public static void main(String[] args) throws Exception {
ParameterNameDiscoverer discoverer = new DefaultParameterNameDiscoverer();
Method declaredMethod = HttpUtils.class.getDeclaredMethod("getClient", HttpHost.class);
String[] names = discoverer.getParameterNames(declaredMethod);
System.out.println(names[0]);
}
protected void loadArgsAsVariables() {
// shortcut if no args need to be loaded
if (ObjectUtils.isEmpty(args)) {
return;
}
String key = toString(method);
Method targetMethod = methodCache.get(key);
if (targetMethod == null) {
targetMethod = AopUtils.getMostSpecificMethod(method, targetClass);
if (targetMethod == null) {
targetMethod = method;
}
methodCache.put(key, targetMethod);
}
// save arguments as indexed variables
for (int i = 0; i < args.length; i++) {
setVariable("p" + i, args[i]);
}
String[] parameterNames = paramDiscoverer.getParameterNames(targetMethod);
// save parameter names (if discovered)
if (parameterNames != null) {
for (int i = 0; i < parameterNames.length; i++) {
setVariable(parameterNames[i], args[i]);
}
}
}
protected Object[] findArgs(HttpServletRequest request, Method method) {
String[] names = paramNameDiscoverer.getParameterNames(method);
if (names == null) {
log.warn("Unable to lookup parameter names for method " + method);
return null;
}
List<Object> args = new ArrayList<Object>();
Class<?>[] types = method.getParameterTypes();
for (int i = 0, count = types.length; i < count; i++) {
args.add(findArg(request, types[i], names[i]));
}
return args.toArray();
}
/** {@inheritDoc} */
public void validate(final Method method) {
final String[] parameterNames = parameterNameDiscoverer.getParameterNames(method);
Assert.notNull(
parameterNames,
"Cannot get parameter names because the class file was compiled without debug information.");
for (int i = 0; i < parameterNames.length; i++) {
if (name.equals(parameterNames[i])) {
position = i;
break;
}
}
Assert.isTrue(
position >= 0, "Cannot find parameter with name [" + name + "] in " + method + ".");
}
/**
* Instantiate the bean using a named factory method. The method may be static, if the bean
* definition parameter specifies a class, rather than a "factory-bean", or an instance variable
* on a factory object itself configured using Dependency Injection.
*
* <p>Implementation requires iterating over the static or instance methods with the name
* specified in the RootBeanDefinition (the method may be overloaded) and trying to match with the
* parameters. We don't have the types attached to constructor args, so trial and error is the
* only way to go here. The explicitArgs array may contain argument values passed in
* programmatically via the corresponding getBean method.
*
* @param beanName the name of the bean
* @param mbd the merged bean definition for the bean
* @param explicitArgs argument values passed in programmatically via the getBean method, or
* {@code null} if none (-> use constructor argument values from bean definition)
* @return a BeanWrapper for the new instance
*/
public BeanWrapper instantiateUsingFactoryMethod(
final String beanName, final RootBeanDefinition mbd, final Object[] explicitArgs) {
BeanWrapperImpl bw = new BeanWrapperImpl();
this.beanFactory.initBeanWrapper(bw);
Object factoryBean;
Class<?> factoryClass;
boolean isStatic;
String factoryBeanName = mbd.getFactoryBeanName();
if (factoryBeanName != null) {
if (factoryBeanName.equals(beanName)) {
throw new BeanDefinitionStoreException(
mbd.getResourceDescription(),
beanName,
"factory-bean reference points back to the same bean definition");
}
factoryBean = this.beanFactory.getBean(factoryBeanName);
if (factoryBean == null) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"factory-bean '"
+ factoryBeanName
+ "' (or a BeanPostProcessor involved) returned null");
}
if (mbd.isSingleton() && this.beanFactory.containsSingleton(beanName)) {
throw new IllegalStateException(
"About-to-be-created singleton instance implicitly appeared "
+ "through the creation of the factory bean that its bean definition points to");
}
factoryClass = factoryBean.getClass();
isStatic = false;
} else {
// It's a static factory method on the bean class.
