springMVC源码解析--HandlerMethodArgumentResolverComposite参数解析器集合（二）

不念不忘少年蓝@ 2022-07-13 12:27 130阅读 0赞

上一篇博客[springMVC源码分析--HandlerMethodArgumentResolver参数解析器（一）][springMVC_--HandlerMethodArgumentResolver]中我们已经介绍了参数解析相关的东西，并且也提到了HandlerMethodArgumentResolverComposite，其简单来说就是所有的参数解析器的链表，保存了springMVC提供的所有的参数解析器，采用职责链的模式来完成参数解析器的查找，并完成参数解析生成目标对象。

完整源码及说明如下：

public class HandlerMethodArgumentResolverComposite implements HandlerMethodArgumentResolver {
    
    	protected final Log logger = LogFactory.getLog(getClass());
    
    	//保存springMVC提供的所有的参数解析器
    	private final List<HandlerMethodArgumentResolver> argumentResolvers =
    			new LinkedList<HandlerMethodArgumentResolver>();
    
    	//用于缓存已经查找过的参数解析器
    	private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache =
    			new ConcurrentHashMap<MethodParameter, HandlerMethodArgumentResolver>(256);
    	//获取所有的参数解析器
    	public List<HandlerMethodArgumentResolver> getResolvers() {
    		return Collections.unmodifiableList(this.argumentResolvers);
    	}
    
    	//判断参数解析器是否支持参数解析
    	@Override
    	public boolean supportsParameter(MethodParameter parameter) {
    		return (getArgumentResolver(parameter) != null);
    	}
    
    	//返回参数解析器解析后的数据
    	@Override
    	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
    			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
    
    		HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
    		if (resolver == null) {
    			throw new IllegalArgumentException("Unknown parameter type [" + parameter.getParameterType().getName() + "]");
    		}
    		return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
    	}
    
    	//获取支持某个参数解析的参数解析器
    	private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
    		HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
    		if (result == null) {
    			for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) {
    				if (logger.isTraceEnabled()) {
    					logger.trace("Testing if argument resolver [" + methodArgumentResolver + "] supports [" +
    							parameter.getGenericParameterType() + "]");
    				}
    				if (methodArgumentResolver.supportsParameter(parameter)) {
    					result = methodArgumentResolver;
    					this.argumentResolverCache.put(parameter, result);
    					break;
    				}
    			}
    		}
    		return result;
    	}
    
    	//添加参数解析器
    	public HandlerMethodArgumentResolverComposite addResolver(HandlerMethodArgumentResolver resolver) {
    		this.argumentResolvers.add(resolver);
    		return this;
    	}
    	//获取参数解析器集合
    	public HandlerMethodArgumentResolverComposite addResolvers(List<? extends HandlerMethodArgumentResolver> resolvers) {
    		if (resolvers != null) {
    			for (HandlerMethodArgumentResolver resolver : resolvers) {
    				this.argumentResolvers.add(resolver);
    			}
    		}
    		return this;
    	}
    
    }

[springMVC_--HandlerMethodArgumentResolver]: http://blog.csdn.net/qq924862077/article/details/54177442