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社区首页 >问答首页 >ClassNotFoundException MySqlConnector IntelliJ

问ClassNotFoundException MySqlConnector IntelliJ
EN

Stack Overflow用户
提问于 2022-03-17 00:39:08
回答 1查看 851关注 0票数 -2

我正在用JavaFX编写一个模板方法设计模式示例程序，我无法连接到我的MySQL数据库。我正在使用IntelliJ，并将MySQLConnector.jar添加到库中，但是我还是得到了ClassNotFoundException。

代码语言：javascript
运行
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Error

    java.lang.ClassNotFoundException: com.mysql.jdbc.driver
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:375)
    at sample.DatabaseOperation.openConnection(DatabaseOperation.java:24)
    at sample.DatabaseOperation.template(DatabaseOperation.java:14)
    at sample.Controller.initialize(Controller.java:44)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2655)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3331)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3287)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3255)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3227)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3203)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3196)
    at sample.Main.start(Main.java:13)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:833)
Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:465)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:364)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:901)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
    at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: javafx.fxml.LoadException: 
/C:/Users/grego/Downloads/code-with-quarkus/TemplateMethodExample/out/production/TemplateMethodExample/sample/sample.fxml

    at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2707)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2685)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3331)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3287)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3255)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3227)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3203)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3196)
    at sample.Main.start(Main.java:13)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    ... 1 more
Caused by: java.lang.NullPointerException: Cannot invoke "java.sql.Connection.createStatement()" because "this.connection" is null
    at sample.InitialLoad.select(InitialLoad.java:10)
    at sample.DatabaseOperation.template(DatabaseOperation.java:17)
    at sample.Controller.initialize(Controller.java:44)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2655)
    ... 17 more
Exception running application sample.Main

Process finished with exit code 1

模板法

代码语言：javascript
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package sample;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

public abstract class DatabaseOperation {
public Connection connection;
public ResultSet resultSet;

public final ResultSet template() throws SQLException {
    openConnection();
    insert();
    update();
    select();
    closeConnection();
    return resultSet;
}

public final void openConnection() {
    try {
        Class.forName("com.mysql.jdbc.driver");
        connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/employees", "user", "password");
    } catch (ClassNotFoundException | SQLException e) {
        e.printStackTrace();
    }
}

public final void closeConnection(){
    try {
        connection.close();
    } catch (SQLException throwables) {
        throwables.printStackTrace();
    }
    System.out.println("Connection closed");
}

public abstract void select() throws SQLException;

public abstract void insert();

public abstract void update();

}

类扩展模板。

代码语言：javascript
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package sample;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class InitialLoad extends DatabaseOperation {
    @Override
    public void select() throws SQLException {
        Statement statement = connection.createStatement();
        resultSet = statement.executeQuery("select * from employees");
    }
@Override
public void insert() {

}

@Override
public void update() {

}
}

控制器

代码语言：javascript
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package sample;

import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;

import javax.xml.crypto.Data;
import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class Controller implements Initializable {
public TableColumn col_emp_no;
public TableColumn col_birth_date;
public TableColumn col_first_name;
public TableColumn col_last_name;
public TableColumn col_gender;
public TableColumn col_hire_date;
@FXML
TableView tableView;

@Override
public void initialize(URL url, ResourceBundle resourceBundle) {
    col_emp_no.setCellValueFactory(new PropertyValueFactory<>("emp_no"));
    col_birth_date.setCellValueFactory(new PropertyValueFactory<>("birth_date"));
    col_first_name.setCellValueFactory(new PropertyValueFactory<>("first_name"));
    col_last_name.setCellValueFactory(new PropertyValueFactory<>("last_name"));
    col_gender.setCellValueFactory(new PropertyValueFactory<>("gender"));
    col_hire_date.setCellValueFactory(new PropertyValueFactory<>("hire_date"));

    DatabaseOperation initialLoad = new InitialLoad();
    try {
        initialLoad.template();
    } catch (SQLException throwables) {
        throwables.printStackTrace();
    }

