Spring源码：注册bean——XmlBeanDefinitionReader.registerBeanDefinitions(Documnt doc, Resource resouce)

小咪咪 2023-06-21 07:28 7阅读 0赞

**目录**

1、截取 XmlBeanDefinitionReader.registerBeanDefinitions(Documnt doc, Resource resouce) 部分代码

2、XmlReaderContext、DefaultNamespaceHandlerResolver

3、加载及注册bean，委托给 DefaultBeanDefinitionDocumentReader

DefaultBeanDefinitionDocumentReader 源码

BeanDefinitionReaderUtils 源码

DefaultListableBeanFactory 源码

4、getBean 的过程

--------------------

# 1、截取 XmlBeanDefinitionReader.registerBeanDefinitions(Documnt doc, Resource resouce) 部分代码 #

代码如下

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {
    
        private Class<? extends BeanDefinitionDocumentReader> documentReaderClass = DefaultBeanDefinitionDocumentReader.class;
        private ProblemReporter problemReporter = new FailFastProblemReporter();
        private ReaderEventListener eventListener = new EmptyReaderEventListener();
        private SourceExtractor sourceExtractor = new NullSourceExtractor();
        @Nullable
        private NamespaceHandlerResolver namespaceHandlerResolver;
    
        // 在AbstractBeanDefinitionReader类继承的代码，这里写在这里加深理解  start
        private final BeanDefinitionRegistry registry;
        public final BeanDefinitionRegistry getRegistry() {
            return this.registry;
        }
        // 在AbstractBeanDefinitionReader类继承的代码，这里写在这里加深理解  end
        
        /**
        * doc:xml配置文件解析后的Document
        * resource：配置文件资源
        *
        */
        public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
            BeanDefinitionDocumentReader documentReader = this.createBeanDefinitionDocumentReader();
            /**
            * 获取BeanDefinitionRegistry接口，getBeanDefinitionCount方法在
            * DefaultListableBeanFactory 实现了，代码如下
    private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap(256);
    public int getBeanDefinitionCount() {
            return this.beanDefinitionMap.size();
        }
            * beanDefinitionMap 实际就是注册BeanDefinition的容器，这里主要用于获取已经注册的 BeanDefinition 数量
            */
            int countBefore = this.getRegistry().getBeanDefinitionCount();
            // 核心方法，加载及注册 bean，委托给 DefaultBeanDefinitionDocumentReader 来处理
            // this.createReaderContext:生成xmlreader的上下文context，其中有配置好的命名空间
            documentReader.registerBeanDefinitions(doc, this.createReaderContext(resource));
            return this.getRegistry().getBeanDefinitionCount() - countBefore;
        }
        // 创建 DefaultBeanDefinitionDocumentReader
        protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
            return (BeanDefinitionDocumentReader)BeanUtils.instantiateClass(this.documentReaderClass);
        }
    
        // 生成xmlreader的上下文context，其中有配置好的命名空间
        public XmlReaderContext createReaderContext(Resource resource) {
            return new XmlReaderContext(resource, this.problemReporter, this.eventListener, this.sourceExtractor, this, this.getNamespaceHandlerResolver());
        }
        // 获取命名空间的处理器
        public NamespaceHandlerResolver getNamespaceHandlerResolver() {
            if(this.namespaceHandlerResolver == null) {
                this.namespaceHandlerResolver = this.createDefaultNamespaceHandlerResolver();
            }
    
            return this.namespaceHandlerResolver;
        }
    
        protected NamespaceHandlerResolver createDefaultNamespaceHandlerResolver() {
            ClassLoader cl = this.getResourceLoader() != null?this.getResourceLoader().getClassLoader():this.getBeanClassLoader();
            // 命名空间处理器，待了解
            return new DefaultNamespaceHandlerResolver(cl);
        }
    }

# 2、XmlReaderContext、DefaultNamespaceHandlerResolver  #

//TODO

# 3、加载及注册bean，委托给 DefaultBeanDefinitionDocumentReader #

## DefaultBeanDefinitionDocumentReader 源码 ##

package org.springframework.beans.factory.xml;
    
    import java.io.IOException;
    import java.net.URISyntaxException;
    import java.util.LinkedHashSet;
    import java.util.Set;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.beans.factory.BeanDefinitionStoreException;
    import org.springframework.beans.factory.config.BeanDefinitionHolder;
    import org.springframework.beans.factory.parsing.BeanComponentDefinition;
    import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
    import org.springframework.core.io.Resource;
    import org.springframework.core.io.support.ResourcePatternUtils;
    import org.springframework.lang.Nullable;
    import org.springframework.util.Assert;
    import org.springframework.util.ResourceUtils;
    import org.springframework.util.StringUtils;
    import org.w3c.dom.Document;
    import org.w3c.dom.Element;
    import org.w3c.dom.Node;
    import org.w3c.dom.NodeList;
    
