Spring Boot에서는 머리가 없지만 Spring이나 플레인 자바에서는 머리가 없다고 Swing은 생각하는 이유는 무엇입니까?

Spring Boot에서는 머리가 없지만 Spring이나 플레인 자바에서는 머리가 없다고 Swing은 생각하는 이유는 무엇입니까?

다음 코드가 작동합니다.

import javax.swing.*;

public class HeadlessExceptionDemo {

   public static void main(String[] args) {

      JFrame frame = new JFrame("HeadlessExceptionDemo");
      frame.setSize(800, 600);
      frame.setLocationRelativeTo(null);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);

   }
}

다음 코드도 작동합니다.

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.swing.*;

@Configuration
public class HeadlessExceptionDemo {

   @Bean
   public JFrame frame() {
      JFrame frame = new JFrame("HeadlessExceptionDemo");
      frame.setSize(800, 600);
      frame.setLocationRelativeTo(null);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      return frame;
   }

   public static void main(String[] args) {

      AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(HeadlessExceptionDemo.class);
      JFrame frame = ctx.getBean(JFrame.class);
      frame.setVisible(true);

   }
}

다음 코드는 그렇지 않습니다.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;

import javax.swing.*;

@SpringBootApplication
public class HeadlessExceptionDemo {

    @Bean
    public JFrame frame() {
        JFrame frame = new JFrame("HeadlessExceptionDemo");
        frame.setSize(800, 600);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        return frame;
    }

    public static void main(String[] args) {
        ConfigurableApplicationContext ctx = SpringApplication.run(HeadlessExceptionDemo.class, args);
        JFrame frame = ctx.getBean(JFrame.class);
        frame.setVisible(true);
    }
}

아래에서 예외 발생:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [javax.swing.JFrame]: Factory method 'frame' threw exception; nested exception is java.awt.HeadlessException
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    ... 23 common frames omitted
Caused by: java.awt.HeadlessException: null
    at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207) ~[na:1.8.0_45]
    at java.awt.Window.<init>(Window.java:536) ~[na:1.8.0_45]
    at java.awt.Frame.<init>(Frame.java:420) ~[na:1.8.0_45]
    at javax.swing.JFrame.<init>(JFrame.java:233) ~[na:1.8.0_45]
    at com.inthemoon.snippets.springboot.HeadlessExceptionDemo.frame(HeadlessExceptionDemo.java:15) [classes/:na]
    at com.inthemoon.snippets.springboot.HeadlessExceptionDemo$$EnhancerBySpringCGLIB$$3680a05b.CGLIB$frame$0(<generated>) ~[classes/:na]
    at com.inthemoon.snippets.springboot.HeadlessExceptionDemo$$EnhancerBySpringCGLIB$$3680a05b$$FastClassBySpringCGLIB$$b7def9bc.invoke(<generated>) ~[classes/:na]
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228) ~[spring-core-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:355) ~[spring-context-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at com.inthemoon.snippets.springboot.HeadlessExceptionDemo$$EnhancerBySpringCGLIB$$3680a05b.frame(<generated>) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_45]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_45]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_45]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_45]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    ... 24 common frames omitted

왜요? :)

스프링 부츠 세트java.awt.headless로.true기본적으로 SpringApplication의 소스 코드에 표시됩니다.java:

private boolean headless = true;

...

private void configureHeadlessProperty() {
        System.setProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, System.getProperty(
                SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, Boolean.toString(this.headless)));
}

이것이 왜 이것을 하는지에 대해, 소스 코드에 댓글이 있습니다.setHeadless아이콘 표시 방지 방법:

    /**
     * Sets if the application is headless and should not instantiate AWT. Defaults to
     * {@code true} to prevent java icons appearing.
     * @param headless if the application is headless
     */
    public void setHeadless(boolean headless) {
        this.headless = headless;
    }

이 행 대신에

 SpringApplication.run(Application.class, args);

사용하다

SpringApplicationBuilder builder = new SpringApplicationBuilder(Application.class);
builder.headless(false);
ConfigurableApplicationContext context = builder.run(args);

언급URL : https://stackoverflow.com/questions/36160353/why-does-swing-think-its-headless-under-spring-boot-but-not-under-spring-or-pl