SPRING技术内幕:深入解析SPRING架构与设计原理(第2版)-笔记(一)IOC解析

开始之前先说一下Beanfactory的结构原理:

这里写图片描述

下图是springIOC解析的整个过程:
这里写图片描述这里写图片描述这里写图片描述

IOC容器分为3个步骤:
1、定位
(1)Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
(2)loadBeanDefinitions委派为子类XmlBeanDefinitionReader的重写方法
(3)定位:在方法loadBeanDefinitions(String location, Set actualResources)中语句:
Resource resource = resourceLoader.getResource(location),resourceLoader调用其实现类DefaultResourceLoader的getResource(String location)方法的getResourceByPath(location)定位加载资源,getResourceByPath(location)在FileSystemXmlApplicationContext已经重写,即,调用的FileSystemXmlApplicationContext的实现方法。这也解释了FileSystemXmlApplicationContext有一个getResourceByPath方法的原因(委派机制)。
2、载入
主要实现类:
BeanDefinitionParserDelegate.parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean):

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
/**
* Parse the bean definition itself, without regard to name or aliases. May return
* <code>null</code> if problems occured during the parse of the bean definition.
*/
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;
}

3、注册
主要实现类:
DefaultListableBeanFactory.registerBeanDefinition(String beanName, BeanDefinition beanDefinition)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
//---------------------------------------------------------------------
// Implementation of BeanDefinitionRegistry interface
//---------------------------------------------------------------------

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 ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}

synchronized (this.beanDefinitionMap) {
Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
if (!this.allowBeanDefinitionOverriding) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
}
else {
this.beanDefinitionNames.add(beanName);
this.frozenBeanDefinitionNames = null;
}
this.beanDefinitionMap.put(beanName, beanDefinition);

resetBeanDefinition(beanName);
}
}