文章目录
前言
接上篇文章的SpringBoot的介绍,本文开始为SpringBoot中MVC的配置及底层原理进行学习。
文章来自于博主自学B站雷神SpringBoot2的笔记如有侵权或其他问题请直接私信。
一、SpringMVC自动配置概览
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.(大多场景我们都无需自定义配置)
The auto-configuration adds the following features on top of Spring’s defaults:
- Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
○ 内容协商视图解析器和BeanName视图解析器 - Support for serving static resources, including support for WebJars (covered later in this document)).
○ 静态资源(包括webjars) - Automatic registration of Converter, GenericConverter, and Formatter beans.
○ 自动注册 Converter,GenericConverter,Formatter - Support for HttpMessageConverters (covered later in this document).
○ 支持 HttpMessageConverters (后来我们配合内容协商理解原理) - Automatic registration of MessageCodesResolver (covered later in this document).
○ 自动注册 MessageCodesResolver (国际化用) - Static index.html support.
○ 静态index.html 页支持 - Custom Favicon support (covered later in this document).
○ 自定义 Favicon - Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).
○ 自动使用 ConfigurableWebBindingInitializer ,(DataBinder负责将请求数据绑定到JavaBean上)
二、简单功能分析
2.1、静态资源访问
2.1.1、静态资源目录
只要静态资源放在类路径下: called /static (or /public or /resources or /META-INF/resources)
访问 : 当前项目根路径/ + 静态资源名 **
==原理: 静态映射/。==
请求进来,先去找Controller看能不能处理。不能处理的所有请求又都交给静态资源处理器。静态资源也找不到则响应404页面
spring:
mvc:
static-path-pattern: /res/**
改变访问资源的请求前缀
resources:
static-locations: [classpath:/haha/]
改变静态资源的默认储存位置
2.1.2、静态资源访问前缀
默认无前缀
spring:
mvc:
static-path-pattern: /res/**
当前项目 + static-path-pattern + 静态资源名 = 静态资源文件夹下找
2.1.3、webjar
自动映射 /webjars/**
https://www.webjars.org/
<dependency>
<groupId>org.webjars</groupId>
<artifactId>jquery</artifactId>
<version>3.5.1</version>
</dependency>
访问地址:http://localhost:8080/webjars/jquery/3.5.1/jquery.js 后面地址要按照依赖里面的包路径
2.2、欢迎页支持
- 静态资源路径下 index.html
○ 可以配置静态资源路径
○ 但是不可以配置静态资源的访问前缀。否则导致 index.html不能被默认访问
spring:
# mvc:
# static-path-pattern: /res/** 这个会导致welcome page功能失效
resources:
static-locations: [classpath:/haha/]
或者某个controller能处理/index
2.3、自定义 Favicon
favicon.ico 放在静态资源目录下即可。
spring:
# mvc:
# static-path-pattern: /res/** 这个会导致 Favicon 功能失效
2.4、静态资源配置原理
- SpringBoot启动默认加载 xxxAutoConfiguration 类(自动配置类)
- SpringMVC功能的自动配置类 WebMvcAutoConfiguration,生效
@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {}
- 给容器中配了什么。
@Configuration(proxyBeanMethods = false)
@Import(EnableWebMvcConfiguration.class)
@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
@Order(0)
public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {}
- 配置文件的相关属性和xxx进行了绑定。WebMvcProperties == spring.mvc、ResourceProperties == spring.resources
2.4.1、配置类只有一个有参构造器
//有参构造器所有参数的值都会从容器中确定
//ResourceProperties resourceProperties;获取和spring.resources绑定的所有的值的对象
//WebMvcProperties mvcProperties 获取和spring.mvc绑定的所有的值的对象
//ListableBeanFactory beanFactory Spring的beanFactory
//HttpMessageConverters 找到所有的HttpMessageConverters
//ResourceHandlerRegistrationCustomizer 找到 资源处理器的自定义器。=========
//DispatcherServletPath
//ServletRegistrationBean 给应用注册Servlet、Filter....
public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
ObjectProvider<DispatcherServletPath> dispatcherServletPath,
ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
this.resourceProperties = resourceProperties;
this.mvcProperties = mvcProperties;
this.beanFactory = beanFactory;
this.messageConvertersProvider = messageConvertersProvider;
this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
this.dispatcherServletPath = dispatcherServletPath;
this.servletRegistrations = servletRegistrations;
}
2.4.2、资源处理的默认规则
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
if (!this.resourceProperties.isAddMappings()) {
logger.debug("Default resource handling disabled");
return;
}
Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
//webjars的规则
if (!registry.hasMappingForPattern("/webjars/**")) {
customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
.addResourceLocations("classpath:/META-INF/resources/webjars/")
.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
}
//
String staticPathPattern = this.mvcProperties.getStaticPathPattern();
if (!registry.hasMappingForPattern(staticPathPattern)) {
customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
.addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
}
}
spring:
# mvc:
# static-path-pattern: /res/**
resources:
add-mappings: false 禁用所有静态资源规则
@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {
private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",
"classpath:/resources/", "classpath:/static/", "classpath:/public/" };
/**
* Locations of static resources. Defaults to classpath:[/META-INF/resources/,
* /resources/, /static/, /public/].
