ratpack.render.RenderableDecoratorSupport Maven / Gradle / Ivy
/*
* Copyright 2014 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 com.google.common.base.Predicates;
import com.google.common.collect.Iterables;
import com.google.common.reflect.TypeToken;
import ratpack.util.Types;
import ratpack.util.internal.InternalRatpackError;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;
/**
* A convenience base class for {@link RenderableDecorator} implementations.
*
* This base class provides an implementation for the {@link #getType()} method based on the type parameter {@code T}.
*
* Like {@link RendererSupport} implementations, the value for type variable {@code T} must be a concrete type or a parameterized type
* with the {@code ?} wildcard for all variables due to runtime type erasure.
*
* @param the type of object-to-render that this decorator decorates
*/
public abstract class RenderableDecoratorSupport implements RenderableDecorator {
private final Class type;
protected RenderableDecoratorSupport() {
TypeToken typeToken = new TypeToken(getClass()) {
};
Type type = typeToken.getType();
if (type instanceof Class) {
this.type = Types.cast(typeToken.getRawType());
} else if (type instanceof ParameterizedType) {
Iterable typeArgs = Arrays.asList(((ParameterizedType) type).getActualTypeArguments());
if (Iterables.any(typeArgs, Predicates.not((t) -> t.getTypeName().equals("?")))) {
throw new IllegalArgumentException("Invalid renderable type " + type + ": due to type erasure, type parameter T of RenderableDecorator must be a Class or a parameterized type with '?' for all type variables (e.g. List)");
}
this.type = Types.cast(typeToken.getRawType());
} else {
throw new InternalRatpackError("Unhandled type for RenderableDecorator: " + type.getClass());
}
}
/**
* {@inheritDoc}
*/
@Override
public Class getType() {
return type;
}
}