[CONF] Apache Camel: HTTP (page edited)

confluence Sat, 15 Nov 2008 02:27:08 -0800

Page Edited : CAMEL : HTTP

HTTP has been edited by Claus Ibsen (Nov 15, 2008).

Change summary:

CAMEL-656

Content:

HTTP Component

The http: component provides HTTP based endpoints for consuming external HTTP resources (as a client to call external servers using HTTP).

URI format

http:hostname[:port][/resourceUri][?options]

Will default use port 80 for http and 443 for https.

camel-http vs camel-jetty

You can only produce to endpoints generated by the HTTP component. Therefore it should never be used as input into your camel Routes. To bind/expose an HTTP endpoint via a http server as input to a camel route, you can use the Jetty Component

Options

Name	Default Value	Description
httpClient.XXX	null	Setting options on the HttpClientParams. For instance httpClient.SoTimeout(5000) will set the SO_TIMEOUT to 5 seconds.

Message Headers

Name	Type	Description
HttpProducer.QUERY	String	URI parameters. Will override existing URI parameters set directly on the endpoint. Is set on the IN message.
HttpProducer.HTTP_URI	String	Camel 1.5.1: URI to call. Will override existing URI set directly on the endpoint. Is set on the IN message.
HttpProducer.HTTP_RESPONSE_CODE	int	The http response code from the external server. Is 200 for OK. Is set on the OUT message.

Message Body

Camel will store the http response from the external server on the OUT body. All headers from the IN message will be copied to the OUT message so headers is preserved during routing.
Additionally Camel will add the http response headers as well to the OUT message.

Response code

Camel will handle according to the http response code:

response code is between 100..299 then Camel regard it as a success response
response code is between 300..399 then Camel regard it as a redirection was returned and will throw a HttpOperationFailedException with the information
response code is 400+ then Camel regard it as a external server failure and will throw a HttpOperationFailedException with the information

Calling using GET or POST

In Camel 1.5 the following algorithm is used to determine if either GET or POST http method should be used:
1. Use method provided in header
2. GET is query string is provided in header
3. GET if endpoint is configured with a query string
4. POST if there is data to send (body is not null)
5. GET otherwise

Configuring URI to call

You can set the http producer's URI directly form the endpoint URI. In the route below Camel will call our to the external server oldhost using HTTP.

from("direct:start")
	    .to("http://oldhost");

And the equivalent spring sample:

<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
  <route>
    <from uri="direct:start"/>
    <to uri="http://oldhost"/>
  </route>
</camelContext>

In Camel 1.5.1 you can override the http endpoint URI by adding a header with the key HttpProducer.HTTP_URI on the message.

from("direct:start")
            .setHeader(org.apache.camel.component.http.HttpProducer.HTTP_URI, constant("http://newhost"))
	    .to("http://oldhost");

In the sample above Camel will call the http://newhost despite the endpoint is configured with http://oldhost.

Configuring URI Parameters

The http producer supports URI parameters to be sent to the HTTP server. The URI parameters can either be set directly on the endpoint URI or as a header with the key HttpProducer.QUERY on the message.

from("direct:start")
	    .to("http://oldhost?order=123&detail=short");

Or options provided in a header:

from("direct:start")
            .setHeader(org.apache.camel.component.http.HttpProducer.HTTP_QUERY, constant("order=123&detail=short"))
	    .to("http://oldhost");

How to set the http method (GET/POST/PUT/DELETE/HEAD/OPTIONS/TRACE) to the HTTP producer

The HTTP component provides a way to set the HTTP request method by setting the message header. Here is an example;

from("direct:start")
            .setHeader(org.apache.camel.component.http.HttpMethods.HTTP_METHOD, constant(org.apache.camel.component.http.HttpMethods.POST))
	    .to("http://www.google.com")
            .to("mock:results");

The method can be written a bit shorter using the string constant:

.setHeader(org.apache.camel.component.http.HttpMethods.HTTP_METHOD, constant("POST"))

And the equivalent spring sample:

<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
  <route>
    <from uri="direct:start"/>
    <setHeader headerName="http.requestMethod">
        <constant>POST</constant>
    </setHeader>
    <to uri="http://www.google.com"/>
    <to uri="mock:results"/>
  </route>
</camelContext>

Setting charset to send data

If you are using POST to send data you can configure the charset using the Exchange property:

exchange.setProperty(Exchange.CHARSET_NAME, "iso-8859-1");

Or the HttpClient options: httpClient.contentCharset=iso-8859-1

Sample with scheduled poll

The sample polls the Google homepage every 10 seconds and write the page to the file message.html

from("timer://foo?fixedRate=true&delay=0&period=10000")
    .to("http://www.google.com")
    .setHeader(FileComponent.HEADER_FILE_NAME, "message.html").to("file:target/google");

URI Parameters from the endpoint URI

In this sample we have the complete URI endpoint that is just what you would have typed in a web browser. Multiple URI parameters can of course be set using the & as separator, just as you would in the web browser. Camel does no tricks here.

// we query for Camel at the Google page
template.sendBody("http://www.google.com/search?q=Camel", null);

URI Parameters from the Message

Map headers = new HashMap();
headers.put(HttpProducer.QUERY, "q=Camel&lr=lang_en");
// we query for Camel and English language at Google
template.sendBody("http://www.google.com/search", null, headers);

In the header value above notice that it should not be prefixed with ? and you can separate parameters as usual with the & char.

Getting the Response Code

You can get the http response code from the http component by getting the value from out message header with HttpProducer.HTTP_RESPONSE_CODE.

Exchange exchange = template.send("http://www.google.com/search", new Processor() {
            public void process(Exchange exchange) throws Exception {
                exchange.getIn().setHeader(HttpProducer.QUERY, constant("hl=en&q=activemq"));
            }
   });
   Message out = exchange.getOut();
   int responseCode = out.getHeader(HttpProducer.HTTP_RESPONSE_CODE, Integer.class);

Advanced Usage

If you need more control over the http producer you should use the HttpComponent where you can set various classes to give you custom behavior.