Camel Component: AHC - 6.3

Talend ESB Mediation Developer Guide

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6.3
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Design and Development
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Talend ESB

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

The component uses the Async Http Client library.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
   <groupId>org.apache.camel</groupId>
   <artifactId>camel-ahc</artifactId>
   <version>x.x.x</version>
   <!-- use the same version as your Camel core version -->
</dependency>

URI format and Options

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

This 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&..., where option can be:

Table 1. AhcEndpoint Options

Option

Value

Behavior

throwExceptionOnFailure

true

Option to disable throwing the AhcOperationFailedException in case of failed responses from the remote server. This allows you to get all responses regardless of the HTTP status code.

bridgeEndpoint

false

The entire list of entries from the feed is set:

If the option is true, then the Exchange.HTTP_URI header is ignored, and use the endpoint's URI for request. You may also set the throwExcpetionOnFailure to be false to let the AhcProducer send all the fault response back.

transferException

false

If enabled and an exchange failed processing on the consumer side, and if the caused exception was sent back serialized in the response as a application/x-java-serialized-object content type (for example using Jetty or SERVLET Camel components). On the producer side the exception will be deserialized and thrown as is, instead of the AhcOperationFailedException. The caused exception is required to be serialized.

client

null

To use a custom com.ning.http.client.AsyncHttpClient.

clientConfig

null

To configure the AsyncHttpClient to use a custom com.ning.http.client.AsyncHttpClientConfig instance. This instance replaces any instance configured at the component level.

clientConfig.x

null

To configure additional properties of the com.ning.http.client.AsyncHttpClientConfig instance used by the endpoint. Note that configuration options set using this parameter will be merged with those set using the clientConfig parameter or the instance set at the component level with properties set using this parameter taking priority.

clientConfig.realm.x

null

Starting with Camel 2.11, to configure realm properties of the com.ning.http.client.AsyncHttpClientConfig. The options can be used are the options from com.ning.http.client.Realm.RealmBuilder.. For example, to set scheme, you can configure clientConfig.realm.scheme=DIGEST.

binding

null

To use a custom org.apache.camel.component.ahc.AhcBinding.

sslContextParameters

null

Starting with Camel 2.9, reference to a org.apache.camel.util.jsse.SSLContext

Parameters in the Registry.  This reference overrides any configured SSLContextParameters at the component level.  See Using the JSSE Configuration Utility.  Note that configuring this option will override any SSL/TLS configuration options provided through the clientConfig option at the endpoint or component level.

bufferSize

4096

Starting with Camel 2.10.3, the initial in-memory buffer size used when transferring data between Camel and AHC Client.


Table 2. AhcComponent Options

Option

Value

Behavior

client

null

To use a custom com.ning.http.client.AsyncHttpClient.

clientConfig

null

To configure the AsyncHttpClient to use a custom com.ning.http.client.AsyncHttpClientConfig.

binding

null

To use a custom org.apache.camel.component.ahc.AhcBinding.

sslContextParameters

null

Starting with Camel 2.9, to configure custom SSL/TLS configuration options at the component level. See Using the JSSE Configuration Utility for more details. Note that configuring this option will override any SSL/TLS configuration options provided through the clientConfig option at the endpoint or component level.


Message Headers

Camel AHC uses these headers:

Header

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, the header will be used to build the request URI with the HTTP_URI. If the path is start with "/", http producer will try to find the relative path based on the Exchange.HTTP_BASE_URI header or the exchange.getFromEndpoint().get

EndpointUri().

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 AhcOperationFailedException with the information.

    Note

    The option, throwExceptionOnFailure, can be set to false to prevent the AhcOperationFailedException from being thrown for failed response codes. This allows you to get any response from the remote server.

AhcOperationFailedException

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.lang.String, if server provided a body as response

Calling using GET or POST

The following algorithm is used to determine whether the 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("http4://oldhost");

And the equivalent Spring sample:

<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
   <route>
      <from uri="direct:start"/>
      <to uri="http4://oldhost"/>
   </route>
</camelContext>

You can override the HTTP endpoint URI by adding a header with the key, Exchange.HTTP_URI, on the message.

from("direct:start")
   .setHeader(Exchange.HTTP_URI, constant("http://newhost"))
   .to("http4://oldhost");

Configuring URI Parameters

The ahc 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 Exchange.HTTP_QUERY on the message.