    public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader {
        public static final String BEAN_ELEMENT = "bean";
        public static final String NESTED_BEANS_ELEMENT = "beans";
        public static final String ALIAS_ELEMENT = "alias";
        public static final String NAME_ATTRIBUTE = "name";
        public static final String ALIAS_ATTRIBUTE = "alias";
        public static final String IMPORT_ELEMENT = "import";
        public static final String RESOURCE_ATTRIBUTE = "resource";
        public static final String PROFILE_ATTRIBUTE = "profile";
        protected final Log logger = LogFactory.getLog(this.getClass());
        @Nullable
        private XmlReaderContext readerContext;
        @Nullable
        private BeanDefinitionParserDelegate delegate;
    
        public DefaultBeanDefinitionDocumentReader() {
        }
    
        public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
            // 这个readerContext就是上面传进来的读取xml的context上下文
            this.readerContext = readerContext;
            // doc.getDocumentElement() 获取 XML 的根节点root，传入方法内
            this.doRegisterBeanDefinitions(doc.getDocumentElement());
        }
    
        protected final XmlReaderContext getReaderContext() {
            Assert.state(this.readerContext != null, "No XmlReaderContext available");
            return this.readerContext;
        }
    
        @Nullable
        protected Object extractSource(Element ele) {
            return this.getReaderContext().extractSource(ele);
        }
        
        // 根节点传入解析
        protected void doRegisterBeanDefinitions(Element root) {
            // Delegate 中文解释 委托
            // BeanDefinitionParserDelegate 解释 BeanDefinition委托解析类
            BeanDefinitionParserDelegate parent = this.delegate;
            // 创建解析委托类
            this.delegate = this.createDelegate(this.getReaderContext(), root, parent);
            if(this.delegate.isDefaultNamespace(root)) {
                String profileSpec = root.getAttribute("profile");
                if(StringUtils.hasText(profileSpec)) {
                    String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, ",; ");
                    if(!this.getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
                        if(this.logger.isDebugEnabled()) {
                            this.logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + this.getReaderContext().getResource());
                        }
    
                        return;
                    }
                }
            }
            // 模板方法
            this.preProcessXml(root);
            // 核心方法：正式解析生成 BeanDefinition
            this.parseBeanDefinitions(root, this.delegate);
            // 模板方法
            this.postProcessXml(root);
            // 保留委托类，省的重复创建
            this.delegate = parent;
        }
        // 创建 BeanDefinitionParserDelegate：https://blog.csdn.net/ruanhao1203/article/details/103504087
        protected BeanDefinitionParserDelegate createDelegate(XmlReaderContext readerContext, Element root, @Nullable BeanDefinitionParserDelegate parentDelegate) {
            BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
            delegate.initDefaults(root, parentDelegate);
            return delegate;
        }
        // 解析并生成 BeanDefinition
        protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
            // 判断命名空间是不是 spring默认的：http://www.springframework.org/schema/beans
            if(delegate.isDefaultNamespace(root)) {
                // 获取 beans 下所有 bean标签，也可能是其他标签，这里以bean为例
                NodeList nl = root.getChildNodes();
    
                for(int i = 0; i < nl.getLength(); ++i) {
                    // 单个bean标签
                    Node node = nl.item(i);
                    if(node instanceof Element) {
                        Element ele = (Element)node;
    // 判断命名空间是不是 spring默认的：http://www.springframework.org/schema/beans
                        if(delegate.isDefaultNamespace(ele)) {
                            // spring默认命名空间下 元素解析
                            this.parseDefaultElement(ele, delegate);
                        } else {// 自定义命名空间解析
                            delegate.parseCustomElement(ele);
                        }
                    }
                }
            } else {// 自定义命名空间解析
                delegate.parseCustomElement(root);
            }
    
        }
        // spring默认命名空间下 元素解析
        private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
            if(delegate.nodeNameEquals(ele, "import")) {
                this.importBeanDefinitionResource(ele);
            } else if(delegate.nodeNameEquals(ele, "alias")) {
                this.processAliasRegistration(ele);
            } else if(delegate.nodeNameEquals(ele, "bean")) {// bean标签解析
                this.processBeanDefinition(ele, delegate);
            } else if(delegate.nodeNameEquals(ele, "beans")) {
                this.doRegisterBeanDefinitions(ele);
            }
    
        }
    
        protected void importBeanDefinitionResource(Element ele) {
            String location = ele.getAttribute("resource");
            if(!StringUtils.hasText(location)) {
                this.getReaderContext().error("Resource location must not be empty", ele);
            } else {
                location = this.getReaderContext().getEnvironment().resolveRequiredPlaceholders(location);
                Set<Resource> actualResources = new LinkedHashSet(4);
                boolean absoluteLocation = false;
    
                try {
                    absoluteLocation = ResourcePatternUtils.isUrl(location) || ResourceUtils.toURI(location).isAbsolute();
                } catch (URISyntaxException var11) {
                    ;
                }
    
                int importCount;
                if(absoluteLocation) {
                    try {
                        importCount = this.getReaderContext().getReader().loadBeanDefinitions(location, actualResources);
                        if(this.logger.isTraceEnabled()) {
                            this.logger.trace("Imported " + importCount + " bean definitions from URL location [" + location + "]");
                        }
                    } catch (BeanDefinitionStoreException var10) {
                        this.getReaderContext().error("Failed to import bean definitions from URL location [" + location + "]", ele, var10);
                    }
                } else {
                    try {
                        Resource relativeResource = this.getReaderContext().getResource().createRelative(location);
                        if(relativeResource.exists()) {
                            importCount = this.getReaderContext().getReader().loadBeanDefinitions(relativeResource);
                            actualResources.add(relativeResource);
                        } else {
                            String baseLocation = this.getReaderContext().getResource().getURL().toString();
                            importCount = this.getReaderContext().getReader().loadBeanDefinitions(StringUtils.applyRelativePath(baseLocation, location), actualResources);
                        }
    
                        if(this.logger.isTraceEnabled()) {
                            this.logger.trace("Imported " + importCount + " bean definitions from relative location [" + location + "]");
                        }
                    } catch (IOException var8) {
                        this.getReaderContext().error("Failed to resolve current resource location", ele, var8);
                    } catch (BeanDefinitionStoreException var9) {
                        this.getReaderContext().error("Failed to import bean definitions from relative location [" + location + "]", ele, var9);
                    }
                }
    
                Resource[] actResArray = (Resource[])actualResources.toArray(new Resource[0]);
                this.getReaderContext().fireImportProcessed(location, actResArray, this.extractSource(ele));
            }
        }
    
        protected void processAliasRegistration(Element ele) {
            String name = ele.getAttribute("name");
            String alias = ele.getAttribute("alias");
            boolean valid = true;
            if(!StringUtils.hasText(name)) {
                this.getReaderContext().error("Name must not be empty", ele);
                valid = false;
            }
    
            if(!StringUtils.hasText(alias)) {
                this.getReaderContext().error("Alias must not be empty", ele);
                valid = false;
            }
    
            if(valid) {
                try {
                    this.getReaderContext().getRegistry().registerAlias(name, alias);
                } catch (Exception var6) {
                    this.getReaderContext().error("Failed to register alias '" + alias + "' for bean with name '" + name + "'", ele, var6);
                }
    
                this.getReaderContext().fireAliasRegistered(name, alias, this.extractSource(ele));
            }
    
        }
        // bean标签解析
        protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
            // 解析过程参考parseBeanDefinitionElement：https://blog.csdn.net/ruanhao1203/article/details/103504087
            BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
            if(bdHolder != null) {
                // 
                bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
    
                try {
                    // 注册bean
                    // this.getReaderContext.getRegistry():获取BeanDefinitionRegistry
                    // BeanDefinitionReaderUtils 继续往下看
                    BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, this.getReaderContext().getRegistry());
                } catch (BeanDefinitionStoreException var5) {
                    this.getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, var5);
                }
    
                this.getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
            }
    
        }
    
        protected void preProcessXml(Element root) {
        }
    
        protected void postProcessXml(Element root) {
        }
    }

## BeanDefinitionReaderUtils 源码 ##

package org.springframework.beans.factory.support;
    
    import org.springframework.beans.factory.BeanDefinitionStoreException;
    import org.springframework.beans.factory.config.BeanDefinition;
    import org.springframework.beans.factory.config.BeanDefinitionHolder;
    import org.springframework.lang.Nullable;
    import org.springframework.util.ClassUtils;
    import org.springframework.util.ObjectUtils;
    import org.springframework.util.StringUtils;
    
    public abstract class BeanDefinitionReaderUtils {
        public static final String GENERATED_BEAN_NAME_SEPARATOR = "#";
    
        public BeanDefinitionReaderUtils() {
        }
        // 创建 BeanDefinition，被上一个类源码调用
        public static AbstractBeanDefinition createBeanDefinition(@Nullable String parentName, @Nullable String className, @Nullable ClassLoader classLoader) throws ClassNotFoundException {
            GenericBeanDefinition bd = new GenericBeanDefinition();
            bd.setParentName(parentName);
            if(className != null) {
                if(classLoader != null) {
                    bd.setBeanClass(ClassUtils.forName(className, classLoader));
                } else {
                    bd.setBeanClassName(className);
                }
            }
    
