linux上不能显示Jfreechart的图片文件

出现错误：

Jan 23, 2015 4:19:21 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [DisplayChart] in context with path [/aldb] threw exception [Chart image not found] with root cause
javax.servlet.ServletException: Chart image not found
   at org.jfree.chart.servlet.DisplayChart.service(DisplayChart.java:149)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
   at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
   at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
   at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
   at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
   at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
   at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
   at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
   at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
   at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
   at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
   at org.apache.coyote.AbstractProtocol $AbstractConnectionHandler.process(AbstractProtocol.java:607)    at org.apache.tomcat.util.net.JIoEndpoint$ SocketProcessor.run(JIoEndpoint.java:313)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
   at java.lang.Thread.run(Thread.java:722)

html源代码：

/DisplayChart?filename=jfreechart-5351821214105924657.png

文件存在：

find / -name jfreechart-5351821214105924657.png -print
/home/soft/tomcat7/temp/jfreechart-5351821214105924657.png

ll /home/soft/tomcat7/temp/jfreechart-5351821214105924657.png
-rw-r--r-- 1 root root 21517 Jan 23 16:19 /home/soft/tomcat7/temp/jfreechart-5351821214105924657.png

相关代码：

 1 File file = new File(System.getProperty("java.io.tmpdir"), filename);  
 2     if (!(file.exists())) {  
 3       throw new ServletException("File '" + file.getAbsolutePath() + "' does not exist");  
 4     }  
 5   
 6     boolean isChartInUserList = false;  
 7     ChartDeleter chartDeleter = (ChartDeleter)session.getAttribute("JFreeChart_Deleter");  
 8   
 9     if (chartDeleter != null) {  
10       isChartInUserList = chartDeleter.isChartAvailable(filename);  
11     }  
12   
13     boolean isChartPublic = false;  
14     if ((filename.length() >= 6) &&   
15       (filename.substring(0, 6).equals("public"))) {  
16       isChartPublic = true;  
17     }  
18   
19     boolean isOneTimeChart = false;  
20     if (filename.startsWith(ServletUtilities.getTempOneTimeFilePrefix())) {  
21       isOneTimeChart = true;  
22     }  
23   
24     if ((isChartInUserList) || (isChartPublic) || (isOneTimeChart))  
25     {  
26       ServletUtilities.sendTempFile(file, response);  
27       if (isOneTimeChart)  
28         file.delete();  
29     }  
30     else  
31     {  
32       throw new ServletException("Chart image not found");  
33     }

解决方法：

ServletUtilities.setTempOneTimeFilePrefix("jfreechart"); // 加了这个即可；使得上面代码的第20行结果为true；
String filename = ServletUtilities.saveChartAsPNG(chart, 1024, 400, null, session);

官方解释：

My web application runs fine on my Windows development machine, but when I deploy it to the Unix/Linux production server, it doesn't work. What is the problem?

Most likely your server does not have X11 running. This is a Java (AWT/Java2D) issue, not something that is specific to JFreeChart. There is some more information at Sun's website: