Red Hat Summit Red Hat SummitSupportoConsoleSviluppatoriInizia una provaContatti

Questo contenuto non è disponibile nella lingua selezionata.

8.2. Message Filter

Overview
Copia collegamento

A message filter is a processor that eliminates undesired messages based on specific criteria. In Apache Camel, the message filter pattern, shown in Figure 8.2, “Message Filter Pattern”, is implemented by the filter() Java DSL command. The filter() command takes a single predicate argument, which controls the filter. When the predicate is true, the incoming message is allowed to proceed, and when the predicate is false, the incoming message is blocked.

Figure 8.2. Message Filter Pattern

Message filter pattern
View larger image
Message filter pattern

Java DSL example
Copia collegamento

The following example shows how to create a route from endpoint, seda:a, to endpoint, seda:b, that blocks all messages except for those messages whose foo header have the value, bar: 
RouteBuilder builder = new RouteBuilder() {
    public void configure() {
        from("seda:a").filter(header("foo").isEqualTo("bar")).to("seda:b");
    }
};
Copy to Clipboard Toggle word wrap
To evaluate more complex filter predicates, you can invoke one of the supported scripting languages, such as XPath, XQuery, or SQL (see Expression and Predicate Languages). The following example defines a route that blocks all messages except for those containing a person element whose name attribute is equal to James: 
from("direct:start").
        filter().xpath("/person[@name='James']").
        to("mock:result");
Copy to Clipboard Toggle word wrap

XML configuration example
Copia collegamento

The following example shows how to configure the route with an XPath predicate in XML (see Expression and Predicate Languages): 
<camelContext id="simpleFilterRoute" xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="seda:a"/>
    <filter>
      <xpath>$foo = 'bar'</xpath>
      <to uri="seda:b"/>
    </filter>
  </route>
  </camelContext>
Copy to Clipboard Toggle word wrap
Filtered endpoint required inside </filter> tag
Make sure you put the endpoint you want to filter (for example, <to uri="seda:b"/>) before the closing </filter> tag or the filter will not be applied (in 2.8+, omitting this will result in an error).

Filtering with beans
Copia collegamento

Here is an example of using a bean to define the filter behavior: 
from("direct:start")
     .filter().method(MyBean.class, "isGoldCustomer").to("mock:result").end()
     .to("mock:end");
 
public static class MyBean {
    public boolean isGoldCustomer(@Header("level") String level) { 
        return level.equals("gold"); 
    }
}
Copy to Clipboard Toggle word wrap

Using stop()
Copia collegamento

Available as of Camel 2.0
Stop is a special type of filter that filters out all messages. Stop is convenient to use in a Content-Based Router when you need to stop further processing in one of the predicates.
In the following example, we do not want messages with the word Bye in the message body to propagate any further in the route. We prevent this in the when() predicate using .stop(). 
from("direct:start")
    .choice()
        .when(bodyAs(String.class).contains("Hello")).to("mock:hello")
        .when(bodyAs(String.class).contains("Bye")).to("mock:bye").stop()
        .otherwise().to("mock:other")
    .end()
    .to("mock:result");
Copy to Clipboard Toggle word wrap

Knowing if Exchange was filtered or not
Copia collegamento

Available as of Camel 2.5
The Message Filter EIP will add a property on the Exchange which states if it was filtered or not.
The property has the key Exchannge.FILTER_MATCHED which has the String value of CamelFilterMatched. Its value is a boolean indicating true or false. If the value is true then the Exchange was routed in the filter block.
Torna in cima
Red Hat logoGithubredditYoutubeTwitter

Formazione

Prova, acquista e vendi

Community

Informazioni sulla documentazione di Red Hat

Aiutiamo gli utenti Red Hat a innovarsi e raggiungere i propri obiettivi con i nostri prodotti e servizi grazie a contenuti di cui possono fidarsi. Esplora i nostri ultimi aggiornamenti.

Rendiamo l’open source più inclusivo

Red Hat si impegna a sostituire il linguaggio problematico nel codice, nella documentazione e nelle proprietà web. Per maggiori dettagli, visita il Blog di Red Hat.

Informazioni su Red Hat

Forniamo soluzioni consolidate che rendono più semplice per le aziende lavorare su piattaforme e ambienti diversi, dal datacenter centrale all'edge della rete.

Theme

© 2025 Red Hat