BeanDefinitionParserDelegate与资源解析

继续上一次的分析

XmlBeanDefinitionReader.java 中

1、registerBeanDefinitions方法

documentReader.registerBeanDefinitions(doc, createReaderContext(resource));

注册Bean definition， 第二个参数是createReaderContext(resource)

2、createReaderContext方法

3、XmlReaderContext

XmlReaderContext继承自ReaderContext，和XmlBeanDefinitionReader一起使用，提供了访问NamespaceHandlerResolver

4、registerBeanDefinitions方法

方法作用：见方法的英文描述

5、doRegisterBeanDefinitions方法，参数为xml文档的根元素

/**
	 * Register each bean definition within the given root {@code <beans/>} element.
	 * @throws IllegalStateException if {@code <beans profile="..."} attribute is present
	 * and Environment property has not been set
	 * @see #setEnvironment
	 */
	protected void doRegisterBeanDefinitions(Element root) {
		String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
		if (StringUtils.hasText(profileSpec)) {
			Assert.state(this.environment != null, "environment property must not be null");
			String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
			if (!this.environment.acceptsProfiles(specifiedProfiles)) {
				return;
			}
		}

		// any nested <beans> elements will cause recursion in this method. In
		// order to propagate and preserve <beans> default-* attributes correctly,
		// keep track of the current (parent) delegate, which may be null. Create
		// the new (child) delegate with a reference to the parent for fallback purposes,
		// then ultimately reset this.delegate back to its original (parent) reference.
		// this behavior emulates a stack of delegates without actually necessitating one.
		BeanDefinitionParserDelegate parent = this.delegate;
		this.delegate = createHelper(readerContext, root, parent);

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

		this.delegate = parent;
	}

　　这里用到了模板方法的设计模式

preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
这三个方法执行顺序是不变的。子类可以重写preProcessXml方法和postProcessXml方法， 实现对XML配置文件的自定义扩展。类似于JUnit中的setUp，testXXX与tearDown方法

。

6、BeanDefinitionParserDelegate类： 有状态的委托类，用来解析Xml中bean的定义

定义的成员变量

public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";

    public static final String MULTI_VALUE_ATTRIBUTE_DELIMITERS = ",; ";

    /** @deprecated as of Spring 3.1 in favor of {@link #MULTI_VALUE_ATTRIBUTE_DELIMITERS} */
    public static final String BEAN_NAME_DELIMITERS = MULTI_VALUE_ATTRIBUTE_DELIMITERS;

    /**
     * Value of a T/F attribute that represents true.
     * Anything else represents false. Case seNsItive.
     */
    public static final String TRUE_VALUE = "true";

    public static final String FALSE_VALUE = "false";

    public static final String DEFAULT_VALUE = "default";

    public static final String DESCRIPTION_ELEMENT = "description";

    public static final String AUTOWIRE_NO_VALUE = "no";

    public static final String AUTOWIRE_BY_NAME_VALUE = "byName";

    public static final String AUTOWIRE_BY_TYPE_VALUE = "byType";

    public static final String AUTOWIRE_CONSTRUCTOR_VALUE = "constructor";

    public static final String AUTOWIRE_AUTODETECT_VALUE = "autodetect";

    public static final String DEPENDENCY_CHECK_ALL_ATTRIBUTE_VALUE = "all";

    public static final String DEPENDENCY_CHECK_SIMPLE_ATTRIBUTE_VALUE = "simple";

    public static final String DEPENDENCY_CHECK_OBJECTS_ATTRIBUTE_VALUE = "objects";

    public static final String NAME_ATTRIBUTE = "name";

    public static final String BEAN_ELEMENT = "bean";

    public static final String META_ELEMENT = "meta";

    public static final String ID_ATTRIBUTE = "id";

    public static final String PARENT_ATTRIBUTE = "parent";

    public static final String CLASS_ATTRIBUTE = "class";

    public static final String ABSTRACT_ATTRIBUTE = "abstract";

    public static final String SCOPE_ATTRIBUTE = "scope";

    public static final String SINGLETON_ATTRIBUTE = "singleton";

    public static final String LAZY_INIT_ATTRIBUTE = "lazy-init";

    public static final String AUTOWIRE_ATTRIBUTE = "autowire";

    public static final String AUTOWIRE_CANDIDATE_ATTRIBUTE = "autowire-candidate";

    public static final String PRIMARY_ATTRIBUTE = "primary";

    public static final String DEPENDENCY_CHECK_ATTRIBUTE = "dependency-check";

    public static final String DEPENDS_ON_ATTRIBUTE = "depends-on";

    public static final String INIT_METHOD_ATTRIBUTE = "init-method";

    public static final String DESTROY_METHOD_ATTRIBUTE = "destroy-method";

    public static final String FACTORY_METHOD_ATTRIBUTE = "factory-method";

    public static final String FACTORY_BEAN_ATTRIBUTE = "factory-bean";

    public static final String CONSTRUCTOR_ARG_ELEMENT = "constructor-arg";

    public static final String INDEX_ATTRIBUTE = "index";

    public static final String TYPE_ATTRIBUTE = "type";

    public static final String VALUE_TYPE_ATTRIBUTE = "value-type";

    public static final String KEY_TYPE_ATTRIBUTE = "key-type";

    public static final String PROPERTY_ELEMENT = "property";

    public static final String REF_ATTRIBUTE = "ref";

    public static final String VALUE_ATTRIBUTE = "value";

    public static final String LOOKUP_METHOD_ELEMENT = "lookup-method";

    public static final String REPLACED_METHOD_ELEMENT = "replaced-method";

    public static final String REPLACER_ATTRIBUTE = "replacer";

