ratpack.render.RendererSupport Maven / Gradle / Ivy
/*
* Copyright 2013 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ratpack.render;
import ratpack.handling.Context;
import ratpack.util.internal.Types;
/**
* A {@link Renderer} super class that provides a {@link #getType()} implementation based on the generic type of the impl.
*
* Implementations need only to declare the type they render as the value for type variable {@code T} and implement {@link #render(ratpack.handling.Context, Object)}.
*
* import ratpack.handling.Context;
* import ratpack.render.RendererSupport;
*
* // A type of thing to be rendered
* public class Thing {
* private final String name;
*
* public Thing(String name) {
* this.name = name;
* }
*
* public String getName() {
* return this.name;
* }
* }
*
* // Renderer implementation
* public class ThingRenderer extends RendererSupport<Thing> {
* public void render(Context context, Thing thing) {
* context.render("Thing: " + thing.getName());
* }
* }
*
*
* @param The type of object this renderer renders
*/
public abstract class RendererSupport implements Renderer {
private final Class type;
/**
* Constructor.
*
* Determines the value for {@link #getType()} by reflecting for {@code T}
*/
protected RendererSupport() {
this(RendererSupport.class);
}
/**
* Constructor.
*
* Only necessary for abstract implementations that propagate the generic type {@code T}.
* Almost all implementations should use the {@link #RendererSupport()} default constructor}.
*
* @param type the most specialised parent type of {@code this} that does not have a concrete type for {@code T}
*/
protected RendererSupport(Class type) {
this.type = Types.findImplParameterTypeAtIndex(getClass(), type, 0);
}
/**
* The type of object that this renderer can render (the type for {@code T}).
*
* @return The type of object that this renderer can render.
*/
@Override
public Class getType() {
return type;
}
/**
* {@inheritDoc}
*/
abstract public void render(Context context, T object) throws Exception;
}