/* DubboNamespaceHandler */
public class DubboNamespaceHandler extends NamespaceHandlerSupport {
	// 检查是否有DubboNamespaceHandler的多个版本
    static {
        Version.checkDuplicate(DubboNamespaceHandler.class);
    }

    @Override
    public void init() {
        // init()方法中注册各个元素的解析器
        registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
        registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
        registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
		registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
        registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
        registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
        registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
        registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
        registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
        registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));
    }

}

/* DubboBeanDefinitionParser */
public class DubboBeanDefinitionParser implements BeanDefinitionParser {

    private static final Logger logger = LoggerFactory.getLogger(DubboBeanDefinitionParser.class);
    private static final Pattern GROUP_AND_VERION = Pattern.compile("^[\\-.0-9_a-zA-Z]+(\\:[\\-.0-9_a-zA-Z]+)?$");
    private final Class<?> beanClass; // 解析元素对应的类
    private final boolean required; // 属性是否必须，若true且不存在，则自动生成

    public DubboBeanDefinitionParser(Class<?> beanClass, boolean required) {
        this.beanClass = beanClass;
        this.required = required;
    }
    
    @Override
    public BeanDefinition parse(Element element, ParserContext parserContext) {
        return parse(element, parserContext, beanClass, required);
    }

