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Chapter 44. Passing Information into Resource Classes and Methods


JAX-RS specifies a number of annotations that allow the developer to control where the information passed into resources come from. The annotations conform to common HTTP concepts such as matrix parameters in a URI. The standard APIs allow the annotations to be used on method parameters, bean properties, and resource class fields. Apache CXF provides an extension that allows for the injection of a sequence of parameters to be injected into a bean.

44.1. Basics of injecting data


Parameters, fields, and bean properties that are initialized using data from the HTTP request message have their values injected into them by the runtime. The specific data that is injected is specified by a set of annotations described in Section 44.2, “Using JAX-RS APIs”.
The JAX-RS specification places a few restrictions on when the data is injected. It also places a few restrictions on the types of objects into which request data can be injected.

When data is injected

Request data is injected into objects when they are instantiated due to a request. This means that only objects that directly correspond to a resource can use the injection annotations. As discussed in Chapter 43, Creating Resources, these objects will either be a root resource decorated with the @Path annotation or an object returned from a sub-resource locator method.

Supported data types

The specific set of data types that data can be injected into depends on the annotation used to specify the source of the injected data. However, all of the injection annotations support at least the following set of data types:
  • primitives such as int, char, or long
  • Objects that have a constructor that accepts a single String argument
  • Objects that have a static valueOf() method that accepts a single String argument
  • List<T>, Set<T>, or SortedSet<T> objects where T satisfies the other conditions in the list
Where injection annotations have different requirements for supported data types, the differences will be highlighted in the discussion of the annotation.