Groovy type coercion examples

Coercion.groovy

// for a simple Java POJO
def patch = ["add","path", 42] as Patch // explicit coercion
Patch patch = ["add","path", 42]        // implicit coercion
def patch = new Patch("add","path", 42) // default invocation

// mocking via coercion
def service = [getValue: { UUID id -> 42 }] as CounterService  // map coercion
def service = { UUID id -> 42 } as CounterService              // closure coercion
assert 42 == service.getValue(UUID.randomUUID())

// GroovyBean with auto-generated map constructor (plus getter and setter)
// equals() and hashcode() generated via @EqualsAndHashCode annotation
@EqualsAndHashCode
class Patch {
   String op;
   String path;
   long value;
}

def patch = [op: 'add', path: 'path', value: 42] as Patch  // explicit
Patch patch = [op: 'add', path: 'path', value: 42]         // implicit

// facilitating native map syntax for REST payloads
def patch = [
        "op"   : "add",
        "path" : "path",
        "value": 42
]

RestAssured
        .given()
            .contentType("application/json-patch+json")
            .body(patch)
        .patch(someUrl)

CounterService.java

public class CounterService {
 ...
    public long getValue(UUID id) {
        return counters.get(id);
    }
}

Patch.java

public class Patch {

    public final String op;
    public final String path;
    public final long value;

    @JsonCreator
    public Patch(@JsonProperty(value = "op", required = true) String op,
            @JsonProperty(value = "path", required = true) String path,
            @JsonProperty(value = "value", required = true) long value) {
        this.op = op;
        this.path = path;
        this.value = value;
        verifyOperation();
    }

    private void verifyOperation() {
        if (!"ADD".equalsIgnoreCase(op)) {
            throw new InvalidPatchOperationException("Currently only ADD is supported for PATCH.");
        }
    }
}