/*
* 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.messaging.handler.annotation.support;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.config.BeanExpressionContext;
import org.springframework.beans.factory.config.BeanExpressionResolver;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.messaging.Message;
import org.springframework.messaging.handler.annotation.ValueConstants;
import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
import org.springframework.util.ClassUtils;
/**
* Abstract base class for resolving method arguments from a named value. Message headers,
* and path variables are examples of named values. Each may have a name, a required flag,
* and a default value.
*
* <p>Subclasses define how to do the following:
* <ul>
* <li>Obtain named value information for a method parameter
* <li>Resolve names into argument values
* <li>Handle missing argument values when argument values are required
* <li>Optionally handle a resolved value
* </ul>
*
* <p>A default value string can contain ${...} placeholders and Spring Expression
* Language {@code #{...}} expressions. For this to work a {@link ConfigurableBeanFactory}
* must be supplied to the class constructor.
*
* <p>A {@link ConversionService} may be used to apply type conversion to the resolved
* argument value if it doesn't match the method parameter type.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 4.0
*/
public abstract class AbstractNamedValueMethodArgumentResolver implements HandlerMethodArgumentResolver {
private final ConversionService conversionService;
private final ConfigurableBeanFactory configurableBeanFactory;
private final BeanExpressionContext expressionContext;
private final Map<MethodParameter, NamedValueInfo> namedValueInfoCache = new ConcurrentHashMap<>(256);
/**
* Constructor with a {@link ConversionService} and a {@link BeanFactory}.
* @param cs conversion service for converting values to match the
* target method parameter type
* @param beanFactory a bean factory to use for resolving {@code ${...}} placeholder
* and {@code #{...}} SpEL expressions in default values, or {@code null} if default
* values are not expected to contain expressions
*/
protected AbstractNamedValueMethodArgumentResolver(ConversionService cs, ConfigurableBeanFactory beanFactory) {
this.conversionService = (cs != null ? cs : DefaultConversionService.getSharedInstance());
this.configurableBeanFactory = beanFactory;
this.expressionContext = (beanFactory != null ? new BeanExpressionContext(beanFactory, null) : null);
}
@Override
public Object resolveArgument(MethodParameter parameter, Message<?> message) throws Exception {
NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
MethodParameter nestedParameter = parameter.nestedIfOptional();
Object resolvedName = resolveStringValue(namedValueInfo.name);
if (resolvedName == null) {
throw new IllegalArgumentException(
"Specified name must not resolve to null: [" + namedValueInfo.name + "]");
}
Object arg = resolveArgumentInternal(nestedParameter, message, resolvedName.toString());
if (arg == null) {
if (namedValueInfo.defaultValue != null) {
arg = resolveStringValue(namedValueInfo.defaultValue);
}
else if (namedValueInfo.required && !nestedParameter.isOptional()) {
handleMissingValue(namedValueInfo.name, nestedParameter, message);
}
arg = handleNullValue(namedValueInfo.name, arg, nestedParameter.getNestedParameterType());
}
else if ("".equals(arg) && namedValueInfo.defaultValue != null) {
arg = resolveStringValue(namedValueInfo.defaultValue);
}
if (parameter != nestedParameter || !ClassUtils.isAssignableValue(parameter.getParameterType(), arg)) {
arg = this.conversionService.convert(arg, TypeDescriptor.forObject(arg), new TypeDescriptor(parameter));
}
handleResolvedValue(arg, namedValueInfo.name, parameter, message);
return arg;
}
/**
* Obtain the named value for the given method parameter.
*/
private NamedValueInfo getNamedValueInfo(MethodParameter parameter) {
NamedValueInfo namedValueInfo = this.namedValueInfoCache.get(parameter);
if (namedValueInfo == null) {
namedValueInfo = createNamedValueInfo(parameter);
namedValueInfo = updateNamedValueInfo(parameter, namedValueInfo);
this.namedValueInfoCache.put(parameter, namedValueInfo);
}
return namedValueInfo;
}
/**
* Create the {@link NamedValueInfo} object for the given method parameter. Implementations typically
* retrieve the method annotation by means of {@link MethodParameter#getParameterAnnotation(Class)}.
* @param parameter the method parameter
* @return the named value information
*/
protected abstract NamedValueInfo createNamedValueInfo(MethodParameter parameter);
/**
* Create a new NamedValueInfo based on the given NamedValueInfo with sanitized values.
*/
private NamedValueInfo updateNamedValueInfo(MethodParameter parameter, NamedValueInfo info) {
String name = info.name;
if (info.name.isEmpty()) {
name = parameter.getParameterName();
if (name == null) {
throw new IllegalArgumentException("Name for argument type [" + parameter.getParameterType().getName() +
"] not available, and parameter name information not found in class file either.");
}
}
String defaultValue = (ValueConstants.DEFAULT_NONE.equals(info.defaultValue) ? null : info.defaultValue);
return new NamedValueInfo(name, info.required, defaultValue);
}
/**
* Resolve the given annotation-specified value,
* potentially containing placeholders and expressions.
*/
private Object resolveStringValue(String value) {
if (this.configurableBeanFactory == null) {
return value;
}
String placeholdersResolved = this.configurableBeanFactory.resolveEmbeddedValue(value);
BeanExpressionResolver exprResolver = this.configurableBeanFactory.getBeanExpressionResolver();
if (exprResolver == null) {
return value;
}
return exprResolver.evaluate(placeholdersResolved, this.expressionContext);
}
/**
* Resolves the given parameter type and value name into an argument value.
* @param parameter the method parameter to resolve to an argument value
* @param message the current request
* @param name the name of the value being resolved
* @return the resolved argument. May be {@code null}
* @throws Exception in case of errors
*/
protected abstract Object resolveArgumentInternal(MethodParameter parameter, Message<?> message, String name)
throws Exception;
/**
* Invoked when a named value is required, but
* {@link #resolveArgumentInternal(MethodParameter, Message, String)} returned {@code null} and
* there is no default value. Subclasses typically throw an exception in this case.
* @param name the name for the value
* @param parameter the method parameter
* @param message the message being processed
*/
protected abstract void handleMissingValue(String name, MethodParameter parameter, Message<?> message);
/**
* A {@code null} results in a {@code false} value for {@code boolean}s or an
* exception for other primitives.
*/
private Object handleNullValue(String name, Object value, Class<?> paramType) {
if (value == null) {
if (Boolean.TYPE.equals(paramType)) {
return Boolean.FALSE;
}
else if (paramType.isPrimitive()) {
throw new IllegalStateException("Optional " + paramType + " parameter '" + name +
"' is present but cannot be translated into a null value due to being " +
"declared as a primitive type. Consider declaring it as object wrapper " +
"for the corresponding primitive type.");
}
}
return value;
}
/**
* Invoked after a value is resolved.
* @param arg the resolved argument value
* @param name the argument name
* @param parameter the argument parameter type
* @param message the message
*/
protected void handleResolvedValue(Object arg, String name, MethodParameter parameter, Message<?> message) {
}
/**
* Represents the information about a named value, including name, whether it's
* required and a default value.
*/
protected static class NamedValueInfo {
private final String name;
private final boolean required;
private final String defaultValue;
protected NamedValueInfo(String name, boolean required, String defaultValue) {
this.name = name;
this.required = required;
this.defaultValue = defaultValue;
}
}
}