请教一个，数据库连接的问题。（在线等待）
我现在有以下的代码：
Connection con;
Statement stmt;
ResultSet res; // add
Class.forName( "com.mysql.jdbc.Driver ").newInstance();
con = DriverManager.getConnection( "jdbc:mysql://localhost:3306/test ", "root ", " ");
stmt = con.createStatement();
res = stmt.executeQuery( "select * from username ");
...........
这段java代码，在一个单独的Java程序（也就是有mail函数的那种）中正常执行。但是如果把这个代码，放到web开发的Java程序中就会出错。
「con = DriverManager.getConnection( "jdbc:mysql://localhost:3306/test ", "root ", " ");」出错，出错的信息如下：
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.net.SocketException
MESSAGE: java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:3306 connect,resolve)
STACKTRACE:
java.net.SocketException: java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:3306 connect,resolve)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:151)
at com.mysql.jdbc.MysqlIO. <init> (MysqlIO.java:280)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1765)
at com.mysql.jdbc.Connection. <init> (Connection.java:430)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:268)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at Login.LoginJavaBean.strCheck(LoginJavaBean.java:16)
at Login.LoginServlet.doGet(LoginServlet.java:16)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:199)
at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:50)
at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:128)
at java.security.AccessController.doPrivileged(Native Method)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:124)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:139)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2460)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:133)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:119)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:127)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:157)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
at java.lang.Thread.run(Unknown Source)
** END NESTED EXCEPTION **
想请教各位，如何解决这个问题。
[解决办法]
权限问题。放开mysql的权限
[解决办法]
晕倒，干嘛密码是空的？好歹也设置个123吧？
[解决办法]
java.security.AccessControlException: access denied (java.lang.RuntimePermission exitVM)
=============================================================
没有权限。。。
test这个不是mysql自带的数据库么，username是你在里面建的一个表？另外看一下驱动有没有放到/WEB-INF/lib目录下
[解决办法]
我看是你的mysql的问题。。看看mysql服务启动了吗？
要是启动了。。还不行你先用修复工具修复mysql。。。
出现的问题是不能连接mysql数据库
[解决办法]
按照下面的方法确认一次:(从log看楼主用的是tomcat)
1)Code
连接字符用
DriverManager.getConnection( "jdbc:mysql://localhost:3306/test?user=root&password=123 ");
2)tomcat policy修改(path=apache-tomcat-5.x/conf/catalina.policy)
追加
grant {
// All Web Application can access localhost mysql
permission java.net.SocketPermission "localhost:3306 ", "connect ";
};
3)restart tomcat
