前言
来讨论创建bean过程中的属性注入，在spring的ioc容器启动过程中，会把定义的bean封装成beandefinition注册到一个concurrenthashmap中，bean注册完成后，就会对单利的且lazy-init=false 的bean进行实例化。创建bean的代码在 abstractautowirecapablebeanfactory#docreatebean 中，当bean创建成功之后，会调用abstractautowirecapablebeanfactory#populatebean 方法进行属性注入。本篇文章主要就是分析该方法是如何实现bean的属性注入的。
这里先上一个属性注入的流程图，待会儿可以根据这个图来看代码
属性注入：abstractautowirecapablebeanfactory#populatebean
abstractautowirecapablebeanfactory#populatebean 方法的主要功能就是属性填充，源码如下
//使用 bean 定义中的属性值填充给定 beanwrapper 中的 bean 实例。
@suppresswarnings("deprecation") // for postprocesspropertyvalues
protected void populatebean(string beanname, rootbeandefinition mbd, @nullable beanwrapper bw) {
if (bw == null) {
//判断是否有property属性
if (mbd.haspropertyvalues()) {
throw new beancreationexception(
mbd.getresourcedescription(), beanname, "cannot apply property values to null instance");
}
else {
//没有任何属性可以填充
// skip property population phase for null instance.
return;
}
}
// give any instantiationawarebeanpostprocessors the opportunity to modify the
// state of the bean before properties are set. this can be used, for example,
// to support styles of field injection.
//让 instantiationawarebeanpostprocessors 也在属性注入之前改变bean的状态
if (!mbd.issynthetic() && hasinstantiationawarebeanpostprocessors()) {
for (beanpostprocessor bp : getbeanpostprocessors()) {
if (bp instanceof instantiationawarebeanpostprocessor) {
instantiationawarebeanpostprocessor ibp = (instantiationawarebeanpostprocessor) bp;
if (!ibp.postprocessafterinstantiation(bw.getwrappedinstance(), beanname)) {
return;
}
}
}
}
//从 rootbeandefinition 获取所有的propertyvalues
propertyvalues pvs = (mbd.haspropertyvalues() ? mbd.getpropertyvalues() : null);
int resolvedautowiremode = mbd.getresolvedautowiremode();
//根据名字获取根据type注入
if (resolvedautowiremode == autowire_by_name || resolvedautowiremode == autowire_by_type) {
mutablepropertyvalues newpvs = new mutablepropertyvalues(pvs);
// add property values based on autowire by name if applicable.
//如果适用，根据名称添加基于自动装配的属性值。
if (resolvedautowiremode == autowire_by_name) {
autowirebyname(beanname, mbd, bw, newpvs);
}
// add property values based on autowire by type if applicable.
//如果适用，根据类型添加基于自动装配的属性值
if (resolvedautowiremode == autowire_by_type) {
autowirebytype(beanname, mbd, bw, newpvs);
}
pvs = newpvs;
}
//后置处理器是否已经注册,初始化好了
boolean hasinstawarebpps = hasinstantiationawarebeanpostprocessors();
//是否要检查依赖，默认false
boolean needsdepcheck = (mbd.getdependencycheck() != abstractbeandefinition.dependency_check_none);
propertydescriptor[] filteredpds = null;
if (hasinstawarebpps) {
if (pvs == null) {
pvs = mbd.getpropertyvalues();
}
//获取后置处理器
for (beanpostprocessor bp : getbeanpostprocessors()) {
//如果是bean实例化后置处理器
if (bp instanceof instantiationawarebeanpostprocessor) {
instantiationawarebeanpostprocessor ibp = (instantiationawarebeanpostprocessor) bp;
//
propertyvalues pvstouse = ibp.postprocessproperties(pvs, bw.getwrappedinstance(), beanname);
if (pvstouse == null) {
if (filteredpds == null) {
filteredpds = filterpropertydescriptorsfordependencycheck(bw, mbd.allowcaching);
}
//对需要依赖检查的属性进行后置处理
pvstouse = ibp.postprocesspropertyvalues(pvs, filteredpds, bw.getwrappedinstance(), beanname);
if (pvstouse == null) {
return;
}
}
pvs = pvstouse;
}
}
}
if (needsdepcheck) {
if (filteredpds == null) {
filteredpds = filterpropertydescriptorsfordependencycheck(bw, mbd.allowcaching);
}
checkdependencies(beanname, mbd, filteredpds, pvs);
}
if (pvs != null) {
//依赖注入入口，讲属性应用到bean中
applypropertyvalues(beanname, mbd, bw, pvs);
}
}
方法中的重要代码
- autowirebyname : 根据属性名进行注入
- autowirebytype：根据类型注入bean
- instantiationawarebeanpostprocessor.postprocesspropertyvalues :该方法是在工厂将给定的属性值应用于给定的 bean 之前对给定的属性值进行处理，比如：requiredannotationbeanpostprocessor类中对属性的验证。
- applypropertyvalues：属性的填充
autowirebyname是根据名字注入，源码如下
protected void autowirebyname(
string beanname, abstractbeandefinition mbd, beanwrapper bw, mutablepropertyvalues pvs) {
//寻找beanwrapper中需要依赖的属性
string[] propertynames = unsatisfiednonsimpleproperties(mbd, bw);
for (string propertyname : propertynames) {
if (containsbean(propertyname)) {
//递归实例化的bean
object bean = getbean(propertyname);
pvs.add(propertyname, bean);
//注册依赖的bean，加入 dependentbeanmap 中
registerdependentbean(propertyname, beanname);
if (logger.istraceenabled()) {
logger.trace("added autowiring by name from bean name '" + beanname +
"' via property '" + propertyname + "' to bean named '" + propertyname + "'");
}
}
else {
if (logger.istraceenabled()) {
logger.trace("not autowiring property '" + propertyname + "' of bean '" + beanname +
"' by name: no matching bean found");
}
}
}
}
这个方法很简单，就是先找到依赖的bean，递归初始化，然后加入 pvs中
//定义“按类型自动装配”（按类型的 bean 属性）行为的抽象方法
protected void autowirebytype(
string beanname, abstractbeandefinition mbd, beanwrapper bw, mutablepropertyvalues pvs) {
//类型转换器
typeconverter converter = getcustomtypeconverter();
if (converter == null) {
converter = bw;
}
set<string> autowiredbeannames = new linkedhashset<>(4);
//找到需要注入的属性
string[] propertynames = unsatisfiednonsimpleproperties(mbd, bw);
for (string propertyname : propertynames) {
try {
//属性描述
propertydescriptor pd = bw.getpropertydescriptor(propertyname);
// don't try autowiring by type for type object: never makes sense,
// even if it technically is a unsatisfied, non-simple property.
if (object.class != pd.getpropertytype()) {
//获取对象的set方法
methodparameter methodparam = beanutils.getwritemethodparameter(pd);
// do not allow eager init for type matching in case of a prioritized post-processor.
boolean eager = !(bw.getwrappedinstance() instanceof priorityordered);
//依赖描述
dependencydescriptor desc = new autowirebytypedependencydescriptor(methodparam, eager);
//【重要】得到依赖的属性的值，存储到 autowiredbeannames 集合中
//提供了对集合如：@autowired private list<a> as; 支持，根据类型走到所有的bean注入其中
object autowiredargument = resolvedependency(desc, beanname, autowiredbeannames, converter);
if (autowiredargument != null) {
//添加到pvs
pvs.add(propertyname, autowiredargument);
}
for (string autowiredbeanname : autowiredbeannames) {
//注入依赖的bean
registerdependentbean(autowiredbeanname, beanname);
if (logger.istraceenabled()) {
logger.trace("autowiring by type from bean name '" + beanname + "' via property '" +
propertyname + "' to bean named '" + autowiredbeanname + "'");
}
}
//清理掉依赖
autowiredbeannames.clear();
}
}
catch (beansexception ex) {
throw new unsatisfieddependencyexception(mbd.getresourcedescription(), beanname, propertyname, ex);
}
}
}
看到这，我们大概清楚了，其实在populatebean 方法中会先从rootbeandefinition 中获取 bean的属性(propertyvalues)，同时也会根据rootbeandefinition的autowiremode自动注入模式来根据name或者type寻主bean的依赖的属性。
根据类型注入和根据名字注入都是先从beanwrapper 中找到bean的依赖的属性，然后根据属性类型找到匹配的bean，实现依赖注入。还提供了对集合如：@autowired private list<a> as; 集合注入的支持。
属性寻找好之后都会封装成 propertyvalues，然后传给applypropertyvalues应用到bean身上。
abstractautowirecapablebeanfactory#applypropertyvalues
我们可以认为前面的代码是在为当前bean寻找依赖的的属性，封装到 propertyvalues中，在applypropertyvalues中才是把属性应用到当前bean。
//处理对象之间的引用，使用深拷贝
protected void applypropertyvalues(string beanname, beandefinition mbd, beanwrapper bw, propertyvalues pvs) {
if (pvs.isempty()) {
return;
}
if (system.getsecuritymanager() != null && bw instanceof beanwrapperimpl) {
((beanwrapperimpl) bw).setsecuritycontext(getaccesscontrolcontext());
}
mutablepropertyvalues mpvs = null;
list<propertyvalue> original;
if (pvs instanceof mutablepropertyvalues) {
mpvs = (mutablepropertyvalues) pvs;
//判断mpvs中的值是否已经转成了对应的类型，已经转了就可以直接设置值到 beanwrapper了
if (mpvs.isconverted()) {
// shortcut: use the pre-converted values as-is.