    @SuppressWarnings("unchecked")
    private static BeanDefinition parse(Element element, ParserContext parserContext,
                                        Class<?> beanClass, boolean required) {
        // 元素BeanDefinition
        RootBeanDefinition beanDefinition = new RootBeanDefinition();
        beanDefinition.setBeanClass(beanClass);
        beanDefinition.setLazyInit(false);
        String id = element.getAttribute("id"); // 属性id
        if ((id == null || id.length() == 0) && required) {
            String generatedBeanName = element.getAttribute("name");
            if (generatedBeanName == null || generatedBeanName.length() == 0) {
                if (ProtocolConfig.class.equals(beanClass)) {
                    generatedBeanName = "dubbo";
                } else {
                    generatedBeanName = element.getAttribute("interface");
                }
            }
            if (generatedBeanName == null || generatedBeanName.length() == 0) {
                generatedBeanName = beanClass.getName();
            }
            id = generatedBeanName;
            int counter = 2;
            while (parserContext.getRegistry().containsBeanDefinition(id)) {
                id = generatedBeanName + (counter++); // 确保id的唯一性
            }
        }
        if (id != null && id.length() > 0) {
            if (parserContext.getRegistry().containsBeanDefinition(id)) {
                throw new IllegalStateException("Duplicate spring bean id " + id);
            }
            // 注册BeanDefinition
            parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
            beanDefinition.getPropertyValues().addPropertyValue("id", id);
        }
        if (ProtocolConfig.class.equals(beanClass)) {
            for (String name : parserContext.getRegistry().getBeanDefinitionNames()) {
                BeanDefinition definition = parserContext.getRegistry().getBeanDefinition(name);
                PropertyValue property = definition.getPropertyValues().getPropertyValue("protocol");
                if (property != null) {
                    Object value = property.getValue();
                    if (value instanceof ProtocolConfig && id.equals(((ProtocolConfig) value).getName())) {
                        // 相同的ProtocolConfig实例已存在，建立RuntimeBeanReference
                        definition.getPropertyValues().addPropertyValue("protocol", new RuntimeBeanReference(id));
                    }
                }
            }
        } else if (ServiceBean.class.equals(beanClass)) {
            String className = element.getAttribute("class"); // 服务实现类名
            if (className != null && className.length() > 0) {
                RootBeanDefinition classDefinition = new RootBeanDefinition();
                classDefinition.setBeanClass(ReflectUtils.forName(className));
                classDefinition.setLazyInit(false);
                // 解析 <dubbo:service/>下的子节点
                parseProperties(element.getChildNodes(), classDefinition);
                // 内部bean的占位符BeanDefinitionHolder
                beanDefinition.getPropertyValues().addPropertyValue("ref",
                        new BeanDefinitionHolder(classDefinition, id + "Impl"));
            }
        } else if (ProviderConfig.class.equals(beanClass)) {
            /*
            <dubbo:provider >
                <dubbo:service...
            </dubbo:provider>
             */
            parseNested(element, parserContext, ServiceBean.class, true, "service", "provider",
                    id, beanDefinition);
        } else if (ConsumerConfig.class.equals(beanClass)) {
            /*
            <dubbo:consumer>
                <dubbo:reference interface="com.example.dubbodemoapi.demo.DemoService"/>
            </dubbo:consumer>
            */
            parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer",
                    id, beanDefinition);
        }
        Set<String> props = new HashSet<String>(); // 属性
        ManagedMap parameters = null; // parameters
        for (Method setter : beanClass.getMethods()) {
            String name = setter.getName(); // 方法名
            if (name.length() > 3 && name.startsWith("set")
                    && Modifier.isPublic(setter.getModifiers())
                    && setter.getParameterTypes().length == 1) {
                Class<?> type = setter.getParameterTypes()[0];
                // 根据方法名获取属性
                String property = StringUtils.camelToSplitName(name.substring(3, 4).toLowerCase() + name.substring(4), "-");
                props.add(property);
                Method getter = null;
                try {
                    getter = beanClass.getMethod("get" + name.substring(3), new Class<?>[0]);
                } catch (NoSuchMethodException e) {
                    try {
                        getter = beanClass.getMethod("is" + name.substring(3), new Class<?>[0]);
                    } catch (NoSuchMethodException e2) {
                    }
                }
                if (getter == null
                        || !Modifier.isPublic(getter.getModifiers())
                        || !type.equals(getter.getReturnType())) {
                    continue;
                }
                if ("parameters".equals(property)) {
                    // 解析内部 <dubbo:parameter key="" value="" /> 标签
                    parameters = parseParameters(element.getChildNodes(), beanDefinition);
                } else if ("methods".equals(property)) {
                    // 解析内部 <dubbo:method /> 标签
                    parseMethods(id, element.getChildNodes(), beanDefinition, parserContext);
                } else if ("arguments".equals(property)) {
                    // 解析 <dubbo:argument /> 标签
                    parseArguments(id, element.getChildNodes(), beanDefinition, parserContext);
                } else {
                    String value = element.getAttribute(property); // 从当前元素获取property属性值
                    if (value != null) {
                        value = value.trim();
                        if (value.length() > 0) {
                            if ("registry".equals(property) && RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(value)) {
                                RegistryConfig registryConfig = new RegistryConfig();
                                registryConfig.setAddress(RegistryConfig.NO_AVAILABLE); // 注册中心地址N/A
                                beanDefinition.getPropertyValues().addPropertyValue(property, registryConfig);
                            } else if ("registry".equals(property) && value.indexOf(',') != -1) { // 多注册中心
                                parseMultiRef("registries", value, beanDefinition, parserContext);
                            } else if ("provider".equals(property) && value.indexOf(',') != -1) { // 多提供者
                                parseMultiRef("providers", value, beanDefinition, parserContext);
                            } else if ("protocol".equals(property) && value.indexOf(',') != -1) { // 多协议
                                parseMultiRef("protocols", value, beanDefinition, parserContext);
                            } else {
                                Object reference;
                                if (isPrimitive(type)) { // 方法参数类型是基本类型或包装类型
                                    if ("async".equals(property) && "false".equals(value)
                                            || "timeout".equals(property) && "0".equals(value)
                                            || "delay".equals(property) && "0".equals(value)
                                            || "version".equals(property) && "0.0.0".equals(value)
                                            || "stat".equals(property) && "-1".equals(value)
                                            || "reliable".equals(property) && "false".equals(value)) {
                                        // 兼容旧版本xsd中的default值
                                        value = null;
                                    }
                                    reference = value;
                                } else if ("protocol".equals(property)
                                        && ExtensionLoader.getExtensionLoader(Protocol.class).hasExtension(value)
                                        && (!parserContext.getRegistry().containsBeanDefinition(value)
                                        || !ProtocolConfig.class.getName().equals(parserContext.getRegistry().getBeanDefinition(value).getBeanClassName()))) {
                                    if ("dubbo:provider".equals(element.getTagName())) {
                                        logger.warn("Recommended replace <dubbo:provider protocol=\"" + value + "\" ... /> to <dubbo:protocol name=\"" + value + "\" ... />");
                                    }
                                    // 兼容旧版本配置
                                    ProtocolConfig protocol = new ProtocolConfig();
                                    protocol.setName(value);
                                    reference = protocol;
                                } else if ("onreturn".equals(property)) { // 方法执行返回后拦截
                                    int index = value.lastIndexOf("."); // 实例ref.方法
                                    String returnRef = value.substring(0, index);
                                    String returnMethod = value.substring(index + 1);
                                    reference = new RuntimeBeanReference(returnRef);
                                    beanDefinition.getPropertyValues().addPropertyValue("onreturnMethod", returnMethod);
                                } else if ("onthrow".equals(property)) {
                                    int index = value.lastIndexOf("."); // 实例ref.方法
                                    String throwRef = value.substring(0, index);
                                    String throwMethod = value.substring(index + 1);
                                    reference = new RuntimeBeanReference(throwRef);
                                    beanDefinition.getPropertyValues().addPropertyValue("onthrowMethod", throwMethod);
                                } else {
                                    // ref属性
                                    if ("ref".equals(property) && parserContext.getRegistry().containsBeanDefinition(value)) {
                                        BeanDefinition refBean = parserContext.getRegistry().getBeanDefinition(value);
                                        if (!refBean.isSingleton()) {
                                            throw new IllegalStateException("The exported service ref " + value + " must be singleton! Please set the " + value + " bean scope to singleton, eg: <bean id=\"" + value + "\" scope=\"singleton\" ...>");
                                        }
                                    }
                                    reference = new RuntimeBeanReference(value);
                                }
                                beanDefinition.getPropertyValues().addPropertyValue(property, reference);
                            }
                        }
                    }
                }
            }
        }
        NamedNodeMap attributes = element.getAttributes(); // 从元素获取属性map
        int len = attributes.getLength();
        for (int i = 0; i < len; i++) {
            Node node = attributes.item(i);
            String name = node.getLocalName();
            if (!props.contains(name)) {
                if (parameters == null) {
                    parameters = new ManagedMap();
                }
                String value = node.getNodeValue(); // 属性值
                parameters.put(name, new TypedStringValue(value, String.class));
            }
        }
        if (parameters != null) {
            beanDefinition.getPropertyValues().addPropertyValue("parameters", parameters);
        }
        return beanDefinition;
    }

