WebDAV, web-based distributed authoring and versioning, is a set of extensions to the HTTP protocol that is a convenient replacement for FTP when developing web sites. Many editing tools can save to a WebDAV server directly and several operating systems can provide a filesystem to a WebDAV server.

From www.webdav.org:

What is WebDAV?
Briefly: WebDAV stands for "Web-based Distributed Authoring and Versioning". It is a set of extensions to the HTTP protocol which allows users to collaboratively edit and manage files on remote web servers.

The WebDAV site also contains pointers to programs which understand WebDAV.

Configuring the WebDAV Servlet

The WebDAV servlet must be enabled explicitly. By default, it also requires a logged in user playing the 'webdav' role and requires a secure (SSL) connection. These can be relaxed, but having the defaults require security makes it unlikely that a webmaster will enable WebDAV by mistake.

The following example is a typical WebDAV configuration. The explicit servlet-mapping and setting enable to 'write' is necessary. Since secure is left as the default, it will require an SSL connection.

<servlet>
  <servlet-name>webdav</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <enable>write</enable>
  </init>
</servlet>

<servlet-mapping url-pattern='/webdav/*' servlet-name='webdav'/>

<authenticator>
  <type>com.caucho.server.security.XmlAuthenticator</type>
  <init>
    <user>Harry Potter:quidditch:webdav</user>
    <password-digest>none</password-digest>
  </init>
</authenticator>

<login-config>
  <auth-method>basic</auth-method>
</login-config>

<security-constraint url-pattern='/webdav/*' role-name='webdav'/>

The following example is not recommended because it would allow anyone to update the site:

<servlet>
  <servlet-name>webdav</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <enable>write</enable>
    <secure>false</secure>
    <role>*</role>
  </init>
</servlet>

<servlet-mapping url-pattern='/webdav/*' servlet-name='webdav'/>

The WebDAV servlet can point to a different directory by setting the root parameter. The path is relative to the web-app, and allows path variables. For example, the following would read and write files from WEB-INF/webdav:

<servlet>
  <servlet-name>webdav</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <root>WEB-INF/webdav</root>
    <enable>write</enable>
    <role>webdav</role>
  </init>
</servlet>

<servlet-mapping url-pattern='/webdav/*' servlet-name='webdav'/>

Configuring Windows

Recent versions of Windows and the Windows Office suite directly support WebDAV. WebDAV is configured in "My Network Places".

When browsing "My Network Places" in IE, click on Tools/Map Network Drive from the menu. IE will open a dialog. The dialog contains a link to "Create a shortcut to Web folder or FTP site". Clicking on that will open the "Add Network Place Wizard".

The Add Network Place Wizard will ask for the location of the WebDAV server. Type the full URL, e.g. http://www.foo.com/webdav and complete the dialog.

Adding the WebDAV link will let you save directly to your server. Windows programs can load and save to the server. You can also open an IE window to the mapped folder and use it as a normal folder.

Custom Path Sources

The WebDAV servlet can be customized to use a source other than the default path source. For example, it would be possible to use WebDAV with files stored in a database.

There's a <path-source>java:comp/env/my-path</path-source> parameter in the WebDavServlet(see Configuring the WebDAV Servlet). You configure an object with the JNDI name java:comp/env/my-path using resource to configure a custom class that extends com.caucho.servlets.webdav.AbstractPath

<resource jndi-name='resin/webdav'>
  <type>test.foo.MyDataSource</type>
  <init>
    <my-foo>bar</my-foo>
  </init>
</resource>

<servlet>
  <servlet-name>webdav</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <enable>write</enable>
    <path-source>resin/webdav</path-source>
  </init>
</servlet>

<servlet-mapping url-pattern='/webdav/*' servlet-name='webdav'/>

You can completely customize your WebDav backend, linking it to databases or some EJB-based data source or whatever.

FAQ

How do I configure the WebDAV servlet to recognize more than one root folder?

There's a "root" parameter for the WebDavServlet (see Configuring the WebDAV Servlet). You can set that and use several separate webdav instances.

<servlet>
  <servlet-name>webdav1</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <root>/opt/root1</root>
  </init>
</servlet>

<servlet>
  <servlet-name>webdav2</servlet-name>
  <servlet-class>com.caucho.servlets.webdav.WebDavServlet</servlet-class>
  <init>
    <root>/opt/root1</root>
  </init>
</servlet>

<servlet-mapping url-pattern='/root1' servlet-name='webdav1'/>
<servlet-mapping url-pattern='/root2' servlet-name='webdav2'/>

Can I make the root path match a user name?

It's possible, but you need to write a bit of code.

As discussed in Custom Path Sources, you can customize the data source by creating your own ApplicationPath.

In this case, you probably want to extend com.caucho.servlets.webdav.FilePath and override the getPath method.