try {
//为实例化对象设置属性
bw.setpropertyvalues(mpvs);
return;
}
catch (beansexception ex) {
throw new beancreationexception(
mbd.getresourcedescription(), beanname, "error setting property values", ex);
}
}
//获取属性值的原始类型
original = mpvs.getpropertyvaluelist();
}
else {
//如果类型不是mutablepropertyvalues ， 就使用原生属性获取方法
original = arrays.aslist(pvs.getpropertyvalues());
}
//获取用户自定义的型转换器
typeconverter converter = getcustomtypeconverter();
if (converter == null) {
converter = bw;
}
//解析器：用于 bean 工厂实现的 helper 类，将 bean 定义对象中包含的值，解析为应用于目标 bean 实例的实际值。
beandefinitionvalueresolver valueresolver = new beandefinitionvalueresolver(this, beanname, mbd, converter);
// create a deep copy, resolving any references for values.
//存放类型转换过的属性，把bean的属性解析值新建拷贝，把拷贝的数据注入到对象
list<propertyvalue> deepcopy = new arraylist<>(original.size());
boolean resolvenecessary = false;
//类型转换，把属性转换为对应的类型
for (propertyvalue pv : original) {
if (pv.isconverted()) {
//属性值不需要转
deepcopy.add(pv);
}
else {
//属性名
string propertyname = pv.getname();
//原始属性值，它的类型是一个 如： runtimebeanreference<otherbean> 引用类型
object originalvalue = pv.getvalue();
//转换属性值，将引用转换为 ioc 容器中实例化对象引用 otherbean
object resolvedvalue = valueresolver.resolvevalueifnecessary(pv, originalvalue);
object convertedvalue = resolvedvalue;
boolean convertible = bw.iswritableproperty(propertyname) &&
!propertyaccessorutils.isnestedorindexedproperty(propertyname);
if (convertible) {
//使用用户自定义的转换器转换
convertedvalue = convertforproperty(resolvedvalue, propertyname, bw, converter);
}
// possibly store converted value in merged bean definition,
// in order to avoid re-conversion for every created bean instance.
if (resolvedvalue == originalvalue) {
if (convertible) {
//设置转换之后的值到pv ，把依赖的bean设置给propertyvalue
pv.setconvertedvalue(convertedvalue);
}
deepcopy.add(pv);
}
else if (convertible && originalvalue instanceof typedstringvalue &&
!((typedstringvalue) originalvalue).isdynamic() &&
!(convertedvalue instanceof collection || objectutils.isarray(convertedvalue))) {
pv.setconvertedvalue(convertedvalue);
deepcopy.add(pv);
}
else {
resolvenecessary = true;
//转换好的依赖的属性最终放到一个arraylist中
deepcopy.add(new propertyvalue(pv, convertedvalue));
}
}
}
if (mpvs != null && !resolvenecessary) {
mpvs.setconverted();
}
// set our (possibly massaged) deep copy.