    /**
     * 判断cls是否是基本类型或其包装类型
     * @param cls
     * @return
     */
    private static boolean isPrimitive(Class<?> cls) {
        return cls.isPrimitive() || cls == Boolean.class || cls == Byte.class
                || cls == Character.class || cls == Short.class || cls == Integer.class
                || cls == Long.class || cls == Float.class || cls == Double.class
                || cls == String.class || cls == Date.class || cls == Class.class;
    }

    /**
     * 解析多处的引用
     * @param property 属性名
     * @param value 属性值
     * @param beanDefinition RootBeanDefinition
     * @param parserContext 解析器上下文
     */
    @SuppressWarnings("unchecked")
    private static void parseMultiRef(String property, String value, RootBeanDefinition beanDefinition,
                                      ParserContext parserContext) {
        String[] values = value.split("\\s*[,]+\\s*");
        ManagedList list = null;
        for (int i = 0; i < values.length; i++) {
            String v = values[i];
            if (v != null && v.length() > 0) {
                if (list == null) {
                    list = new ManagedList();
                }
                list.add(new RuntimeBeanReference(v));
            }
        }
        beanDefinition.getPropertyValues().addPropertyValue(property, list);
    }

    /**
     * 解析element内部元素
     * @param element 父元素
     * @param parserContext 解析器上下文
     * @param beanClass ServiceBean/ReferenceBean
     * @param required 是否必须
     * @param tag service/reference
     * @param property provider/consumer
     * @param ref element id(父节点id)
     * @param beanDefinition element BeanDefinition
     */
    private static void parseNested(Element element, ParserContext parserContext, Class<?> beanClass, boolean required,
                                    String tag, String property, String ref, BeanDefinition beanDefinition) {
        NodeList nodeList = element.getChildNodes();
        if (nodeList != null && nodeList.getLength() > 0) {
            boolean first = true;
            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i);
                if (node instanceof Element) {
                    if (tag.equals(node.getNodeName())
                            || tag.equals(node.getLocalName())) { // tag--service/reference
                        if (first) {
                            first = false;
                            String isDefault = element.getAttribute("default");
                            if (isDefault == null || isDefault.length() == 0) {
                                beanDefinition.getPropertyValues()
                                        .addPropertyValue("default", "false");
                            }
                        }
                        // beanClass ServiceBean/ReferenceBean
                        BeanDefinition subDefinition = parse((Element) node, parserContext, beanClass, required);
                        if (subDefinition != null && ref != null && ref.length() > 0) { // ref 父节点id
                            subDefinition.getPropertyValues().addPropertyValue(property, new RuntimeBeanReference(ref)); // property: provider/consumer
                        }
                    }
                }
            }
        }
    }

    /**
     * 解析 <dubbo:service/>下的子节点
     * @param nodeList <dubbo:service/>下的子节点
     * @param beanDefinition class BeanDefinition
     */
    private static void parseProperties(NodeList nodeList, RootBeanDefinition beanDefinition) {
        if (nodeList != null && nodeList.getLength() > 0) {
            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i); // 获取第i个Node
                if (node instanceof Element) {
                    if ("property".equals(node.getNodeName()) // <property name="xx" ...
                            || "property".equals(node.getLocalName())) {
                        String name = ((Element) node).getAttribute("name");
                        if (name != null && name.length() > 0) {
                            String value = ((Element) node).getAttribute("value"); // <property name="xx" value="..."/>
                            String ref = ((Element) node).getAttribute("ref"); // <property name="xx" ref="..."/>
                            if (value != null && value.length() > 0) {
                                beanDefinition.getPropertyValues().addPropertyValue(name, value);
                            } else if (ref != null && ref.length() > 0) {
                                beanDefinition.getPropertyValues().addPropertyValue(name, new RuntimeBeanReference(ref)); // 建立RuntimeBeanReference
                            } else {
                                throw new UnsupportedOperationException("Unsupported <property name=\"" + name + "\"> sub tag, Only supported <property name=\"" + name + "\" ref=\"...\" /> or <property name=\"" + name + "\" value=\"...\" />");
                            }
                        }
                    }
                }
            }
        }
    }

