Version: 9.4.20.v20190813 |

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://www.eclipse.org/jetty/javadoc/9.4.20.v20190813/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` can be added to the entire server by enabling the `gzip.mod` module. It may also be added to individual contexts in a context xml file.

> ### Note

> Jetty 9 only compresses using GZip. Using deflate HTTP compression is not supported and will not function.

### Gzip Rules

`GzipHandler` will gzip 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 gzip
- 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

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.

The `GzipHandler` installs an output interceptor which passes through to the `DefaultServlet`. If the content served by `DefaultServlet` is already compressed, the `GzipHandler` does nothing; if it is not compressed, the content is compressed on-the-fly.

> ### Note

> Automatic precompression by the `DefaultServlet` can be configured. Read more about the `DefaultServlet` here.

### Gzip Configuration

minGzipSize
  Content will only be compressed if content length is either unknown or greater than `minGzipSize`.
checkGzExists (Deprecated)
  False by default. If set to true, the handler will check for pre-compressed content.
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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