HTTP

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.

Options

Message Headers

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

HttpOperationFailedException

This exception contains the following information

• the http status code
• the http status line (text of the status code)
• redirect location if server returned a redirect
• responseBody as a java.io.InputStream if server provided a body as response

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>

Configuring charset

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.

Setting MaxConnectionsPerHost

The Http Component have a org.apache.commons.httpclient.HttpConnectionManager where you can configure various global configuration for the given component.
By global, we mean, that any endpoint the component creates has the same shared HttpConnectionManager. So if we want to set a different value for the max connection per host, we need to define on the http component and not on the endpoint URI that we usually uses. So here comes:

First we define the http component in spring XML. Yes we can use the same scheme name http that Camel otherwise will auto discover and create the component with default settings. What we need is to overrule this so we can set our options. In the sample below we set the max connection to 5 instead of the default of 2.

TODO: snippet

And then we can just use it as we normally do in our routes:
TOOD: snippet 2

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