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Posted to dev@tomcat.apache.org by "Konstantin Kolinko (Confluence)" <no...@apache.org> on 2019/11/25 00:30:09 UTC
[CONF] Apache Tomcat > KnownIssues
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[KnownIssues](https://cwiki.apache.org/confluence/display/TOMCAT/KnownIssues?src=mail&src.mail.product=confluence-
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| | | | |  | | Konstantin
Kolinko edited this page
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| | Here's the version comments
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| | |  | | Konstantin
Kolinko edited at [12:24
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| | | Corrected formatting.
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| | |  | | Konstantin
Kolinko edited at [12:23
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| | | Add a permalink. Fix formatting and links.
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# FAQ / Known Issues
_Permalink_ to this page: [
https://cwiki.apache.org/confluence/x/DColBg](https://cwiki.apache.org/confluence/x/DColBg)
## Questions
1. [What are the known issues in any given Tomcat version?](/confluence/pages/viewpage.action?pageId=103098892)
2. [What are the known issues with the Oracle JRE?](/confluence/pages/viewpage.action?pageId=103098892)
3. [What are the known issues with the OpenJDK?](/confluence/pages/viewpage.action?pageId=103098892)
4. [I'm using the Java ImageIO to dynamically serve images and get strange Exceptions from time to time. Is this a bug in Tomcat?](/confluence/pages/viewpage.action?pageId=103098892)
## Answers
### |
Anchor
---
| | TomcatIssues
---|---
| TomcatIssues
What are the known issues in any given Tomcat version?
To determine the known issues for any given Tomcat version, you'll need to
review the following:
...
See chapter [Looking for known
issues](https://tomcat.apache.org/bugreport.html#Looking_for_known_issues) on
Tomcat web site.
###
Anchor
---
| | OracleJREIssues
---|---
| OracleJREIssues
What are the known issues with the Oracle JRE?
* [jps.exe and jvisualvm.exe cannot detect tomcat using jdk1.6.0_23 onwards](https://bz.apache.org/bugzilla/show_bug.cgi?id=50518) — Fixed in Java 1.6.0_25.
###
Anchor
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| | OpenJDKIssues
---|---
| OpenJDKIssues
What are the known issues with the OpenJDK?
* There have been reports that java.util.logging does not work properly in OpenJDK 1.7.0.9 and OpenJDK6 1.6.0_32. The symptom is "`java.lang.ClassNotFoundException: 1catalina.org.apache.juli.FileHandler`" errors when you start Tomcat. See these threads from [March 2013](https://marc.info/?t=136253269400001&r=1&w=2) and [July 2013](https://marc.info/?t=137371445700004&r=1&w=2). This issue was absent in earlier versions and should be fixed in a later version of those JDKs.
###
Anchor
---
| | ImageIOIssues
---|---
| ImageIOIssues
I'm using the Java ImageIO to dynamically serve images and get strange
Exceptions from time to time. Is this a bug in Tomcat?
Imagine you have a servlet which dynamically generates images and serves them
via javax.imageio.ImageIO. To write the image to the OutputStream, perhaps you
are doing something like this:
 Code Block
---
| language | java
---|---
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
BufferedImage img = createMyImage(); // makes a BufferedImage
response.setContentType("image/png");
try (OutputStream out = response.getOutputStream()) { // try-with-resources
ImageIO.write(img, "PNG", out);
} catch (IOException ex) {
// Client aborted connection
}
}
Now, although there shouldn't be any Exception logged (because the IOException
which occurs when the client aborted the connection is ignored), you see
strange Exceptions in Tomcat's log which may belong to other Servlets/JSP (at
least with Sun/Oracle JVM on Windows), saying that the response has already
been committed, although you didn't write anything to it at that time. For
example:
No Format
---
13.07.2011 00:13:51 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [myApp.MyServlet] in context with path [] threw exception
java.lang.IllegalStateException: Cannot create a session after the response has been committed
at org.apache.catalina.connector.Request.doGetSession(Request.java:2734)
...
or maybe you use the ISAPI Redirector for IIS on Windows, and get these logs:
No Format
---
[Tue Jul 12 06:04:49.812 2011] [4124:2444] [error] ajp_connection_tcp_get_message::jk_ajp_common.c (1296): wrong message format 0xdaed from 127.0.0.1:8019
#### Is this a bug in Tomcat?
Actually, it's a bug (or at least a strange behavior) in the Java ImageIO.
