spring源码之IOC的依赖注入

//AbstractApplicationContext类的方法
//创建并返回DefaultListableBeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    refreshBeanFactory();
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (logger.isDebugEnabled()) {
        logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
    }
    return beanFactory;
}

//AbstractRefreshableApplicationContext类的方法
protected final void refreshBeanFactory() throws BeansException {
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        beanFactory.setSerializationId(getId());
        customizeBeanFactory(beanFactory);
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

//AbstractXmlApplicationContext类的方法
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
    // Create a new XmlBeanDefinitionReader for the given BeanFactory.
    XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

    // Configure the bean definition reader with this context‘s
    // resource loading environment.
    beanDefinitionReader.setEnvironment(this.getEnvironment());
    beanDefinitionReader.setResourceLoader(this);
    beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

    // Allow a subclass to provide custom initialization of the reader,
    // then proceed with actually loading the bean definitions.
    initBeanDefinitionReader(beanDefinitionReader);
    loadBeanDefinitions(beanDefinitionReader);
}

//AbstractXmlApplicationContext类的方法
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
    Resource[] configResources = getConfigResources();
    if (configResources != null) {
        reader.loadBeanDefinitions(configResources);
    }
    String[] configLocations = getConfigLocations();
    if (configLocations != null) {
        reader.loadBeanDefinitions(configLocations);
    }
}

//AbstractBeanDefinitionReader类的方法
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
    Assert.notNull(locations, "Location array must not be null");
    int counter = 0;
    for (String location : locations) {
        counter += loadBeanDefinitions(location);
    }
    return counter;
}

//AbstractBeanDefinitonReader类的方法
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
    return loadBeanDefinitions(location, null);
}

//AbstractBeanDefinitionReader类的方法
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
    ResourceLoader resourceLoader = getResourceLoader();
    if (resourceLoader == null) {
        throw new BeanDefinitionStoreException(
                "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
    }

    if (resourceLoader instanceof ResourcePatternResolver) {
        // Resource pattern matching available.
        try {
            Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
            int loadCount = loadBeanDefinitions(resources);
            if (actualResources != null) {
                for (Resource resource : resources) {
                    actualResources.add(resource);
                }
            }
            if (logger.isDebugEnabled()) {
                logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
            }
            return loadCount;
        }
        catch (IOException ex) {
            throw new BeanDefinitionStoreException(
                    "Could not resolve bean definition resource pattern [" + location + "]", ex);
        }
    }
    else {
        // Can only load single resources by absolute URL.
        Resource resource = resourceLoader.getResource(location);
        int loadCount = loadBeanDefinitions(resource);
        if (actualResources != null) {
            actualResources.add(resource);
        }
        if (logger.isDebugEnabled()) {
            logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
        }
        return loadCount;
    }
}

//AbstractBeanDefinitionReader类的方法
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
    Assert.notNull(resources, "Resource array must not be null");
    int counter = 0;
    for (Resource resource : resources) {
        counter += loadBeanDefinitions(resource);
    }
    return counter;
}

//XmlBeanDefinitionReader类的方法
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
    return loadBeanDefinitions(new EncodedResource(resource));
}

//XmlBeanDefintionReader类的方法
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
    Assert.notNull(encodedResource, "EncodedResource must not be null");
    if (logger.isInfoEnabled()) {
        logger.info("Loading XML bean definitions from " + encodedResource.getResource());
    }

    //使用ThreadLocal，实现随用随取
    Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
    if (currentResources == null) {
        currentResources = new HashSet<EncodedResource>(4);
        this.resourcesCurrentlyBeingLoaded.set(currentResources);
    }
    //判断资源文件有没有重复载入
    if (!currentResources.add(encodedResource)) {
        throw new BeanDefinitionStoreException(
                "Detected cyclic loading of " + encodedResource + " - check your import definitions!");
    }
    try {
        InputStream inputStream = encodedResource.getResource().getInputStream();
        try {
            InputSource inputSource = new InputSource(inputStream);
            if (encodedResource.getEncoding() != null) {
                inputSource.setEncoding(encodedResource.getEncoding());
            }
            return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
        }
        finally {
            inputStream.close();
        }
    }
    catch (IOException ex) {
        throw new BeanDefinitionStoreException(
                "IOException parsing XML document from " + encodedResource.getResource(), ex);
    }
    finally {
        currentResources.remove(encodedResource);
        if (currentResources.isEmpty()) {
            this.resourcesCurrentlyBeingLoaded.remove();
        }
    }
}

