springMVC源码分析--HandlerMethod

悠悠 2022-07-13 03:08 214阅读 0赞

在之前的博客中我们已经接触过HandlerMethod，接下来我们简单介绍一下HandlerMethod，简单来说HandlerMethod包含的信息包括类、方法和参数的一个信息类，通过其两个构造函数我们就可以了解其功能，对应着springMVC的Controller来说就是某个url对应的某个Controller执行的方法。

/**
    	 * 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;
    	}

完整源码如下：

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;
    
    	//创建一个实例，根据bean实例和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;
    	}
    	//根据bean，方法名以及参数类型创建实例
    	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;
    	}
    	//根据bean名称，BeanFactory工厂和method方法创建实例
    	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());
    	}
    
    	//获取方法上的注解，单个注解，如果没有注解则返回方法本身
    	public <A extends Annotation> A getMethodAnnotation(Class<A> annotationType) {
    		return AnnotatedElementUtils.findMergedAnnotation(this.method, annotationType);
    	}
    
    	//创建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());
    		}
    	}
    
    }