org.springframework.beans.factory.support.ConstructorResolver Maven / Gradle / Ivy
/*
* Copyright 2002-2007 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.beans.factory.support;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.springframework.beans.BeanMetadataElement;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
import org.springframework.beans.TypeMismatchException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.UnsatisfiedDependencyException;
import org.springframework.beans.factory.config.ConstructorArgumentValues;
import org.springframework.beans.factory.config.TypedStringValue;
import org.springframework.core.MethodParameter;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;
/**
* Helper class for resolving constructors and factory methods.
* Performs constructor resolution through argument matching.
*
* Operates on an {@link AbstractBeanFactory} and an {@link InstantiationStrategy}.
* Used by {@link AbstractAutowireCapableBeanFactory}.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 2.0
* @see #autowireConstructor
* @see #instantiateUsingFactoryMethod
* @see AbstractAutowireCapableBeanFactory
*/
abstract class ConstructorResolver {
private final AbstractBeanFactory beanFactory;
private final InstantiationStrategy instantiationStrategy;
/**
* Create a new ConstructorResolver for the given factory and instantiation strategy.
* @param beanFactory the BeanFactory to work with
* @param instantiationStrategy the instantiate strategy for creating bean instances
*/
public ConstructorResolver(AbstractBeanFactory beanFactory, InstantiationStrategy instantiationStrategy) {
this.beanFactory = beanFactory;
this.instantiationStrategy = instantiationStrategy;
}
/**
* "autowire constructor" (with constructor arguments by type) behavior.
* Also applied if explicit constructor argument values are specified,
* matching all remaining arguments with beans from the bean factory.
*
This corresponds to constructor injection: In this mode, a Spring
* bean factory is able to host components that expect constructor-based
* dependency resolution.
* @param beanName the name of the bean
* @param mbd the merged bean definition for the bean
* @return a BeanWrapper for the new instance
*/
protected BeanWrapper autowireConstructor(String beanName, RootBeanDefinition mbd) {
BeanWrapper bw = new BeanWrapperImpl();
this.beanFactory.initBeanWrapper(bw);
Constructor constructorToUse = (Constructor) mbd.resolvedConstructorOrFactoryMethod;
Object[] argsToUse = null;
if (constructorToUse != null) {
// Found a cached constructor...
argsToUse = mbd.resolvedConstructorArguments;
if (argsToUse == null) {
Object[] argsToResolve = mbd.preparedConstructorArguments;
BeanDefinitionValueResolver valueResolver =
new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, bw);
argsToUse = new Object[argsToResolve.length];
for (int i = 0; i < argsToResolve.length; i++) {
Object argValue = argsToResolve[i];
if (argValue instanceof BeanMetadataElement) {
String argName = "constructor argument with index " + i;
argsToUse[i] = valueResolver.resolveValueIfNecessary(argName, argValue);
}
else {
argsToUse[i] = argValue;
}
}
}
}
else {
// Need to determine the constructor...
Constructor[] candidates = mbd.getBeanClass().getDeclaredConstructors();
AutowireUtils.sortConstructors(candidates);
int minTypeDiffWeight = Integer.MAX_VALUE;
ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
ConstructorArgumentValues resolvedValues = new ConstructorArgumentValues();
int minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
for (int i = 0; i < candidates.length; i++) {
Constructor constructor = candidates[i];
Class[] paramTypes = constructor.getParameterTypes();
if (constructorToUse != null && argsToUse.length > paramTypes.length) {
// Already found greedy constructor that can be satisfied ->
// do not look any further, there are only less greedy constructors left.
break;
}
if (paramTypes.length < minNrOfArgs) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
minNrOfArgs + " constructor arguments specified but no matching constructor found in bean '" +
beanName + "' " +
"(hint: specify index and/or type arguments for simple parameters to avoid type ambiguities)");
}
// Try to resolve arguments for current constructor.
try {
ArgumentsHolder args = createArgumentArray(beanName, mbd, resolvedValues, bw, paramTypes, constructor);
int typeDiffWeight = args.getTypeDifferenceWeight(paramTypes);
// Choose this constructor if it represents the closest match.
if (typeDiffWeight < minTypeDiffWeight) {
constructorToUse = constructor;
argsToUse = args.arguments;
minTypeDiffWeight = typeDiffWeight;
}
}
catch (UnsatisfiedDependencyException ex) {
if (this.beanFactory.logger.isTraceEnabled()) {
this.beanFactory.logger.trace(
"Ignoring constructor [" + constructor + "] of bean '" + beanName + "': " + ex);
}
if (i == candidates.length - 1 && constructorToUse == null) {
throw ex;
}
else {
// Swallow and try next constructor.
