Spring Ioc源码分析 之 Bean的加载（五）：实例化Bean

//AbstractAutowireCapableBeanFactory.java

//创建Bean的实例对象
	protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
		// Make sure bean class is actually resolved at this point.
		//解析beanName 为 class
		Class<?> beanClass = resolveBeanClass(mbd, beanName);

		//检查确认Bean是可实例化的
		if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
					"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
		}
                 //如果存在 Supplier 回调，则使用给定的回调方法初始化策略
		Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
		if (instanceSupplier != null) {
			return obtainFromSupplier(instanceSupplier, beanName);
		}
                //使用 FactoryBean 的 factory-method 来创建，支持静态工厂和实例工厂
		if (mbd.getFactoryMethodName() != null)  {
			//调用工厂方法实例化
			return instantiateUsingFactoryMethod(beanName, mbd, args);
		}

		// Shortcut when re-creating the same bean...
		//构造函数自动注入进行实例化
		boolean resolved = false;
		boolean autowireNecessary = false;
		if (args == null) {
			synchronized (mbd.constructorArgumentLock) {
				if (mbd.resolvedConstructorOrFactoryMethod != null) {
				    // 如果已缓存的解析的构造函数或者工厂方法不为空，则可以利用构造函数解析
			       	// 因为需要根据参数确认到底使用哪个构造函数，该过程比较消耗性能，所有采用缓存机制
					resolved = true;
					autowireNecessary = mbd.constructorArgumentsResolved;
				}
			}
		}
		// 如果已经解析过，不需要再次解析
		if (resolved) {
			if (autowireNecessary) {
				//构造函数自动注入进行实例化
				//一个类有多个构造函数，每个构造函数都有不同的参数，所以需要根据参数锁定构造函数进行 bean 的实例化
				return autowireConstructor(beanName, mbd, null, null);
			}
			else {
				//使用默认的无参构造方法实例化
				return instantiateBean(beanName, mbd);
			}
		}

		// Need to determine the constructor...
		//需要根据参数解析构造函数
		Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
		if (ctors != null ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
				mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
			//使用容器的自动装配特性，调用匹配的构造方法实例化
			return autowireConstructor(beanName, mbd, ctors, args);
		}

		// No special handling: simply use no-arg constructor.
		//使用默认的无参构造方法实例化
		return instantiateBean(beanName, mbd);
	}
复制代码

public interface Supplier<T> {

    T get();
    
}
复制代码

// RootBeanDefinition.java

public <T> RootBeanDefinition(@Nullable Class<T> beanClass, String scope, @Nullable Supplier<T> instanceSupplier) {
	super();
	setBeanClass(beanClass);
	setScope(scope);
	// 设置 instanceSupplier 属性
	setInstanceSupplier(instanceSupplier);
}

//AbstractAutowireCapableBeanFactory.java

public BeanWrapper autowireConstructor(final String beanName, final RootBeanDefinition mbd,
		@Nullable Constructor<?>[] chosenCtors, @Nullable final Object[] explicitArgs) {

	// 封装 BeanWrapperImpl 对象，并完成初始化
	BeanWrapperImpl bw = new BeanWrapperImpl();
	this.beanFactory.initBeanWrapper(bw);

	Constructor<?> constructorToUse = null;// 最终使用的构造函数
	ArgumentsHolder argsHolderToUse = null;// 构造参数
	Object[] argsToUse = null;// 构造参数

	// 判断有无显式指定参数,如果有则优先使用,如 xxxBeanFactory.getBean("teacher", "李华",3);
<1>	if (explicitArgs != null) {
		argsToUse = explicitArgs;
	}
	// 没有显式指定参数,则解析配置文件中的参数
<2>	else {
		Object[] argsToResolve = null;
		synchronized (mbd.constructorArgumentLock) {
			// 优先尝试从缓存中获取,spring对参数的解析过程是比较复杂也耗时的,所以这里先尝试从缓存中获取已经解析过的构造函数参数
			constructorToUse = (Constructor<?>) mbd.resolvedConstructorOrFactoryMethod;
                        //如果构造方法和参数都不为Null
			if (constructorToUse != null && mbd.constructorArgumentsResolved) {
				// Found a cached constructor...
				// 获取缓存中的构造参数
				argsToUse = mbd.resolvedConstructorArguments;
				if (argsToUse == null) {
					argsToResolve = mbd.preparedConstructorArguments;
				}
			}
		}
		// 缓存中存在,则解析存储在 BeanDefinition 中的参数
		// 如给定方法的构造函数 A(int ,int )，则通过此方法后就会把配置文件中的("1","1")转换为 (1,1)
		// 缓存中的值可能是原始值也有可能是最终值
		if (argsToResolve != null) {
			argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve);
		}
	}