*/
private String[] staticLocations = CLASSPATH_RESOURCE_LOCATIONS;
2.4. 3、欢迎页的处理规则
HandlerMapping:处理器映射。保存了每一个Handler能处理哪些请求。
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
this.mvcProperties.getStaticPathPattern());
welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());
return welcomePageHandlerMapping;
}
WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {
if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
//要用欢迎页功能,必须是/**
logger.info("Adding welcome page: " + welcomePage.get());
setRootViewName("forward:index.html");
}
else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
// 调用Controller /index
logger.info("Adding welcome page template: index");
setRootViewName("index");
}
}
2.4.4、favicon
由于favicon.ico图标是由浏览器自动发送请求/favicon.ico获取并保存在session域中的。因此,如果我们在配置文件中设置了静态资源访问前缀,那么浏览器发送的/favicon.ico由于不符合访问前缀要求,就会获取不到相对应的图标了(图标也是静态资源的一种)。
所以我们设置favicon图标的时候必须使用默认的前缀。
三、请求参数处理
3.0、请求映射
最基本的requestmapping("/")
3.1、rest使用与原理
- @xxxMapping;
- Rest风格支持(使用HTTP请求方式动词来表示对资源的操作)
- 以前:/getUser 获取用户 /deleteUser 删除用户 /editUser 修改用户 /saveUser 保存用户
- 现在: /user GET-获取用户 DELETE-删除用户 PUT-修改用户 POST-保存用户
- 核心Filter;HiddenHttpMethodFilter
- 用法: 表单method=post,隐藏域 _method=put
- SpringBoot中手动开启
- 扩展:如何把_method 这个名字换成我们自己喜欢的。
@RequestMapping(value = "/user",method = RequestMethod.GET)
public String getUser(){
return "GET-张三";
}
@RequestMapping(value = "/user",method = RequestMethod.POST)
public String saveUser(){
return "POST-张三";
}
@RequestMapping(value = "/user",method = RequestMethod.PUT)
public String putUser(){
return "PUT-张三";
}
@RequestMapping(value = "/user",method = RequestMethod.DELETE)
public String deleteUser(){
return "DELETE-张三";
}
@Bean
@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled", matchIfMissing = false)
public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
return new OrderedHiddenHttpMethodFilter();
}
//自定义filter
@Bean
public HiddenHttpMethodFilter hiddenHttpMethodFilter(){
HiddenHttpMethodFilter methodFilter = new HiddenHttpMethodFilter();
methodFilter.setMethodParam("_m");
return methodFilter;
}
新注解@GetMapping();@PostMapping();@PutMapping();@DeleteMapping();
还有@PatchMapping,它是对Put的补充,区别是Patch是部分更新,Put是全部更新,这些注解都是Spring4.3引入的.
