主题
之前学习了@Autowired下SpringBean是怎么注入到属性中的.
https://www.cnblogs.com/abcwt112/p/12541783.html
现在学习下远古时代的XML是怎么注入的.
Ac初始化
入口是XML的AC.
new的时候回做refresh方法
refresh之前的文章分享过大致做了什么
https://www.cnblogs.com/abcwt112/p/12388982.html
其中这一步会去掉BeanFactory的getBean方法去初始化配置的bean.
属性注入
BF的getBean里面有无数逻辑.其中注入属性的是这一段
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#populateBean
1 /**
2 * Populate the bean instance in the given BeanWrapper with the property values
3 * from the bean definition.
4 * @param beanName the name of the bean
5 * @param mbd the bean definition for the bean
6 * @param bw the BeanWrapper with bean instance
7 */
8 @SuppressWarnings("deprecation") // for postProcessPropertyValues
9 protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
10 if (bw == null) {
11 if (mbd.hasPropertyValues()) {
12 throw new BeanCreationException(
13 mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
14 }
15 else {
16 // Skip property population phase for null instance.
17 return;
18 }
19 }
20
21 // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
22 // state of the bean before properties are set. This can be used, for example,
23 // to support styles of field injection.
24 boolean continueWithPropertyPopulation = true;
25
26 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
27 for (BeanPostProcessor bp : getBeanPostProcessors()) {
28 if (bp instanceof InstantiationAwareBeanPostProcessor) {
29 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
30 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
31 continueWithPropertyPopulation = false;
32 break;
33 }
34 }
35 }
36 }
37
38 if (!continueWithPropertyPopulation) {
39 return;
40 }
41
42 PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
43
44 int resolvedAutowireMode = mbd.getResolvedAutowireMode();
45 if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
46 MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
47 // Add property values based on autowire by name if applicable.
48 if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
49 autowireByName(beanName, mbd, bw, newPvs);
50 }
51 // Add property values based on autowire by type if applicable.
52 if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
53 autowireByType(beanName, mbd, bw, newPvs);
54 }
55 pvs = newPvs;
56 }
57
58 boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
59 boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
60
61 PropertyDescriptor[] filteredPds = null;
62 if (hasInstAwareBpps) {
63 if (pvs == null) {
64 pvs = mbd.getPropertyValues();
65 }
66 for (BeanPostProcessor bp : getBeanPostProcessors()) {
67 if (bp instanceof InstantiationAwareBeanPostProcessor) {
68 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
69 PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
70 if (pvsToUse == null) {
71 if (filteredPds == null) {
72 filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
73 }
74 pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
75 if (pvsToUse == null) {
76 return;
77 }
78 }
79 pvs = pvsToUse;
80 }
81 }
82 }
83 if (needsDepCheck) {
84 if (filteredPds == null) {
85 filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
86 }
87 checkDependencies(beanName, mbd, filteredPds, pvs);
88 }
89
90 if (pvs != null) {
91 applyPropertyValues(beanName, mbd, bw, pvs);
92 }
93 }
如果XML里bean是这样配置的:
其中最后91行的 applyPropertyValues(beanName, mbd, bw, pvs);
就是把对象中的属性(pvs)转化成对象,设置到bw(BeanWrapper.封装了原始对象)中去.
比如beanName是a. pvs是a对象里的属性集,其中包含b
具体逻辑是调用Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue); 来获取要注入的属性对应的bean.
最终也是通过BF.getBean去取Bean.再set到beanwrapper上去.
XML配置中还有一种情况是使用默认的自动配置
这个时候bean的属性是不需要配置的.spring会自动根据类型(byType)或者名称(byName)去匹配.
原理是在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#populateBean中
1 int resolvedAutowireMode = mbd.getResolvedAutowireMode();
2 if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
3 MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
4 // Add property values based on autowire by name if applicable.
5 if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
6 autowireByName(beanName, mbd, bw, newPvs);
7 }
8 // Add property values based on autowire by type if applicable.
9 if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
10 autowireByType(beanName, mbd, bw, newPvs);
11 }
12 pvs = newPvs;
13 }
resolvedAutowireMode默认情况下是0.是不会自动装配的.如果配置了就会进对应的autowiredByXXX方法.会找出missing property values然后设置到MutablePropertyValues中.所以最后掉applyPropertyValues方法的时候还是会填充这些属性.
原文地址：https://www.cnblogs.com/abcwt112/p/12557232.html