【飞天奔月出品】javax.imageio.IIOException: Can't create output stream!tomcat 验证码，图片(原理)

 

 

 

今天  发布人员反映 sitemanager 验证码 在developer/QA(内网203) 两个环境都正常,但是在 stagine 环境(正式服务器上面)死活不出来,不显示

分析了下, 我首先将 web.xml 统统注释掉,仅仅保留 

<servlet>

<servlet-name>SecurityImageServlet</servlet-name>

<servlet-class>com.feilong.web.servlet.SecurityImageServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>SecurityImageServlet</servlet-name>

<url-pattern>/servlet/securityImage</url-pattern>

</servlet-mapping>

发现图片还是显示不了 

 

异常代码：

javax.imageio.IIOException: Can't create output stream!
javax.imageio.ImageIO.write(ImageIO.java:1560)
com.jumbo.brandstore.util.SecurityUtil.generateSecurityImage(SecurityUtil.java:90)
com.jumbo.brandstore.web.servlet.SecurityImageServlet.service(SecurityImageServlet.java:57)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

root cause

javax.imageio.IIOException: Can't create cache file!
javax.imageio.ImageIO.createImageOutputStream(ImageIO.java:397)
javax.imageio.ImageIO.write(ImageIO.java:1558)
com.jumbo.brandstore.util.SecurityUtil.generateSecurityImage(SecurityUtil.java:90)
com.jumbo.brandstore.web.servlet.SecurityImageServlet.service(SecurityImageServlet.java:57)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

root cause

java.io.IOException: No such file or directory
java.io.UnixFileSystem.createFileExclusively(Native Method)
java.io.File.checkAndCreate(File.java:1704)
java.io.File.createTempFile(File.java:1792)
javax.imageio.stream.FileCacheImageOutputStream.<init>(FileCacheImageOutputStream.java:71)
com.sun.imageio.spi.OutputStreamImageOutputStreamSpi.createOutputStreamInstance(OutputStreamImageOutputStreamSpi.java:50)
javax.imageio.ImageIO.createImageOutputStream(ImageIO.java:393)
javax.imageio.ImageIO.write(ImageIO.java:1558)
com.jumbo.brandstore.util.SecurityUtil.generateSecurityImage(SecurityUtil.java:90)
com.jumbo.brandstore.web.servlet.SecurityImageServlet.service(SecurityImageServlet.java:57)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

 

妖怪了,  其他项目用这个验证码 都很正常，这台服务器上有 stagine-frontend2, 这个应用的 验证码也是正常的 

看了文档   http://blog.sina.com.cn/s/blog_5999840701009t06.html

1.可以 修改验证码程序 

把

ImageIO.write(image, "jpeg", response.getOutputStream());

修改为

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(response.getOutputStream());

encoder.encode(image);

2.tomcat 的temp 目录必须有

一打听, 原来 tomcat -sitemanager 的temp 目录 删除过,而frontend 里面的保留着 

为什么 ImageIO.write 这种方式 需要 temp 目录 呢？

带着疑问，看看源码（Java的开源好处真心不错） ：

    public static ImageOutputStream createImageOutputStream(Object output)
        throws IOException {
        if (output == null) {
            throw new IllegalArgumentException("output == null!");
        }

        Iterator iter;
        // Ensure category is present
        try {
            iter = theRegistry.getServiceProviders(ImageOutputStreamSpi.class,
                                                   true);
        } catch (IllegalArgumentException e) {
            return null;
        }

        boolean usecache = getUseCache() && hasCachePermission();

        while (iter.hasNext()) {
            ImageOutputStreamSpi spi = (ImageOutputStreamSpi)iter.next();
            if (spi.getOutputClass().isInstance(output)) {
                try {
                    return spi.createOutputStreamInstance(output,
                                                          usecache,
                                                          getCacheDirectory());
                } catch (IOException e) {
                    throw new IIOException("Can't create cache file!", e);
                }
            }
        }

        return null;
    }

 

会调用 cache 文件夹 ，他所谓的cache 文件夹是怎么样定义的呢？

    private static boolean hasCachePermission() {
        Boolean hasPermission = getCacheInfo().getHasPermission();

        if (hasPermission != null) {
            return hasPermission.booleanValue();
        } else {
            try {
                SecurityManager security = System.getSecurityManager();
                if (security != null) {
                    File cachedir = getCacheDirectory();
                    String cachepath;

                    if (cachedir != null) {
                        cachepath = cachedir.getPath();
                    } else {
                        cachepath = getTempDir();

                        if (cachepath == null) {
                            getCacheInfo().setHasPermission(Boolean.FALSE);
                            return false;
                        }
                    }

                    security.checkWrite(cachepath);
                }
            } catch (SecurityException e) {
                getCacheInfo().setHasPermission(Boolean.FALSE);
                return false;
            }

            getCacheInfo().setHasPermission(Boolean.TRUE);
            return true;
        }
    }

 

写得也很清楚，如果自己设置了 set CacheDirectory 那么会使用自定义的，否则调用   getTempDir（）

   /**
     * Returns the default temporary (cache) directory as defined by the
     * java.io.tmpdir system property.
     */
    private static String getTempDir() {
        GetPropertyAction a = new GetPropertyAction("java.io.tmpdir");
        return (String)AccessController.doPrivileged(a);
    }

 

Oh， 会读取变量java.io.tmpdir!

大家还记得 tomcat 启动的时候，会显示

Using CATALINA_BASE:   /home/appuser/appservers/tomcat-feilong
Using CATALINA_HOME:   /home/appuser/appservers/tomcat-feilong
Using CATALINA_TMPDIR: /home/appuser/appservers/tomcat-feilong/temp
Using JRE_HOME:        /usr/lib/jvm/java-6-sun
Using CLASSPATH:       /home/appuser/appservers/tomcat-feilong/bin/bootstrap.jar

 

 $CATALINA_TMPDIR 这个变量就是 我们的temp 文件夹 

而tomcat 启动的时候，调用jvm会设置  java.io.tmpdir  参数 

看 

rem   CATALINA_TMPDIR (Optional) Directory path location of temporary directory

rem                   the JVM should use (java.io.tmpdir).  Defaults to

rem                   %CATALINA_BASE%\temp.

 

 

 

%_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION%

 

 

这下终于弄明白了， ImageIO.write(image, "JPEG", os) 这种方式 来生成图片、验证码 tomcat必须要有temp文件夹的来龙去脉了