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[[ref-temporary-directories]]
=== Temporary Directories

Jetty itself has no temporary directories, but you can assign a directory for each web application, into which the WAR is unpacked, JSPs compiled on-the-fly, etc.
If you do not assign a specific temporary directory, Jetty will create one as needed when your web application starts.
Whether you set the location of the temporary directory - or you let Jetty create one for you - you also have a choice to either keep or delete the temporary directory when the web application stops.

==== The default temp directory

By default, Jetty will create a temporary directory for each web application. The name of the directory will be of the form:

....
"jetty-"+host+"-"+port+"-"+resourceBase+"-_"+context+"-"+virtualhost+"-"+randomdigits+".dir"
....

For example:

....
jetty-0.0.0.0-8080-test.war-_test-any-8900275691885214790.dir
....

Where `0.0.0.0` is the host address, `8080` is the port, `test.war` is the resourceBase, `test` is the context path (with / converted to _), `any` is the virtual host, and `randomdigits` are a string of digits guaranteed to be unique.

Once the temp directory is created, it is retrievable as the value (as a File) of the context attribute `javax.servlet.context.tempdir.`

===== The location of the temp directory

By default, Jetty will create this directory inside the directory named by the `java.io.tmpdir` System property.
You can instruct Jetty to use a different parent directory by setting the context attribute `org.eclipse.jetty.webapp.basetempdir` to the name of the desired parent directory.
The directory named by this attribute _must_ exist and be __writeable__.

As usual with Jetty, you can either set this attribute in a context xml file, or you can do it in code.

Here's an example of setting it in an xml file:

[source, xml, subs="{sub-order}"]
----
<Configure class="org.eclipse.jetty.webapp.WebAppContext">

  <Set name="contextPath">/test</Set>
  <Set name="war">foo.war</Set>

  <Call name="setAttribute">
    <Arg>org.eclipse.jetty.webapp.basetempdir</Arg>
    <Arg>/home/my/foo</Arg>
  </Call>
</Configure>
----

The equivalent in code is:

[source, java, subs="{sub-order}"]
----
WebAppContext context = new WebAppContext();
context.setContextPath("/test");
context.setWar("foo.war");
context.setAttribute("org.eclipse.jetty.webapp.basetempdir", "/tmp/foo");
----

==== Setting a specific temp directory

There are several ways to use a particular directory as the temporary directory:

===== Call WebAppContext.setTempDirectory(String dir)
As before this can be accomplished with an xml file or directly in code. Here's an example of setting the temp directory in xml:

[source, xml, subs="{sub-order}"]
----
<Configure class="org.eclipse.jetty.webapp.WebAppContext">

  <Set name="contextPath">/test</Set>
  <Set name="war">foo.war</Set>

  <Set name="tempDirectory">/some/dir/foo</Set>
</Configure>
----

Here's an example of doing it with java code:

[source, java, subs="{sub-order}"]
----
WebAppContext context = new WebAppContext();
context.setContextPath("/test");
context.setWar("foo.war");
context.setTempDirectory(new File("/some/dir/foo"));
----

===== Set the javax.servlet.context.tempdir context attribute
You should set this context attribute with the name of directory you want to use as the temp directory. Again, you can do this in xml:

[source, xml, subs="{sub-order}"]
----
<Configure class="org.eclipse.jetty.webapp.WebAppContext">

  <Set name="contextPath">/test</Set>
  <Set name="war">foo.war</Set>

  <Call name="setAttribute">
    <Arg>javax.servlet.context.tempdir</Arg>
    <Arg>/some/dir/foo</Arg>
  </Call>

</Configure>
----

Or in java:

[source, java, subs="{sub-order}"]
----
WebAppContext context = new WebAppContext();
context.setContextPath("/test");
context.setWar("foo.war");
context.setAttribute("javax.servlet.context.tempdir", "/some/dir/foo");
----

Once a temporary directory has been created by either of these methods, a file instance for it is set as the value of the `javax.servlet.context.tempdir` attribute of the web application.

____
[NOTE]
Be wary of setting an explicit temp directory if you are likely to change the jars in WEB-INF/lib between redeployments.
There is a JVM bug concerning link:http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4774421[caching of jar contents.]
____

==== The "work" directory

Mostly for backward compatibility, from Jetty 9.1.1 onwards, it is possible to create a directory named "work" in the `$\{jetty.base}` directory.
If such a directory is found, it is assumed you want to use it as the parent directory for all of the temporary directories of the webapps in `$\{jetty.base}`.
Moreover, as has historically been the case, these temp directories inside the work directory are not cleaned up when Jetty exits (or more correctly speaking, the `temp` directory corresponding to a context is not cleaned up when that context stops).

When a work directory is used, the algorithm for generating the name of the context-specific temp directories omits the random digit string.
This ensures the name of the directory remains consistent across context restarts.

==== Persisting the temp directory

Sometimes it is useful to keep the contents of the temporary directory between restarts of the web application.
By default, Jetty will *not* persist the temp directory.
To configure Jetty to keep it, use link:{JDURL}/org/eclipse/jetty/webapp/WebAppContext.html[WebAppContext.setPersistTempDirectory(true)].

____
[NOTE]
Be aware that if you call `setPersistTempDirectory(true)`, but let Jetty create a new temp directory each time (i.e. you do NOT set an explicit temp directory), then you will accumulate temp directories in your chosen temp directory location.
____