/*
* 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.method.annotation;
import java.beans.ConstructorProperties;
import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.MethodParameter;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.util.Assert;
import org.springframework.validation.BindException;
import org.springframework.validation.Errors;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.bind.support.WebRequestDataBinder;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
/**
* Resolve {@code @ModelAttribute} annotated method arguments and handle
* return values from {@code @ModelAttribute} annotated methods.
*
* <p>Model attributes are obtained from the model or created with a default
* constructor (and then added to the model). Once created the attribute is
* populated via data binding to Servlet request parameters. Validation may be
* applied if the argument is annotated with {@code @javax.validation.Valid}.
* or Spring's own {@code @org.springframework.validation.annotation.Validated}.
*
* <p>When this handler is created with {@code annotationNotRequired=true}
* any non-simple type argument and return value is regarded as a model
* attribute with or without the presence of an {@code @ModelAttribute}.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 3.1
*/
public class ModelAttributeMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
private static final ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();
protected final Log logger = LogFactory.getLog(getClass());
private final boolean annotationNotRequired;
/**
* 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 ModelAttributeMethodProcessor(boolean annotationNotRequired) {
this.annotationNotRequired = annotationNotRequired;
}
/**
* Returns {@code true} if the parameter is annotated with
* {@link ModelAttribute} or, if in default resolution mode, for any
* method parameter that is not a simple type.
*/
@Override
public boolean supportsParameter(MethodParameter parameter) {
return (parameter.hasParameterAnnotation(ModelAttribute.class) ||
(this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType())));
}
/**
* Resolve the argument from the model or if not found instantiate it with
* its default if it is available. The model attribute is then populated
* with request values via data binding and optionally validated
* if {@code @java.validation.Valid} is present on the argument.
* @throws BindException if data binding and validation result in an error
* and the next method parameter is not of type {@link Errors}
* @throws Exception if WebDataBinder initialization fails
*/
@Override
public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
String name = ModelFactory.getNameForParameter(parameter);
Object attribute = (mavContainer.containsAttribute(name) ? mavContainer.getModel().get(name) :
createAttribute(name, parameter, binderFactory, webRequest));
if (!mavContainer.isBindingDisabled(name)) {
ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
if (ann != null && !ann.binding()) {
mavContainer.setBindingDisabled(name);
}
}
WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
if (binder.getTarget() != null) {
if (!mavContainer.isBindingDisabled(name)) {
bindRequestParameters(binder, webRequest);
}
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
throw new BindException(binder.getBindingResult());
}
}
// Add resolved attribute and BindingResult at the end of the model
Map<String, Object> bindingResultModel = binder.getBindingResult().getModel();
mavContainer.removeAttributes(bindingResultModel);
mavContainer.addAllAttributes(bindingResultModel);
return (parameter.getParameterType().isInstance(attribute) ? attribute :
binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter));
}
/**
* Extension point to create the model attribute if not found in the model,
* with subsequent parameter binding through bean properties (unless suppressed).
* <p>The default implementation uses the unique public no-arg constructor, if any,
* which may have arguments: It understands the JavaBeans {@link ConstructorProperties}
* annotation as well as runtime-retained parameter names in the bytecode,
* associating request parameters with constructor arguments by name. If no such
* constructor is found, the default constructor will be used (even if not public),
* assuming subsequent bean property bindings through setter methods.
* @param attributeName the name of the attribute (never {@code null})
* @param parameter the method parameter declaration
* @param binderFactory for creating WebDataBinder instance
* @param webRequest the current request
* @return the created model attribute (never {@code null})
*/
protected Object createAttribute(String attributeName, MethodParameter parameter,
WebDataBinderFactory binderFactory, NativeWebRequest webRequest) throws Exception {
Constructor<?>[] ctors = parameter.getParameterType().getConstructors();
if (ctors.length != 1) {
// No standard data class or standard JavaBeans arrangement ->
// defensively go with default constructor, expecting regular bean property bindings.
return BeanUtils.instantiateClass(parameter.getParameterType());
}
Constructor<?> ctor = ctors[0];
if (ctor.getParameterCount() == 0) {
// A single default constructor -> clearly a standard JavaBeans arrangement.
return BeanUtils.instantiateClass(ctor);
}
// A single data class constructor -> resolve constructor arguments from request parameters.
ConstructorProperties cp = ctor.getAnnotation(ConstructorProperties.class);
String[] paramNames = (cp != null ? cp.value() : parameterNameDiscoverer.getParameterNames(ctor));
Assert.state(paramNames != null, () -> "Cannot resolve parameter names for constructor " + ctor);
Class<?>[] paramTypes = ctor.getParameterTypes();
Assert.state(paramNames.length == paramTypes.length,
() -> "Invalid number of parameter names: " + paramNames.length + " for constructor " + ctor);
Object[] args = new Object[paramTypes.length];
WebDataBinder binder = binderFactory.createBinder(webRequest, null, attributeName);
for (int i = 0; i < paramNames.length; i++) {
args[i] = binder.convertIfNecessary(
webRequest.getParameterValues(paramNames[i]), paramTypes[i], new MethodParameter(ctor, i));
}
return BeanUtils.instantiateClass(ctor, args);
}
/**
* Extension point to bind the request to the target object.
* @param binder the data binder instance to use for the binding
* @param request the current request
*/
protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest request) {
((WebRequestDataBinder) binder).bind(request);
}
/**
* Validate the model attribute if applicable.
* <p>The default implementation checks for {@code @javax.validation.Valid},
* Spring's {@link org.springframework.validation.annotation.Validated},
* and custom annotations whose name starts with "Valid".
* @param binder the DataBinder to be used
* @param parameter the method parameter declaration
*/
protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {
Annotation[] annotations = parameter.getParameterAnnotations();
for (Annotation ann : annotations) {
Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class);
if (validatedAnn != null || ann.annotationType().getSimpleName().startsWith("Valid")) {
Object hints = (validatedAnn != null ? validatedAnn.value() : AnnotationUtils.getValue(ann));
Object[] validationHints = (hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});
binder.validate(validationHints);
break;
}
}
}
/**
* Whether to raise a fatal bind exception on validation errors.
* @param binder the data binder used to perform data binding
* @param parameter the method parameter declaration
* @return {@code true} if the next method argument is not of type {@link Errors}
*/
protected boolean isBindExceptionRequired(WebDataBinder binder, MethodParameter parameter) {
int i = parameter.getParameterIndex();
Class<?>[] paramTypes = parameter.getMethod().getParameterTypes();
boolean hasBindingResult = (paramTypes.length > (i + 1) && Errors.class.isAssignableFrom(paramTypes[i + 1]));
return !hasBindingResult;
}
/**
* Return {@code true} if there is a method-level {@code @ModelAttribute}
* or, in default resolution mode, for any return value type that is not
* a simple type.
*/
@Override
public boolean supportsReturnType(MethodParameter returnType) {
return (returnType.hasMethodAnnotation(ModelAttribute.class) ||
(this.annotationNotRequired && !BeanUtils.isSimpleProperty(returnType.getParameterType())));
}
/**
* Add non-null return values to the {@link ModelAndViewContainer}.
*/
@Override
public void handleReturnValue(Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
if (returnValue != null) {
String name = ModelFactory.getNameForReturnValue(returnValue, returnType);
mavContainer.addAttribute(name, returnValue);
}
}
}