If you look at the declarations of ClientBuilder, Client, WebTarget, Invocation, and Invocation.Builder, you’ll notice that they all implement the Configurable interface. Each one of these interfaces has its own scope of properties and registered components that it inherits from wherever it was created from. You can also override or add registered components or properties for each one of these components. For example:
Client client = ClientBuilder.newBuilder()
.property("authentication.mode", "Basic")
.property("username", "bburke")
.property("password", "geheim")
.build();
WebTarget target1 = client.target("http://facebook.com");
WebTarget target2 = client.target("http://google.com")
.property("username", "wburke")
.register(JacksonJsonProvider.class);
If you viewed the properties of target1 you’d find the same properties as those defined on the client instances, as WebTargets inherit their configuration from the Client or WebTarget they were created from. The target2 variable overrides the username property and registers a provider specifically for target2. So, target2’s configuration properties and registered components will be a little bit different than target1’s. This way of configuration scoping makes it much easier for you to share initialization code so you can avoid creating a lot of extra objects you don’t need and reduce the amount of code you have to write.