bean的创建（五）第二部分 寻找bean的工厂方法实例化

instanceWrapper = createBeanInstance(beanName, mbd, args);

AbstractAutowireCapableBeanFactory.createBeanInstance

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
        // Make sure bean class is actually resolved at this point.确保实际已经解析了beanClass，如果是表达式，会进行表达式的运算得到className
        Class<?> beanClass = resolveBeanClass(mbd, beanName);

        if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                    "Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
        }

//如果存在工厂方法，那么说明需要通过静态工厂的方式获取bean
        if (mbd.getFactoryMethodName() != null)  {
            return instantiateUsingFactoryMethod(beanName, mbd, args);
        }

        // Shortcut when re-creating the same bean...
        boolean resolved = false;
        boolean autowireNecessary = false;
        if (args == null) {
            synchronized (mbd.constructorArgumentLock) {
                if (mbd.resolvedConstructorOrFactoryMethod != null) {
                    resolved = true;
                    autowireNecessary = mbd.constructorArgumentsResolved;
                }
            }
        }
        if (resolved) {
            if (autowireNecessary) {
                return autowireConstructor(beanName, mbd, null, null);
            }
            else {
                return instantiateBean(beanName, mbd);
            }
        }

        // Need to determine the constructor...
        Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
        if (ctors != null ||
                mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
                mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
            return autowireConstructor(beanName, mbd, ctors, args);
        }

        // No special handling: simply use no-arg constructor.
        return instantiateBean(beanName, mbd);
    }

AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod

protected BeanWrapper instantiateUsingFactoryMethod(
            String beanName, RootBeanDefinition mbd, Object[] explicitArgs) {

        return new ConstructorResolver(this).instantiateUsingFactoryMethod(beanName, mbd, explicitArgs);
    }

ConstructorResolver.instantiateUsingFactoryMethod

public BeanWrapper instantiateUsingFactoryMethod(
            final String beanName, final RootBeanDefinition mbd, final Object[] explicitArgs) {

        BeanWrapperImpl bw = new BeanWrapperImpl();
//初始化这个bean包装器，内部给这个包装器设置了类型转化器和自定的转化器
        this.beanFactory.initBeanWrapper(bw);

        Object factoryBean;
        Class<?> factoryClass;
        boolean isStatic;

        String factoryBeanName = mbd.getFactoryBeanName();
//如果存在factoryBeanName   比如<bean id="helloWorld" factory-bean="helloWorld" factory-method="getSayHi"></bean>
        if (factoryBeanName != null) {
//如果工厂bean的名字和自己相同，那么直接抛错
            if (factoryBeanName.equals(beanName)) {
                throw new BeanDefinitionStoreException(mbd.getResourceDescription(), beanName,
                        "factory-bean reference points back to the same bean definition");
            }
//使用getBean获取到依赖的那个工厂bean
            factoryBean = this.beanFactory.getBean(factoryBeanName);
            if (factoryBean == null) {
                throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "factory-bean '" + factoryBeanName + "' (or a BeanPostProcessor involved) returned null");
            }
            if (mbd.isSingleton() && this.beanFactory.containsSingleton(beanName)) {
                throw new IllegalStateException("About-to-be-created singleton instance implicitly appeared " +
                        "through the creation of the factory bean that its bean definition points to");
            }
            factoryClass = factoryBean.getClass();
            isStatic = false;
        }
        else {
            // It's a static factory method on the bean class.
            if (!mbd.hasBeanClass()) {
                throw new BeanDefinitionStoreException(mbd.getResourceDescription(), beanName,
                        "bean definition declares neither a bean class nor a factory-bean reference");
            }
            factoryBean = null;
            factoryClass = mbd.getBeanClass();
            isStatic = true;
        }

        Method factoryMethodToUse = null;
        ArgumentsHolder argsHolderToUse = null;
        Object[] argsToUse = null;
//如果用户已经指定了构造参数，那么直接使用用户指定的构造参数
        if (explicitArgs != null) {
            argsToUse = explicitArgs;
        }
        else {
            Object[] argsToResolve = null;
            synchronized (mbd.constructorArgumentLock) {
//获取已经解析后的构造器或者工厂方法
                factoryMethodToUse = (Method) mbd.resolvedConstructorOrFactoryMethod;
                //如果已经解析好了，那么尝试从缓存中获取参数
if (factoryMethodToUse != null && mbd.constructorArgumentsResolved) {
                    // Found a cached factory method...
                    argsToUse = mbd.resolvedConstructorArguments;
//如果缓存中没有，那么就从准备的（也就是解析配置文件时，BeanDefinition存储的参数）构造参数中获取，这个时候的参数还是原始（配置文件中）的，没有进行类型转换的参数
                    if (argsToUse == null) {
                        argsToResolve = mbd.preparedConstructorArguments;
                    }
                }
            }
            if (argsToResolve != null) {
//解析准备的配置参数
                argsToUse = resolvePreparedArguments(beanName, mbd, bw, factoryMethodToUse, argsToResolve);
            }
        }
//如果没有缓存，那么说明这是第一次访问，需要从头开始解析
        if (factoryMethodToUse == null || argsToUse == null) {
            // Need to determine the factory method...
            // Try all methods with this name to see if they match the given arguments.
//判断是否被cglib代理过的，如果代理过，那么就返回其父类
            factoryClass = ClassUtils.getUserClass(factoryClass);
//获取这个类定义的所有方法
            Method[] rawCandidates = getCandidateMethods(factoryClass, mbd);
            List<Method> candidateSet = new ArrayList<Method>();
            for (Method candidate : rawCandidates) {
//获取工厂方法
                if (Modifier.isStatic(candidate.getModifiers()) == isStatic && mbd.isFactoryMethod(candidate)) {
                    candidateSet.add(candidate);
                }
            }
            Method[] candidates = candidateSet.toArray(new Method[candidateSet.size()]);
            //给重载的方法排序，public修饰和参数长的排在前面
AutowireUtils.sortFactoryMethods(candidates);

            ConstructorArgumentValues resolvedValues = null;
            boolean autowiring = (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
            int minTypeDiffWeight = Integer.MAX_VALUE;
            Set<Method> ambiguousFactoryMethods = null;

            int minNrOfArgs;
            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.
//如果用户没有传递参数进来，那么我们需要获取配置的参数
                ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
                resolvedValues = new ConstructorArgumentValues();
//解析构造参数，通过BeanDefinitionValueResolver进行解析，解析好后放置到resolvedValues中，这里主要是将beanref的解析好和以下表达式什么的，没有进行参数类型的转换。
                minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
            }

            List<Exception> causes = null;

            for (int i = 0; i < candidates.length; i++) {
                Method candidate = candidates[i];
//获取当前方法的参数类型
                Class<?>[] paramTypes = candidate.getParameterTypes();

                if (paramTypes.length >= minNrOfArgs) {
                    ArgumentsHolder argsHolder;

                    if (resolvedValues != null) {
                        // Resolved constructor arguments: type conversion and/or autowiring necessary.
                        try {
//获取这些方法的参数名
                            String[] paramNames = null;
                            ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
                            if (pnd != null) {
                                paramNames = pnd.getParameterNames(candidate);
                            }
//由于实际方法的参数和配置的参数之间存在位置，类型需要转化的问题，所以需要尝试换成符合对应方法的参数
                            argsHolder = createArgumentArray(
                                    beanName, mbd, resolvedValues, bw, paramTypes, paramNames, candidate, autowiring);
                        }
                        catch (UnsatisfiedDependencyException ex) {
                            if (this.beanFactory.logger.isTraceEnabled()) {
                                this.beanFactory.logger.trace("Ignoring factory method [" + candidate +
                                        "] of bean '" + beanName + "': " + ex);
                            }
                            if (i == candidates.length - 1 && argsHolderToUse == null) {
                                if (causes != null) {
                                    for (Exception cause : causes) {
                                        this.beanFactory.onSuppressedException(cause);
                                    }
                                }
                                throw ex;
                            }
                            else {
                                // Swallow and try next overloaded factory method.
                                if (causes == null) {
                                    causes = new LinkedList<Exception>();
                                }
                                causes.add(ex);
                                continue;
                            }
                        }
                    }

                    else {
//如果配置里面没有参数，那么就使用用户设置的参数
                        // Explicit arguments given -> arguments length must match exactly.
                        if (paramTypes.length != explicitArgs.length) {
                            continue;
                        }
                        argsHolder = new ArgumentsHolder(explicitArgs);
                    }

                    int typeDiffWeight = (mbd.isLenientConstructorResolution() ?
                            argsHolder.getTypeDifferenceWeight(paramTypes) : argsHolder.getAssignabilityWeight(paramTypes));
                    // Choose this factory method if it represents the closest match.
                    if (typeDiffWeight < minTypeDiffWeight) {
                        factoryMethodToUse = candidate;
                        argsHolderToUse = argsHolder;
                        argsToUse = argsHolder.arguments;
                        minTypeDiffWeight = typeDiffWeight;
                        ambiguousFactoryMethods = null;
                    }
                    // Find out about ambiguity: In case of the same type difference weight
                    // for methods with the same number of parameters, collect such candidates
                    // and eventually raise an ambiguity exception.
                    // However, only perform that check in non-lenient constructor resolution mode,
                    // and explicitly ignore overridden methods (with the same parameter signature).
                    else if (factoryMethodToUse != null && typeDiffWeight == minTypeDiffWeight &&
                            !mbd.isLenientConstructorResolution() &&
                            paramTypes.length == factoryMethodToUse.getParameterTypes().length &&
                            !Arrays.equals(paramTypes, factoryMethodToUse.getParameterTypes())) {
                        if (ambiguousFactoryMethods == null) {
                            ambiguousFactoryMethods = new LinkedHashSet<Method>();
                            ambiguousFactoryMethods.add(factoryMethodToUse);
                        }
                        ambiguousFactoryMethods.add(candidate);
                    }
                }
            }

            if (factoryMethodToUse == null) {
                List<String> argTypes = new ArrayList<String>(minNrOfArgs);
                if (explicitArgs != null) {
                    for (Object arg : explicitArgs) {
                        argTypes.add(arg != null ? arg.getClass().getSimpleName() : "null");
                    }
                }
                else {
                    Set<ValueHolder> valueHolders = new LinkedHashSet<ValueHolder>(resolvedValues.getArgumentCount());
                    valueHolders.addAll(resolvedValues.getIndexedArgumentValues().values());
                    valueHolders.addAll(resolvedValues.getGenericArgumentValues());
                    for (ValueHolder value : valueHolders) {
                        String argType = (value.getType() != null ? ClassUtils.getShortName(value.getType()) :
                                (value.getValue() != null ? value.getValue().getClass().getSimpleName() : "null"));
                        argTypes.add(argType);
                    }
                }
                String argDesc = StringUtils.collectionToCommaDelimitedString(argTypes);
                throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "No matching factory method found: " +
                        (mbd.getFactoryBeanName() != null ?
                            "factory bean '" + mbd.getFactoryBeanName() + "'; " : "") +
                        "factory method '" + mbd.getFactoryMethodName() + "(" + argDesc + ")'. " +
                        "Check that a method with the specified name " +
                        (minNrOfArgs > 0 ? "and arguments " : "") +
                        "exists and that it is " +
                        (isStatic ? "static" : "non-static") + ".");
            }
            else if (void.class == factoryMethodToUse.getReturnType()) {
                throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "Invalid factory method '" + mbd.getFactoryMethodName() +
                        "': needs to have a non-void return type!");
            }
            else if (ambiguousFactoryMethods != null) {
                throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "Ambiguous factory method matches found in bean '" + beanName + "' " +
                        "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): " +
                        ambiguousFactoryMethods);
            }

            if (explicitArgs == null && argsHolderToUse != null) {
                argsHolderToUse.storeCache(mbd, factoryMethodToUse);
            }
        }

        try {
            Object beanInstance;

            if (System.getSecurityManager() != null) {
                final Object fb = factoryBean;
                final Method factoryMethod = factoryMethodToUse;
                final Object[] args = argsToUse;
                beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                    @Override
                    public Object run() {
                        return beanFactory.getInstantiationStrategy().instantiate(
                                mbd, beanName, beanFactory, fb, factoryMethod, args);
                    }
                }, beanFactory.getAccessControlContext());
            }
            else {
                beanInstance = this.beanFactory.getInstantiationStrategy().instantiate(
                        mbd, beanName, this.beanFactory, factoryBean, factoryMethodToUse, argsToUse);
            }

            if (beanInstance == null) {
                return null;
            }
            bw.setWrappedInstance(beanInstance);
            return bw;
        }
        catch (Throwable ex) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                    "Bean instantiation via factory method failed", ex);
        }
    }

ConstructorResolver.resolvePreparedArguments

private Object[] resolvePreparedArguments(
            String beanName, RootBeanDefinition mbd, BeanWrapper bw, Member methodOrCtor, Object[] argsToResolve) {
//获取构造方法或者工厂方法的参数类型
        Class<?>[] paramTypes = (methodOrCtor instanceof Method ?
                ((Method) methodOrCtor).getParameterTypes() : ((Constructor<?>) methodOrCtor).getParameterTypes());
//获取自定义的类型转化器，如果没有就是用bean包装器·，这个包装器在上面已经注册了默认的转化器和自定的转化器。
        TypeConverter converter = (this.beanFactory.getCustomTypeConverter() != null ?
                this.beanFactory.getCustomTypeConverter() : bw);、
//构建BeanDefinition值的解析器，用于转化value
        BeanDefinitionValueResolver valueResolver =
                new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, converter);
        Object[] resolvedArgs = new Object[argsToResolve.length];
        for (int argIndex = 0; argIndex < argsToResolve.length; argIndex++) {
//获取当前下标参数值
            Object argValue = argsToResolve[argIndex];
//包装成方法参数对象，持有对应的方法，参数的位置
            MethodParameter methodParam = MethodParameter.forMethodOrConstructor(methodOrCtor, argIndex);
//解析这个方法所在的类，参数的类型
            GenericTypeResolver.resolveParameterType(methodParam, methodOrCtor.getDeclaringClass());
//参数是AutowiredArgumentMarker只只是个标记类，标记为自动装配的参数，这里会解析@Value注解的参数，还有会根据字段的类型去包装成某些延迟获取数据的对象，比如DependencyObjectFactory（依赖工厂bean，这种类型字段可以通过getObject获取数据），这里是方法参数的获取所以不用去管field的。最后内部会通过DefaultListableBeanFactory.doResolveDependency方法根据参数类型去获取bean
            if (argValue instanceof AutowiredArgumentMarker) {
                argValue = resolveAutowiredArgument(methodParam, beanName, null, converter);
            }
//这种类型数据一般是在解析xml配置的时候生成的，比如xml中的ref指定的bean会包装成RuntimeBeanReference，当spring看到这种类型的时候就知道，我要去BeanFactory中寻找叫这个名字的bean
            else if (argValue instanceof BeanMetadataElement) {
//使用上面new出来的BeanDefinitionValueResolver进行解析
                argValue = valueResolver.resolveValueIfNecessary("constructor argument", argValue);
            }
//如果只是普通的字符串，那么经过表达式解析器之后直接返回
            else if (argValue instanceof String) {
                argValue = this.beanFactory.evaluateBeanDefinitionString((String) argValue, mbd);
            }
            Class<?> paramType = paramTypes[argIndex];
            try {
//将得到的数据进行类型转换
                resolvedArgs[argIndex] = converter.convertIfNecessary(argValue, paramType, methodParam);
            }
            catch (TypeMismatchException ex) {
                String methodType = (methodOrCtor instanceof Constructor ? "constructor" : "factory method");
                throw new UnsatisfiedDependencyException(
                        mbd.getResourceDescription(), beanName, argIndex, paramType,
                        "Could not convert " + methodType + " argument value of type [" +
                        ObjectUtils.nullSafeClassName(argValue) +
                        "] to required type [" + paramType.getName() + "]: " + ex.getMessage());
            }
        }
//返回解析好的参数
        return resolvedArgs;
    }

DefaultListableBeanFactory.resolveDependency

public Object resolveDependency(DependencyDescriptor descriptor, String beanName,
            Set<String> autowiredBeanNames, TypeConverter typeConverter) throws BeansException {
//获取参数名
        descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
//如果对应的字段或参数类型是Option类型的，那么创建Option，对应的值用get获取，其实内部的值依然是调用 doResolveDependency获取的
        if (descriptor.getDependencyType().equals(javaUtilOptionalClass)) {
            return new OptionalDependencyFactory().createOptionalDependency(descriptor, beanName);
        }
//如果这个字段或参数是对象工厂，那么返回依赖工厂，对应的值用个getObject获取
        else if (ObjectFactory.class == descriptor.getDependencyType()) {
            return new DependencyObjectFactory(descriptor, beanName);
        }
//如果这个字段或参数类型为javax.inject.Provider，那么返回DependencyProvider，通过get获取值
        else if (javaxInjectProviderClass == descriptor.getDependencyType()) {
            return new DependencyProviderFactory().createDependencyProvider(descriptor, beanName);
        }
        else {
            Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(descriptor, beanName);
            if (result == null) {
//解析依赖
                result = doResolveDependency(descriptor, beanName, autowiredBeanNames, typeConverter);
            }
            return result;
        }
    }

