在之前的部落格中我們已經接觸過HandlerMethod，接下來我們簡單介紹一下HandlerMethod，簡單來說HandlerMethod包含的資訊包括類、方法和引數的一個資訊類，通過其兩個建構函式我們就可以瞭解其功能，對應著springMVC的Controller來說就是某個url對應的某個Controller執行的方法。

/**
	 * Create an instance from a bean instance and a method.
	 */
	public HandlerMethod(Object bean, Method method) {
		Assert.notNull(bean, "Bean is required");
		Assert.notNull(method, "Method is required");
		this.bean = bean;
		this.beanFactory = null;
		this.beanType = ClassUtils.getUserClass(bean);
		this.method = method;
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
		this.parameters = initMethodParameters();
		this.resolvedFromHandlerMethod = null;
	}
 

/**
	 * Create an instance from a bean instance, method name, and parameter types.
	 * @throws NoSuchMethodException when the method cannot be found
	 */
	public HandlerMethod(Object bean, String methodName, Class<?>... parameterTypes) throws NoSuchMethodException {
		Assert.notNull(bean, "Bean is required");
		Assert.notNull(methodName, "Method name is required");
		this.bean = bean;
		this.beanFactory = null;
		this.beanType = ClassUtils.getUserClass(bean);
		this.method = bean.getClass().getMethod(methodName, parameterTypes);
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(this.method);
		this.parameters = initMethodParameters();
		this.resolvedFromHandlerMethod = null;
	}
 

public class HandlerMethod {

	/** Logger that is available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());

	private final Object bean;

	private final BeanFactory beanFactory;

	private final Class<?> beanType;

	private final Method method;

	private final Method bridgedMethod;

	private final MethodParameter[] parameters;

	private final HandlerMethod resolvedFromHandlerMethod;

	//建立一個例項，根據bean例項和method方法
	public HandlerMethod(Object bean, Method method) {
		Assert.notNull(bean, "Bean is required");
		Assert.notNull(method, "Method is required");
		this.bean = bean;
		this.beanFactory = null;
		this.beanType = ClassUtils.getUserClass(bean);
		this.method = method;
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
		this.parameters = initMethodParameters();
		this.resolvedFromHandlerMethod = null;
	}
	//根據bean，方法名以及引數型別建立例項
	public HandlerMethod(Object bean, String methodName, Class<?>... parameterTypes) throws NoSuchMethodException {
		Assert.notNull(bean, "Bean is required");
		Assert.notNull(methodName, "Method name is required");
		this.bean = bean;
		this.beanFactory = null;
		this.beanType = ClassUtils.getUserClass(bean);
		this.method = bean.getClass().getMethod(methodName, parameterTypes);
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(this.method);
		this.parameters = initMethodParameters();
		this.resolvedFromHandlerMethod = null;
	}
	//根據bean名稱，BeanFactory工廠和method方法建立例項
	public HandlerMethod(String beanName, BeanFactory beanFactory, Method method) {
		Assert.hasText(beanName, "Bean name is required");
		Assert.notNull(beanFactory, "BeanFactory is required");
		Assert.notNull(method, "Method is required");
		this.bean = beanName;
		this.beanFactory = beanFactory;
		this.beanType = ClassUtils.getUserClass(beanFactory.getType(beanName));
		this.method = method;
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
		this.parameters = initMethodParameters();
		this.resolvedFromHandlerMethod = null;
	}

	protected HandlerMethod(HandlerMethod handlerMethod) {
		Assert.notNull(handlerMethod, "HandlerMethod is required");
		this.bean = handlerMethod.bean;
		this.beanFactory = handlerMethod.beanFactory;
		this.beanType = handlerMethod.beanType;
		this.method = handlerMethod.method;
		this.bridgedMethod = handlerMethod.bridgedMethod;
		this.parameters = handlerMethod.parameters;
		this.resolvedFromHandlerMethod = handlerMethod.resolvedFromHandlerMethod;
	}
	private HandlerMethod(HandlerMethod handlerMethod, Object handler) {
		Assert.notNull(handlerMethod, "HandlerMethod is required");
		Assert.notNull(handler, "Handler object is required");
		this.bean = handler;
		this.beanFactory = handlerMethod.beanFactory;
		this.beanType = handlerMethod.beanType;
		this.method = handlerMethod.method;
		this.bridgedMethod = handlerMethod.bridgedMethod;
		this.parameters = handlerMethod.parameters;
		this.resolvedFromHandlerMethod = handlerMethod;
	}


	private MethodParameter[] initMethodParameters() {
		int count = this.bridgedMethod.getParameterTypes().length;
		MethodParameter[] result = new MethodParameter[count];
		for (int i = 0; i < count; i++) {
			result[i] = new HandlerMethodParameter(i);
		}
		return result;
	}

	public Object getBean() {
		return this.bean;
	}

	public Method getMethod() {
		return this.method;
	}

	public Class<?> getBeanType() {
		return this.beanType;
	}

	protected Method getBridgedMethod() {
		return this.bridgedMethod;
	}
	
	public MethodParameter[] getMethodParameters() {
		return this.parameters;
	}

	public HandlerMethod getResolvedFromHandlerMethod() {
		return this.resolvedFromHandlerMethod;
	}

	public MethodParameter getReturnType() {
		return new HandlerMethodParameter(-1);
	}

	public MethodParameter getReturnValueType(Object returnValue) {
		return new ReturnValueMethodParameter(returnValue);
	}

	public boolean isVoid() {
		return Void.TYPE.equals(getReturnType().getParameterType());
	}

	//獲取方法上的註解，單個註解，如果沒有註解則返回方法本身
	public <A extends Annotation> A getMethodAnnotation(Class<A> annotationType) {
		return AnnotatedElementUtils.findMergedAnnotation(this.method, annotationType);
	}

	//建立handlerMethod
	public HandlerMethod createWithResolvedBean() {
		Object handler = this.bean;
		if (this.bean instanceof String) {
			String beanName = (String) this.bean;
			handler = this.beanFactory.getBean(beanName);
		}
		return new HandlerMethod(this, handler);
	}
	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof HandlerMethod)) {
			return false;
		}
		HandlerMethod otherMethod = (HandlerMethod) other;
		return (this.bean.equals(otherMethod.bean) && this.method.equals(otherMethod.method));
	}

	@Override
	public int hashCode() {
		return (this.bean.hashCode() * 31 + this.method.hashCode());
	}

	@Override
	public String toString() {
		return this.method.toGenericString();
	}


	/**
	 * A MethodParameter with HandlerMethod-specific behavior.
	 */
	protected class HandlerMethodParameter extends SynthesizingMethodParameter {

		public HandlerMethodParameter(int index) {
			super(HandlerMethod.this.bridgedMethod, index);
		}

		@Override
		public Class<?> getContainingClass() {
			return HandlerMethod.this.getBeanType();
		}

		@Override
		public <T extends Annotation> T getMethodAnnotation(Class<T> annotationType) {
			return HandlerMethod.this.getMethodAnnotation(annotationType);
		}
	}


	/**
	 * A MethodParameter for a HandlerMethod return type based on an actual return value.
	 */
	private class ReturnValueMethodParameter extends HandlerMethodParameter {

		private final Object returnValue;

		public ReturnValueMethodParameter(Object returnValue) {
			super(-1);
			this.returnValue = returnValue;
		}

		@Override
		public Class<?> getParameterType() {
			return (this.returnValue != null ? this.returnValue.getClass() : super.getParameterType());
		}
	}

}