java.sql.SQLException：无法在 IntelliJ Web 应用程序中为连接 URL 'null' 创建类 '' 的 JDBC 驱动程序

Posted 2023-02-24

【中文标题】java.sql.SQLException：无法在 IntelliJ Web 应用程序中为连接 URL \'null\' 创建类 \'\' 的 JDBC 驱动程序

【英文标题】：java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null' in IntelliJ web applicationjava.sql.SQLException：无法在 IntelliJ Web 应用程序中为连接 URL 'null' 创建类 '' 的 JDBC 驱动程序

【发布时间】：2021-11-16 00:01:52

【问题描述】：

我正在尝试使用 IntelliJ 上的 servlet 构建一个小型 Web 应用程序。我正在尝试使用 JDBC 将 mysql DB 与应用程序连接起来。

我有所需的 Maven 依赖项，检查了我的 context.xml 文件。 我手动尝试使用已成功连接的 IntelliJ 上的 GUI 连接 MySQL DB。

<Context>

<Resource name="jdbc/student_tracker"
          auth="Container" type="javax.sql.DataSource"
          maxActive="20" maxIdle="5" maxWait="10000"
          username="webstudent" password="webstudent"
          driverClassName="com.mysql.jdbc.Driver"
          url="jdbc:mysql://localhost:3306/web_student_tracker"/>
</Context>

这里是 Servlet

@WebServlet(name = "TestServlet", value = "/TestServlet")
public class TestServlet extends HttpServlet 

    private static final long serialVersionUID = 1L;

    // Define datasource/connection pool for Resource Injection
    @Resource(name="jdbc/student_tracker")
    private DataSource dataSource;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 

        // Step 1:  Set up the printwriter
        PrintWriter out = response.getWriter();
        response.setContentType("text/plain");

        // Step 2:  Get a connection to the database
        Connection myConn = null;
        Statement myStmt = null;
        ResultSet myRs = null;

        try 
            myConn = dataSource.getConnection();

            // Step 3:  Create a SQL statements
            String sql = "select * from student";
            myStmt = myConn.createStatement();

            // Step 4:  Execute SQL query
            myRs = myStmt.executeQuery(sql);

            // Step 5:  Process the result set
            while (myRs.next()) 
                String email = myRs.getString("email");
                out.println(email);
            
        
        catch (Exception exc) 
            exc.printStackTrace();
        
    

错误

java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'
    at org.apache.tomcat.dbcp.dbcp2.DriverFactory.createDriver(DriverFactory.java:74)
    at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createConnectionFactory(BasicDataSource.java:472)
    at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:538)
    at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:744)
    at com.application.student_tracker.TestServlet.doGet(TestServlet.java:36)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:196)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:364)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:624)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1650)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.sql.SQLException: No suitable driver
    at java.sql.DriverManager.getDriver(DriverManager.java:315)
    at org.apache.tomcat.dbcp.dbcp2.DriverFactory.createDriver(DriverFactory.java:59)

【问题讨论】：

好像您的上下文文件没有部署到 Tomcat。您是如何将其添加到您的项目中的？它位于何处？

【参考方案1】：

如果您将 JNDI 用于 DataSource，您必须在 $CATALINA_HOME/lib. 中拥有 JDBC 驱动程序，请将 mysql-connector 复制到 $CATALINA_HOME/lib

也将其从您的 WEB-INF/lib 中删除

参考号：JNDI Datasource HOW-TO