BeanDefinition的解析就是将对bean的定义转换为spring内部的数据结构
准备两个类和spring的xml文件 UserService.java ` public class UserService {
private UserDto userDto;
private Map<String,String> map;
public UserDto getUserDto() {
return userDto;
}
public void setUserDto(UserDto userDto) {
this.userDto = userDto;
}
public Map<String, String> getMap() {
return map;
}
public void setMap(Map<String, String> map) {
this.map = map;
}
} `
UserDto.java ` public class UserDto { String name; int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void initMethod(){
System.out.println("initMethod start--------------");
}
} `
spring的配置文件bean.xml `
<bean id="userService" class="service.UserService">
<property name="map">
<map>
<entry key="name" value="test"/>
<entry key="age" value="20"/>
</map>
</property>
<property name="userDto" ref="userDto"></property>
</bean>
<!--创建bean-->
<bean id="userDto" class="dto.UserDto" init-method="initMethod" name="dto" lazy-init="true">
<property name="age" value="20"/>
<property name="name" value="保质期已过"/>
</bean>
`
main方法测试
` public static void main(String[] args) {
//1.资源定位
Resource resource = new ClassPathResource("bean.xml");
//2.创建IOC容器,这里使用DefaultListableBeanFactory作为IOC容器
DefaultListableBeanFactory defaultListableBeanFactory = new DefaultListableBeanFactory();
//3.读取BeanDefinition并注册到IOC容器中
BeanDefinitionReader reader = new XmlBeanDefinitionReader(defaultListableBeanFactory);
reader.loadBeanDefinitions(resource);
} `
具体的过程是由BeanDefinitionDocumentReader的实现类DefaultBeanDefinitionDocumentReader.registerBeanDefinitions方法实现
DefaultBeanDefinitionDocumentReader.java `public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();//root代表根节点<beans>
doRegisterBeanDefinitions(root);
}`
在doRegisterBeanDefinitions会调用parseBeanDefinitions方法，在parseBeanDefinitions中会调用parseDefaultElement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)) {//节点的名称是bean
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}`
具体的解析过程会委托给BeanDefinitionParseDelegate.parseBeanDefinitionElement完成，这个类包含对bean规则定义的解析，比如bean属性（id,name,init-method等）的设定，property的设置
`protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//处理给定的bean定义——》BeanDefinition
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));
}
}`
parseBeanDefinitionElement方法
`public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
//获取bean的id,name属性
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
List<String> aliases = new ArrayList<>();
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");
}
}
//检查beanName是否存在
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
//对Bean元素的详细解析
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;
}`
parseBeanDefinitionElement 方法
`public AbstractBeanDefinition parseBeanDefinitionElement( Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
//创建BeanDefinition，为bean定义信息的载入做准备
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
//解析bean的属性
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
//解析bean的元素
parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//解析bean的构造函数
parseConstructorArgElements(ele, bd);
//解析property
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;
}`
parseBeanDefinitionAttributes方法，完成对bean属性的解析，比如init-method,lazy-init等，如果没有设置属性会设置默认值
`public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName, @Nullable BeanDefinition containingBean, AbstractBeanDefinition bd) {
if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
error("Old 1.x 'singleton' attribute in use - upgrade to 'scope' declaration", ele);
}
//设置scope
else if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE));
}
else if (containingBean != null) {
// Take default from containing bean in case of an inner bean definition.
bd.setScope(containingBean.getScope());
}
if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
}
//设置懒加载
String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
if (isDefaultValue(lazyInit)) {
lazyInit = this.defaults.getLazyInit();
}
bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
//设置自动注入
String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
bd.setAutowireMode(getAutowireMode(autowire));
if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) {
String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE);
bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, MULTI_VALUE_ATTRIBUTE_DELIMITERS));
}
String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE);
if (isDefaultValue(autowireCandidate)) {
String candidatePattern = this.defaults.getAutowireCandidates();
if (candidatePattern != null) {
String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern);
bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName));
}
}
else {
bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate));
}
if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
}
//设置初始化方法
if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) {
String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE);
bd.setInitMethodName(initMethodName);
}
else if (this.defaults.getInitMethod() != null) {
bd.setInitMethodName(this.defaults.getInitMethod());
bd.setEnforceInitMethod(false);
}
//设置销毁方法
if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) {
String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE);
bd.setDestroyMethodName(destroyMethodName);
}
else if (this.defaults.getDestroyMethod() != null) {
bd.setDestroyMethodName(this.defaults.getDestroyMethod());
bd.setEnforceDestroyMethod(false);
}
if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
}
if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
}
return bd;
}`
parsePropertyElements完成对property的解析，获取元素后判断是否是elment,如果是的会调用parsePropertyElement进行元素和属性的解析，生成PropertyValue对象，将PropertyValue对象放入集合中，最后添加到BeanDefinition中
`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);
}
}
}`
parsePropertyElement解析Property节点
`public void parsePropertyElement(Element ele, BeanDefinition bd) {
//获取属性name的值，比如<property name="age" value="20"/> 获取到的就是“age”
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;
}
//对元素value值的解析，ref,value,子元素
Object val = parsePropertyValue(ele, bd, propertyName);
//创建PropertyValue对象
PropertyValue pv = new PropertyValue(propertyName, val);
parseMetaElements(ele, pv);
pv.setSource(extractSource(ele));
//将PropertyValue对象放入集合中
bd.getPropertyValues().addPropertyValue(pv);
}
finally {
this.parseState.pop();
}
}`
parsePropertyValue对value,ref,elment的解析
`public Object parsePropertyValue(Element ele, BeanDefinition bd, @Nullable 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.
