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();
- }
- }
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