	// 缓存不存在,则需要解析构造函数参数,以确定使用哪一个构造函数来进行实例化
<3>	if (constructorToUse == null) {
		// Need to resolve the constructor.
		boolean autowiring = (chosenCtors != null ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
		// 用于承载解析后的构造函数参数的值
		ConstructorArgumentValues resolvedValues = null;

		//参数个数
<4>		int minNrOfArgs;
		if (explicitArgs != null) {
			minNrOfArgs = explicitArgs.length;
		}
		else {
			// 从 BeanDefinition 中获取构造参数，也就是从配置文件中提取构造参数
			ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
			resolvedValues = new ConstructorArgumentValues();
			// 能解析到的参数个数
			minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
		}

		// Take specified constructors, if any.
		//使用指定的构造函数，如果有的话
<5>		Constructor<?>[] candidates = chosenCtors;
		//没有
		if (candidates == null) {
			Class<?> beanClass = mbd.getBeanClass();
			try {
				//通过反射获取所有构造函数
				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);
			}
		}

		// 对所有构造函数进行排序,public 且 参数最多的构造函数会排在第一位
<6>		AutowireUtils.sortConstructors(candidates);
		int minTypeDiffWeight = Integer.MAX_VALUE;
		//模棱两可的构造函数集合
		Set<Constructor<?>> ambiguousConstructors = null;
		LinkedList<UnsatisfiedDependencyException> causes = null;

		// 迭代所有构造函数，解析确定使用哪一个构造函数
<7>		for (Constructor<?> candidate : candidates) {
			// 获取该构造函数的参数类型
<8>			Class<?>[] paramTypes = candidate.getParameterTypes();

			// 如果已经找到选用的构造函数或者需要的参数个数小于当前的构造函数参数个数，则终止。
			// 因为，已经按照参数个数降序排列了
			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;
			}
			// 参数个数不等，跳过
			if (paramTypes.length < minNrOfArgs) {
				continue;
			}

			// 参数持有者 ArgumentsHolder 对象
			ArgumentsHolder argsHolder;
<9>			if (resolvedValues != null) {
				try {
					// 获取注解上的参数名称 by @ConstructorProperties
					String[] paramNames = ConstructorPropertiesChecker.evaluate(candidate, paramTypes.length);
					if (paramNames == null) {
						ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
						if (pnd != null) {
							// 获取指定构造函数的参数名称
							paramNames = pnd.getParameterNames(candidate);
						}
					}
					// 根据构造函数和构造参数，创建参数持有者 ArgumentsHolder 对象
					argsHolder = createArgumentArray(beanName, mbd, resolvedValues, bw, paramTypes, paramNames,
							getUserDeclaredConstructor(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<>();
					}
					causes.add(ex);
					continue;
				}
			}
			else {
				// Explicit arguments given -> arguments length must match exactly.
				if (paramTypes.length != explicitArgs.length) {
					continue;
				}
				// 根据 getBean()传入的 explicitArgs ，创建 ArgumentsHolder 对象
				argsHolder = new ArgumentsHolder(explicitArgs);
			}

