[CONF] Apache Camel: HTTP (page edited)

confluence Thu, 02 Apr 2009 07:44:29 -0700

Page Edited : CAMEL : HTTP

HTTP has been edited by Claus Ibsen (Apr 02, 2009).

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
throwException	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.
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
HttpConstants.HTTP_URI	String	URI to call. Will override existing URI set directly on the endpoint. Is set on the IN message.
HttpConstants.HTTP_PATH	String	Request URI's path. Is set on the IN message.
HttpConstants.HTTP_QUERY	String	URI parameters. Will override existing URI parameters set directly on the endpoint. Is set on the IN message.
HttpConstants.HTTP_CHARACTER_ENCODING	String	Character encoding. Is set on the IN message.
HttpConstants.HTTP_CONTENT_TYPE	String	Content type. Is set on the IN message.
HttpConstants.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

throwException

The option throwException can be set to false 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 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 `throwException=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 throwException 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.

// We set throwException 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:8123/myserver?throwException=false&user=Camel", new AggregationStrategy() {
    public Exchange aggregate(Exchange original, Exchange resource) {
        // get the response code
        Integer code = resource.getOut().getHeader(HttpConstants.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:8123/myserver")
        .process(new Processor() {
            public void process(Exchange exchange) throws Exception {
                exchange.getOut().setBody("Page not found");
                exchange.getOut().setHeader(HttpConstants.HTTP_RESPONSE_CODE, 404);
            }
        });

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.

<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>

[CONF] Apache Camel: HTTP (page edited)

HTTP Component

URI format

Options

Message Headers

Camel 1.x

Camel 2.0

Message Body

Response code

HttpOperationFailedException

Calling using GET or POST

Configuring URI to call

Configuring URI Parameters

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

Configuring charset

Sample with scheduled poll

URI Parameters from the endpoint URI

URI Parameters from the Message

Getting the Response Code

Using `throwException=false` to get any response back

Advanced Usage

Setting MaxConnectionsPerHost

See Also

Reply via email to

[CONF] Apache Camel: HTTP (page edited)

HTTP Component

URI format

Options

Message Headers

Camel 1.x

Camel 2.0

Message Body

Response code

HttpOperationFailedException

Calling using GET or POST

Configuring URI to call

Configuring URI Parameters

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

Configuring charset

Sample with scheduled poll

URI Parameters from the endpoint URI

URI Parameters from the Message

Getting the Response Code

Using throwException=false to get any response back

Advanced Usage

Setting MaxConnectionsPerHost

See Also

Reply via email to

Using `throwException=false` to get any response back