com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException：無法創建與數據庫服務器的連接

Question

我想前言：我使用的是 MySQL Java 連接器 v. 8.0.23，所以過時的連接器不是問題。 它被添加到我的項目的類路徑中，也被添加到 Maven 依賴項中。

為了隱私起見，我刪除了連接信息。 這是在運行 MySQL 8 的 TomCat 服務器上。

錯誤

每次嘗試連接到我的數據庫（在線托管的 RDS AWS 數據庫）時，我都會收到以下異常。

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:400)
    at com.mysql.jdbc.Util.getInstance(Util.java:383)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:958)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:937)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:872)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2326)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2079)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:400)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:270)
    at com.personal.personal_website.DatabaseConnect.getRemoteConnection(DatabaseConnect.java:24)
    at org.apache.jsp.courses_jsp._jspService(courses_jsp.java:122)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:466)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:382)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    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:199)
    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:143)
    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:353)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
    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:1629)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
    at com.mysql.jdbc.ConnectionImpl.getServerCharset(ConnectionImpl.java:2999)
    at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1885)
    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1814)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1207)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2249)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2280)
    ... 42 more
23-Feb-2021 16:17:36.401 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [C:\Program Files\apache-tomcat-8.5.63\webapps\manager]
23-Feb-2021 16:17:36.465 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [C:\Program Files\apache-tomcat-8.5.63\webapps\manager] has finished in [62] ms

Maven 依賴關系

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.23</version>
        </dependency>

連接 Class

public class DatabaseConnect {
    Connection con = null;

    public Connection getRemoteConnection() {
        try {
            // Find driver
            Class.forName("com.mysql.jdbc.Driver");
            String dbName = "";
            String userName = "";
            String password = "";
            String hostname = "";
            String port = "3306";
            String jdbcUrl = "jdbc:mysql://" + hostname + ":" + port + "/" + dbName + "?user=" + userName + "&password=" + password;

            // Make Connection
            System.out.println("Getting remote connection with connection string.");
            con = DriverManager.getConnection(jdbcUrl);
            System.out.println("Remote connection successful.");
        } catch (ClassNotFoundException | SQLException e) { e.printStackTrace();}

        return con;
    }
}

Answer 1

評論中的 Doyle 設法弄清楚了。 驅動程序 class 名稱更改為 MySQL 8。

代替

Class.forName("com.mysql.jdbc.Driver");

我用了

Class.forName("com.mysql.cj.jdbc.Driver");

來源： https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-driver-name.html