			//通过构造函数参数差异值对比,得出最适合使用的构造函数
				// isLenientConstructorResolution 判断解析构造函数的时候是否以宽松模式还是严格模式（默认宽松）
				// 严格模式：解析构造函数时，必须所有的都需要匹配，否则抛出异常
				// 宽松模式：使用具有"最接近的模式"进行匹配
			int typeDiffWeight = (mbd.isLenientConstructorResolution() ?
					argsHolder.getTypeDifferenceWeight(paramTypes) : argsHolder.getAssignabilityWeight(paramTypes));
			// Choose this constructor if it represents the closest match.
			// 如果它代表着当前最接近的匹配则选择其作为构造函数
			//差异值越小，越匹配，每次和分数最小的去比较
<10>			if (typeDiffWeight < minTypeDiffWeight) {
				constructorToUse = candidate;
				argsHolderToUse = argsHolder;
				argsToUse = argsHolder.arguments;
				minTypeDiffWeight = typeDiffWeight;
				ambiguousConstructors = null;
			}
			// 如果两个构造方法与参数值类型列表之间的差异量一致，那么这两个方法都可以作为
	                // 候选项，这个时候就出现歧义了，这里先把有歧义的构造方法放入ambiguousConstructors
			else if (constructorToUse != null && typeDiffWeight == minTypeDiffWeight) {
				if (ambiguousConstructors == null) {
					ambiguousConstructors = new LinkedHashSet<>();
					ambiguousConstructors.add(constructorToUse);
				}
				//把候选构造函数 加入到 模棱两可的构造函数集合中
				ambiguousConstructors.add(candidate);
			}
		}

		// 没有可执行的构造方法，抛出异常
		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)");
		}
		//如果模棱两可的构造函数不为空，且为 严格模式，则抛异常
		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);
		}
            
                 // 将解析的构造函数、参数 加入缓存
<11>		if (explicitArgs == null) {
			/*
                	 * 缓存相关信息，比如：
                	 *   1. 已解析出的构造方法对象 resolvedConstructorOrFactoryMethod
                	 *   2. 构造方法参数列表是否已解析标志 constructorArgumentsResolved
                	 *   3. 参数值列表 resolvedConstructorArguments 或 preparedConstructorArguments
                	 *
                	 * 这些信息可用在其他地方，用于进行快捷判断
                	 */
			argsHolderToUse.storeCache(mbd, constructorToUse);
		}
	}

	try {
		//获取Bean的初始化策略
		final InstantiationStrategy strategy = beanFactory.getInstantiationStrategy();
		Object beanInstance;

		//创建 Bean 对象
<12>		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 {
			beanInstance = strategy.instantiate(mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
		}

		//设置到 bw 中
		bw.setBeanInstance(beanInstance);
		return bw;
	}
	catch (Throwable ex) {
		throw new BeanCreationException(mbd.getResourceDescription(), beanName,
				"Bean instantiation via constructor failed", ex);
	}
	}
复制代码

Object[] argsToResolve = null;
	synchronized (mbd.constructorArgumentLock) {
		// 优先尝试从缓存中获取,spring对参数的解析过程是比较复杂也耗时的,所以这里先尝试从缓存中获取已经解析过的构造函数参数
		constructorToUse = (Constructor<?>) mbd.resolvedConstructorOrFactoryMethod;
		//如果构造方法和参数都不为Null
		if (constructorToUse != null && mbd.constructorArgumentsResolved) {
			// Found a cached constructor...
			// 获取缓存中的构造参数
			argsToUse = mbd.resolvedConstructorArguments;
			if (argsToUse == null) {
				argsToResolve = mbd.preparedConstructorArguments;
			}
		}
	}
	// 缓存中存在,则解析存储在 BeanDefinition 中的参数
	// 如给定方法的构造函数 A(int ,int )，则通过此方法后就会把配置文件中的("1","1")转换为 (1,1)
	// 缓存中的值可能是原始值也有可能是最终值
	if (argsToResolve != null) {
		argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve);
	}

        //参数个数
	int minNrOfArgs;
	if (explicitArgs != null) {
		minNrOfArgs = explicitArgs.length;
	}
	else {
		// 从 BeanDefinition 中获取构造参数，也就是从配置文件中提取构造参数
		ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
		resolvedValues = new ConstructorArgumentValues();
		// 能解析到的参数个数
		minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
	}

// 获取该构造函数的参数类型
	Class<?>[] paramTypes = candidate.getParameterTypes();

