/*
* Copyright 2002-2017 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 org.springframework.web.servlet.mvc.method.annotation;
import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.util.PatternMatchUtils;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
import org.springframework.web.servlet.RequestToViewNameTranslator;
/**
* Handles return values of types {@code void} and {@code String} interpreting them
* as view name reference. As of 4.2, it also handles general {@code CharSequence}
* types, e.g. {@code StringBuilder} or Groovy's {@code GString}, as view names.
*
* <p>A {@code null} return value, either due to a {@code void} return type or
* as the actual return value is left as-is allowing the configured
* {@link RequestToViewNameTranslator} to select a view name by convention.
*
* <p>A String return value can be interpreted in more than one ways depending
* on the presence of annotations like {@code @ModelAttribute} or
* {@code @ResponseBody}. Therefore this handler should be configured after
* the handlers that support these annotations.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 3.1
*/
public class ViewNameMethodReturnValueHandler implements HandlerMethodReturnValueHandler {
@Nullable
private String[] redirectPatterns;
/**
* Configure one more simple patterns (as described in
* {@link PatternMatchUtils#simpleMatch}) to use in order to recognize
* custom redirect prefixes in addition to "redirect:".
* <p>Note that simply configuring this property will not make a custom
* redirect prefix work. There must be a custom View that recognizes the
* prefix as well.
* @since 4.1
*/
public void setRedirectPatterns(@Nullable String... redirectPatterns) {
this.redirectPatterns = redirectPatterns;
}
/**
* The configured redirect patterns, if any.
*/
@Nullable
public String[] getRedirectPatterns() {
return this.redirectPatterns;
}
@Override
public boolean supportsReturnType(MethodParameter returnType) {
Class<?> paramType = returnType.getParameterType();
return (void.class == paramType || CharSequence.class.isAssignableFrom(paramType));
}
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
if (returnValue instanceof CharSequence) {
String viewName = returnValue.toString();
mavContainer.setViewName(viewName);
if (isRedirectViewName(viewName)) {
mavContainer.setRedirectModelScenario(true);
}
}
else if (returnValue != null){
// should not happen
throw new UnsupportedOperationException("Unexpected return type: " +
returnType.getParameterType().getName() + " in method: " + returnType.getMethod());
}
}
/**
* Whether the given view name is a redirect view reference.
* The default implementation checks the configured redirect patterns and
* also if the view name starts with the "redirect:" prefix.
* @param viewName the view name to check, never {@code null}
* @return "true" if the given view name is recognized as a redirect view
* reference; "false" otherwise.
*/
protected boolean isRedirectViewName(String viewName) {
return (PatternMatchUtils.simpleMatch(this.redirectPatterns, viewName) || viewName.startsWith("redirect:"));
}
}