}
}
}
if (constructorToUse == null) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Could not resolve matching constructor");
}
mbd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
Object beanInstance = this.instantiationStrategy.instantiate(
mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
bw.setWrappedInstance(beanInstance);
return bw;
}
/**
* Instantiate the bean using a named factory method. The method may be static, if the
* bean definition parameter specifies a class, rather than a "factory-bean", or
* an instance variable on a factory object itself configured using Dependency Injection.
*
Implementation requires iterating over the static or instance methods with the
* name specified in the RootBeanDefinition (the method may be overloaded) and trying
* to match with the parameters. We don't have the types attached to constructor args,
* so trial and error is the only way to go here. The explicitArgs array may contain
* argument values passed in programmatically via the corresponding getBean method.
* @param beanName the name of the bean
* @param mbd the merged bean definition for the bean
* @param explicitArgs argument values passed in programmatically via the getBean
* method, or null if none (-> use constructor argument values from bean definition)
* @return a BeanWrapper for the new instance
*/
public BeanWrapper instantiateUsingFactoryMethod(String beanName, RootBeanDefinition mbd, Object[] explicitArgs) {
BeanWrapper bw = new BeanWrapperImpl();
this.beanFactory.initBeanWrapper(bw);
Class factoryClass = null;
Object factoryBean = null;
boolean isStatic = true;
if (mbd.getFactoryBeanName() != null) {
factoryBean = this.beanFactory.getBean(mbd.getFactoryBeanName());
factoryClass = factoryBean.getClass();
isStatic = false;
}
else {
// It's a static factory method on the bean class.
factoryClass = mbd.getBeanClass();
}
Method factoryMethodToUse = (Method) mbd.resolvedConstructorOrFactoryMethod;
Object[] argsToUse = null;
if (factoryMethodToUse != null) {
// Found a cached factory method...
if (explicitArgs != null) {
argsToUse = explicitArgs;
}
else {
argsToUse = mbd.resolvedConstructorArguments;
if (argsToUse == null) {
Object[] argsToResolve = mbd.preparedConstructorArguments;
BeanDefinitionValueResolver valueResolver =
new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, bw);
argsToUse = new Object[argsToResolve.length];
for (int i = 0; i < argsToResolve.length; i++) {
Object argValue = argsToResolve[i];
if (argValue instanceof BeanMetadataElement) {
String argName = "factory method argument with index " + i;
argsToUse[i] = valueResolver.resolveValueIfNecessary(argName, argValue);
}
else {
argsToUse[i] = argValue;
}
}
}
}
}
else {
// Need to determine the factory method...
// Try all methods with this name to see if they match the given arguments.
Method[] candidates = ReflectionUtils.getAllDeclaredMethods(factoryClass);
int minTypeDiffWeight = Integer.MAX_VALUE;
ConstructorArgumentValues resolvedValues = null;
int minNrOfArgs = 0;
if (explicitArgs != null) {
minNrOfArgs = explicitArgs.length;
}
else {
// We don't have arguments passed in programmatically, so we need to resolve the
// arguments specified in the constructor arguments held in the bean definition.
ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
resolvedValues = new ConstructorArgumentValues();
minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
}
for (int i = 0; i < candidates.length; i++) {
Method factoryMethod = candidates[i];
Class[] paramTypes = factoryMethod.getParameterTypes();
if (Modifier.isStatic(factoryMethod.getModifiers()) == isStatic &&
factoryMethod.getName().equals(mbd.getFactoryMethodName()) &&
paramTypes.length >= minNrOfArgs) {
ArgumentsHolder args = null;
if (resolvedValues != null) {
// Resolved contructor arguments: type conversion and/or autowiring necessary.
try {
args = createArgumentArray(
beanName, mbd, resolvedValues, bw, paramTypes, factoryMethod);
}
catch (UnsatisfiedDependencyException ex) {
if (this.beanFactory.logger.isTraceEnabled()) {
this.beanFactory.logger.trace("Ignoring factory method [" + factoryMethod +
"] of bean '" + beanName + "': " + ex);
}
if (i == candidates.length - 1 && factoryMethodToUse == null) {
throw ex;
}
else {
// Swallow and try next overloaded factory method.
continue;
}
}
}
else {
// Explicit arguments given -> arguments length must match exactly.
if (paramTypes.length != explicitArgs.length) {
continue;
}
args = new ArgumentsHolder(explicitArgs);
}
int typeDiffWeight = args.getTypeDifferenceWeight(paramTypes);
// Choose this constructor if it represents the closest match.
if (typeDiffWeight < minTypeDiffWeight) {
factoryMethodToUse = factoryMethod;
argsToUse = args.arguments;
minTypeDiffWeight = typeDiffWeight;
}
}
}
if (factoryMethodToUse == null) {
throw new BeanDefinitionStoreException("No matching factory method found: " +
(mbd.getFactoryBeanName() != null ?