    /**
     * 解析内部 <dubbo:parameter key="" value="" /> 标签
     * @param nodeList 节点列表
     * @param beanDefinition 父元素BeanDefinition
     * @return
     */
    @SuppressWarnings("unchecked")
    private static ManagedMap parseParameters(NodeList nodeList, RootBeanDefinition beanDefinition) {
        if (nodeList != null && nodeList.getLength() > 0) {
            ManagedMap parameters = null;
            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i);
                if (node instanceof Element) {
                    if ("parameter".equals(node.getNodeName()) // <dubbo:parameter key="" value="" /> 标签
                            || "parameter".equals(node.getLocalName())) {
                        if (parameters == null) {
                            parameters = new ManagedMap();
                        }
                        String key = ((Element) node).getAttribute("key");
                        String value = ((Element) node).getAttribute("value");
                        boolean hide = "true".equals(((Element) node).getAttribute("hide"));
                        if (hide) {
                            key = Constants.HIDE_KEY_PREFIX + key; // 隐藏配置参数
                        }
                        parameters.put(key, new TypedStringValue(value, String.class));
                    }
                }
            }
            return parameters;
        }
        return null;
    }

    /**
     * 解析 内部<dubbo:method /> 标签
     * @param id 父元素id
     * @param nodeList 内部节点列表
     * @param beanDefinition 父元素BeanDefinition
     * @param parserContext 解析器上下文
     */
    @SuppressWarnings("unchecked")
    private static void parseMethods(String id, NodeList nodeList, RootBeanDefinition beanDefinition,
                                     ParserContext parserContext) {
        if (nodeList != null && nodeList.getLength() > 0) {
            ManagedList methods = null;
            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i);
                if (node instanceof Element) {
                    Element element = (Element) node;
                    // <dubbo:method />标签
                    if ("method".equals(node.getNodeName()) || "method".equals(node.getLocalName())) {
                        String methodName = element.getAttribute("name"); // 方法名
                        if (methodName == null || methodName.length() == 0) {
                            throw new IllegalStateException("<dubbo:method> name attribute == null");
                        }
                        if (methods == null) {
                            methods = new ManagedList();
                        }
                        BeanDefinition methodBeanDefinition = parse(((Element) node),
                                parserContext, MethodConfig.class, false);
                        String name = id + "." + methodName;
                        BeanDefinitionHolder methodBeanDefinitionHolder = new BeanDefinitionHolder(
                                methodBeanDefinition, name);
                        methods.add(methodBeanDefinitionHolder);
                    }
                }
            }
            if (methods != null) {
                beanDefinition.getPropertyValues().addPropertyValue("methods", methods);
            }
        }
    }

    /**
     * 解析 <dubbo:argument /> 标签
     * @param id 父元素id
     * @param nodeList 内部元素节点列表
     * @param beanDefinition 父元素BeanDefinition
     * @param parserContext 解析器上下文
     */
    @SuppressWarnings("unchecked")
    private static void parseArguments(String id, NodeList nodeList, RootBeanDefinition beanDefinition,
                                       ParserContext parserContext) {
        if (nodeList != null && nodeList.getLength() > 0) {
            ManagedList arguments = null;
            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i);
                if (node instanceof Element) {
                    Element element = (Element) node;
                    // <dubbo:argument /> 标签
                    if ("argument".equals(node.getNodeName()) || "argument".equals(node.getLocalName())) {
                        String argumentIndex = element.getAttribute("index"); // index属性
                        if (arguments == null) {
                            arguments = new ManagedList();
                        }
                        BeanDefinition argumentBeanDefinition = parse(((Element) node),
                                parserContext, ArgumentConfig.class, false);
                        String name = id + "." + argumentIndex;
                        BeanDefinitionHolder argumentBeanDefinitionHolder = new BeanDefinitionHolder(
                                argumentBeanDefinition, name);
                        arguments.add(argumentBeanDefinitionHolder);
                    }
                }
            }
            if (arguments != null) {
                beanDefinition.getPropertyValues().addPropertyValue("arguments", arguments);
            }
        }
    }
}