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 |
---|---|---|
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 |
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 |
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. Is set on the IN message. |
Exchange.HTTP_PATH |
String |
Request URI's path. Is set on the IN message. |
Exchange.HTTP_QUERY |
String |
URI parameters. Will override existing URI parameters set directly on the endpoint. Is set on the IN message. |
Exchange.HTTP_CHARACTER_ENCODING |
String |
Character encoding. Is set on the IN message. |
Exchange.HTTP_CONTENT_TYPE |
String |
Content type. Is set on the IN message. |
Exchange.HTTP_RESPONSE_CODE |
int |
The http response code from the external server. Is 200 for OK. Is set on the OUT message. |
NOTE from Camel 2.0m2, we move the message headers' constants from HttpConstants to Exchange
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
throwExceptionOnFailure
The option
throwExceptionOnFailure
can be set tofalse
to prevent the HttpOperationFailedException to be 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
- 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.
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>
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.
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);
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 an unit test that simulates a http status code 404, there is some assertion code etc.
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.
And then we can just use it as we normally do in our routes: