我编写了一个测试Java APP，它运行正常BUt这个Web应用程序会抛出类似于同一个cfg.xml文件的异常
<property name="hibernate.bytecode.use_reflection_optimizer">false</property>
<property name="hibernate.connection.autocommit">true</property>
<property name="hibernate.connection.release_mode">auto</property>
<property name="hibernate.current_session_context_class">thread</property>
<property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
<property name="hibernate.connection.password">1234</property>
<property name="hibernate.connection.url">jdbc:postgresql://localhost/postgres</property>
<property name="hibernate.connection.username">postgres</property>
<property name="hibernate.default_schema">public</property>
<property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property>
<property name="hibernate.ejb.discard_pc_on_close">false</property>
<property name="hibernate.query.jpaql_strict_compliance">true</property>
<property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
<property name="hibernate.transaction.flush_before_completion">false</property>
<property name="hibernate.show_sql">false</property>
<property name="hibernate.generate_statistics">false</property>
<property name="hibernate.use_sql_comments">false</property>
<property name="hibernate.connection.pool_size">100</property>
当我按“保存”按钮时，我得到以下异常：
javax.servlet.ServletException: org.hibernate.exception.JDBCConnectionException: Cannot open connection
javax.faces.webapp.FacesServlet.service(FacesServlet.java:325)
root cause
javax.faces.el.EvaluationException: org.hibernate.exception.JDBCConnectionException: Cannot open connection
javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
javax.faces.component.UICommand.broadcast(UICommand.java:315)
javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775)
javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267)
com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
root cause
org.hibernate.exception.JDBCConnectionException: Cannot open connection
org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:98)
org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142)
org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85)
org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
$Proxy108.beginTransaction(Unknown Source)
com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.apache.el.parser.AstValue.invoke(AstValue.java:196)
org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98)
javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
javax.faces.component.UICommand.broadcast(UICommand.java:315)
javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775)
javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267)
com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
root cause
java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost/postgres
java.sql.DriverManager.getConnection(Unknown Source)
java.sql.DriverManager.getConnection(Unknown Source)
org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133)
org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142)
org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85)
org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
$Proxy108.beginTransaction(Unknown Source)
com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.apache.el.parser.AstValue.invoke(AstValue.java:196)
org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98)
javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
javax.faces.component.UICommand.broadcast(UICommand.java:315)
javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775)
javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267)
com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
块引用
答案 0 :(得分：6)
遇到异常时，有必要检查堆栈跟踪中最底层的根本原因。在这种情况下，它是以下内容：
java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost/postgres
这只是意味着URL错误或者当前运行时类路径中不存在所需的驱动程序。由于URL根据PostgreSQL JDBC documentation看起来很好，因此在当前运行时类路径中缺少驱动程序。
因此，要解决此问题，您需要将JDBC驱动程序JAR文件放在webapp的运行时类路径中。 /WEB-INF/lib是webapp的默认运行时类路径所涵盖的文件夹之一。只需删除PostgreSQL JDBC驱动程序JAR文件并重新部署即可。
答案 1 :(得分：1)
我没有查看你的配置文件，但我认为它至少配置得相当好，因为堆栈跟踪表明它正在尝试连接到localhost JDBC url的postgres数据库。
看起来最大的问题是它无法找到postgres JDBC驱动程序：
根本原因
java.sql.SQLException：没有为jdbc找到合适的驱动程序：postgresql：// localhost / postgres java.sql.DriverManager.getConnection（Unknown Source）java.sql.DriverManager.getConnection（Unknown Source）org.hibernate.connection .DriverManagerConnectionProvider.getConnection（DriverManagerConnectionProvider.java:133）
确保JAR文件位于类路径中。你可以在这里下载它，如果你还没有它： http://jdbc.postgresql.org/
答案 2 :(得分：0)
这里有什么问题？
异常非常明确：
org.hibernate.exception.JDBCConnectionException：无法打开连接
确保您可以连接到您连接的数据库，配置正确，没有阻止连接的网络问题等。
答案 3 :(得分：0)
验证您是否在classpath中拥有数据库驱动程序的jar。 验证驱动程序类名称是否正确。 验证connection.url是否正确。 我得到了同样的错误。唯一不同的是，我使用的是Oracle 11g。我在classpath中有ojdbc14.jar，驱动程序类名称是正确的但是connection.url属性是错误的。 Oracle 11g的正确格式是
JDBC：预言：瘦：@localhost：1521：global_dsn_name