MVC自动配置原理

目录

一、官网阅读

二、ContentNegotiatingViewResolver  （内容协商视图解析器）

ViewResolver 的源码： 

resolveViewName 

getCandidateViews 

三、Formatter 转换器和格式化器

四、修改SpringBoot的默认配置

五、扩展使用SpringMVC

⚪实现视图跳转

---

一、官网阅读

官网地址：Spring Boot Reference Documentation

二、ContentNegotiatingViewResolver  （内容协商视图解析器）

ContentNegotiatingViewResolver  实现了视图解析器的类，就可以把它看做视图解析器

ViewResolver 的源码： 

public interface ViewResolver {
    @Nullable
    //resolveViewName 解析视图
    View resolveViewName(String viewName, Locale locale) throws Exception;
}

resolveViewName 

@Nullable
public View resolveViewName(String viewName, Locale locale) throws Exception {
    RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
    Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");
    List requestedMediaTypes = this.getMediaTypes(((ServletRequestAttributes)attrs).getRequest());
    if (requestedMediaTypes != null) {
        //getCandidateViews 获取候选视图
        List candidateViews = this.getCandidateViews(viewName, locale, requestedMediaTypes);
        //getBestView  获取最好的视图
        View bestView = this.getBestView(candidateViews, requestedMediaTypes, attrs);
        if (bestView != null) {
            return bestView;
        }
    }
    String mediaTypeInfo = this.logger.isDebugEnabled() && requestedMediaTypes != null ? " given " + requestedMediaTypes.toString() : "";
    if (this.useNotAcceptableStatusCode) {
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Using 406 NOT_ACCEPTABLE" + mediaTypeInfo);
        }
        return NOT_ACCEPTABLE_VIEW;
    } else {
        this.logger.debug("View remains unresolved" + mediaTypeInfo);
        return null;
    }
}

getCandidateViews 

private List getCandidateViews(String viewName, Locale locale, List requestedMediaTypes) throws Exception {
    List candidateViews = new ArrayList();
    if (this.viewResolvers != null) {
        Assert.state(this.contentNegotiationManager != null, "No ContentNegotiationManager set");
        Iterator var5 = this.viewResolvers.iterator();
        while(var5.hasNext()) {
            ViewResolver viewResolver = (ViewResolver)var5.next();
            View view = viewResolver.resolveViewName(viewName, locale);
            if (view != null) {
                candidateViews.add(view);
            }
            Iterator var8 = requestedMediaTypes.iterator();
            while(var8.hasNext()) {
                MediaType requestedMediaType = (MediaType)var8.next();
                List extensions = this.contentNegotiationManager.resolveFileExtensions(requestedMediaType);
                Iterator var11 = extensions.iterator();
                while(var11.hasNext()) {
                    String extension = (String)var11.next();
                    String viewNameWithExtension = viewName + '.' + extension;
                    view = viewResolver.resolveViewName(viewNameWithExtension, locale);
                    if (view != null) {
                        candidateViews.add(view);
                    }
                }
            }
        }
    }
    if (!CollectionUtils.isEmpty(this.defaultViews)) {
        candidateViews.addAll(this.defaultViews);
    }
    return candidateViews;
}

//全面扩展SpringMVC
//如果想要diy一些定制化的功能，只需要写这个组件
// 然后将它交给springboot，springboot就睡帮助我们进行自动装配
@Configuration
public class MyMvcConfig implements WebMvcConfigurer {
    //ContentNegotiatingViewResolver 实现了视图解析器的类，就可以把它看做视图解析器
    @Bean
    public ViewResolver myViewResolver(){
        return new MyViewResolver();
    }
 
    //
    public static class MyViewResolver implements ViewResolver{
        @Override
        public View resolveViewName(String viewName, Locale locale) throws IOException{
            return null;
        }
    }
}

三、Formatter 转换器和格式化器

@Bean
@Override
public FormattingConversionService mvcConversionService() {
	Format format = this.mvcProperties.getFormat();
	WebConversionService conversionService = new WebConversionService(new DateTimeFormatters()
			.dateFormat(format.getDate()).timeFormat(format.getTime()).dateTimeFormat(format.getDateTime()));
	addFormatters(conversionService);
	return conversionService;
}

public DateTimeFormatters dateFormat(String pattern) {
	if (isIso(pattern)) {
		this.dateFormatter = DateTimeFormatter.ISO_LOCAL_DATE;
		this.datePattern = "yyyy-MM-dd";
	}
	else {
		this.dateFormatter = formatter(pattern);
		this.datePattern = pattern;
	}
	return this;
}

四、修改SpringBoot的默认配置

SpringBoot在自动配置很多组件的时候，先看容器中有没有用户自己配置的（如果用户自己配置@bean），如果有就用用户配置的，如果没有就用自动配置的；

如果有些组件可以存在多个，例如视图解析器，可以将用户配置的和默认的组合起来使用

五、扩展使用SpringMVC

编写类型为WebMvcConfigurer的@Configuration注解类

且不能标注@EnableWebMvc注解；

需要自己写一个；

新建一个包：config，创建类MyMvcConfig；

⚪实现视图跳转

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {
 
    //视图跳转
    @Override
    public void addViewControllers(ViewControllerRegistry registry){
        registry.addViewController("/zhang").setViewName("test");
    }
}