Linux是一套免费使用和自由传播的类Unix操作系统，是一个基于POSIX和UNIX的多用户、多任务、支持多线程和多CPU的操作系统。它能运行主要的UNIX工具软件、应用程序和网络协议。它支持32位和64位硬件。Linux继承了Unix以网络为核心的设计思想，是一个性能稳定的多用户网络操作系统。本人在调用微博登录接口时，报 java.awt.HeadlessException 错误，总结了一下解决方案。
部署到 Tomcat 服务器时报 java.awt.HeadlessException 错误，具体日志如下：java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207)
at java.awt.Window.(Window.java:535)
at java.awt.Frame.(Frame.java:420)
at java.awt.Frame.(Frame.java:385)
at javax.swing.SwingUtilities$SharedOwnerFrame.(SwingUtilities.java:1757)
at javax.swing.SwingUtilities.getSharedOwnerFrame(SwingUtilities.java:1832)
at javax.swing.JOptionPane.getRootFrame(JOptionPane.java:1697)
at javax.swing.JOptionPane.showOptionDialog(JOptionPane.java:863)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:667)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:638)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:609)
at weibo4j.util.BareBonesBrowserLaunch.openURL(BareBonesBrowserLaunch.java:29)
at com.yoodb.platform.front.controller.FLoginController.wbLogin(FLoginController.java:275)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
网上搜索后，原因是没有配置Headless Mode，Headless模式是系统的一种配置模式。在该模式下，系统缺少了显示设备、键盘或鼠标。修改配置 ${TOMCAT_HOME}/bin/catalina.sh 或 ${TOMCAT_HOME}/bin/catalina.bat 文件步骤如下：
在所有类似一下代码出修改：exec "$_RUNJDB" "$LOGGING_CONFIG" $LOGGING_MANAGER $JAVA_OPTS $CATALINA_OPTS \
-Djava.endorsed.dirs="$JAVA_ENDORSED_DIRS" -classpath "$CLASSPATH" \
-sourcepath "$CATALINA_HOME"/../../java \
-Djava.security.manager \
-Djava.security.policy=="$CATALINA_BASE"/conf/catalina.policy \
-Dcatalina.base="$CATALINA_BASE" \
-Dcatalina.home="$CATALINA_HOME" \
-Djava.io.tmpdir="$CATALINA_TMPDIR" \
org.apache.catalina.startup.Bootstrap "$@" start
修改内容之后为：exec "$_RUNJDB" "$LOGGING_CONFIG" $LOGGING_MANAGER $JAVA_OPTS $CATALINA_OPTS \
-Djava.endorsed.dirs="$JAVA_ENDORSED_DIRS" -classpath "$CLASSPATH" \
-sourcepath "$CATALINA_HOME"/../../java \
-Djava.security.manager \
-Djava.security.policy=="$CATALINA_BASE"/conf/catalina.policy \
-Dcatalina.base="$CATALINA_BASE" \
-Dcatalina.home="$CATALINA_HOME" \
-Djava.io.tmpdir="$CATALINA_TMPDIR" \
-Djava.awt.headless=false \
org.apache.catalina.startup.Bootstrap "$@" start
只是在倒数第二行增加了 “ -Djava.awt.headless=false \ ” 参数，以tomcat 7 为例共修改了 7 处地方，注意如果 “ -Djava.awt.headless=false \ ” 参数为“ -Djava.awt.headless=true \ ” 时则会报如下错误：java.awt.HeadlessException
at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207)
at java.awt.Window.(Window.java:535)
at java.awt.Frame.(Frame.java:420)
at java.awt.Frame.(Frame.java:385)
at javax.swing.SwingUtilities$SharedOwnerFrame.(SwingUtilities.java:1757)
at javax.swing.SwingUtilities.getSharedOwnerFrame(SwingUtilities.java:1832)
at javax.swing.JOptionPane.getRootFrame(JOptionPane.java:1697)
at javax.swing.JOptionPane.showOptionDialog(JOptionPane.java:863)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:667)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:638)
at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:609)
at weibo4j.util.BareBonesBrowserLaunch.openURL(BareBonesBrowserLaunch.java:29)
at com.yoodb.platform.front.controller.FLoginController.wbLogin(FLoginController.java:275)
启动tomcat之后报 server using ':0.0' as the value of the DISPLAY variable. 错误，具体日志如下：server using ':0.0' as the value of the DISPLAY variable.] with root cause
java.lang.InternalError: Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable.
at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
at sun.awt.X11GraphicsEnvironment.access$200(X11GraphicsEnvironment.java:65)
at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:110)
at java.security.AccessController.doPrivileged(Native Method)
at sun.awt.X11GraphicsEnvironment.(X11GraphicsEnvironment.java:74)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:191)
at java.awt.GraphicsEnvironment.createGE(GraphicsEnvironment.java:102)
at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(GraphicsEnvironment.java:81)
at sun.awt.X11.XToolkit.(XToolkit.java:120)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:191)
at java.awt.Toolkit$2.run(Toolkit.java:869)
at java.security.AccessController.doPrivileged(Native Method)
解决方式使用 linux 命令，vim /etc/profile 编辑文件，在文件中增加 export DISPLAY=localhost:0.0 (jdk已配置)参数具体如下：[root@iZ256w2hluuZ ~]# vim /etc/profile
export DISPLAY=localhost:0.0
JAVA_HOME=/usr/java/jdk1.7.0_71
JRE_HOME=/usr/java/jdk1.7.0_71/jre
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
执行 linux 命令，是环境变量立即生效，具体如下：[root@iZ256w2hluuZ ~]# source /etc/profile