beginTransaction(Unknown Source)

Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:78)
        at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
        ... 15 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
        ... 18 more

这是我的hibernate xml:

<hibernate-configuration>
    <session-factory>

        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://127.0.0.1:3306/test</property>

        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">xxxxxx</property>

        <property name="show_sql">false</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <property name="connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
        <property name="hibernate.c3p0.max_statements">200</property>

        <property name="hibernate.c3p0.min_size">20</property>
        <property name="hibernate.c3p0.max_size">200</property>
        <property name="hibernate.c3p0.idle_test_period">300</property>
        <property name="hibernate.c3p0.timeout">300</property>

        <property name="hibernate.c3p0.max_statements">200</property>
        <property name="current_session_context_class">thread</property>

    </session-factory>
</hibernate-configuration>

Answer 1

就我而言，问题是 c3p0-0.9.2.1.jar 文件没有被 maven 复制到src/main/webapp/web-inf/libs

Answer 2

我会推荐两件事来解决这个问题：首先，尝试用大写字母提及您的数据库名称。尽管 db 仍然不区分大小写，但有时使用大写字母也可以正常运行。

其次，这个问题可能是由于您可能在会话工厂值中附加了一些额外的内容而引起的。例如（我将采用我使用过的代码并遇到这个问题并摆脱它）：我的 xml 的一部分如下所示：

    <session-factory>
    <property name="hbm2ddl.auto">update</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="connection.url">jdbc:mysql://10.184.56.183:3306/******?relaxAutoCommit=true&amp;autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=utf8</property>
    <property name="connection.username">******</property>
    <property name="connection.password">******</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="hibernate.connection.pool_size">5</property>
    <property name="hibernate.connection.shutdown">true</property>
    <property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
    <property name="hibernate.cache.use_second_level_cache">false</property>
    <property name="hibernate.cache.use_query_cache">false</property>
    <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
    <property name="hibernate.c3p0.min_size">2</property>
    <property name="hibernate.c3p0.max_size">5</property>
    <property name="hibernate.c3p0.timeout">108000</property>
    <property name="hibernate.c3p0.max_statements">50</property>
    <property name="hibernate.c3p0.idle_test_period">1000</property>
    <property name="hibernate.c3p0.validate">true</property>
    <property name="hibernate.c3p0.acquire_increment">5</property>       

因此，请继续修剪额外的值，例如清理数据库连接 URL 和其他内容。我在从数据库表生成代码时也遇到了问题。所以我创建了一个不同的配置 xml 并使其尽可能简单，仅此而已。一切都很顺利。