if (!mbd.hasBeanClass()) {
throw new BeanDefinitionStoreException(
mbd.getResourceDescription(),
beanName,
"bean definition declares neither a bean class nor a factory-bean reference");
}
factoryBean = null;
factoryClass = mbd.getBeanClass();
isStatic = true;
}
Method factoryMethodToUse = null;
ArgumentsHolder argsHolderToUse = null;
Object[] argsToUse = null;
if (explicitArgs != null) {
argsToUse = explicitArgs;
} else {
Object[] argsToResolve = null;
synchronized (mbd.constructorArgumentLock) {
factoryMethodToUse = (Method) mbd.resolvedConstructorOrFactoryMethod;
if (factoryMethodToUse != null && mbd.constructorArgumentsResolved) {
// Found a cached factory method...
argsToUse = mbd.resolvedConstructorArguments;
if (argsToUse == null) {
argsToResolve = mbd.preparedConstructorArguments;
}
}
}
if (argsToResolve != null) {
argsToUse = resolvePreparedArguments(beanName, mbd, bw, factoryMethodToUse, argsToResolve);
}
}
if (factoryMethodToUse == null || argsToUse == null) {
// Need to determine the factory method...
// Try all methods with this name to see if they match the given arguments.
factoryClass = ClassUtils.getUserClass(factoryClass);
Method[] rawCandidates = getCandidateMethods(factoryClass, mbd);
List<Method> candidateSet = new ArrayList<Method>();
for (Method candidate : rawCandidates) {
if (Modifier.isStatic(candidate.getModifiers()) == isStatic
&& mbd.isFactoryMethod(candidate)) {
candidateSet.add(candidate);
}
}
Method[] candidates = candidateSet.toArray(new Method[candidateSet.size()]);
AutowireUtils.sortFactoryMethods(candidates);
ConstructorArgumentValues resolvedValues = null;
boolean autowiring =
(mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
int minTypeDiffWeight = Integer.MAX_VALUE;
Set<Method> ambiguousFactoryMethods = null;
int minNrOfArgs;
if (explicitArgs != null) {
minNrOfArgs = explicitArgs.length;
} else {
// We don't have arguments passed in programmatically, so we need to resolve the
// arguments specified in the constructor arguments held in the bean definition.
ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
resolvedValues = new ConstructorArgumentValues();
minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
}
List<Exception> causes = null;
for (int i = 0; i < candidates.length; i++) {
Method candidate = candidates[i];
Class<?>[] paramTypes = candidate.getParameterTypes();
if (paramTypes.length >= minNrOfArgs) {
ArgumentsHolder argsHolder;
if (resolvedValues != null) {
// Resolved constructor arguments: type conversion and/or autowiring necessary.
try {
String[] paramNames = null;
ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
if (pnd != null) {
paramNames = pnd.getParameterNames(candidate);
}
argsHolder =
createArgumentArray(
beanName,
mbd,
resolvedValues,
bw,
paramTypes,
paramNames,
candidate,
autowiring);
} catch (UnsatisfiedDependencyException ex) {
if (this.beanFactory.logger.isTraceEnabled()) {
this.beanFactory.logger.trace(
"Ignoring factory method ["
+ candidate
+ "] of bean '"
+ beanName
+ "': "
+ ex);
}
if (i == candidates.length - 1 && argsHolderToUse == null) {
if (causes != null) {
for (Exception cause : causes) {
this.beanFactory.onSuppressedException(cause);
}
}
throw ex;
} else {
// Swallow and try next overloaded factory method.
if (causes == null) {
causes = new LinkedList<Exception>();
}
causes.add(ex);
continue;
}
}
} else {
// Explicit arguments given -> arguments length must match exactly.
if (paramTypes.length != explicitArgs.length) {
continue;
}
argsHolder = new ArgumentsHolder(explicitArgs);
}
int typeDiffWeight =
(mbd.isLenientConstructorResolution()
? argsHolder.getTypeDifferenceWeight(paramTypes)
: argsHolder.getAssignabilityWeight(paramTypes));
// Choose this factory method if it represents the closest match.
if (typeDiffWeight < minTypeDiffWeight) {
factoryMethodToUse = candidate;
argsHolderToUse = argsHolder;
argsToUse = argsHolder.arguments;
minTypeDiffWeight = typeDiffWeight;
ambiguousFactoryMethods = null;
}
// Find out about ambiguity: In case of the same type difference weight
// for methods with the same number of parameters, collect such candidates
// and eventually raise an ambiguity exception.