When the ImageIO writes to an OutputStream and gets an IOException during
writing, it could happen that some later time, when the ImageWriter is
garbage-collected, the flush() method is called on that OutputStream. Tomcat
recycles OutputStream objects to save resources, so it could be that when
flush() is called from the ImageIO, the particular OutputStream object already
belongs to another Response, which can produce the above errors, when the
Servlet tries to get a Session for example, or can generally lead to broken
responses.
See also [here](https://nerd.dk/blogs/bug-tomcat-or-java2d) or this [Bug
report](https://bz.apache.org/bugzilla/show_bug.cgi?id=37516).
#### So how to resolve the errors?
To resolve this, I'm using an OutputStream decorator class which decorates
Tomcat's OutputStream and prevents any flush() calls. Additionally, when
close() is called on that Stream, it nulls-out the reference to Tomcat's
OutputStream and prevents any other operations:
 Code Block
---
| language | java
---|---
/**
* A OutputStream which can be used to write Images
* with the ImageIO in servlets.
*/
public class MyImageIOOutputStream extends OutputStream {
private OutputStream out;
private volatile boolean isActive = true;
public MyImageIOOutputStream(OutputStream out) {
this.out = out;
}
@Override
public void close() throws IOException {
if (isActive) {
isActive = false; // deactivate
try {
out.close();
} finally {
out = null;
}
}
}
@Override
public void flush() throws IOException {
if(isActive) {
out.flush();
}
// otherwise do nothing (prevent polluting the stream)
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
if (isActive)
out.write(b, off, len);
}
@Override
public void write(byte[] b) throws IOException {
if (isActive)
out.write(b);
}
@Override
public void write(int b) throws IOException {
if (isActive)
out.write(b);
}
...
---
...
}
---
Now you just have to use this Decorater class instead of using Tomcat's
OutputStream directly:
 Code Block
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| language | java
---|---
...
response.setContentType("image/png");
---
...
try (OutputStream out = new MyImageIOOutputStream(response.getOutputStream())) {
---
...
ImageIO.write(img, "PNG", out);
---
...
} catch (IOException ex) {
---
...
// Client aborted connection
---
...
}
---
and the errors should be gone away.
An alternative would be to write the Image contents to a
ByteArrayOutputStream, and using its writeTo() method to write the contents to
the Servlet's Response. However that would require some additional memory, as
the contents have to be buffered.
#### Are there any other corresponding cases of this bug?
The third party PDF generating software module PD4ML has had a corresponding
problem when calling the render() methods in class org.zefer.pd4ml.PD4ML with
response.getOutputStream() as argument. That causes the response stream to be
closed from a finalizer() method of a class called PD4Device. When using an
Apache/Tomcat connector, this unexpected stream close from the finalizer
thread has occationally caused responses to be sent to wrong requestor
(request/response mix up). The workarounds described above for ImageIO works
perfectly in this case too.
...
PD4ML has fixed this bug in their latest releases, but sites using older
versions of the library can still be affected. PD4ML version 3.2.3 definitely
has this flaw, but the currently latest version 3.8.0 is fixed. The release
notes document gives no clues where in between the problem was fixed, and the
vendor was not able to tell either in [this bug
report](https://pd4ml.com/support/pdf-generation-troubleshooting-f4/pd4device-
finalize-closes-output-stream-and-causes-mixup-t543.html).
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