    public static final String ARG_TYPE_ELEMENT = "arg-type";

    public static final String ARG_TYPE_MATCH_ATTRIBUTE = "match";

    public static final String REF_ELEMENT = "ref";

    public static final String IDREF_ELEMENT = "idref";

    public static final String BEAN_REF_ATTRIBUTE = "bean";

    public static final String LOCAL_REF_ATTRIBUTE = "local";

    public static final String PARENT_REF_ATTRIBUTE = "parent";

    public static final String VALUE_ELEMENT = "value";

    public static final String NULL_ELEMENT = "null";

    public static final String ARRAY_ELEMENT = "array";

    public static final String LIST_ELEMENT = "list";

    public static final String SET_ELEMENT = "set";

    public static final String MAP_ELEMENT = "map";

    public static final String ENTRY_ELEMENT = "entry";

    public static final String KEY_ELEMENT = "key";

    public static final String KEY_ATTRIBUTE = "key";

    public static final String KEY_REF_ATTRIBUTE = "key-ref";

    public static final String VALUE_REF_ATTRIBUTE = "value-ref";

    public static final String PROPS_ELEMENT = "props";

    public static final String PROP_ELEMENT = "prop";

    public static final String MERGE_ATTRIBUTE = "merge";

    public static final String QUALIFIER_ELEMENT = "qualifier";

    public static final String QUALIFIER_ATTRIBUTE_ELEMENT = "attribute";

    public static final String DEFAULT_LAZY_INIT_ATTRIBUTE = "default-lazy-init";

    public static final String DEFAULT_MERGE_ATTRIBUTE = "default-merge";

    public static final String DEFAULT_AUTOWIRE_ATTRIBUTE = "default-autowire";

    public static final String DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE = "default-dependency-check";

    public static final String DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE = "default-autowire-candidates";

    public static final String DEFAULT_INIT_METHOD_ATTRIBUTE = "default-init-method";

    public static final String DEFAULT_DESTROY_METHOD_ATTRIBUTE = "default-destroy-method";

    protected final Log logger = LogFactory.getLog(getClass());

    private final XmlReaderContext readerContext;

    private final DocumentDefaultsDefinition defaults = new DocumentDefaultsDefinition();

    private final ParseState parseState = new ParseState();

    private Environment environment;

    /**
     * Stores all used bean names so we can enforce uniqueness on a per
     * beans-element basis. Duplicate bean ids/names may not exist within the
     * same level of beans element nesting, but may be duplicated across levels.
     */
    private final Set<String> usedNames = new HashSet<String>();

7、createHelper方法

	protected BeanDefinitionParserDelegate createHelper(XmlReaderContext readerContext, Element root, BeanDefinitionParserDelegate parentDelegate) {
		BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext, environment);
		delegate.initDefaults(root, parentDelegate);
		return delegate;
	}

this.readerContext.fireDefaultsRegistered(this.defaults);　　

激发默认值的注册

8、initDefaults方法

	/**
	 * Initialize the default lazy-init, autowire, dependency check settings,
	 * init-method, destroy-method and merge settings. Support nested 'beans'
	 * element use cases by falling back to the given parent in case the
	 * defaults are not explicitly set locally.
	 * @see #populateDefaults(DocumentDefaultsDefinition, DocumentDefaultsDefinition, org.w3c.dom.Element)
	 * @see #getDefaults()
	 */
	public void initDefaults(Element root, BeanDefinitionParserDelegate parent) {
		populateDefaults(this.defaults, (parent != null ? parent.defaults : null), root);
		this.readerContext.fireDefaultsRegistered(this.defaults);
	}

　　

9、populateDefaults方法   装配根元素beans的默认值

	/**
	 * Populate the given DocumentDefaultsDefinition instance with the default lazy-init,
	 * autowire, dependency check settings, init-method, destroy-method and merge settings.
	 * Support nested 'beans' element use cases by falling back to
	 * <literal>parentDefaults</literal> in case the defaults are not explicitly set
	 * locally.
	 * @param defaults the defaults to populate
	 * @param parentDefaults the parent BeanDefinitionParserDelegate (if any) defaults to fall back to
	 * @param root the root element of the current bean definition document (or nested beans element)
	 */
	protected void populateDefaults(DocumentDefaultsDefinition defaults, DocumentDefaultsDefinition parentDefaults, Element root) {
		String lazyInit = root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(lazyInit)) {
			lazyInit = parentDefaults != null ? parentDefaults.getLazyInit() : FALSE_VALUE;
		}
		defaults.setLazyInit(lazyInit);

		String merge = root.getAttribute(DEFAULT_MERGE_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(merge)) {
			merge = parentDefaults != null ? parentDefaults.getMerge() : FALSE_VALUE;
		}
		defaults.setMerge(merge);

		String autowire = root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE);
		if (DEFAULT_VALUE.equals(autowire)) {
			autowire = parentDefaults != null ? parentDefaults.getAutowire() : AUTOWIRE_NO_VALUE;
		}
		defaults.setAutowire(autowire);

		// don't fall back to parentDefaults for dependency-check as it's no
		// longer supported in <beans> as of 3.0. Therefore, no nested <beans>
		// would ever need to fall back to it.
		defaults.setDependencyCheck(root.getAttribute(DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE));

		if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) {
			defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setAutowireCandidates(parentDefaults.getAutowireCandidates());
		}

		if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) {
			defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setInitMethod(parentDefaults.getInitMethod());
		}

		if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) {
			defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
		}
		else if (parentDefaults != null) {
			defaults.setDestroyMethod(parentDefaults.getDestroyMethod());
		}

		defaults.setSource(this.readerContext.extractSource(root));
	}