// However, only perform that check in non-lenient constructor resolution mode,
// and explicitly ignore overridden methods (with the same parameter signature).
else if (factoryMethodToUse != null
&& typeDiffWeight == minTypeDiffWeight
&& !mbd.isLenientConstructorResolution()
&& paramTypes.length == factoryMethodToUse.getParameterTypes().length
&& !Arrays.equals(paramTypes, factoryMethodToUse.getParameterTypes())) {
if (ambiguousFactoryMethods == null) {
ambiguousFactoryMethods = new LinkedHashSet<Method>();
ambiguousFactoryMethods.add(factoryMethodToUse);
}
ambiguousFactoryMethods.add(candidate);
}
}
}
if (factoryMethodToUse == null) {
List<String> argTypes = new ArrayList<String>(minNrOfArgs);
if (explicitArgs != null) {
for (Object arg : explicitArgs) {
argTypes.add(arg != null ? arg.getClass().getSimpleName() : "null");
}
} else {
Set<ValueHolder> valueHolders =
new LinkedHashSet<ValueHolder>(resolvedValues.getArgumentCount());
valueHolders.addAll(resolvedValues.getIndexedArgumentValues().values());
valueHolders.addAll(resolvedValues.getGenericArgumentValues());
for (ValueHolder value : valueHolders) {
String argType =
(value.getType() != null
? ClassUtils.getShortName(value.getType())
: (value.getValue() != null
? value.getValue().getClass().getSimpleName()
: "null"));
argTypes.add(argType);
}
}
String argDesc = StringUtils.collectionToCommaDelimitedString(argTypes);
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"No matching factory method found: "
+ (mbd.getFactoryBeanName() != null
? "factory bean '" + mbd.getFactoryBeanName() + "'; "
: "")
+ "factory method '"
+ mbd.getFactoryMethodName()
+ "("
+ argDesc
+ ")'. "
+ "Check that a method with the specified name "
+ (minNrOfArgs > 0 ? "and arguments " : "")
+ "exists and that it is "
+ (isStatic ? "static" : "non-static")
+ ".");
} else if (void.class.equals(factoryMethodToUse.getReturnType())) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Invalid factory method '"
+ mbd.getFactoryMethodName()
+ "': needs to have a non-void return type!");
} else if (ambiguousFactoryMethods != null) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Ambiguous factory method matches found in bean '"
+ beanName
+ "' "
+ "(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): "
+ ambiguousFactoryMethods);
}
if (explicitArgs == null && argsHolderToUse != null) {
argsHolderToUse.storeCache(mbd, factoryMethodToUse);
}
}
try {
Object beanInstance;
if (System.getSecurityManager() != null) {
final Object fb = factoryBean;
final Method factoryMethod = factoryMethodToUse;
final Object[] args = argsToUse;
beanInstance =
AccessController.doPrivileged(
new PrivilegedAction<Object>() {
@Override
public Object run() {
return beanFactory
.getInstantiationStrategy()
.instantiate(mbd, beanName, beanFactory, fb, factoryMethod, args);
}
},
beanFactory.getAccessControlContext());
} else {
beanInstance =
this.beanFactory
.getInstantiationStrategy()
.instantiate(
mbd, beanName, this.beanFactory, factoryBean, factoryMethodToUse, argsToUse);
}
if (beanInstance == null) {
return null;
}
bw.setWrappedInstance(beanInstance);
return bw;
} catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(),
beanName,
"Bean instantiation via factory method failed",
ex);
}
}
/**
* 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);
}
}