"factory bean '" + mbd.getFactoryBeanName() + "'; " : "") +
"factory method '" + mbd.getFactoryMethodName() + "'");
}
mbd.resolvedConstructorOrFactoryMethod = factoryMethodToUse;
}
Object beanInstance = this.instantiationStrategy.instantiate(
mbd, beanName, this.beanFactory, factoryBean, factoryMethodToUse, argsToUse);
if (beanInstance == null) {
return null;
}
bw.setWrappedInstance(beanInstance);
return bw;
}
/**
* Resolve the constructor arguments for this bean into the resolvedValues object.
* This may involve looking up other beans.
* This method is also used for handling invocations of static factory methods.
*/
private int resolveConstructorArguments(
String beanName, RootBeanDefinition mbd, BeanWrapper bw,
ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) {
BeanDefinitionValueResolver valueResolver =
new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, bw);
int minNrOfArgs = cargs.getArgumentCount();
for (Iterator it = cargs.getIndexedArgumentValues().entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
int index = ((Integer) entry.getKey()).intValue();
if (index < 0) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Invalid constructor argument index: " + index);
}
if (index > minNrOfArgs) {
minNrOfArgs = index + 1;
}
ConstructorArgumentValues.ValueHolder valueHolder =
(ConstructorArgumentValues.ValueHolder) entry.getValue();
if (valueHolder.isConverted()) {
resolvedValues.addIndexedArgumentValue(index, valueHolder);
}
else {
String argName = "constructor argument with index " + index;
Object resolvedValue = valueResolver.resolveValueIfNecessary(argName, valueHolder.getValue());
ConstructorArgumentValues.ValueHolder resolvedValueHolder =
new ConstructorArgumentValues.ValueHolder(resolvedValue, valueHolder.getType());
resolvedValueHolder.setSource(valueHolder);
resolvedValues.addIndexedArgumentValue(index, resolvedValueHolder);
}
}
for (Iterator it = cargs.getGenericArgumentValues().iterator(); it.hasNext();) {
ConstructorArgumentValues.ValueHolder valueHolder =
(ConstructorArgumentValues.ValueHolder) it.next();
if (valueHolder.isConverted()) {
resolvedValues.addGenericArgumentValue(valueHolder);
}
else {
String argName = "constructor argument";
Object resolvedValue = valueResolver.resolveValueIfNecessary(argName, valueHolder.getValue());
ConstructorArgumentValues.ValueHolder resolvedValueHolder =
new ConstructorArgumentValues.ValueHolder(resolvedValue, valueHolder.getType());
resolvedValueHolder.setSource(valueHolder);
resolvedValues.addGenericArgumentValue(resolvedValueHolder);
}
}
return minNrOfArgs;
}
/**
* Create an array of arguments to invoke a constructor or factory method,
* given the resolved constructor argument values.
*/
private ArgumentsHolder createArgumentArray(
String beanName, RootBeanDefinition mbd, ConstructorArgumentValues resolvedValues,
BeanWrapper bw, Class[] paramTypes, Object methodOrCtor)
throws UnsatisfiedDependencyException {
String methodType = (methodOrCtor instanceof Constructor ? "constructor" : "factory method");
ArgumentsHolder args = new ArgumentsHolder(paramTypes.length);
Set usedValueHolders = new HashSet(paramTypes.length);
boolean resolveNecessary = false;
for (int index = 0; index < paramTypes.length; index++) {
// Try to find matching constructor argument value, either indexed or generic.
ConstructorArgumentValues.ValueHolder valueHolder =
resolvedValues.getArgumentValue(index, paramTypes[index], usedValueHolders);
// If we couldn't find a direct match and are not supposed to autowire,
// let's try the next generic, untyped argument value as fallback:
// it could match after type conversion (for example, String -> int).
if (valueHolder == null &&
mbd.getResolvedAutowireMode() != RootBeanDefinition.AUTOWIRE_CONSTRUCTOR) {
valueHolder = resolvedValues.getGenericArgumentValue(null, usedValueHolders);
}
if (valueHolder != null) {
// We found a potential match - let's give it a try.
