Version: 9.4.2.v20170220 |

Gzip Handler
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## Gzip Handler

### Info

- Classname: `org.eclipse.jetty.server.handler.gzip.GzipHandler`
- Maven Artifact: org.eclipse.jetty:jetty-servlets
- Javadoc: http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/server/handler/gzip/GzipHandler.html
- Xref: http://download.eclipse.org/jetty/stable-9/xref/org/eclipse/jetty/server/handler/gzip/GzipHandler.html

### Usage

The Jetty `GzipHandler` is a compression handler that you can apply to any dynamic resource (servlet). It fixes many of the bugs in commonly available compression filters: it works with asynchronous servlets; it handles all ways to set content length. It has been tested with Jetty continuations and suspending requests. Some user-agents might be excluded from compression to avoid common browser bugs (yes, this means IE!).

The `GzipHandler` is added to the entire server by the `etc/jetty-gzip.xml` file from the `gzip.mod` module. It may also be added to individual contexts in a context xml file.

### Gzip Rules

`GzipHandler` will gzip or deflate the content of a response if:

- It is mapped to a matching path
- The request method is configured to support gzip
- The request is not from an excluded User-Agent
- accept-encoding header is set to either gzip, deflate or a combination of those
- The response status code is >=200 and <300
- The content length is unknown or more than the minGzipSize initParameter or the minGzipSize is 0(default)
- The content-type does not match an excluded mime-type
- No content-encoding is specified by the resource

If both gzip and deflate are specified in the accept-encoding header, then gzip will be used.

Compressing the content can greatly improve the network bandwidth usage, but at the cost of memory and CPU cycles. The DefaultServlet is capable of serving pre-compressed static content, which saves memory and CPU. By default, the `GzipHandler` will check to see if pre-compressed content exists, and pass the request through to be handled by the `DefaultServlet`.

### Gzip Configuration

minGzipSize
  Content will only be compressed if content length is either unknown or greater than `minGzipSize`.
checkGzExists
  True by default. If set to false, the handler will not check for pre-compressed content.
compressionLevel
  The compression level used for deflate compression. (0-9).
includedMethods
  List of HTTP methods to compress. If not set, only `GET` requests are compressed.
includedMimeTypes
  List of MIME types to compress.
excludedMimeTypes
  List of MIME types not to compress.
excludedAgentPatterns
  A list of regex patterns for User-Agent names from which requests should not be compressed.
excludedPaths
  List of paths to exclude from compression. Performs a `String.startsWith(String)` comparison to check if the path matches. If it does match then there is no compression. To match subpaths use excludePathPatterns instead.
includedPaths
  List of paths to consider for compression.
includePaths
  List of paths to definitely consider for compression.

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