try {
//把解析好的属性 设置到 beanwrapper 中
bw.setpropertyvalues(new mutablepropertyvalues(deepcopy));
}
catch (beansexception ex) {
throw new beancreationexception(
mbd.getresourcedescription(), beanname, "error setting property values", ex);
}
}
这里主要进行属性转换，然后应用到bean身上，这里的属性转换比如: 在beandefinition中属性可能是用字符串类型来描述的，需要把属性转成真实的原始属性类型。
- 首先判断属性是否需要转换类型，如果不需要转直接应用于bean。比如：
<property name="otherbean" ref="otherbean" />这种属性值其实是个字符串“otherbean” ，需要解析成容器中的otherbean实例的引用。 - 如果属性值需要类型转换，比如：属性值是容器中的另外一个bean，则需要根据属性值解析出引用的对象然后注入到对象的属性上，应用到bean。
通过 beandefinitionvalueresolver 类中的 resolvevalueifnecessary()方法中进行属性值的解析， 对属性值的注入是通过 bw.setpropertyvalues()方法完成
解析： beandefinitionvalueresolver#resolvevalueifnecessary
给定一个 propertyvalue根据属性值进行类型解析，必要时解析对工厂中其他 bean 的引用
@nullable
public object resolvevalueifnecessary(object argname, @nullable object value) {
// we must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
//对属性值是引用类型的解析
if (value instanceof runtimebeanreference) {
//比如：<property name="xx" ref="xxbean" 就是引用类型，会走这里
runtimebeanreference ref = (runtimebeanreference) value;
//对引用类型属性进行解析
return resolvereference(argname, ref);
}
///对属性值是引用容器中另一个 bean 名称的解析
else if (value instanceof runtimebeannamereference) {
string refname = ((runtimebeannamereference) value).getbeanname();
refname = string.valueof(doevaluate(refname));
//判断容器中是否有这个bean
if (!this.beanfactory.containsbean(refname)) {
throw new beandefinitionstoreexception(
"invalid bean name '" + refname + "' in bean reference for " + argname);
}
return refname;
}
else if (value instanceof beandefinitionholder) {
// resolve beandefinitionholder: contains beandefinition with name and aliases.
//解析 beandefinitionholder：包含带有名称和别名的 beandefinition
beandefinitionholder bdholder = (beandefinitionholder) value;
//解析内部 bean
return resolveinnerbean(argname, bdholder.getbeanname(), bdholder.getbeandefinition());
}
else if (value instanceof beandefinition) {
// resolve plain beandefinition, without contained name: use dummy name.
//解析纯 beandefinition，不包含名称
beandefinition bd = (beandefinition) value;
string innerbeanname = "(inner bean)" + beanfactoryutils.generated_bean_name_separator +
objectutils.getidentityhexstring(bd);
return resolveinnerbean(argname, innerbeanname, bd);
}
//对数组类型解析
else if (value instanceof managedarray) {
// may need to resolve contained runtime references.
managedarray array = (managedarray) value;
class<?> elementtype = array.resolvedelementtype;
if (elementtype == null) {
string elementtypename = array.getelementtypename();
if (stringutils.hastext(elementtypename)) {
try {
elementtype = classutils.forname(elementtypename, this.beanfactory.getbeanclassloader());
array.resolvedelementtype = elementtype;
}
catch (throwable ex) {
// improve the message by showing the context.
throw new beancreationexception(
this.beandefinition.getresourcedescription(), this.beanname,
"error resolving array type for " + argname, ex);
}
}
else {
elementtype = object.class;
}
}
return resolvemanagedarray(argname, (list<?>) value, elementtype);
}
//对集合类型解析
else if (value instanceof managedlist) {
// may need to resolve contained runtime references.
return resolvemanagedlist(argname, (list<?>) value);
}
//对set类型解析
else if (value instanceof managedset) {
// may need to resolve contained runtime references.
return resolvemanagedset(argname, (set<?>) value);
}
//对map类型解析
else if (value instanceof managedmap) {
// may need to resolve contained runtime references.