}
}

Main

代码语言：javascript
运行
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package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root, 300, 275));
        primaryStage.show();
    }


public static void main(String[] args) {
    launch(args);
}
}

提前谢谢你！

更新：

在使用Maven时，我仍然会遇到相同的错误

代码语言：javascript
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[INFO] 
[INFO] --- javafx-maven-plugin:0.0.6:run (default-cli) @ TemplateMethodMaven ---
[INFO] Toolchain in javafx-maven-plugin null
java.lang.ClassNotFoundException: com.mysql.jdbc.driver
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:636)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:182)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:375)
    at org.example.DatabaseOperation.openConnection(DatabaseOperation.java:24)
    at org.example.DatabaseOperation.template(DatabaseOperation.java:14)
    at org.example.PrimaryController.initialize(PrimaryController.java:44)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2655)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:2516)
    at org.example.App.loadFXML(App.java:31)
    at org.example.App.start(App.java:20)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:831)
Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:465)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:364)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:901)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
    at java.base/java.lang.Thread.run(Thread.java:831)
Caused by: javafx.fxml.LoadException: 
/C:/Users/grego/Downloads/code-with-quarkus/TemplateMethodMaven/target/classes/org/example/primary.fxml
    at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2707)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2685)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:2516)
    at org.example.App.loadFXML(App.java:31)
    at org.example.App.start(App.java:20)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    ... 1 more
Caused by: java.lang.NullPointerException: Cannot invoke "java.sql.Connection.createStatement()" because "this.connection" is null
    at org.example.InitialLoad.select(InitialLoad.java:10)
    at org.example.DatabaseOperation.template(DatabaseOperation.java:17)
    at org.example.PrimaryController.initialize(PrimaryController.java:44)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2655)
    ... 13 more
Exception running application org.example.App
[ERROR] Command execution failed.
org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1)
    at org.apache.commons.exec.DefaultExecutor.executeInternal (DefaultExecutor.java:404)
    at org.apache.commons.exec.DefaultExecutor.execute (DefaultExecutor.java:166)
    at org.openjfx.JavaFXBaseMojo.executeCommandLine (JavaFXBaseMojo.java:567)
    at org.openjfx.JavaFXBaseMojo.executeCommandLine (JavaFXBaseMojo.java:434)
    at org.openjfx.JavaFXRunMojo.execute (JavaFXRunMojo.java:105)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:77)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:568)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
    at org.codehaus.classworlds.Launcher.main (Launcher.java:47)
org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1)
    at org.apache.commons.exec.DefaultExecutor.executeInternal(DefaultExecutor.java:404)
    at org.apache.commons.exec.DefaultExecutor.execute(DefaultExecutor.java:166)
    at org.openjfx.JavaFXBaseMojo.executeCommandLine(JavaFXBaseMojo.java:567)
    at org.openjfx.JavaFXBaseMojo.executeCommandLine(JavaFXBaseMojo.java:434)
    at org.openjfx.JavaFXRunMojo.execute(JavaFXRunMojo.java:105)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:193)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)
at org.codehaus.classworlds.Launcher.main(Launcher.java:47)
mysql
intellij-idea
javafx
classnotfoundexception
mysql-connector
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2022-03-18 15:46:04

请参阅这是Idea JavaFX项目设置指南，具体参考关于添加其他模块的一节。

您需要添加的mysql JDBC连接器的maven模块：

代码语言：javascript
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<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.28</version>
</dependency>

如果不提供module-info.java，则应用程序代码将位于类路径上，而mysql连接器也将位于类路径上，因此访问应该可以正常工作，而不会进行其他更改。

如果您提供了一个module-info.java，您将需要在您的模块-info.java中要求适当的模块：

  • 标准jdbc和sql访问代码的requires java.sql。
  • 用于mysql驱动程序的requires mysql.connector.java。

示例module-info.java (替换模块名称并根据需要修改需求子句)：

代码语言：javascript
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module com.example.sql {
    requires javafx.controls;
    requires javafx.fxml;
    requires mysql.connector.java;
    requires java.sql;

    opens com.example.sql to javafx.fxml;
    exports com.example.sql;
}

当您试图打开数据库连接时，由于多种原因，您的代码是错误的，也是不必要的：

代码语言：javascript
运行
复制
Class.forName("com.mysql.jdbc.driver");

一旦通过添加正确的库和模块命令正确配置了访问，执行这一行将产生以下警告：

代码语言：javascript
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复制
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

因此，两者都是：

  • 驱动程序名错误，应该是com.mysql.cj.jdbc.Driver 和
  • 不需要显式加载驱动程序

jdbc将根据需要通过服务提供者接口自动加载它。SPI很复杂，您不必担心它的实际工作方式，只需假设它是这样的。

更多信息在以下内容的答案中：

在Oracle jdbc教程之后，您将得到如下连接代码：

代码语言：javascript
运行
复制
public Connection getConnection() throws SQLException {
    Properties connectionProps = new Properties();
    connectionProps.put("user", "apple");
    connectionProps.put("password", "cider");

    Connection conn = DriverManager.getConnection(
                "jdbc:mysql://localhost:1433/",
                connectionProps
    );

    System.out.println("Connected to database");

    return conn;
}

从start方法调用此方法似乎是试图为我启动一个连接(它实际上没有连接，因为我没有设置本地mysql服务器)。

票数 1
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/71505791

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