// Do not consider the same value definition multiple times!
usedValueHolders.add(valueHolder);
args.rawArguments[index] = valueHolder.getValue();
if (valueHolder.isConverted()) {
Object convertedValue = valueHolder.getConvertedValue();
args.arguments[index] = convertedValue;
args.preparedArguments[index] = convertedValue;
}
else {
try {
Object originalValue = valueHolder.getValue();
Object convertedValue = bw.convertIfNecessary(originalValue, paramTypes[index],
MethodParameter.forMethodOrConstructor(methodOrCtor, index));
args.arguments[index] = convertedValue;
ConstructorArgumentValues.ValueHolder sourceHolder =
(ConstructorArgumentValues.ValueHolder) valueHolder.getSource();
Object sourceValue = sourceHolder.getValue();
if (originalValue == sourceValue || sourceValue instanceof TypedStringValue) {
// Either a converted value or still the original one: store converted value.
sourceHolder.setConvertedValue(convertedValue);
args.preparedArguments[index] = convertedValue;
}
else {
resolveNecessary = true;
args.preparedArguments[index] = sourceValue;
}
}
catch (TypeMismatchException ex) {
throw new UnsatisfiedDependencyException(
mbd.getResourceDescription(), beanName, index, paramTypes[index],
"Could not convert " + methodType + " argument value of type [" +
ObjectUtils.nullSafeClassName(valueHolder.getValue()) +
"] to required type [" + paramTypes[index].getName() + "]: " + ex.getMessage());
}
}
}
else {
// No explicit match found: we're either supposed to autowire or
// have to fail creating an argument array for the given constructor.
if (mbd.getResolvedAutowireMode() != RootBeanDefinition.AUTOWIRE_CONSTRUCTOR) {
throw new UnsatisfiedDependencyException(
mbd.getResourceDescription(), beanName, index, paramTypes[index],
"Ambiguous " + methodType + " argument types - " +
"did you specify the correct bean references as " + methodType + " arguments?");
}
Map matchingBeans = findAutowireCandidates(beanName, paramTypes[index]);
if (matchingBeans.size() != 1) {
throw new UnsatisfiedDependencyException(
mbd.getResourceDescription(), beanName, index, paramTypes[index],
"There are " + matchingBeans.size() + " beans of type [" + paramTypes[index].getName() +
"] available for autowiring: " + matchingBeans.keySet() +
". There should have been exactly 1 to be able to autowire " +
methodType + " of bean '" + beanName + "'.");
}
Map.Entry entry = (Map.Entry) matchingBeans.entrySet().iterator().next();
String autowiredBeanName = (String) entry.getKey();
Object autowiredBean = entry.getValue();
args.rawArguments[index] = autowiredBean;
args.arguments[index] = autowiredBean;
if (mbd.isSingleton()) {
this.beanFactory.registerDependentBean(autowiredBeanName, beanName);
}
if (this.beanFactory.logger.isDebugEnabled()) {
this.beanFactory.logger.debug("Autowiring by type from bean name '" + beanName +
"' via " + methodType + " to bean named '" + autowiredBeanName + "'");
}
}
}
if (resolveNecessary) {
mbd.preparedConstructorArguments = args.preparedArguments;
}
else {
mbd.resolvedConstructorArguments = args.arguments;
}
return args;
}
/**
* Find bean instances that match the required type.
* Called during autowiring for the specified bean.
*
If a subclass cannot obtain information about bean names by type,
* a corresponding exception should be thrown.
* @param beanName the name of the bean that is about to be wired
* @param requiredType the type of the autowired constructor argument
* @return a Map of candidate names and candidate instances that match
* the required type (never null)
* @throws BeansException in case of errors
* @see #autowireConstructor
*/
protected abstract Map findAutowireCandidates(String beanName, Class requiredType) throws BeansException;
/**
* Private inner class for holding argument combinations.
*/
private static class ArgumentsHolder {
public Object rawArguments[];
public Object arguments[];
public Object preparedArguments[];
public ArgumentsHolder(int size) {
this.rawArguments = new Object[size];
this.arguments = new Object[size];
this.preparedArguments = new Object[size];
}
public ArgumentsHolder(Object[] args) {
this.rawArguments = args;
this.arguments = args;
this.preparedArguments = args;
}
public int getTypeDifferenceWeight(Class[] paramTypes) {
// If valid arguments found, determine type difference weight.
// Try type difference weight on both the converted arguments and
// the raw arguments. If the raw weight is better, use it.
// Decrease raw weight by 1024 to prefer it over equal converted weight.
int typeDiffWeight = AutowireUtils.getTypeDifferenceWeight(paramTypes, this.arguments);
int rawTypeDiffWeight = AutowireUtils.getTypeDifferenceWeight(paramTypes, this.rawArguments) - 1024;
return (rawTypeDiffWeight < typeDiffWeight ? rawTypeDiffWeight : typeDiffWeight);
}
}
}