return resolvemanagedmap(argname, (map<?, ?>) value);
}
//对properties解析
else if (value instanceof managedproperties) {
properties original = (properties) value;
properties copy = new properties();
original.foreach((propkey, propvalue) -> {
if (propkey instanceof typedstringvalue) {
propkey = evaluate((typedstringvalue) propkey);
}
if (propvalue instanceof typedstringvalue) {
propvalue = evaluate((typedstringvalue) propvalue);
}
if (propkey == null || propvalue == null) {
throw new beancreationexception(
this.beandefinition.getresourcedescription(), this.beanname,
"error converting properties key/value pair for " + argname + ": resolved to null");
}
copy.put(propkey, propvalue);
});
return copy;
}
//解析字符串类型的属性值
else if (value instanceof typedstringvalue) {
// convert value to target type here.
typedstringvalue typedstringvalue = (typedstringvalue) value;
object valueobject = evaluate(typedstringvalue);
try {
//目标类型
class<?> resolvedtargettype = resolvetargettype(typedstringvalue);
if (resolvedtargettype != null) {
//目标类型进行解析
return this.typeconverter.convertifnecessary(valueobject, resolvedtargettype);
}
else {
//类型没获取到，就返回object类型
return valueobject;
}
}
catch (throwable ex) {
// improve the message by showing the context.
throw new beancreationexception(
this.beandefinition.getresourcedescription(), this.beanname,
"error converting typed string value for " + argname, ex);
}
}
else if (value instanceof nullbean) {
return null;
}
else {
return evaluate(value);
}
}
这个方法中就是根据属性的值的类型进行解析，如：string，array,list,set,map的类型，比较复杂的就是属性值依赖的是一个bean，那么就需要根据依赖的bean的名字找到容器中的bean的实例，查找如下：
/**
* resolve a reference to another bean in the factory.
*/
//关联对象的解析
@nullable
private object resolvereference(object argname, runtimebeanreference ref) {
try {
object bean;
//引用对象的名称
string refname = ref.getbeanname();
refname = string.valueof(doevaluate(refname));
//如果对象在父容器中，从父容器获取
if (ref.istoparent()) {
if (this.beanfactory.getparentbeanfactory() == null) {
throw new beancreationexception(
this.beandefinition.getresourcedescription(), this.beanname,
"can't resolve reference to bean '" + refname +
"' in parent factory: no parent factory available");
}
//如果对象在父容器中，从父容器获取
bean = this.beanfactory.getparentbeanfactory().getbean(refname);
}
else {
//[重要]根据依赖的bean的名字，从当前容器中获取bean
bean = this.beanfactory.getbean(refname);
//把依赖的bean的实例和当前对象建议依赖关系，使用 dependentbeanmap 去维护关系
this.beanfactory.registerdependentbean(refname, this.beanname);
}
if (bean instanceof nullbean) {
bean = null;
}
return bean;
}
catch (beansexception ex) {
throw new beancreationexception(
this.beandefinition.getresourcedescription(), this.beanname,
"cannot resolve reference to bean '" + ref.getbeanname() + "' while setting " + argname, ex);
}
}
* for each element in the managed array, resolve reference if necessary.
*/
//解析数组
private object resolvemanagedarray(object argname, list<?> ml, class<?> elementtype) {
object resolved = array.newinstance(elementtype, ml.size());
for (int i = 0; i < ml.size(); i++) {
array.set(resolved, i, resolvevalueifnecessary(new keyedargname(argname, i), ml.get(i)));
}
return resolved;
}
/**
* for each element in the managed list, resolve reference if necessary.
*/
//解析list
private list<?> resolvemanagedlist(object argname, list<?> ml) {
list<object> resolved = new arraylist<>(ml.size());
for (int i = 0; i < ml.size(); i++) {
resolved.add(resolvevalueifnecessary(new keyedargname(argname, i), ml.get(i)));
}
return resolved;
}
/**
* for each element in the managed set, resolve reference if necessary.
*/
//解析set
private set<?> resolvemanagedset(object argname, set<?> ms) {
set<object> resolved = new linkedhashset<>(ms.size());
int i = 0;
for (object m : ms) {
resolved.add(resolvevalueifnecessary(new keyedargname(argname, i), m));
i++;
}
return resolved;
}
/**
* for each element in the managed map, resolve reference if necessary.