//Property中含有子元素
if (subElement != null) {
error(elementName + " must not contain more than one sub-element", ele);
}
else {
subElement = (Element) node;
}
}
}
//ref属性
boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE);
//value属性
boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE);
//如果两个属性都存在，则报错
if ((hasRefAttribute && hasValueAttribute) ||
((hasRefAttribute || hasValueAttribute) && subElement != null)) {
error(elementName +
" is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele);
}
//如果是ref属性，返回RuntimeBeanReference对象
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;
}
//如果是value属性，返回TypedStringValue
else if (hasValueAttribute) {
TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));
valueHolder.setSource(extractSource(ele));
return valueHolder;
}
//如果还有子元素，则继续解析子元素，里面包含map,set,list的解析
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;
}
}`
parsePropertySubElement判断节点名称，这里以map集合为例，判断如果是map节点则调用parseMapElement，解析entry节点的属性key和value的值，将值放到新的map中并返回
`public Map<Object, Object> parseMapElement(Element mapEle, @Nullable BeanDefinition bd) { String defaultKeyType = mapEle.getAttribute(KEY_TYPE_ATTRIBUTE); String defaultValueType = mapEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
List<Element> entryEles = DomUtils.getChildElementsByTagName(mapEle, ENTRY_ELEMENT);
ManagedMap<Object, Object> map = new ManagedMap<>(entryEles.size());
map.setSource(extractSource(mapEle));
map.setKeyTypeName(defaultKeyType);
map.setValueTypeName(defaultValueType);
map.setMergeEnabled(parseMergeAttribute(mapEle));
for (Element entryEle : entryEles) {
// Should only have one value child element: ref, value, list, etc.
// Optionally, there might be a key child element.
NodeList entrySubNodes = entryEle.getChildNodes();
Element keyEle = null;
Element valueEle = null;
for (int j = 0; j < entrySubNodes.getLength(); j++) {
Node node = entrySubNodes.item(j);
if (node instanceof Element) {
Element candidateEle = (Element) node;
if (nodeNameEquals(candidateEle, KEY_ELEMENT)) {
if (keyEle != null) {
error("<entry> element is only allowed to contain one <key> sub-element", entryEle);
}
else {
keyEle = candidateEle;
}
}
else {
// Child element is what we're looking for.
if (nodeNameEquals(candidateEle, DESCRIPTION_ELEMENT)) {
// the element is a <description> -> ignore it
}
else if (valueEle != null) {
error("<entry> element must not contain more than one value sub-element", entryEle);
}
else {
valueEle = candidateEle;
}
}
}
}
// Extract key from attribute or sub-element.
Object key = null;
boolean hasKeyAttribute = entryEle.hasAttribute(KEY_ATTRIBUTE);
boolean hasKeyRefAttribute = entryEle.hasAttribute(KEY_REF_ATTRIBUTE);
if ((hasKeyAttribute && hasKeyRefAttribute) ||
(hasKeyAttribute || hasKeyRefAttribute) && keyEle != null) {
error("<entry> element is only allowed to contain either " +
"a 'key' attribute OR a 'key-ref' attribute OR a <key> sub-element", entryEle);
}
if (hasKeyAttribute) {
key = buildTypedStringValueForMap(entryEle.getAttribute(KEY_ATTRIBUTE), defaultKeyType, entryEle);
}
else if (hasKeyRefAttribute) {
String refName = entryEle.getAttribute(KEY_REF_ATTRIBUTE);
if (!StringUtils.hasText(refName)) {
error("<entry> element contains empty 'key-ref' attribute", entryEle);
}
RuntimeBeanReference ref = new RuntimeBeanReference(refName);
ref.setSource(extractSource(entryEle));
key = ref;
}
else if (keyEle != null) {
key = parseKeyElement(keyEle, bd, defaultKeyType);
}
else {
error("<entry> element must specify a key", entryEle);
}
// Extract value from attribute or sub-element.
Object value = null;
boolean hasValueAttribute = entryEle.hasAttribute(VALUE_ATTRIBUTE);
boolean hasValueRefAttribute = entryEle.hasAttribute(VALUE_REF_ATTRIBUTE);
boolean hasValueTypeAttribute = entryEle.hasAttribute(VALUE_TYPE_ATTRIBUTE);
if ((hasValueAttribute && hasValueRefAttribute) ||
(hasValueAttribute || hasValueRefAttribute) && valueEle != null) {
error("<entry> element is only allowed to contain either " +
"'value' attribute OR 'value-ref' attribute OR <value> sub-element", entryEle);
}
if ((hasValueTypeAttribute && hasValueRefAttribute) ||
(hasValueTypeAttribute && !hasValueAttribute) ||
(hasValueTypeAttribute && valueEle != null)) {
error("<entry> element is only allowed to contain a 'value-type' " +
"attribute when it has a 'value' attribute", entryEle);
}
if (hasValueAttribute) {
String valueType = entryEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
if (!StringUtils.hasText(valueType)) {
valueType = defaultValueType;
}
value = buildTypedStringValueForMap(entryEle.getAttribute(VALUE_ATTRIBUTE), valueType, entryEle);
}
else if (hasValueRefAttribute) {
String refName = entryEle.getAttribute(VALUE_REF_ATTRIBUTE);
if (!StringUtils.hasText(refName)) {
error("<entry> element contains empty 'value-ref' attribute", entryEle);
}
RuntimeBeanReference ref = new RuntimeBeanReference(refName);
ref.setSource(extractSource(entryEle));
value = ref;
}
else if (valueEle != null) {
value = parsePropertySubElement(valueEle, bd, defaultValueType);
}
else {
error("<entry> element must specify a value", entryEle);
}
// Add final key and value to the Map.
map.put(key, value);
}
return map;
}`
