Stream Component

The stream: component provides access to the, 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:

    <!-- use the same version as your Camel core version -->

URI format


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


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&...


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) to use text-based streams (for example, message body is a String object). If not provided, Camel uses the JVM default Charset.
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.
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.

Message content

The stream: component supports either String or byte[] for writing to streams. Just add either String or byte[] content to the
The special stream:header URI is used for custom output streams. Just add a object to in the key header.
See samples for an example.


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

public void testStringContent() throws Exception {
    template.sendBody("direct:in", "Hello Text World\n");

public void testBinaryContent() {
    template.sendBody("direct:in", "Hello Bytes World\n".getBytes());

protected RouteBuilder createRouteBuilder() {
    return new RouteBuilder() {
        public void configure() {

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.

private OutputStream mystream = new MyOutputStream();
private StringBuffer sb = new StringBuffer();

public void testStringContent() {
    template.sendBody("direct:in", "Hello");
    // StreamProducer appends \n in text mode
    assertEquals("Hello\n", sb.toString());

public void testBinaryContent() {
    template.sendBody("direct:in", "Hello".getBytes());
    // StreamProducer is in binary mode so no \n is appended
    assertEquals("Hello", sb.toString());

protected RouteBuilder createRouteBuilder() {
    return new RouteBuilder() {
        public void configure() {
            from("direct:in").setHeader("stream", constant(mystream)).

private class MyOutputStream extends OutputStream {

    public void write(int b) throws IOException {

The following sample demonstrates how to continuously read a file stream (analogous to the UNIX tail command):


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.

See Also

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