/**
* Retrieve all candidate methods for the given class, considering the {@link
* RootBeanDefinition#isNonPublicAccessAllowed()} flag. Called as the starting point for factory
* method determination.
*/
private Method[] getCandidateMethods(final Class<?> factoryClass, final RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
return AccessController.doPrivileged(
new PrivilegedAction<Method[]>() {
@Override
public Method[] run() {
return (mbd.isNonPublicAccessAllowed()
? ReflectionUtils.getAllDeclaredMethods(factoryClass)
: factoryClass.getMethods());
}
});
} else {
return (mbd.isNonPublicAccessAllowed()
? ReflectionUtils.getAllDeclaredMethods(factoryClass)
: factoryClass.getMethods());
}
}
/**
* 带有参数的实例化Bean方法，主要完成的功能如下： 1. 构造函数参数的确定 1）根据explicitArgs参数判断 2）从缓存中获取 3）从配置文件获取 2. 构造函数的确定 3.
* 根据确定的构造函数转换对应的参数类型 4. 构造函数不确定性的验证 5. 根据实例化策略以及得到的构造函数和构造函数参数实例化bean
*/
public BeanWrapper autowireConstructor(
final String beanName,
final RootBeanDefinition mbd,
Constructor<?>[] chosenCtors,
final Object[] explicitArgs) {
BeanWrapperImpl bw = new BeanWrapperImpl();
this.beanFactory.initBeanWrapper(bw);
// 定义选取的构造函数
Constructor<?> constructorToUse = null;
// 定义选取的构造函数参数
ArgumentsHolder argsHolderToUse = null;
Object[] argsToUse = null;
// 如果getBean调用时指定了方法参数，则直接使用
if (explicitArgs != null) {
argsToUse = explicitArgs;
}
// getBean方法未指定参数，则从配置文件中解析
else {
Object[] argsToResolve = null;
// 尝试从缓存中获取bean的构造函数以及参数
// 解析bean定义的构造函数较为耗时，因此在完成解析后会将解析后的构造函数以及参数放入BeanDefinition中的相关字段作为缓存
// mbd.resolvedConstructorOrFactoryMethod存放的是构造函数
// mbd.resolvedConstructorArguments存放的是处理后的构造函数参数
// mbd.preparedConstructorArguments存放的是原生的构造函数参数（参数类型未经过处理）
synchronized (mbd.constructorArgumentLock) {
constructorToUse = (Constructor<?>) mbd.resolvedConstructorOrFactoryMethod;
if (constructorToUse != null && mbd.constructorArgumentsResolved) {
// Found a cached constructor...
argsToUse = mbd.resolvedConstructorArguments;
if (argsToUse == null) {
argsToResolve = mbd.preparedConstructorArguments;
}
}
}
// 如果缓存中存在
if (argsToResolve != null) {
// 解析参数类型，将构造参数的类型转换为最终的类型
// eg: 构造函数A(int, int)
// 通过此方法后就会把配置中的("1", "1")转换为(1, 1)
argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve);
}
}
// 缓存中不存在
if (constructorToUse == null) {
// Need to resolve the constructor.
boolean autowiring =
(chosenCtors != null
|| mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
// 存放解析后的构造函数参数的值
ConstructorArgumentValues resolvedValues = null;
int minNrOfArgs;
if (explicitArgs != null) {
minNrOfArgs = explicitArgs.length;
} else {
// 提取配置文件中的构造函数参数
ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
resolvedValues = new ConstructorArgumentValues();
minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
}
// Take specified constructors, if any.
// 获取bean的class类的所有构造函数
Constructor<?>[] candidates = chosenCtors;
if (candidates == null) {
Class<?> beanClass = mbd.getBeanClass();
try {
candidates =
(mbd.isNonPublicAccessAllowed()
? beanClass.getDeclaredConstructors()
: beanClass.getConstructors());
} catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Resolution of declared constructors on bean Class ["
+ beanClass.getName()
+ "] from ClassLoader ["
+ beanClass.getClassLoader()
+ "] failed",
ex);
}
}
// 排序给定的构造函数，public构造函数优先，参数数量降序
AutowireUtils.sortConstructors(candidates);
int minTypeDiffWeight = Integer.MAX_VALUE;
Set<Constructor<?>> ambiguousConstructors = null;
LinkedList<UnsatisfiedDependencyException> causes = null;
for (int i = 0; i < candidates.length; i++) {
Constructor<?> candidate = candidates[i];
Class<?>[] paramTypes = candidate.getParameterTypes();
// 如果已经找到选用的构造函数，并且构造函数所需的参数个数小于配置的构造函数参数个数则终止，因为构造函数已经按照参数个数降序
if (constructorToUse != null && argsToUse.length > paramTypes.length) {
// Already found greedy constructor that can be satisfied ->
// do not look any further, there are only less greedy constructors left.
