项目应用服务器tomcat7,在开发(windows)、测试环境(linux 64bit)均正常。在生产环境(linux 64bit)一直启动不起来，也没有报错。
最终定位问题：执行到bufferedimage.createGraphics();便停止不动了。最终在启动脚本增加
JAVA_OPTS="-Djava.awt.headless=true"解决问题。
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问题解决了，但是至于为什么造成这种问题，还是不是很明白。
参照了http://www.oschina.net/translate/using-headless-mode-in-java-se的文章,依旧是一头雾水。
按照上述文章的介绍，写了一个测试类：
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
boolean headless_check = ge.isHeadless();
System.out.println("================java.awt.headless:"+headless_check);
输出结果：在测试环境(linux),抛出异常：
Exception in thread "main" java.lang.InternalError: Can't connect to X11 window server using 'localhost:10.0' 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.<clinit>(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 java.awt.image.BufferedImage.createGraphics(BufferedImage.java:1182) at com.tydic.BufferedImageCreateGraphicBug.main(BufferedImageCreateGraphicBug.java:23)
但是在生产环境（linux）,打印结果
================java.awt.headless:false
,写一个java类在生产环境（linux）上执行如下代码：
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = bi.createGraphics();
g2.setBackground(Color.RED);
g2.clearRect(0, 0, width, height);
System.getProperty("user.dir");
File f = new File(filename);
try {
ImageIO.write(bi, formatName , f);
} catch (IOException e) {
e.printStackTrace();
}
可以正常生成图片！
但是在web应用中，却无法生成图片，且没有抛出异常，一直卡住不动，不知为什么.
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