*/
//解析map
private map<?, ?> resolvemanagedmap(object argname, map<?, ?> mm) {
map<object, object> resolved = new linkedhashmap<>(mm.size());
mm.foreach((key, value) -> {
object resolvedkey = resolvevalueifnecessary(argname, key);
object resolvedvalue = resolvevalueifnecessary(new keyedargname(argname, key), value);
resolved.put(resolvedkey, resolvedvalue);
});
return resolved;
}
属性值解析完成之后 是封装成一个 mutablepropertyvalues，通过 beanwrapperimpl.setpropertyvalues()方法完成值的注入，beanwrapperimpl中注入方法又是由abstractpropertyaccessor#setpropertyvalue(java.lang.string, java.lang.object)去完成。
abstractpropertyaccessor#setpropertyvalue
@override
public void setpropertyvalues(propertyvalues pvs, boolean ignoreunknown, boolean ignoreinvalid)
throws beansexception {
list<propertyaccessexception> propertyaccessexceptions = null;
//拿到所有的属性列表
list<propertyvalue> propertyvalues = (pvs instanceof mutablepropertyvalues ?
((mutablepropertyvalues) pvs).getpropertyvaluelist() : arrays.aslist(pvs.getpropertyvalues()));
for (propertyvalue pv : propertyvalues) {
try {
// this method may throw any beansexception, which won't be caught
// here, if there is a critical failure such as no matching field.
// we can attempt to deal only with less serious exceptions.
//设置属性值
setpropertyvalue(pv);
}
...省略...
@override
public void setpropertyvalue(string propertyname, @nullable object value) throws beansexception {
//属性访问器
abstractnestablepropertyaccessor nestedpa;
try {
nestedpa = getpropertyaccessorforpropertypath(propertyname);
}
catch (notreadablepropertyexception ex) {
throw new notwritablepropertyexception(getrootclass(), this.nestedpath + propertyname,
"nested property in path '" + propertyname + "' does not exist", ex);
}
//属性助手
propertytokenholder tokens = getpropertynametokens(getfinalpath(nestedpa, propertyname));
//通过属性访问器为属性设置值
nestedpa.setpropertyvalue(tokens, new propertyvalue(propertyname, value));
}
这里看到，属性的注入交给了 abstractnestablepropertyaccessor 属性访问器去完成
protected void setpropertyvalue(propertytokenholder tokens, propertyvalue pv) throws beansexception {
if (tokens.keys != null) {
processkeyedproperty(tokens, pv);
}
else {
//走这里
processlocalproperty(tokens, pv);
}
}
private void processlocalproperty(propertytokenholder tokens, propertyvalue pv) {
//属性处理器
propertyhandler ph = getlocalpropertyhandler(tokens.actualname);
if (ph == null || !ph.iswritable()) {
if (pv.isoptional()) {
if (logger.isdebugenabled()) {
logger.debug("ignoring optional value for property '" + tokens.actualname +
"' - property not found on bean class [" + getrootclass().getname() + "]");
}
return;
}
else {
throw createnotwritablepropertyexception(tokens.canonicalname);
}
}
object oldvalue = null;
try {
//原生值
object originalvalue = pv.getvalue();
object valuetoapply = originalvalue;
...省略...
//这是重点，通过 propertyhandler 把属性值设置给对象
ph.setvalue(valuetoapply);
}
catch (typemismatchexception ex) {
throw ex;
}
这里的属性值通过 propertyhandler去设置
@override
public void setvalue(@nullable object value) throws exception {
//得到属性的set方法
method writemethod = (this.pd instanceof generictypeawarepropertydescriptor ?
((generictypeawarepropertydescriptor) this.pd).getwritemethodforactualaccess() :
this.pd.getwritemethod());
if (system.getsecuritymanager() != null) {
accesscontroller.doprivileged((privilegedaction<object>) () -> {
reflectionutils.makeaccessible(writemethod);
return null;
});
try {
accesscontroller.doprivileged((privilegedexceptionaction<object>)
() -> writemethod.invoke(getwrappedinstance(), value), acc);
}
catch (privilegedactionexception ex) {
throw ex.getexception();
}
}
else {
//设置访问权限
reflectionutils.makeaccessible(writemethod);
//调用set方法把属性值设置进去
writemethod.invoke(getwrappedinstance(), value);
}
}
这里就是得到属性的set方法，然后调用set方法把值注入进去。
构造器注入参数
在之前分析bean的创建的时候我们就说到，在 abstractautowirecapablebeanfactory#createbeaninstance 中会通过反射获取到bean的构造器，如果是有参构造就会走autowireconstructor 方法，通过有参构造创建实例
protected beanwrapper createbeaninstance(string beanname, rootbeandefinition mbd, @nullable object[] args) {
// make sure bean class is actually resolved at this point.
class<?> beanclass = resolvebeanclass(mbd, beanname);
...省略...
