/*
* 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 java.util.Collections;
import java.util.Map;
import javax.servlet.ServletRequest;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.Converter;
import org.springframework.util.StringUtils;
import org.springframework.validation.DataBinder;
import org.springframework.web.bind.ServletRequestDataBinder;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.method.annotation.ModelAttributeMethodProcessor;
import org.springframework.web.servlet.HandlerMapping;
/**
* A Servlet-specific {@link ModelAttributeMethodProcessor} that applies data
* binding through a WebDataBinder of type {@link ServletRequestDataBinder}.
*
* <p>Also adds a fall-back strategy to instantiate the model attribute from a
* URI template variable or from a request parameter if the name matches the
* model attribute name and there is an appropriate type conversion strategy.
*
* @author Rossen Stoyanchev
* @since 3.1
*/
public class ServletModelAttributeMethodProcessor extends ModelAttributeMethodProcessor {
/**
* Class constructor.
* @param annotationNotRequired if "true", non-simple method arguments and
* return values are considered model attributes with or without a
* {@code @ModelAttribute} annotation
*/
public ServletModelAttributeMethodProcessor(boolean annotationNotRequired) {
super(annotationNotRequired);
}
/**
* Instantiate the model attribute from a URI template variable or from a
* request parameter if the name matches to the model attribute name and
* if there is an appropriate type conversion strategy. If none of these
* are true delegate back to the base class.
* @see #createAttributeFromRequestValue
*/
@Override
protected final Object createAttribute(String attributeName, MethodParameter methodParam,
WebDataBinderFactory binderFactory, NativeWebRequest request) throws Exception {
String value = getRequestValueForAttribute(attributeName, request);
if (value != null) {
Object attribute = createAttributeFromRequestValue(
value, attributeName, methodParam, binderFactory, request);
if (attribute != null) {
return attribute;
}
}
return super.createAttribute(attributeName, methodParam, binderFactory, request);
}
/**
* Obtain a value from the request that may be used to instantiate the
* model attribute through type conversion from String to the target type.
* <p>The default implementation looks for the attribute name to match
* a URI variable first and then a request parameter.
* @param attributeName the model attribute name
* @param request the current request
* @return the request value to try to convert, or {@code null} if none
*/
protected String getRequestValueForAttribute(String attributeName, NativeWebRequest request) {
Map<String, String> variables = getUriTemplateVariables(request);
String variableValue = variables.get(attributeName);
if (StringUtils.hasText(variableValue)) {
return variableValue;
}
String parameterValue = request.getParameter(attributeName);
if (StringUtils.hasText(parameterValue)) {
return parameterValue;
}
return null;
}
@SuppressWarnings("unchecked")
protected final Map<String, String> getUriTemplateVariables(NativeWebRequest request) {
Map<String, String> variables = (Map<String, String>) request.getAttribute(
HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);
return (variables != null ? variables : Collections.emptyMap());
}
/**
* Create a model attribute from a String request value (e.g. URI template
* variable, request parameter) using type conversion.
* <p>The default implementation converts only if there a registered
* {@link Converter} that can perform the conversion.
* @param sourceValue the source value to create the model attribute from
* @param attributeName the name of the attribute (never {@code null})
* @param methodParam the method parameter
* @param binderFactory for creating WebDataBinder instance
* @param request the current request
* @return the created model attribute, or {@code null} if no suitable
* conversion found
* @throws Exception
*/
protected Object createAttributeFromRequestValue(String sourceValue, String attributeName,
MethodParameter methodParam, WebDataBinderFactory binderFactory, NativeWebRequest request)
throws Exception {
DataBinder binder = binderFactory.createBinder(request, null, attributeName);
ConversionService conversionService = binder.getConversionService();
if (conversionService != null) {
TypeDescriptor source = TypeDescriptor.valueOf(String.class);
TypeDescriptor target = new TypeDescriptor(methodParam);
if (conversionService.canConvert(source, target)) {
return binder.convertIfNecessary(sourceValue, methodParam.getParameterType(), methodParam);
}
}
return null;
}
/**
* This implementation downcasts {@link WebDataBinder} to
* {@link ServletRequestDataBinder} before binding.
* @see ServletRequestDataBinderFactory
*/
@Override
protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest request) {
ServletRequest servletRequest = request.getNativeRequest(ServletRequest.class);
ServletRequestDataBinder servletBinder = (ServletRequestDataBinder) binder;
servletBinder.bind(servletRequest);
}
}