HTTP has been edited by Claus Ibsen (Jul 06, 2009).

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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 by default use port 80 for HTTP and 443 for HTTPS.

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

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
throwExceptionOnFailure true Camel 2.0: Option to disable throwing the HttpOperationFailedException in case of failed responses from the remote server. This allows you to get all responses regardles of the HTTP status code.
httpBindingRef null Reference to a org.apache.camel.component.http.HttpBinding in the Registry.
username null Username for Basic HTTP Authentication.
password null Password for Basic HTTP Authentication.
proxyHost null The proxy host name * only for >= Camel 1.6.2 *.
proxyPort null The proxy port number * only for >= Camel 1.6.2 *.
proxyUsername null Username for proxy authentication * only for >= Camel 1.6.2 *.
proxyPassword null Password for proxy authentication * only for >= Camel 1.6.2 *.
httpClientConfigurerRef null Reference to a org.apache.camel.component.http.HttpClientConfigurer in the Registry.
httpClient.XXX null Setting options on the HttpClientParams. For instance httpClient.soTimeout=5000 will set the SO_TIMEOUT to 5 seconds.

Message Headers

Camel 1.x

Name Type Description
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.
HttpProducer.QUERY String URI parameters. Will override existing URI parameters set directly on the endpoint. Is set on the In message.

Camel 2.0

Name Type Description
Exchange.HTTP_URI String URI to call. Will override existing URI set directly on the endpoint.
Exchange.HTTP_PATH String Request URI's path.
Exchange.HTTP_QUERY String URI parameters. Will override existing URI parameters set directly on the endpoint.
Exchange.HTTP_RESPONSE_CODE int The HTTP response code from the external server. Is 200 for OK.
Exchange.HTTP_CHARACTER_ENCODING String Character encoding.
Exchange.CONTENT_TYPE String The HTTP content type. Is set on both the IN and OUT message to provide a content type, such as text/html.
Exchange.CONTENT_ENCODING String The HTTP content encoding. Is set on both the IN and OUT message to provide a content encoding, such as gzip.

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 are preserved during routing. Additionally Camel will add the HTTP response headers as well to the OUT message headers.

Response code

Camel will handle according to the HTTP response code:

  • Response code is in the range 100..299, Camel regards it as a success response.
  • Response code is in the range 300..399, Camel regards it as a redirection response and will throw a HttpOperationFailedException with the information.
  • Response code is 400+, Camel regards it as an external server failure and will throw a HttpOperationFailedException with the information.
    throwExceptionOnFailure

    The option, throwExceptionOnFailure, can be set to false to prevent the HttpOperationFailedException from being thrown for failed response codes. This allows you to get any response from the remote server.
    There is a sample below demonstrating this.

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
  • Response body 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 if 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 out 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.

And the same code in Camel 2.0:

from("direct:start")
            .setHeader(HttpConstants.HTTP_URI, constant("http://newhost"))
	    .to("http://oldhost");

Where Constants is the class, org.apache.camel.component.http.Constants.

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(HttpConstants.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(HttpConstants.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 constants:

.setHeader("CamelHttpMethod", constant("POST"))

And the equivalent Spring sample:

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

Using client tineout - SO_TIMEOUT

See the unit test in this link

Configuring a Proxy

Only for >= Camel 1.6.2
The HTTP component provides a way to configure a proxy.

from("direct:start")
	    .to("http://oldhost?proxyHost=www.myproxy.com&proxyPort=80");

There is also support for proxy authentication via the proxyUsername and proxyPassword options.

Using proxy settings from Java System Properties

Only for >= Camel 1.6.2
The HTTP component will detect Java System Properties for http.proxyHost and http.proxyPort and use them if provided.
See more at SUN http proxy documentation.

Camel will first set the settings from Java System Properties and then the endpoint proxy options if provided.
So you can override the system properties with the endpoint options.

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 & character 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 the 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);

Using throwExceptionOnFailure=false to get any response back

Available as of Camel 2.0
In the route below we want to route a message that we enrich with data returned from a remote HTTP call. As we want any response from the remote server, we set the throwExceptionOnFailure option to false so we get any response in the AggregationStrategy. As the code is based on a unit test that simulates a HTTP status code 404, there is some assertion code etc.

// We set throwExceptionOnFailure to false to let Camel return any response from the remove HTTP server without thrown
// HttpOperationFailedException in case of failures.
// This allows us to handle all responses in the aggregation strategy where we can check the HTTP response code
// and decide what to do. As this is based on an unit test we assert the code is 404
from("direct:start").enrich("http://localhost:8222/myserver?throwExceptionOnFailure=false&user=Camel", new AggregationStrategy() {
    public Exchange aggregate(Exchange original, Exchange resource) {
        // get the response code
        Integer code = resource.getIn().getHeader(Exchange.HTTP_RESPONSE_CODE, Integer.class);
        assertEquals(404, code.intValue());
        return resource;
    }
}).to("mock:result");

// this is our jetty server where we simulate the 404
from("jetty://http://localhost:8222/myserver")
        .process(new Processor() {
            public void process(Exchange exchange) throws Exception {
                exchange.getOut().setBody("Page not found");
                exchange.getOut().setHeader(Exchange.HTTP_RESPONSE_CODE, 404);
            }
        });

Disabling Cookies

To disable cookies you can set the HTTP Client to ignore cookies by adding this URI option:
httpClient.cookiePolicy=ignoreCookies

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 has 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 it on the HTTP component and not on the endpoint URI that we usually use. So here comes:

First, we define the http component in Spring XML. Yes, we use the same scheme name, http, because otherwise Camel 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.

<bean id="http" class="org.apache.camel.component.http.HttpComponent">
    <property name="camelContext" ref="camel"/>
    <property name="httpConnectionManager" ref="myHttpConnectionManager"/>
</bean>

<bean id="myHttpConnectionManager" class="org.apache.commons.httpclient.MultiThreadedHttpConnectionManager">
    <property name="params" ref="myHttpConnectionManagerParams"/>
</bean>

<bean id="myHttpConnectionManagerParams" class="org.apache.commons.httpclient.params.HttpConnectionManagerParams">
    <property name="defaultMaxConnectionsPerHost" value="5"/>
</bean>

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

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring" trace="true">
    <route>
        <from uri="direct:start"/>
        <to uri="http://www.google.com"/>
        <to uri="mock:result"/>
    </route>
</camelContext>

Using HTTPS to authenticate gotchas

An end user reported that he had problem with authenticating with HTTPS. The problem was eventually resolved when he discovered the HTTPS server did not return a HTTP code 401 Authorization Required. The solution was to set the following URI option: httpClient.authenticationPreemptive=true

See Also

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