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

Or options provided in a header:

from("direct:start")
   .setHeader(Exchange.HTTP_QUERY, constant("order=123&detail=short"))
   .to("ahc://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(Exchange.HTTP_METHOD, 
       constant(org.apache.camel.component.http4.HttpMethods.POST))
   .to("http4://www.google.com")
   .to("mock:results");

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="http4://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");

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("ahc: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("ahc: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 AHC component by getting the value from the Out message header with Exchange.HTTP_RESPONSE_CODE .

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

Configuring AsyncHttpClient

The AsyncHttpClient client uses a AsyncHttpClientConfig to configure the client. See the documentation at Async Http Client for more details.

In Camel 2.8, configuration is limited to using the builder pattern provided by AsyncHttpClientConfig.Builder. In Camel 2.8, the AsyncHttpClientConfig doesn't support getters/setters so its not easy to create/configure using a Spring bean style (eg the <bean> tag in the XML file).

The example below shows how to use a builder to create the AsyncHttpClientConfig which we configure on the AhcComponent.

// create a client config builder
AsyncHttpClientConfig.Builder builder = new AsyncHttpClientConfig.Builder();
// use the builder to set the options we want, in this case we want to follow 
redirects and try
// at most 3 retries to send a request to the host
AsyncHttpClientConfig config = 
builder.setFollowRedirects(true).setMaxRequestRetry(3).build();
 
// lookup AhcComponent
AhcComponent component = context.getComponent("ahc", AhcComponent.class);
// and set our custom client config to be used
component.setClientConfig(config);  

In Camel 2.9, the AHC component uses Async HTTP library 1.6.4. This newer version provides added support for plain bean style configuration. The AsyncHttpClientConfigBean class provides getters and setters for the configuration options available in AsyncHttpClientConfig. An instance of AsyncHttpClientConfigBean may be passed directly to the AHC component or referenced in an endpoint URI using the clientConfig URI parameter.

Also available in Camel 2.9 is the ability to set configuration options directly in the URI. URI parameters starting with "clientConfig." can be used to set the various configurable properties of AsyncHttpClientConfig. The properties specified in the endpoint URI are merged with those specified in the configuration referenced by the "clientConfig" URI parameter with those being set using the "clientConfig." parameter taking priority. The AsyncHttpClientConfig instance referenced is always copied for each endpoint such that settings on one endpoint will remain independent of settings on any previously created endpoints. The example below shows how to configure the AHC component using the "clientConfig." type URI parameters.

from("direct:start")
  .to("ahc:http://localhost:8080/foo?clientConfig.maxRequestRetry=3&clientConfig.
followRedirects=true")

SSL Support (HTTPS)

The AHC component supports SSL/TLS configuration through the Camel JSSE Configuration Utility.  This utility greatly decreases the amount of component specific code you need to write and is configurable at the endpoint and component levels.  The following examples demonstrate how to use the utility with the AHC component.

Programmatic configuration of the component:

KeyStoreParameters ksp = new KeyStoreParameters();
ksp.setResource("/users/home/server/keystore.jks");
ksp.setPassword("keystorePassword");
 
KeyManagersParameters kmp = new KeyManagersParameters();
kmp.setKeyStore(ksp);
kmp.setKeyPassword("keyPassword");
 
SSLContextParameters scp = new SSLContextParameters();
scp.setKeyManagers(kmp);
 
AhcComponent component = context.getComponent("ahc", AhcComponent.class);
component.setSslContextParameters(scp));  

Spring DSL based configuration of endpoint:

...
  <camel:sslContextParameters
      id="sslContextParameters">
    <camel:keyManagers
        keyPassword="keyPassword">
      <camel:keyStore
          resource="/users/home/server/keystore.jks"
          password="keystorePassword"/>
    </camel:keyManagers>
  </camel:sslContextParameters>...
...
  <to uri="ahc:https://localhost/foo?sslContextParameters=#sslContextParameters"/>
...