//XmlBeanDefinitionReader类的方法
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
        throws BeanDefinitionStoreException {
    try {
        Document doc = doLoadDocument(inputSource, resource);
        return registerBeanDefinitions(doc, resource);
    }
    catch (BeanDefinitionStoreException ex) {
        throw ex;
    }
    catch (SAXParseException ex) {
        throw new XmlBeanDefinitionStoreException(resource.getDescription(),
                "Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
    }
    catch (SAXException ex) {
        throw new XmlBeanDefinitionStoreException(resource.getDescription(),
                "XML document from " + resource + " is invalid", ex);
    }
    catch (ParserConfigurationException ex) {
        throw new BeanDefinitionStoreException(resource.getDescription(),
                "Parser configuration exception parsing XML from " + resource, ex);
    }
    catch (IOException ex) {
        throw new BeanDefinitionStoreException(resource.getDescription(),
                "IOException parsing XML document from " + resource, ex);
    }
    catch (Throwable ex) {
        throw new BeanDefinitionStoreException(resource.getDescription(),
                "Unexpected exception parsing XML document from " + resource, ex);
    }
}

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
    BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
    int countBefore = getRegistry().getBeanDefinitionCount();
    documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
    return getRegistry().getBeanDefinitionCount() - countBefore;
}

//DefaultBeanDefintionDocumentReader类的方法
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
    this.readerContext = readerContext;
    logger.debug("Loading bean definitions");
    Element root = doc.getDocumentElement();
    doRegisterBeanDefinitions(root);
}

//DefaultBeanDefintionDocumentReader类的方法
protected void doRegisterBeanDefinitions(Element root) {
    BeanDefinitionParserDelegate parent = this.delegate;
    this.delegate = createDelegate(getReaderContext(), root, parent);

    if (this.delegate.isDefaultNamespace(root)) {
        String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
        if (StringUtils.hasText(profileSpec)) {
            String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
                    profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
            if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
                if (logger.isInfoEnabled()) {
                    logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
                            "] not matching: " + getReaderContext().getResource());
                }
                return;
            }
        }
    }

    preProcessXml(root);
    parseBeanDefinitions(root, this.delegate);
    postProcessXml(root);

    this.delegate = parent;
}

//DefaultBeanDefintioinDocumentReader类的方法
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
    if (delegate.isDefaultNamespace(root)) {
        NodeList nl = root.getChildNodes();
        for (int i = 0; i < nl.getLength(); i++) {
            Node node = nl.item(i);
            if (node instanceof Element) {
                Element ele = (Element) node;
                if (delegate.isDefaultNamespace(ele)) {
                    parseDefaultElement(ele, delegate);
                }
                else {
                    delegate.parseCustomElement(ele);
                }
            }
        }
    }
    else {
        delegate.parseCustomElement(root);
    }
}

//DefaultBeanDefintionDocumentReader类的方法
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
    if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
        importBeanDefinitionResource(ele);
    }
    else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
        processAliasRegistration(ele);
    }
    else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
        processBeanDefinition(ele, delegate);
    }
    else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
        // recurse
        doRegisterBeanDefinitions(ele);
    }
}

//DefaultBeanDefintionDocumentReader类的方法
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
    BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
    if (bdHolder != null) {
        bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
        try {
            // Register the final decorated instance.
            BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
        }
        catch (BeanDefinitionStoreException ex) {
            getReaderContext().error("Failed to register bean definition with name ‘" +
                    bdHolder.getBeanName() + "‘", ele, ex);
        }
        // Send registration event.
        getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
    }
}

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
    return parseBeanDefinitionElement(ele, null);
}

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
    String id = ele.getAttribute(ID_ATTRIBUTE);
    String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);

    List<String> aliases = new ArrayList<String>();
    if (StringUtils.hasLength(nameAttr)) {
        String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
        aliases.addAll(Arrays.asList(nameArr));
    }

    String beanName = id;
    if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
        beanName = aliases.remove(0);
        if (logger.isDebugEnabled()) {
            logger.debug("No XML ‘id‘ specified - using ‘" + beanName +
                    "‘ as bean name and " + aliases + " as aliases");
        }
    }

    if (containingBean == null) {
        checkNameUniqueness(beanName, aliases, ele);
    }

    AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
    if (beanDefinition != null) {
        if (!StringUtils.hasText(beanName)) {
            try {
                if (containingBean != null) {
                    beanName = BeanDefinitionReaderUtils.generateBeanName(
                            beanDefinition, this.readerContext.getRegistry(), true);
                }
                else {
                    beanName = this.readerContext.generateBeanName(beanDefinition);
                    // Register an alias for the plain bean class name, if still possible,
                    // if the generator returned the class name plus a suffix.
                    // This is expected for Spring 1.2/2.0 backwards compatibility.
                    String beanClassName = beanDefinition.getBeanClassName();
                    if (beanClassName != null &&
                            beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
                            !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
                        aliases.add(beanClassName);
                    }
                }
                if (logger.isDebugEnabled()) {
                    logger.debug("Neither XML ‘id‘ nor ‘name‘ specified - " +
                            "using generated bean name [" + beanName + "]");
                }
            }
            catch (Exception ex) {
                error(ex.getMessage(), ele);
                return null;
            }
        }
        String[] aliasesArray = StringUtils.toStringArray(aliases);
        return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
    }

    return null;
}

public AbstractBeanDefinition parseBeanDefinitionElement(
        Element ele, String beanName, BeanDefinition containingBean) {

    this.parseState.push(new BeanEntry(beanName));

    String className = null;
    if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
        className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
    }

    try {
        String parent = null;
        if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
            parent = ele.getAttribute(PARENT_ATTRIBUTE);
        }
        AbstractBeanDefinition bd = createBeanDefinition(className, parent);

        parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
        bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));

        parseMetaElements(ele, bd);
        parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
        parseReplacedMethodSubElements(ele, bd.getMethodOverrides());

        parseConstructorArgElements(ele, bd);
        parsePropertyElements(ele, bd);
        parseQualifierElements(ele, bd);

        bd.setResource(this.readerContext.getResource());
        bd.setSource(extractSource(ele));

        return bd;
    }
    catch (ClassNotFoundException ex) {
        error("Bean class [" + className + "] not found", ele, ex);
    }
    catch (NoClassDefFoundError err) {
        error("Class that bean class [" + className + "] depends on not found", ele, err);
    }
    catch (Throwable ex) {
        error("Unexpected failure during bean definition parsing", ele, ex);
    }
    finally {
        this.parseState.pop();
    }

    return null;

}

public void parsePropertyElements(Element beanEle, BeanDefinition bd) {
    NodeList nl = beanEle.getChildNodes();
    for (int i = 0; i < nl.getLength(); i++) {
        Node node = nl.item(i);
        if (isCandidateElement(node) && nodeNameEquals(node, PROPERTY_ELEMENT)) {
            parsePropertyElement((Element) node, bd);
        }
    }
}

public void parsePropertyElement(Element ele, BeanDefinition bd) {
    String propertyName = ele.getAttribute(NAME_ATTRIBUTE);
    if (!StringUtils.hasLength(propertyName)) {
        error("Tag ‘property‘ must have a ‘name‘ attribute", ele);
        return;
    }
    this.parseState.push(new PropertyEntry(propertyName));
    try {
        if (bd.getPropertyValues().contains(propertyName)) {
            error("Multiple ‘property‘ definitions for property ‘" + propertyName + "‘", ele);
            return;
        }
        Object val = parsePropertyValue(ele, bd, propertyName);
        PropertyValue pv = new PropertyValue(propertyName, val);
        parseMetaElements(ele, pv);
        pv.setSource(extractSource(ele));
        bd.getPropertyValues().addPropertyValue(pv);
    }
    finally {
        this.parseState.pop();
    }
}

public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) {
    String elementName = (propertyName != null) ?
                    "<property> element for property ‘" + propertyName + "‘" :
                    "<constructor-arg> element";

