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h2. Stream Component

The *stream:* component provides access to the {{System.in}}, {{System.out}} and {{System.err}} streams as well as allowing streaming of file and URL.

Maven users will need to add the following dependency to their {{pom.xml}} for this component:
{code:xml}
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-stream</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
{code}


h3. URI format

{code}
stream:in[?options]
stream:out[?options]
stream:err[?options]
stream:header[?options]
{code}

In addition, the {{file}} and {{url}} endpoint URIs are supported in *Camel 2.0*:

{code}
stream:file?fileName=/foo/bar.txt
stream:url[?options]
{code}

If the {{stream:header}} URI is specified, the {{stream}} header is used to find the stream to write to. This option is available only for stream producers (that is, it cannot appear in {{from()}}).

You can append query options to the URI in the following format, {{?option=value&option=value&...}}

h3. Options
{div:class=confluenceTableSmall}
|| Name || Default Value || Description ||
| {{delay}} | {{0}} | Initial delay in milliseconds before consuming or producing the stream. |
| {{encoding}} | _JVM Default_ |  As of 1.4, you can configure the encoding (is a [charset name|http://java.sun.com/j2se/1.5.0/docs/api/java/nio/charset/Charset.html]) to use text-based streams (for example, message body is a {{String}} object). If not provided, Camel uses the [JVM default Charset|http://java.sun.com/j2se/1.5.0/docs/api/java/nio/charset/Charset.html#defaultCharset()]. |
| {{promptMessage}} | {{null}} | *Camel 2.0:* Message prompt to use when reading from {{stream:in}}; for example, you could set this to {{Enter a command:}} |
| {{promptDelay}} | {{0}} | *Camel 2.0:* Optional delay in milliseconds before showing the message prompt. |
| {{initialPromptDelay}} | {{2000}} | *Camel 2.0:* Initial delay in milliseconds before showing the message prompt. This delay occurs only once. Can be used during system startup to avoid message prompts being written while other logging is done to the system out. |
| {{fileName}} | {{null}} | *Camel 2.0:* When using the {{stream:file}} URI format, this option specifies the filename to stream to/from. |
| {{url}} | {{null}} | *Camel 2.0:* When using the {{stream:url}} URI format, this option specifies the URL to stream to/from. The input/output stream will be opened using the [JDK URLConnection|http://docs.oracle.com/javase/6/docs/api/java/net/URLConnection.html] facility. |
| {{scanStream}} | {{false}} | *Camel 2.0:* To be used for continuously reading a stream such as the unix {{tail}} command. 
                               *Camel 2.4 to Camel 2.6:* will retry opening the file if it is overwritten, somewhat like {{tail --retry}} |
| {{retry}} | {{false}} | *Camel 2.7:* will retry opening the file if it's overwritten, somewhat like {{tail --retry}} |
| {{scanStreamDelay}} | {{0}} | *Camel 2.0:* Delay in milliseconds between read attempts when using {{scanStream}}. |
| {{groupLines}} | {{0}} | *Camel 2.5:* To group X number of lines in the consumer. For example to group 10 lines and therefore only spit out an [Exchange] with 10 lines, instead of 1 [Exchange] per line. |
| {{autoCloseCount}} | {{0}} | *Camel 2.10.0:* (2.9.3 and 2.8.6) Number of messages to process before closing stream on Producer side. Never close stream by default (only when Producer is stopped). If more messages are sent, the stream is reopened for another {{autoCloseCount}} batch. |
{div}

h3. Message content

The *stream:* component supports either {{String}} or {{byte[]}} for writing to streams. Just add either {{String}} or {{byte[]}} content to the {{message.in.body}}. Messages sent to the *stream:* producer in binary mode are not followed by the newline character (as opposed to the {{String}} messages). Message with {{null}} body will not be appended to the output stream.
The special {{stream:header}} URI is used for custom output streams. Just add a {{java.io.OutputStream}} object to {{message.in.header}} in the key {{header}}.
See samples for an example.

h3. Samples

In the following sample we route messages from the {{direct:in}} endpoint to the {{System.out}} stream:

{code:java}
// Route messages to the standard output.
from("direct:in").to("stream:out");

// Send String payload to the standard output.
// Message will be followed by the newline.
template.sendBody("direct:in", "Hello Text World");

// Send byte[] payload to the standard output.
// No newline will be added after the message.
template.sendBody("direct:in", "Hello Bytes World".getBytes());
{code}

The following sample demonstrates how the header type can be used to determine which stream to use. In the sample we use our own output stream, {{MyOutputStream}}.

{snippet:id=e1|lang=java|url=camel/trunk/components/camel-stream/src/test/java/org/apache/camel/component/stream/StreamHeaderTest.java}

The following sample demonstrates how to continuously read a file stream (analogous to the UNIX {{tail}} command):
{code:java}
from("stream:file?fileName=/server/logs/server.log&scanStream=true&scanStreamDelay=1000").to("bean:logService?method=parseLogLine");
{code}

One gotcha with scanStream (pre Camel 2.7) or scanStream + retry is the file will be re-opened and scanned with each iteration of scanStreamDelay.  Until NIO2 is available we cannot reliably detect when a file is deleted/recreated.

{include:Endpoint See Also}