	///这里的判断构造方法和构造方法参数 都不是空，又由于之前对构造方法做了排序。所以在使用的参数的个数已经大于当前构造方法的参数个数的时候，实际上已经取到了想要的构造方法。
	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;
	}
	// 当前的构造参数个数小于我们要求的个数，跳过
	if (paramTypes.length < minNrOfArgs) {
		continue;
	}

     1. public Hello(Object, Object, Object)
     2. public Hello(Object, Object)
     3. public Hello(Object)
     4. protected Hello(Integer, Object, Object, Object)
     5. protected Hello(Integer, Object, Object)
     6. protected Hello(Integer, Object)

        // 参数持有者 ArgumentsHolder 对象
	ArgumentsHolder argsHolder;
	if (resolvedValues != null) {
		try {
			// 获取注解上的参数名称 by @ConstructorProperties
			String[] paramNames = ConstructorPropertiesChecker.evaluate(candidate, paramTypes.length);
			if (paramNames == null) {
				// ParameterNameDiscoverer 是用于解析方法和构造函数的参数名称的接口，为参数名称探测器
				ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
				if (pnd != null) {
					// 获取指定构造函数的参数名称
					paramNames = pnd.getParameterNames(candidate);
				}
			}
			// 根据构造函数和构造参数，创建参数持有者 ArgumentsHolder 对象
			argsHolder = createArgumentArray(beanName, mbd, resolvedValues, bw, paramTypes, paramNames,
					getUserDeclaredConstructor(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<>();
			}
			causes.add(ex);
			continue;
		}
	}
	else {
		// Explicit arguments given -> arguments length must match exactly.
		if (paramTypes.length != explicitArgs.length) {
			continue;
		}
		// 根据 getBean()传入的 explicitArgs ，创建 ArgumentsHolder 对象
		argsHolder = new ArgumentsHolder(explicitArgs);
	}

//通过构造函数参数差异值对比,得出最适合使用的构造函数
		// isLenientConstructorResolution 判断解析构造函数的时候是否以宽松模式还是严格模式（默认宽松）
		// 严格模式：解析构造函数时，必须所有的都需要匹配，否则抛出异常
		// 宽松模式：使用具有"最接近的模式"进行匹配
	int typeDiffWeight = (mbd.isLenientConstructorResolution() ?
			argsHolder.getTypeDifferenceWeight(paramTypes) : argsHolder.getAssignabilityWeight(paramTypes));
	// Choose this constructor if it represents the closest match.
	// 如果它代表着当前最接近的匹配则选择其作为构造函数
	//差异值越小，越匹配，每次和分数最小的去比较
	if (typeDiffWeight < minTypeDiffWeight) {
		constructorToUse = candidate;
		argsHolderToUse = argsHolder;
		argsToUse = argsHolder.arguments;
		minTypeDiffWeight = typeDiffWeight;
		ambiguousConstructors = null;
	}
	// 如果两个构造方法与参数值类型列表之间的差异量一致，那么这两个方法都可以作为
	// 候选项，这个时候就出现歧义了，这里先把有歧义的构造方法放入ambiguousConstructors
	else if (constructorToUse != null && typeDiffWeight == minTypeDiffWeight) {
		if (ambiguousConstructors == null) {
			ambiguousConstructors = new LinkedHashSet<>();
			ambiguousConstructors.add(constructorToUse);
		}
		//把候选构造函数 加入到 模棱两可的构造函数集合中
		ambiguousConstructors.add(candidate);
	}


/ 没有可执行的构造方法，抛出异常
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)");

/如果模棱两可的构造函数不为空，且为 严格模式，则抛异常
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);
			}

// 将解析的构造函数、参数 加入缓存
if (explicitArgs == null) {
	/*
	 * 缓存相关信息，比如：
	 *   1. 已解析出的构造方法对象 resolvedConstructorOrFactoryMethod
	 *   2. 构造方法参数列表是否已解析标志 constructorArgumentsResolved
	 *   3. 参数值列表 resolvedConstructorArguments 或 preparedConstructorArguments
	 *
	 * 这些信息可用在其他地方，用于进行快捷判断
	 */
	argsHolderToUse.storeCache(mbd, constructorToUse);
	}