// need to determine the constructor...
constructor<?>[] ctors = determineconstructorsfrombeanpostprocessors(beanclass, beanname);
if (ctors != null ||
mbd.getresolvedautowiremode() == rootbeandefinition.autowire_constructor ||
mbd.hasconstructorargumentvalues() || !objectutils.isempty(args)) {
//【重要】构造器注入参数
return autowireconstructor(beanname, mbd, ctors, args);
}
// no special handling: simply use no-arg constructor.
return instantiatebean(beanname, mbd);
}
在autowireconstructor方法中会通过 constructorresolver 对构造器参数进行解析
protected beanwrapper autowireconstructor(
string beanname, rootbeandefinition mbd, @nullable constructor<?>[] ctors, @nullable object[] explicitargs) {
//构造器解析器，注入
return new constructorresolver(this).autowireconstructor(beanname, mbd, ctors, explicitargs);
}
public beanwrapper autowireconstructor(final string beanname, final rootbeandefinition mbd,
@nullable constructor<?>[] chosenctors, @nullable final object[] explicitargs) {
...省略...
else {
//得到构造器参数
constructorargumentvalues cargs = mbd.getconstructorargumentvalues();
//得到构造器参数值
resolvedvalues = new constructorargumentvalues();
//解析参数值【重要】
minnrofargs = resolveconstructorarguments(beanname, mbd, bw, cargs, resolvedvalues);
}
...省略...
try {
//实例化策略
final instantiationstrategy strategy = beanfactory.getinstantiationstrategy();
object beaninstance;
if (system.getsecuritymanager() != null) {
final constructor<?> ctortouse = constructortouse;
final object[] argumentstouse = argstouse;
beaninstance = accesscontroller.doprivileged((privilegedaction<object>) () ->
strategy.instantiate(mbd, beanname, beanfactory, ctortouse, argumentstouse),
beanfactory.getaccesscontrolcontext());
}
else {
//实例化对象，根据有参构造器，使用反射创建实例
beaninstance = strategy.instantiate(mbd, beanname, this.beanfactory, constructortouse, argstouse);
}
bw.setbeaninstance(beaninstance);
return bw;
}
resolveconstructorarguments 方法中又通过 beandefinitionvalueresolver来解析属性值，有参数的值了，就会走反射，根据有参构造器创建实例返回。
private int resolveconstructorarguments(string beanname, rootbeandefinition mbd, beanwrapper bw,
constructorargumentvalues cargs, constructorargumentvalues resolvedvalues) {
typeconverter customconverter = this.beanfactory.getcustomtypeconverter();
typeconverter converter = (customconverter != null ? customconverter : bw);
//属性值的解析器
beandefinitionvalueresolver valueresolver =
new beandefinitionvalueresolver(this.beanfactory, beanname, mbd, converter);
...省略...
for (constructorargumentvalues.valueholder valueholder : cargs.getgenericargumentvalues()) {
if (valueholder.isconverted()) {
resolvedvalues.addgenericargumentvalue(valueholder);
}
else {
//为构造器参数值做解析，这里和之前分析的set注入的属性值解析就一样了
object resolvedvalue =
valueresolver.resolvevalueifnecessary("constructor argument", valueholder.getvalue());
constructorargumentvalues.valueholder resolvedvalueholder = new constructorargumentvalues.valueholder(
resolvedvalue, valueholder.gettype(), valueholder.getname());
resolvedvalueholder.setsource(valueholder);
resolvedvalues.addgenericargumentvalue(resolvedvalueholder);
}
}
return minnrofargs;
}
因为之前 resolvevalueifnecessary方法已经分析过了，这里就不多说了。
总结
到这里属性注入的流程就分析完了，总结都在这个图上
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