blocks|key|2942443|text|这应该是可行的，因为对System.setProperty的调用是在创建工具包之前：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2942444|public+static+void+main(String[]+args)
{
++++//+Set+system+property.
++++//+Call+this+BEFORE+the+toolkit+has+been+initialized,+that+is,
++++//+before+Toolkit.getDefaultToolkit()+has+been+called.
++++System.setProperty("java.awt.headless",+"true");

++++//+This+triggers+creation+of+the+toolkit.
++++//+Because+java.awt.headless+property+is+set+to+true,+this+
++++//+will+be+an+instance+of+headless+toolkit.
++++Toolkit+tk+=+Toolkit.getDefaultToolkit();

++++//+Check+whether+the+application+is
++++//+running+in+headless+mode.
++++GraphicsEnvironment+ge+=+
++++++++GraphicsEnvironment.getLocalGraphicsEnvironment();
++++System.out.println("Headless+mode:+"+%2B+ge.isHeadless());
}|code-block|syntax|javascript|2942445|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This should work because the call to System.setProperty is before the creation of the toolkit:

<pre><code>public static void main(String[] args)
{
 // Set system property.
 // Call this BEFORE the toolkit has been initialized, that is,
 // before Toolkit.getDefaultToolkit() has been called.
 System.setProperty("java.awt.headless", "true");

 // This triggers creation of the toolkit.
 // Because java.awt.headless property is set to true, this 
 // will be an instance of headless toolkit.
 Toolkit tk = Toolkit.getDefaultToolkit();

 // Check whether the application is
 // running in headless mode.
 GraphicsEnvironment ge = 
 GraphicsEnvironment.getLocalGraphicsEnvironment();
 System.out.println("Headless mode: " + ge.isHeadless());
}
</code></pre>

blocks|key|1534089|text|我在一个类中使用main()，它在常量(和其他静态代码)中静态加载JFreeChart的不同部分。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1534090|将静态加载块移动到类的顶部解决了我的问题。|1534091|这不起作用：|BOLD|1534092|++public+class+Foo()+{
++++private+static+final+Color+COLOR_BACKGROUND+=+Color.WHITE;

++++static+{+/*+too+late+!+*/
++++++System.setProperty("java.awt.headless",+"true");
++++++System.out.println(java.awt.GraphicsEnvironment.isHeadless());
++++++/*+--->+prints+false+*/
++++}

++++public+static+void+main()+{}
++}|code-block|syntax|javascript|1534093|通过将静态块移动到类的顶部，让尽可能早地执行静态块！|1534094|++public+class+Foo()+{
++++static+{+/*+works+fine!+!+*/
++++++System.setProperty("java.awt.headless",+"true");
++++++System.out.println(java.awt.GraphicsEnvironment.isHeadless());
++++++/*+--->+prints+true+*/
++++}

++++private+static+final+Color+COLOR_BACKGROUND+=+Color.WHITE;

++++public+static+void+main()+{}
++}|1534095|当考虑到它时，这是完全有意义的:)。朱胡！|1534096|entityMap^0|8|6|0|0|0|6|0|0|F|B|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@$9|12|A|13|B|J]]|D|@]|E|$]]|$1|K|3|L|5|M|7|14|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|15|8|@$9|16|A|17|B|J]]|D|@]|E|$]]|$1|R|3|S|5|M|7|18|8|@]|D|@]|E|$N|O]]|$1|T|3|U|5|6|7|19|8|@]|D|@]|E|$]]|$1|V|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|W|$]]

I was working with a <code>main()</code> in a class which statically loads different parts of JFreeChart in Constants (and other static code).

Moving the static loading block to the top of the class solved my problem.

This doesn't work:

<pre><code> public class Foo() {
 private static final Color COLOR_BACKGROUND = Color.WHITE;

 static { /* too late ! */
 System.setProperty("java.awt.headless", "true");
 System.out.println(java.awt.GraphicsEnvironment.isHeadless());
 /* ---&gt; prints false */
 }

 public static void main() {}
 }
</code></pre>

Have java execute the static block as early as possible by moving it to the top of the class!

<pre><code> public class Foo() {
 static { /* works fine! ! */
 System.setProperty("java.awt.headless", "true");
 System.out.println(java.awt.GraphicsEnvironment.isHeadless());
 /* ---&gt; prints true */
 }

 private static final Color COLOR_BACKGROUND = Color.WHITE;

 public static void main() {}
 }
</code></pre>

When thinking about it this makes perfectly sense :). Juhu!

blocks|key|1034900|text|我认为这个参数可以通过将其作为参数传递给Java虚拟机来设置。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1034901|-Djava.awt.headless=true.不确定这是否会对应用程序的其他组件产生影响。|offset|length|style|CODE|1034902|entityMap^0|0|0|P|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

I think this parameter can be set by passing it as an argument to Java Virtual Machine e.g. 