DefaultListableBeanFactory.doResolveDependency

public Object doResolveDependency(DependencyDescriptor descriptor, String beanName,
            Set<String> autowiredBeanNames, TypeConverter typeConverter) throws BeansException {
//获取字段或方法参数的类型
        Class<?> type = descriptor.getDependencyType();
//获取@Value注解的值
        Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
        if (value != null) {
            if (value instanceof String) {
//如果从@Value中获取到了数据，那么就解析${}占位符。
                String strVal = resolveEmbeddedValue((String) value);
                BeanDefinition bd = (beanName != null && containsBean(beanName) ? getMergedBeanDefinition(beanName) : null);
//动态语言解析
                value = evaluateBeanDefinitionString(strVal, bd);
            }
            TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
//转换类型后返回
            return (descriptor.getField() != null ?
                    converter.convertIfNecessary(value, type, descriptor.getField()) :
                    converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
        }
//如果是数组，那么获取到对应数组类型，然后到BeanFactory中获取到对应的类型
        if (type.isArray()) {
            Class<?> componentType = type.getComponentType();
            DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
            targetDesc.increaseNestingLevel();
//获取符合类型的候选的对象
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, componentType, targetDesc);
            if (matchingBeans.isEmpty()) {
//如果这个字段或参数是必须的，又没有值，那么只好报错了
                if (descriptor.isRequired()) {
                    raiseNoSuchBeanDefinitionException(componentType, "array of " + componentType.getName(), descriptor);
                }
                return null;
            }
            if (autowiredBeanNames != null) {
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
//转换类型
            Object result = converter.convertIfNecessary(matchingBeans.values(), type);
            if (getDependencyComparator() != null && result instanceof Object[]) {
                Arrays.sort((Object[]) result, adaptDependencyComparator(matchingBeans));
            }
            return result;
        }
//处理集合类型
        else if (Collection.class.isAssignableFrom(type) && type.isInterface()) {
            Class<?> elementType = descriptor.getCollectionType();
            if (elementType == null) {
                if (descriptor.isRequired()) {
                    throw new FatalBeanException("No element type declared for collection [" + type.getName() + "]");
                }
                return null;
            }
            DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
            targetDesc.increaseNestingLevel();
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, elementType, targetDesc);
            if (matchingBeans.isEmpty()) {
                if (descriptor.isRequired()) {
                    raiseNoSuchBeanDefinitionException(elementType, "collection of " + elementType.getName(), descriptor);
                }
                return null;
            }
            if (autowiredBeanNames != null) {
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
            Object result = converter.convertIfNecessary(matchingBeans.values(), type);
            if (getDependencyComparator() != null && result instanceof List) {
                Collections.sort((List<?>) result, adaptDependencyComparator(matchingBeans));
            }
            return result;
        }
、        //处理Map类型
        else if (Map.class.isAssignableFrom(type) && type.isInterface()) {
            Class<?> keyType = descriptor.getMapKeyType();
            if (String.class != keyType) {
                if (descriptor.isRequired()) {
                    throw new FatalBeanException("Key type [" + keyType + "] of map [" + type.getName() +
                            "] must be [java.lang.String]");
                }
                return null;
            }
            Class<?> valueType = descriptor.getMapValueType();
            if (valueType == null) {
                if (descriptor.isRequired()) {
                    throw new FatalBeanException("No value type declared for map [" + type.getName() + "]");
                }
                return null;
            }
            DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
            targetDesc.increaseNestingLevel();
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, valueType, targetDesc);
            if (matchingBeans.isEmpty()) {
                if (descriptor.isRequired()) {
                    raiseNoSuchBeanDefinitionException(valueType, "map with value type " + valueType.getName(), descriptor);
                }
                return null;
            }
            if (autowiredBeanNames != null) {
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            return matchingBeans;
        }
        else {
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
            if (matchingBeans.isEmpty()) {
                if (descriptor.isRequired()) {
                    raiseNoSuchBeanDefinitionException(type, "", descriptor);
                }
                return null;
            }
//如果匹配的bean大于一个，那么就查看是否配置了primary属性，如果有就使用primary的那个，没有就报错。
            if (matchingBeans.size() > 1) {
                String primaryBeanName = determineAutowireCandidate(matchingBeans, descriptor);
                if (primaryBeanName == null) {
                    throw new NoUniqueBeanDefinitionException(type, matchingBeans.keySet());
                }
                if (autowiredBeanNames != null) {
                    autowiredBeanNames.add(primaryBeanName);
                }
                return matchingBeans.get(primaryBeanName);
            }
            // We have exactly one match.
            Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
            if (autowiredBeanNames != null) {
                autowiredBeanNames.add(entry.getKey());
            }
            return entry.getValue();
        }
    }