            return bd;
        }
    
        public static String generateBeanName(BeanDefinition beanDefinition, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {
            return generateBeanName(beanDefinition, registry, false);
        }
    
        public static String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry, boolean isInnerBean) throws BeanDefinitionStoreException {
            String generatedBeanName = definition.getBeanClassName();
            if(generatedBeanName == null) {
                if(definition.getParentName() != null) {
                    generatedBeanName = definition.getParentName() + "$child";
                } else if(definition.getFactoryBeanName() != null) {
                    generatedBeanName = definition.getFactoryBeanName() + "$created";
                }
            }
    
            if(!StringUtils.hasText(generatedBeanName)) {
                throw new BeanDefinitionStoreException("Unnamed bean definition specifies neither 'class' nor 'parent' nor 'factory-bean' - can't generate bean name");
            } else if(isInnerBean) {
                String id = generatedBeanName + "#" + ObjectUtils.getIdentityHexString(definition);
                return id;
            } else {
                return uniqueBeanName(generatedBeanName, registry);
            }
        }
    
        public static String uniqueBeanName(String beanName, BeanDefinitionRegistry registry) {
            String id = beanName;
    
            for(int counter = -1; counter == -1 || registry.containsBeanDefinition(id); id = beanName + "#" + counter) {
                ++counter;
            }
    
            return id;
        }
    
        /**
        * 注册bean 到 DefaultListableBeanFactory 中
        *
        *
        */
        public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {
            // bean标签 id值，例如user
            String beanName = definitionHolder.getBeanName();
            // BeanDefinitionRegistry的registerBeanDefinition方法注册bean，此接口方法在 DefaultListableBeanFactory 实现，代码请看下一个源码
            registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
            String[] aliases = definitionHolder.getAliases();
            if(aliases != null) {
                String[] var4 = aliases;
                int var5 = aliases.length;
    
                for(int var6 = 0; var6 < var5; ++var6) {
                    String alias = var4[var6];
                    registry.registerAlias(beanName, alias);
                }
            }
    
        }
    
        public static String registerWithGeneratedName(AbstractBeanDefinition definition, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {
            String generatedName = generateBeanName(definition, registry, false);
            registry.registerBeanDefinition(generatedName, definition);
            return generatedName;
        }
    }

## DefaultListableBeanFactory 源码 ##

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
        
        // BeanDefinition 容器
        private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap(256);
        // BeanDefinition 对应 id的容器
        private volatile List<String> beanDefinitionNames = new ArrayList(256);
    
        public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {
            Assert.hasText(beanName, "Bean name must not be empty");
            Assert.notNull(beanDefinition, "BeanDefinition must not be null");
            if(beanDefinition instanceof AbstractBeanDefinition) {
                try {
                    ((AbstractBeanDefinition)beanDefinition).validate();
                } catch (BeanDefinitionValidationException var8) {
                    throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", var8);
                }
            }
            
            BeanDefinition existingDefinition = (BeanDefinition)this.beanDefinitionMap.get(beanName);
            // 判断是否已存在
            if(existingDefinition != null) {
                if(!this.isAllowBeanDefinitionOverriding()) {
                    throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
                }
    
                if(existingDefinition.getRole() < beanDefinition.getRole()) {
                    if(this.logger.isInfoEnabled()) {
                        this.logger.info("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");
                    }
                } else if(!beanDefinition.equals(existingDefinition)) {
                    if(this.logger.isDebugEnabled()) {
                        this.logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");
                    }
                } else if(this.logger.isTraceEnabled()) {
                    this.logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");
                }
                // 已存在则覆盖
                this.beanDefinitionMap.put(beanName, beanDefinition);
            } else {
                if(this.hasBeanCreationStarted()) {
                    Map var4 = this.beanDefinitionMap;
                    synchronized(this.beanDefinitionMap) {
                        this.beanDefinitionMap.put(beanName, beanDefinition);
                        List<String> updatedDefinitions = new ArrayList(this.beanDefinitionNames.size() + 1);
                        updatedDefinitions.addAll(this.beanDefinitionNames);
                        updatedDefinitions.add(beanName);
                        this.beanDefinitionNames = updatedDefinitions;
                        this.removeManualSingletonName(beanName);
                    }
                } else {
                    // 核心：把BeanDefinition放入容器
                    this.beanDefinitionMap.put(beanName, beanDefinition);
                    this.beanDefinitionNames.add(beanName);
                    this.removeManualSingletonName(beanName);
                }
    
                this.frozenBeanDefinitionNames = null;
            }
    
            if(existingDefinition != null || this.containsSingleton(beanName)) {
                this.resetBeanDefinition(beanName);
            }
    
        }
    }

至此 bean 加载注册过程就结束了。

# 4、getBean 的过程 #