User Guide : Dynamic Methods

JSOG Dynamic Methods give you the ability to build applications that handle JSOG in a declarative way.

Consider this example of a JSON-based web service:

  "search": "lord of the rings",
  "type": "book"
// The Foo web service offers a method that can be used for searching media
public class Foo {
  public JSOG search(@JsonPath(value="$.search", required=true) String search,
                     @JsonPath(value="$.type", required=true) String type,
                     @JsonPath("$.maxResults") int maxResults,
                     @JsonPath("$.year") Integer year) {

      // search and type must exist in the object graph.
      // We retrieve them as strings.

      // maxResults must also exist in the object graph, since it is a primitive
      // (int).

      // year may or may not exist in the object graph, since it is a primitive
      // wrapper (Integer), and can have a null value. Also, it's "required"
      // option is not set, and defaults to false.

// Now we need to create a JsogMethod in order to invoke the search method.
// We can do this by letting JsogMethod look for the first method named "search"
// in the Foo class.
JsogMethod<JSOG> jsogMethod = new JsogMethod<JSOG>(Foo.class, "search");

// or you could look up the method yourself and give it to JsogMethod.
Method method = ...
JsogMethod<JSOG> jsogMethod = new JsogMethod<JSOG>(method);

// The next step is to invoke the method, and you need an instance of Foo
Foo foo = new Foo();

// We also need a JSOG to give it, assume we're using the example JSOG above
JSOG jsog = ...
JSOG result = jsogMethod.invoke(foo, jsog);

JSOG dynamic methods allow us to create methods that can extract specific values out of the object graph, and give them to the method as arguments.

If a required value is missing, invoke will throw an IllegalArgumentException. Any exceptions thrown by the target method will be wrapped in an InvocationTargetException.

Obviously, dynamic methods are aimed toward creating services and other complex systems. JSOGPath only supports basic navigation as of now, but as it becomes more advanced, you can see how this system has the potential to be very powerful. All while hiding away the details and keeping your code clean.