 // ArgumentsHolder.java
        public final Object rawArguments[];

	public final Object arguments[];

	public final Object preparedArguments[];

public void storeCache(RootBeanDefinition mbd, Executable constructorOrFactoryMethod) {
	synchronized (mbd.constructorArgumentLock) {
		mbd.resolvedConstructorOrFactoryMethod = constructorOrFactoryMethod;
		mbd.constructorArgumentsResolved = true;
		if (this.resolveNecessary) {
			mbd.preparedConstructorArguments = this.preparedArguments;
		}
		else {
			mbd.resolvedConstructorArguments = this.arguments;
		}
	}
		}
复制代码

return instantiateBean(beanName, mbd);

//使用默认的无参构造方法实例化Bean对象
	protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
	try {
		Object beanInstance;
		final BeanFactory parent = this;
		//获取系统的安全管理接口，JDK标准的安全管理API
		if (System.getSecurityManager() != null) {
			//这里是一个匿名内置类，根据实例化策略创建实例对象
			beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
					getInstantiationStrategy().instantiate(mbd, beanName, parent),
					getAccessControlContext());
		}
		else {
			//将实例化的对象封装起来
			beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
		}
		BeanWrapper bw = new BeanWrapperImpl(beanInstance);
		initBeanWrapper(bw);
		return bw;
	}
	catch (Throwable ex) {
		throw new BeanCreationException(
				mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
	}
	}
复制代码

//SimpleInstantiationStrategy.java

//使用初始化策略实例化Bean对象
	@Override
	public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
	// Don't override the class with CGLIB if no overrides.
	// 没有覆盖，直接使用反射实例化即可
	if (!bd.hasMethodOverrides()) {
		Constructor<?> constructorToUse;
		synchronized (bd.constructorArgumentLock) {
			//从缓存中获取对象的构造方法或工厂方法
			constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
			//缓存没有
			if (constructorToUse == null) {
				//使用JDK的反射机制，判断要实例化的Bean是否是接口
				final Class<?> clazz = bd.getBeanClass();
				if (clazz.isInterface()) {
					throw new BeanInstantiationException(clazz, "Specified class is an interface");
				}
				try {
					if (System.getSecurityManager() != null) {
						//这里是一个匿名内置类，使用反射机制获取Bean的构造方法
						constructorToUse = AccessController.doPrivileged(
								(PrivilegedExceptionAction<Constructor<?>>) () -> clazz.getDeclaredConstructor());
					}
					else {
						constructorToUse =	clazz.getDeclaredConstructor();
					}
					bd.resolvedConstructorOrFactoryMethod = constructorToUse;
				}
				catch (Throwable ex) {
					throw new BeanInstantiationException(clazz, "No default constructor found", ex);
				}
			}
		}
		//使用BeanUtils实例化，通过反射机制调用”构造方法.newInstance(arg)”来进行实例化
		return BeanUtils.instantiateClass(constructorToUse);
	}
	else {
		// Must generate CGLIB subclass.
		//有方法覆盖，使用CGLIB来实例化对象
		//方法覆盖，在调用目标方法的时候，对调用过程进行拦截，调用实现增强功能的拦截器，返回原来实例的代理
		//所以要用cglib动态代理
		return instantiateWithMethodInjection(bd, beanName, owner);
	}
	}
复制代码

public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
	Assert.notNull(ctor, "Constructor must not be null");
	try {
		// 设置构造方法，可访问
		ReflectionUtils.makeAccessible(ctor);
		// 使用构造方法，创建对象 newInstance
		return (KotlinDetector.isKotlinType(ctor.getDeclaringClass()) ?
				KotlinDelegate.instantiateClass(ctor, args) : ctor.newInstance(args));
	}
	catch (InstantiationException ex) {
		throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
	}
	catch (IllegalAccessException ex) {
		throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
	}
	catch (IllegalArgumentException ex) {
		throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
	}
	catch (InvocationTargetException ex) {
		throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
	}
	}
复制代码

总结