break;
}
if (paramTypes.length < minNrOfArgs) {
continue;
}
ArgumentsHolder argsHolder;
// 构造函数参数从配置文件中获取的情况
if (resolvedValues != null) {
// 有参数则直接根据值构造对应类型的参数
try {
String[] paramNames =
ConstructorPropertiesChecker.evaluate(candidate, paramTypes.length);
if (paramNames == null) {
ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
if (pnd != null) {
// 获取参数名称
paramNames = pnd.getParameterNames(candidate);
}
}
// 根据参数名称和类型创建参数容器
argsHolder =
createArgumentArray(
beanName,
mbd,
resolvedValues,
bw,
paramTypes,
paramNames,
candidate,
autowiring);
} catch (UnsatisfiedDependencyException ex) {
if (this.beanFactory.logger.isTraceEnabled()) {
this.beanFactory.logger.trace(
"Ignoring constructor [" + candidate + "] of bean '" + beanName + "': " + ex);
}
// Swallow and try next constructor.
if (causes == null) {
causes = new LinkedList<UnsatisfiedDependencyException>();
}
causes.add(ex);
continue;
}
}
// 构造函数参数从getBean方法传入的情况
else {
// Explicit arguments given -> arguments length must match exactly.
// 对于构造函数从getBean方法传入的情况，参数数目必须精确匹配
if (paramTypes.length != explicitArgs.length) {
continue;
}
argsHolder = new ArgumentsHolder(explicitArgs);
}
// 检测是否有不确定性的构造函数存在，例如不同构造函数的参数为父子关系
int typeDiffWeight =
(mbd.isLenientConstructorResolution()
? argsHolder.getTypeDifferenceWeight(paramTypes)
: argsHolder.getAssignabilityWeight(paramTypes));
// Choose this constructor if it represents the closest match.
// 选择最为接近的匹配作为构造函数
if (typeDiffWeight < minTypeDiffWeight) {
constructorToUse = candidate;
argsHolderToUse = argsHolder;
argsToUse = argsHolder.arguments;
minTypeDiffWeight = typeDiffWeight;
ambiguousConstructors = null;
} else if (constructorToUse != null && typeDiffWeight == minTypeDiffWeight) {
if (ambiguousConstructors == null) {
ambiguousConstructors = new LinkedHashSet<Constructor<?>>();
ambiguousConstructors.add(constructorToUse);
}
ambiguousConstructors.add(candidate);
}
}
if (constructorToUse == null) {
if (causes != null) {
UnsatisfiedDependencyException ex = causes.removeLast();
for (Exception cause : causes) {
this.beanFactory.onSuppressedException(cause);
}
throw ex;
}
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Could not resolve matching constructor "
+ "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)");
} else if (ambiguousConstructors != null && !mbd.isLenientConstructorResolution()) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Ambiguous constructor matches found in bean '"
+ beanName
+ "' "
+ "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): "
+ ambiguousConstructors);
}
if (explicitArgs == null) {
// 将解析的构造函数加入缓存
argsHolderToUse.storeCache(mbd, constructorToUse);
}
}
// 确定了构造函数以及参数后，使用构造函数对bean进行实例化
try {
Object beanInstance;
if (System.getSecurityManager() != null) {
final Constructor<?> ctorToUse = constructorToUse;
final Object[] argumentsToUse = argsToUse;
beanInstance =
AccessController.doPrivileged(
new PrivilegedAction<Object>() {
@Override
public Object run() {
return beanFactory
.getInstantiationStrategy()
.instantiate(mbd, beanName, beanFactory, ctorToUse, argumentsToUse);
}
},
beanFactory.getAccessControlContext());
} else {
beanInstance =
this.beanFactory
.getInstantiationStrategy()
.instantiate(mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
}
// 将构建的实例加入BeanWrapper中
bw.setWrappedInstance(beanInstance);
return bw;
} catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Bean instantiation via constructor failed", ex);
}
}
