org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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
*
* https://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 org.springframework.web.method.support;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.web.context.request.NativeWebRequest;
/**
* Handles method return values by delegating to a list of registered {@link HandlerMethodReturnValueHandler HandlerMethodReturnValueHandlers}.
* Previously resolved return types are cached for faster lookups.
*
* @author Rossen Stoyanchev
* @since 3.1
*/
public class HandlerMethodReturnValueHandlerComposite implements HandlerMethodReturnValueHandler {
protected final Log logger = LogFactory.getLog(getClass());
private final List returnValueHandlers = new ArrayList<>();
/**
* Return a read-only list with the registered handlers, or an empty list.
*/
public List getHandlers() {
return Collections.unmodifiableList(this.returnValueHandlers);
}
/**
* Whether the given {@linkplain MethodParameter method return type} is supported by any registered
* {@link HandlerMethodReturnValueHandler}.
*/
@Override
public boolean supportsReturnType(MethodParameter returnType) {
return getReturnValueHandler(returnType) != null;
}
@Nullable
private HandlerMethodReturnValueHandler getReturnValueHandler(MethodParameter returnType) {
for (HandlerMethodReturnValueHandler handler : this.returnValueHandlers) {
if (handler.supportsReturnType(returnType)) {
return handler;
}
}
return null;
}
/**
* Iterate over registered {@link HandlerMethodReturnValueHandler HandlerMethodReturnValueHandlers} and invoke the one that supports it.
* @throws IllegalStateException if no suitable {@link HandlerMethodReturnValueHandler} is found.
*/
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);
if (handler == null) {
throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
}
handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
}
@Nullable
private HandlerMethodReturnValueHandler selectHandler(@Nullable Object value, MethodParameter returnType) {
boolean isAsyncValue = isAsyncReturnValue(value, returnType);
for (HandlerMethodReturnValueHandler handler : this.returnValueHandlers) {
if (isAsyncValue && !(handler instanceof AsyncHandlerMethodReturnValueHandler)) {
continue;
}
if (handler.supportsReturnType(returnType)) {
return handler;
}
}
return null;
}
private boolean isAsyncReturnValue(@Nullable Object value, MethodParameter returnType) {
for (HandlerMethodReturnValueHandler handler : this.returnValueHandlers) {
if (handler instanceof AsyncHandlerMethodReturnValueHandler &&
((AsyncHandlerMethodReturnValueHandler) handler).isAsyncReturnValue(value, returnType)) {
return true;
}
}
return false;
}
/**
* Add the given {@link HandlerMethodReturnValueHandler}.
*/
public HandlerMethodReturnValueHandlerComposite addHandler(HandlerMethodReturnValueHandler handler) {
this.returnValueHandlers.add(handler);
return this;
}
/**
* Add the given {@link HandlerMethodReturnValueHandler HandlerMethodReturnValueHandlers}.
*/
public HandlerMethodReturnValueHandlerComposite addHandlers(
@Nullable List handlers) {
if (handlers != null) {
this.returnValueHandlers.addAll(handlers);
}
return this;
}
}