<code>-Djava.awt.headless=true.</code> Not sure if this would have impact on other components of your application.

blocks|key|1534187|text|这是一种完全不同的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1534188|try+{
++++Field+defaultHeadlessField+=+java.awt.GraphicsEnvironment.class.getDeclaredField("defaultHeadless");
++++defaultHeadlessField.setAccessible(true);
++++defaultHeadlessField.set(null,Boolean.FALSE);
++++Field+headlessField+=+java.awt.GraphicsEnvironment.class.getDeclaredField("headless");
++++headlessField.setAccessible(true);
++++headlessField.set(null,Boolean.TRUE);
}+catch+(IllegalAccessException+e)+{
++++e.printStackTrace();
}+catch+(NoSuchFieldException+e)+{
++++e.printStackTrace();
}|code-block|syntax|javascript|1534189|我在一个无头环境(Ubuntu)中成功地利用了服务器端的BufferedImages。这样做的好处是，它不需要在命令行上设置任何-D变量，也不需要设置DISPLAY变量。|1534190|您还可以在任何时候执行此代码。您不需要担心在加载其他类之前调用此函数。|1534191|我认为，如果您试图从无头环境中驱动远程机器上的Swing接口，那么这可能不起作用。|1534192|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Here is a completely different approach. 

<pre><code>try {
 Field defaultHeadlessField = java.awt.GraphicsEnvironment.class.getDeclaredField("defaultHeadless");
 defaultHeadlessField.setAccessible(true);
 defaultHeadlessField.set(null,Boolean.FALSE);
 Field headlessField = java.awt.GraphicsEnvironment.class.getDeclaredField("headless");
 headlessField.setAccessible(true);
 headlessField.set(null,Boolean.TRUE);
} catch (IllegalAccessException e) {
 e.printStackTrace();
} catch (NoSuchFieldException e) {
 e.printStackTrace();
}
</code></pre>

I am using this successfully to draw on server-side BufferedImages in a headless environment (Ubuntu).
The nice thing about this is that it does not require setting any -D variables on the command line, nor do you need to set the DISPLAY variable. 

You can also execute this code at any time. You don't need to worry about invoking this before other classes are loaded.

I suppose this might not work if you were trying to drive a Swing interface on a remote machine from a headless environment.

blocks|key|2942620|text|您可以像这样设置JAVA_TOOL_OPTIONS：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2942621|2942622|+JAVA_TOOL_OPTIONS：-Djava.awt.headless=true|blockquote|2942623|2942624|2942625|然后，任何新进程都将在会话期间使用该设置。您可以将其添加到您的.bashrc或.bash_profile+(或任何shell的启动文件)中，以用于所有后续会话。|2942626|您还可以将其添加到groovy脚本的第一行，如下所示：|2942627|cat+hello.groovy
#!/usr/bin/env+groovy+-Djava.awt.headless=true
println+hello|code-block|syntax|javascript|2942628|entityMap^0|8|H|0|0|0|0|0|V|7|13|D|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|10|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|11|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|12|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|N|3|O|5|6|7|18|8|@]|D|@]|E|$]]|$1|P|3|Q|5|R|7|19|8|@]|D|@]|E|$S|T]]|$1|U|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|V|$]]

You can set the <code>JAVA_TOOL_OPTIONS</code> like this:

<blockquote>
 JAVA_TOOL_OPTIONS: -Djava.awt.headless=true
</blockquote>

Then any new processes will use that setting during the session. You can add it to your <code>.bashrc</code> or <code>.bash_profile</code> (or whatever shell's startup file) for all subsequent sessions.

You can also add it to the first line of a groovy script like this:

<pre><code>cat hello.groovy
#!/usr/bin/env groovy -Djava.awt.headless=true
println hello
</code></pre>

I'm trying to set <code>java.awt.headless=true</code> during the application startup but it appears like I'm too late and the non-headless mode has already started:

<pre><code>static {
 System.setProperty("java.awt.headless", "true");
 /* java.awt.GraphicsEnvironment.isHeadless() returns false */
}
</code></pre>

Is there another way set headless to true beside <code>-Djava.awt.headless=true</code>? I would prefer not configure anything on the console.

Setting java.awt.headless=true programmatically

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我试图在应用程序启动时设置java.awt.headless=true，但似乎太晚了，并且非headless模式已经启动：static {    System.setProperty("java.awt.headless", "true");    /* java.awt.GraphicsEnvironment.isH...

问以编程方式设置java.awt.headless=true
EN

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问以编程方式设置java.awt.headless=trueEN