Is this JAX-WS client call thread safe?

According to the CXF FAQ:

Are JAX-WS client proxies thread safe?

Official JAX-WS answer: No.
According to the JAX-WS spec, the client proxies are NOT thread safe.
To write portable code, you should treat them as non-thread safe and
synchronize access or use a pool of instances or similar.

CXF answer: CXF proxies are thread safe for MANY use cases. The
exceptions are:

• Use of ((BindingProvider)proxy).getRequestContext() – per JAX-WS spec,
  the request context is PER INSTANCE. Thus, anything set there will
  affect requests on other threads. With CXF, you can do:

  ((BindingProvider)proxy).getRequestContext().put("thread.local.request.context","true");
  

  and future calls to getRequestContext() will use a thread
  local request context. That allows the request context to be
  threadsafe. (Note: the response context is always thread local in CXF)

• Settings on the conduit – if you use code or configuration to directly
  manipulate the conduit (like to set TLS settings or similar), those
  are not thread safe. The conduit is per-instance and thus those
  settings would be shared. Also, if you use the FailoverFeature and
  LoadBalanceFeatures, the conduit is replaced on the fly. Thus,
  settings set on the conduit could get lost before being used on the
  setting thread.

• Session support – if you turn on sessions support (see
  jaxws spec), the session cookie is stored in the conduit. Thus, it
  would fall into the above rules on conduit settings and thus be shared
  across threads.
• WS-Security tokens – If use WS-SecureConversation or
  WS-Trust, the retrieved token is cached in the Endpoint/Proxy to avoid
  the extra (and expensive) calls to the STS to obtain tokens. Thus,
  multiple threads will share the token. If each thread has different
  security credentials or requirements, you need to use separate proxy
  instances.

For the conduit issues, you COULD install a new
ConduitSelector that uses a thread local or similar. That’s a bit
complex though.

For most “simple” use cases, you can use CXF proxies on multiple
threads. The above outlines the workarounds for the others.