我一直在努力解决最困难的错误,任何能够帮忙的人都将获得10个饼干。我制作了两个完全相同的JavaFX应用程序,一个使用Maven,另一个没有使用构建工具。没有使用构建工具制作的那个应用程序按预期运行,而使用Maven制作的应用程序总是在Font.loadFont()上返回null,因此会抛出Null Pointer Exception异常。我已经将问题简化到非常简单的应用程序。
这里是不使用Maven的应用程序:
import javafx.application.Application;
import javafx.scene.text.*;
import javafx.stage.Stage;
public class AppWithoutMaven extends Application {
public static void main(String[] args) {
launch(args);
}
@Override public void start(Stage stage) {
Font.loadFont(AppWithoutMaven.class.getResource("Raleway-Medium.ttf").toExternalForm(), 50);
for (String family : Font.getFamilies())
if (family.equals("Raleway Medium"))
System.out.println("The font is loaded");
}
}
上述代码的文件结构、编译和执行方式如下:
![enter image description here](https://istack.dev59.com/KjeIk.webp)
现在是问题所在
这里是使用Maven的项目中几乎相同的代码:package test.font;
import javafx.application.Application;
import javafx.scene.text.*;
import javafx.stage.Stage;
public class App extends Application {
public static void main(String[] args) {
launch(args);
}
@Override public void start(Stage stage) {
Font.loadFont(App.class.getResource("test/font/Raleway-Medium.ttf").toExternalForm(), 50);
for (String family : Font.getFamilies())
if (family.equals("Raleway Medium"))
System.out.println("The font is loaded");
}
}
这里是pom.xml,这可能是我搞砸的地方:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>test.font</groupId>
<artifactId>font-test</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>font-test</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
</project>
目录结构如下:
最后,输出结果(由于空指针异常而导致运行时错误):
daniel@daniel-MS-7B22:~/Programs/fonttest/font-test$ mvn -e exec:java -Dexec.mainClass="test.font.App"
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.inject.internal.cglib.core.$ReflectUtils$1 (file:/usr/share/maven/lib/guice.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of com.google.inject.internal.cglib.core.$ReflectUtils$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building font-test 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.6.0:java (default-cli) @ font-test ---
Exception in Application start method
[WARNING]
java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1 (LauncherImpl.java:973)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2 (LauncherImpl.java:198)
at java.lang.Thread.run (Thread.java:844)
Caused by: java.lang.NullPointerException
at test.font.App.start (App.java:17)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9 (LauncherImpl.java:919)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11 (PlatformImpl.java:449)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$9 (PlatformImpl.java:418)
at java.security.AccessController.doPrivileged (Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$10 (PlatformImpl.java:417)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run (InvokeLaterDispatcher.java:96)
at com.sun.glass.ui.gtk.GtkApplication._runLoop (Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11 (GtkApplication.java:277)
at java.lang.Thread.run (Thread.java:844)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.537 s
[INFO] Finished at: 2018-07-17T00:33:07-04:00
[INFO] Final Memory: 10M/40M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java (default-cli) on project font-test: An exception occured while executing the Java class. Exception in Application start method: NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java (default-cli) on project font-test: An exception occured while executing the Java class. Exception in Application start method
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:213)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)
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:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:309)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:194)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:107)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:955)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:290)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:194)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:564)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. Exception in Application start method
at org.codehaus.mojo.exec.ExecJavaMojo.execute (ExecJavaMojo.java:339)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:208)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)
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:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:309)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:194)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:107)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:955)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:290)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:194)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:564)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1 (LauncherImpl.java:973)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2 (LauncherImpl.java:198)
at java.lang.Thread.run (Thread.java:844)
Caused by: java.lang.NullPointerException
at test.font.App.start (App.java:17)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9 (LauncherImpl.java:919)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11 (PlatformImpl.java:449)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$9 (PlatformImpl.java:418)
at java.security.AccessController.doPrivileged (Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$10 (PlatformImpl.java:417)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run (InvokeLaterDispatcher.java:96)
at com.sun.glass.ui.gtk.GtkApplication._runLoop (Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11 (GtkApplication.java:277)
at java.lang.Thread.run (Thread.java:844)
[ERROR]
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
我知道这是一个奇怪的问题,可能有一个简单的答案。我对Maven有点陌生,感谢您的耐心。如果值得一提的是,我正在使用Ubuntu 18。
src/main/resources
(src/main/filters
)和测试目录src/test/resources
(src/test/filters
)。如果不按照此结构进行设置,Maven将无法将它们复制到目标目录中。 - mr mcwolfgetClass().getResource("Raleway-Medium.ttf").toExternalForm()
,没有任何斜杠,就像没有Maven一样。 - wallek876getResource(String)
时没有前导/
,它会相对于类搜索资源。资源的路径应该是"Raleway-Medium.ttf"
或"/test/font/Raleway-Medium.tff"
。而 mr mcwolf 也是正确的。Maven 只能识别src/main/java
内的.java
文件,这意味着你的资源不会被复制到target/classes
目录中。实际上,在您的目录结构图像中存在target/classes/test/font/Raleway-Medium.tff
的事实实际上很奇怪。你是手动把它放在那儿的吗? - Slaw