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:
<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>
URI format
stream:in[?options] stream:out[?options] stream:err[?options] stream:header[?options]
In addition, the file
and url
endpoint URIs are supported in Camel 2.0:
stream:file?fileName=/foo/bar.txt stream:url[?options]
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&...
Options
Name |
Default Value |
Description |
---|---|---|
|
|
Initial delay in milliseconds before consuming or producing the stream. |
|
JVM Default |
As of 1.4, you can configure the encoding (is a charset name |
|
|
Camel 2.0: Message prompt to use when reading from |
|
|
Camel 2.0: Optional delay in milliseconds before showing the message prompt. |
|
|
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. |
|
|
Camel 2.0: When using the |
|
|
Camel 2.0: When using the |
|
|
Camel 2.0: To be used for continuously reading a stream such as the unix |
|
|
Camel 2.7: will retry opening the file if it's overwritten, somewhat like |
|
|
Camel 2.0: Delay in milliseconds between read attempts when using |
|
|
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. |
|
|
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 |
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).
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.
Samples
In the following sample we route messages from the direct:in
endpoint to the System.out
stream:
// 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());
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
.
The following sample demonstrates how to continuously read a file stream (analogous to the UNIX tail
command):
from("stream:file?fileName=/server/logs/server.log&scanStream=true&scanStreamDelay=1000").to("bean:logService?method=parseLogLine");
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.