Java - 无法将我的 MySQL JAR 文件添加到 eclipse 的构建路径中

Question

public void service(HttpServletRequest req,HttpServletResponse res){
        PrintWriter out;
        try {
            out = res.getWriter();
        } catch (IOException e2) {
            e2.printStackTrace();
            System.out.println("IO thrown");
        }

        try {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
        } catch (InstantiationException e1) {
            e1.printStackTrace();
            System.out.println("Instantiation exception thrown");
        } catch (IllegalAccessException e1) {
            e1.printStackTrace();
            System.out.println("illegal access exception thrown");
        } catch (ClassNotFoundException e1) {
            e1.printStackTrace();
            System.out.println("class not found thrown");
        }
        try {
            connection = DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("SQL exception thrown");
        }

        System.out.println("connection failure");
    }

我尝试将 JAR 文件添加到 Properties->Build path 中，然后我将 JAR 分别添加到 Modulopath 和 Classpath 中的任何一个中，但它都不起作用，因为每次我都有相同的异常

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1358)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1180)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:332)
    at com.practice.Form1.service(Form1.java:23)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
connection failure
    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:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:609)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:810)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1623)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:835)

我对在何处添加 MySQL JAR 感到困惑，因为我无法将其直接添加到 Property->Build Path->Library 中，如图所示

当我打开 Property->Build path 时，它不允许我直接添加 MySQL JAR（作为外部 JAR），我必须选择 Modulopath 或 Classpath

Answer 1

如果Eclipse确实没有给你很好的回应，你可以直接修改隐藏文件（.classpath）

<classpathentry kind="lib" path="WEB-INF/lib/mysql-connector-java-3.0.14-production-bin.jar"/>

我假设您的 jar 文件已就位。 重命名您使用的 mysql 连接器版本

希望能帮助到你。