31.3. XPath Injection

Parameter binding annotation

When using Apache Camel bean integration to invoke a method on a Java bean, you can use the @XPath annotation to extract a value from the exchange and bind it to a method parameter.
For example, consider the following route fragment, which invokes the credit method on an AccountService object: 
from("queue:payments")
    .beanRef("accountService","credit")
    ...
The credit method uses parameter binding annotations to extract relevant data from the message body and inject it into its parameters, as follows: 
public class AccountService {
    ...
    public void credit(
            @XPath("/transaction/transfer/receiver/text()") String name,
            @XPath("/transaction/transfer/amount/text()") String amount
            )
    {
        ...
    }
    ...
}
For more information about bean integration, see Section 2.4, “Bean Integration”.

Namespaces

Table 31.1, “Predefined Namespaces for @XPath” shows the namespaces that are predefined for XPath. You can use these namespace prefixes in the XPath expression that appears in the @XPath annotation.

Table 31.1. Predefined Namespaces for @XPath

Namespace URIPrefix
http://www.w3.org/2001/XMLSchemaxsd
http://www.w3.org/2003/05/soap-envelopesoap

Custom namespaces

You can use the @NamespacePrefix annotation to define custom XML namespaces. Invoke the @NamespacePrefix annotation to initialize the namespaces argument of the @XPath annotation. The namespaces defined by @NamespacePrefix can then be used in the @XPath annotation's expression value.
For example, to associate the prefix, ex, with the custom namespace, http://fusesource.com/examples, invoke the @XPath annotation as follows: 
public class AccountService {
  ...
  public void credit(
    @XPath(
      value = "/ex:transaction/ex:transfer/ex:receiver/text()",
      namespaces = @NamespacePrefix(
        prefix = "ex",
        uri = "http://fusesource.com/examples"
      )
    ) String name,
    @XPath(
      value = "/ex:transaction/ex:transfer/ex:amount/text()",
      namespaces = @NamespacePrefix(
        prefix = "ex",
        uri = "http://fusesource.com/examples"
      )
    ) String amount,
  )
  {
    ...
  }
  ...
}