JDBC测试数据库连接成功，但在访问servlet时显示“注册驱动失败”

[Mrs_Wu]

最近在写JAVA分页的一个demo时遇到的一个问题：
①在测试JDBC数据库连接时，显示测试成功。DBHelper类中连接数据库代码及测试结果如下：

package com.util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.sql.*;

public class DBHelper {

	private static String driver;
	private static String url;
	private static String username;
	private static String password;
	private PreparedStatement pstmt;//定义sql的执行对象
	private ResultSet resultSet;//定义查询返回的结果集合
	private static Connection conn;
	public DBHelper(){};
	static{
		loadConfig();
	}
	//加载数据库配置信息
	public static void loadConfig(){
	try {
		InputStream inStream=DBHelper.class.getResourceAsStream("/jdbc.properties");
		Properties prop=new Properties();//创建一个Properties对象
		prop.load(inStream);
		driver=prop.getProperty("jdbc.driver");
		username=prop.getProperty("jdbc.username");
		password=prop.getProperty("jdbc.password");
		url=prop.getProperty("jdbc.url");
	} catch (Exception e) {
		// TODO Auto-generated catch block
		throw new RuntimeException("读取数据库配置文件异常！",e);
	}
	}

public static Connection getConnection(){
		try {
			Class.forName(driver);
			conn=DriverManager.getConnection(url, username, password);
			System.out.println("数据库连接成功");
		} catch (Exception e) {
		throw new RuntimeException("驱动注册失败！");
		}
		return conn;
}
public void releaseConn(){
	if(resultSet!=null){
		try{
			resultSet.close();
		}
		catch(SQLException e){
			e.printStackTrace();
		}
	}
	if(pstmt!=null){
		try{
			pstmt.close();
		}
		catch(SQLException e){
			e.printStackTrace();
		}
	}
	if(conn!=null){
		try{
			conn.close();
		}
		catch(SQLException e){
			e.printStackTrace();
		}
	}
}
public static void main(String args[]){
	Connection conn=null;
	conn=DBHelper.getConnection();
	if(conn==null){
		System.out.println("数据库连接失败");
	}
	if(conn!=null){
		System.out.println("数据库连接成功");
	}
}
}

（其中url,username,password都放在名为jdbc.properties的一个file中）
测试结果为：
数据库连接成功
数据库连接成功
②通过url访问servlet，出现如下的错误：

MyEclipse错误提示如下：
严重: Servlet.service() for servlet [test] in context with path [/ServletDemo] threw exception
java.lang.RuntimeException: 驱动注册失败！
at com.util.DBHelper.getConnection(DBHelper.java:49)
at dao.StudentDaoImpl.getAllStudent(StudentDaoImpl.java:36)
at dao.StudentDaoImpl.findStudent(StudentDaoImpl.java:15)
at service.StudentServiceImpl.findStudent(StudentServiceImpl.java:23)
at servlet.test.doPost(test.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2521)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2510)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
请问大家有遇到过类似的问题吗？求赐教，谢谢大家！

[Mrs_Wu]

那它显示我连接成功，是不是就意味着我基本的配置信息等都没问题呢？

[孟子E章]

检查jdbc.properties文件里面的配置是否正确，比如key/value必须采用=号，否则，端口没法写了。 另外注意是否有空格等字符，拼写是否正确

[TxWang_]

你好遇到了同样的问题，解决了吗