Version: 9.4.12.v20180830 |

Troubleshooting Locked Files on Windows
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## Troubleshooting Locked Files on Windows

Jetty buffers static content for webapps such as HTML files, CSS files, images, etc. If you are using NIO connectors, Jetty uses memory-mapped files to do this. The problem is that on Windows, memory mapping a file causes the file to lock, so that you cannot update or replace the file. Effectively this means that you have to stop Jetty to update a file.

### Remedy

Jetty provides a configuration switch in the `webdefault.xml` file for the DefaultServlet that enables or disables the use of memory-mapped files. If you are running on Windows and are having file-locking problems, you should set this switch to disable memory-mapped file buffers.

The default `webdefault.xml` file is found in the jetty distribution under the `etc/` directory or in the `jetty-webapp-${VERSION}.jar` artifact at `org/eclipse/jetty/webapp/webdefault.xml`. Edit the file in the distribution or extract it to a convenient disk location and edit it to change `useFileMappedBuffer` to false. The easiest option is to simply edit the default file contained in the jetty distribution itself.

    <init-param>
       <param-name>useFileMappedBuffer</param-name>
       <param-value>true</param-value> <!-- change to false -->
     </init-param>

Make sure to apply your custom `webdefault.xml` file to all of your webapps. You can do that by changing the configuration of the Deployment Manager in `etc/jetty-deploy.xml`.

    <Call id="webappprovider" name="addAppProvider">
      <Arg>
        <New class="org.eclipse.jetty.deploy.providers.WebAppProvider">
          .
          .
          <!-- this should be the new custom webdefault.xml or change should be made in this file -->
          <Set name="defaultsDescriptor"><Property name="jetty.home" default="." />/etc/webdefault.xml</Set>
          <Set name="scanInterval">1</Set>
          <Set name="extractWars">true</Set>
          .
          .
        </New>
      </Arg>
    </Call>

Alternatively, if you have individually configured your webapps with context xml files, you need to call the `WebAppContext.setDefaultsDescriptor(String path)` method:

    <New id="myWebAppContext"  class="org.eclipse.jetty.webapp.WebAppContext">
      <Set name="contextPath">/</Set>
      <Set name="war">./webapps/fredapp</Set>
      <Set name="defaultsDescriptor">/home/fred/jetty/mywebdefaults.xml</Set>
      .
      .
    </New>

Instead, you could redefine the DefaultServlet in your web.xml file, making sure to set useFileMappedBuffer to false:

    <web-app ...>
     ...
     <servlet>
         <servlet-name>Default</servlet-name>
         <servlet-class>org.eclipse.jetty.servlet.DefaultServlet</servlet-class>
         <init-param>
           <param-name>useFileMappedBuffer</param-name>
           <param-value>false</param-value>
         </init-param>
         <load-on-startup>0</load-on-startup>
       </servlet>
     ...
     </web-app>

### Alternate Remedy

You can force a `WebAppContext` to always copy a web app directory on deployment. The base directory of your web app (ie the root directory where your static content exists) will be copied to the temp directory. Configure this in an xml file like so:

    <New id="myWebAppContext"  class="org.eclipse.jetty.webapp.WebAppContext">
      <Set name="contextPath">/</Set>
      <Set name="war">./webapps/fredapp</Set>
      <Set name="copyWebDir">true</Set>
      .
      .
    </New>

> ### Note

> Be careful with this option when using an explicitly settemp directory name - as the name of the temp directory will not unique across redeployments, copying the static content into the same directory name each time may not avoid the locking problem.

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