JavaFX二叉搜索树可视化应用启动报错求助

问题描述 #

使用IntelliJ IDEA开发基于JavaFX的二叉搜索树（BST）可视化应用，源码检查无问题，但启动时报错，核心原因是模块com.special.effect.javafxprojects未将com.special.effect.javafxprojects.BinarySearchTreeApplication包导出至javafx.graphics模块，导致IllegalAccessException。

完整报错信息 #

"C:\Program Files\Java\jdk-19\bin\java.exe" "-javaagent:C:\Users\FAbdu\IntelliJ IDEA 2023.1\lib\idea_rt.jar=60595:C:\Users\FAbdu\IntelliJ IDEA 2023.1\bin" -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8 -classpath C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-controls\19\javafx-controls-19.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-graphics\19\javafx-graphics-19.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-base\19\javafx-base-19.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-fxml\19\javafx-fxml-19.jar;C:\Users\FAbdu\.m2\repository\org\jetbrains\annotations\17.0.0\annotations-17.0.0.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-media\21-ea+5\javafx-media-21-ea+5.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-media\18-ea+1\javafx-media-18-ea+1.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-graphics\18-ea+1\javafx-graphics-18-ea+1.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-base\18-ea+1\javafx-base-18-ea+1.jar -p C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-base\19\javafx-base-19-win.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-base\18-ea+1\javafx-base-18-ea+1-win.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-media\21-ea+5\javafx-media-21-ea+5-win.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-media\18-ea+1\javafx-media-18-ea+1-win.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-graphics\19\javafx-graphics-19-win.jar;C:\Users\FAbdu\.m2\repository\org\jfxcore\javafx-graphics\18-ea+1\javafx-graphics-18-ea+1-win.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-fxml\19\javafx-fxml-19-win.jar;C:\Users\FAbdu\.m2\repository\org\openjfx\javafx-controls\19\javafx-controls-19-win.jar;C:\Users\FAbdu\IdeaProjects\JavaFXprojects\target\classes -m com.special.effect.javafxprojects/com.special.effect.javafxprojects.BinarySearchTreeApplication.BSInterface
Exception in Application constructor
Exception in thread "main" java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:119)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1081)
Caused by: java.lang.RuntimeException: Unable to construct Application instance: class com.special.effect.javafxprojects.BinarySearchTreeApplication.BSInterface
    at javafx.graphics@19/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:891)
    at javafx.graphics@19/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
    at java.base/java.lang.Thread.run(Thread.java:1589)
Caused by: java.lang.IllegalAccessException: class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) cannot access class com.special.effect.javafxprojects.BinarySearchTreeApplication.BSInterface (in module com.special.effect.javafxprojects) because module com.special.effect.javafxprojects does not export com.special.effect.javafxprojects.BinarySearchTreeApplication to module javafx.graphics
    at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:420)
    at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:709)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:493)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:484)
    at javafx.graphics@19/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:803)
    at javafx.graphics@19/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics@19/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics@19/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics@19/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics@19/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics@19/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    ... 1 more

Process finished with exit code 1

应用UI代码 #

public class BSInterface extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        BST<Integer> tree = new BST<>();

        BorderPane pane = new BorderPane();
        BSTbackend view = new BSTbackend(tree);
        pane.setCenter(view);

        TextField tfKey = new TextField();
        tfKey.setPrefColumnCount(3);
        tfKey.setAlignment(Pos.BASELINE_RIGHT);
        Button btnInsert = new Button("INSERT");
        Button btnDelete = new Button("DELETE");
        HBox hBox = new HBox(5);
        hBox.getChildren().addAll(new Label("Enter a key: "),
                tfKey, btnInsert, btnDelete);
        hBox.setAlignment(Pos.CENTER);
        pane.setBottom(hBox);

        btnInsert.setOnAction(e->{
            int key = Integer.parseInt(tfKey.getText());
            if(!tree.search(key)){
                view.displayTree();
                view.setStatus(key + " is not in the tree");
            }else{
                tree.delete(key);
                view.displayTree();
                view.setStatus(key + " is deleted from the tree");
            }
        });

        btnDelete.setOnAction(e->{
            int key = Integer.parseInt(tfKey.getText());
            if(!tree.search(key)){
                view.displayTree();
                view.setStatus(key + " is not in the tree");
            }else{
                tree.delete(key);
                view.displayTree();
                view.setStatus(key + " is deleted from the tree");
            }
        });

        Scene scene = new Scene(pane, 450, 250);
        stage.setTitle("BST Animation");
        stage.setScene(scene);
        stage.show();
    }
}

解决方案 #

该错误由Java模块系统的访问控制机制导致：JavaFX的javafx.graphics模块需要通过反射访问你的BSInterface类（继承自Application），但你的模块未开放对应包的访问权限。

方法1：修改module-info.java #

找到项目中的module-info.java文件，添加导出语句，将包含BSInterface的包明确导出给javafx.graphics模块：

module com.special.effect.javafxprojects {
    requires javafx.controls;
    requires javafx.graphics;
    requires javafx.fxml;

    // 导出目标包给javafx.graphics模块
    exports com.special.effect.javafxprojects.BinarySearchTreeApplication to javafx.graphics;
}

方法2：确保类的访问权限 #

确认BSInterface类使用public修饰符。JavaFX启动器需要访问类的公共构造方法，若类使用默认包访问权限，会触发访问异常。

方法3：检查模块路径配置 #

在IntelliJ IDEA的运行配置中，确认模块路径（Module path）正确包含你的项目模块，且JavaFX依赖已添加到模块路径中，而非仅类路径。

内容的提问来源于stack exchange，提问作者Farkhod Abdukodirov