    // Should only have one child element: ref, value, list, etc.
    NodeList nl = ele.getChildNodes();
    Element subElement = null;
    for (int i = 0; i < nl.getLength(); i++) {
        Node node = nl.item(i);
        if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT) &&
                !nodeNameEquals(node, META_ELEMENT)) {
            // Child element is what we‘re looking for.
            if (subElement != null) {
                error(elementName + " must not contain more than one sub-element", ele);
            }
            else {
                subElement = (Element) node;
            }
        }
    }

    boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE);
    boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE);
    if ((hasRefAttribute && hasValueAttribute) ||
            ((hasRefAttribute || hasValueAttribute) && subElement != null)) {
        error(elementName +
                " is only allowed to contain either ‘ref‘ attribute OR ‘value‘ attribute OR sub-element", ele);
    }

    if (hasRefAttribute) {
        String refName = ele.getAttribute(REF_ATTRIBUTE);
        if (!StringUtils.hasText(refName)) {
            error(elementName + " contains empty ‘ref‘ attribute", ele);
        }
        RuntimeBeanReference ref = new RuntimeBeanReference(refName);
        ref.setSource(extractSource(ele));
        return ref;
    }
    else if (hasValueAttribute) {
        TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));
        valueHolder.setSource(extractSource(ele));
        return valueHolder;
    }
    else if (subElement != null) {
        return parsePropertySubElement(subElement, bd);
    }
    else {
        // Neither child element nor "ref" or "value" attribute found.
        error(elementName + " must specify a ref or value", ele);
        return null;
    }
}

public Object parsePropertySubElement(Element ele, BeanDefinition bd) {
    return parsePropertySubElement(ele, bd, null);
}

public Object parsePropertySubElement(Element ele, BeanDefinition bd, String defaultValueType) {
    if (!isDefaultNamespace(ele)) {
        return parseNestedCustomElement(ele, bd);
    }
    else if (nodeNameEquals(ele, BEAN_ELEMENT)) {
        BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd);
        if (nestedBd != null) {
            nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd);
        }
        return nestedBd;
    }
    else if (nodeNameEquals(ele, REF_ELEMENT)) {
        // A generic reference to any name of any bean.
        String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE);
        boolean toParent = false;
        if (!StringUtils.hasLength(refName)) {
            // A reference to the id of another bean in the same XML file.
            refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE);
            if (!StringUtils.hasLength(refName)) {
                // A reference to the id of another bean in a parent context.
                refName = ele.getAttribute(PARENT_REF_ATTRIBUTE);
                toParent = true;
                if (!StringUtils.hasLength(refName)) {
                    error("‘bean‘, ‘local‘ or ‘parent‘ is required for <ref> element", ele);
                    return null;
                }
            }
        }
        if (!StringUtils.hasText(refName)) {
            error("<ref> element contains empty target attribute", ele);
            return null;
        }
        RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent);
        ref.setSource(extractSource(ele));
        return ref;
    }
    else if (nodeNameEquals(ele, IDREF_ELEMENT)) {
        return parseIdRefElement(ele);
    }
    else if (nodeNameEquals(ele, VALUE_ELEMENT)) {
        return parseValueElement(ele, defaultValueType);
    }
    else if (nodeNameEquals(ele, NULL_ELEMENT)) {
        // It‘s a distinguished null value. Let‘s wrap it in a TypedStringValue
        // object in order to preserve the source location.
        TypedStringValue nullHolder = new TypedStringValue(null);
        nullHolder.setSource(extractSource(ele));
        return nullHolder;
    }
    else if (nodeNameEquals(ele, ARRAY_ELEMENT)) {
        return parseArrayElement(ele, bd);
    }
    else if (nodeNameEquals(ele, LIST_ELEMENT)) {
        return parseListElement(ele, bd);
    }
    else if (nodeNameEquals(ele, SET_ELEMENT)) {
        return parseSetElement(ele, bd);
    }
    else if (nodeNameEquals(ele, MAP_ELEMENT)) {
        return parseMapElement(ele, bd);
    }
    else if (nodeNameEquals(ele, PROPS_ELEMENT)) {
        return parsePropsElement(ele);
    }
    else {
        error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele);
        return null;
    }
}

//BeanDefinitonReaderUtils
public static void registerBeanDefinition(
        BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
        throws BeanDefinitionStoreException {

    // Register bean definition under primary name.
    String beanName = definitionHolder.getBeanName();
    registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

    // Register aliases for bean name, if any.
    String[] aliases = definitionHolder.getAliases();
    if (aliases != null) {
        for (String alias : aliases) {
            registry.registerAlias(beanName, alias);
        }
    }
}