Rest原理(表单提交要使用REST的时候)
- 表单提交会带上_method=PUT
- 请求过来被HiddenHttpMethodFilter拦截
- 请求是否正常,并且是POST
- 获取到_method的值。 无论value是大写还是小写,底层都会统一转换为大写
- 兼容以下请求;PUT.DELETE.PATCH
- 原生request(post),包装模式requesWrapper重写了getMethod方法,返回的是传入的值。
- 过滤器链放行的时候用wrapper。以后的方法调用getMethod是调用requesWrapper的。
- 请求是否正常,并且是POST
Rest使用客户端工具,
- 如PostMan直接发送Put、delete等方式请求,无需Filter。
- 后续关注:DispatcherServlet中的HandlerExecutionChain拦截器执行链(包括自定义的拦截器也会在这里)
先执行拦截器的preHandle方法,如果返回true
放行执行handlerAdapter的handle方法,也就是controller方法
adapter执行完成返回ModelAndView对象
执行拦截器postHandle方法
然后dispatcher把mav对象交给视图解析器解析,获取View对象
响应客户端
配置在org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.java这个类中
spring:
mvc:
hiddenmethod:
filter:
enabled: true #开启页面表单的Rest功能
3.2、请求映射原理
SpringMVC功能分析都从 org.springframework.web.servlet.DispatcherServlet-》doDispatch()
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// 找到当前请求使用哪个Handler(Controller的方法)处理
mappedHandler = getHandler(processedRequest);
//HandlerMapping:处理器映射。/xxx->>xxxx
RequestMappingHandlerMapping:保存了所有@RequestMapping 和handler的映射规则。
所有的请求映射都在HandlerMapping中。
- SpringBoot自动配置欢迎页的 WelcomePageHandlerMapping 。访问 /能访问到index.html;
- SpringBoot自动配置了默认 的 RequestMappingHandlerMapping
- 请求进来,挨个尝试所有的HandlerMapping看是否有请求信息。
- 如果有就找到这个请求对应的handler
- 如果没有就是下一个 HandlerMapping
- 我们需要一些自定义的映射处理,我们也可以自己给容器中放
HandlerMapping
。自定义HandlerMapping
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (HandlerMapping mapping : this.handlerMappings) {
HandlerExecutionChain handler = mapping.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
3.3、普通参数与基本注解
3.1.1、注解:
@PathVariable:可以用来映射URL中的占位符到目标方法的参数.
@RequestHeader:用于获取http请求的header部分信息.
@ModelAttribute:
@RequestParam:获得url上的参数
@MatrixVariable:获得矩阵变量的参数
@CookieValue:获得cookie
@RequestBody:用来接收前端传递给后端的json字符串中的数据的(请求体中的数据的)
@RestController
public class ParameterTestController {
// car/2/owner/zhangsan
@GetMapping("/car/{id}/owner/{username}")
public Map<String,Object> getCar(@PathVariable("id") Integer id,
@PathVariable("username") String name,
@PathVariable Map<String,String> pv,
@RequestHeader("User-Agent") String userAgent,
@RequestHeader Map<String,String> header,
@RequestParam("age") Integer age,
@RequestParam("inters") List<String> inters,
@RequestParam Map<String,String> params,
@CookieValue("_ga") String _ga,
@CookieValue("_ga") Cookie cookie){
Map<String,Object> map = new HashMap<>();
// map.put("id",id);
// map.put("name",name);
// map.put("pv",pv);
// map.put("userAgent",userAgent);
// map.put("headers",header);
map.put("age",age);
map.put("inters",inters);
map.put("params",params);
map.put("_ga",_ga);
System.out.println(cookie.getName()+"===>"+cookie.getValue());
return map;
}
@PostMapping("/save")
public Map postMethod(@RequestBody String content){
Map<String,Object> map = new HashMap<>();
map.put("content",content);
return map;
}
//1、语法: 请求路径:/cars/sell;low=34;brand=byd,audi,yd
//2、SpringBoot默认是禁用了矩阵变量的功能
// 手动开启:原理。对于路径的处理。UrlPathHelper进行解析。
// removeSemicolonContent(移除分号内容)支持矩阵变量的
//3、矩阵变量必须有url路径变量才能被解析
@GetMapping("/cars/{path}")
public Map carsSell(@MatrixVariable("low") Integer low,
@MatrixVariable("brand") List<String> brand,
@PathVariable("path") String path){
Map<String,Object> map = new HashMap<>();
map.put("low",low);
map.put("brand",brand);
map.put("path",path);
return map;
}
// /boss/1;age=20/2;age=10
@GetMapping("/boss/{bossId}/{empId}")
public Map boss(@MatrixVariable(value = "age",pathVar = "bossId") Integer bossAge,
@MatrixVariable(value = "age",pathVar = "empId") Integer empAge){
Map<String,Object> map = new HashMap<>();
map.put("bossAge",bossAge);
map.put("empAge",empAge);
return map;
}
}
3.1.2、Servlet API:
WebRequest、ServletRequest、MultipartRequest、 HttpSession、javax.servlet.http.PushBuilder、Principal、InputStream、Reader、HttpMethod、Locale、TimeZone、ZoneId
ServletRequestMethodArgumentResolver
以上的部分参数
@Override
public boolean supportsParameter(MethodParameter parameter) {
Class<?> paramType = parameter.getParameterType();
return (WebRequest.class.isAssignableFrom(paramType) ||
ServletRequest.class.isAssignableFrom(paramType) ||
MultipartRequest.class.isAssignableFrom(paramType) ||
HttpSession.class.isAssignableFrom(paramType) ||
(pushBuilder != null && pushBuilder.isAssignableFrom(paramType)) ||
Principal.class.isAssignableFrom(paramType) ||
InputStream.class.isAssignableFrom(paramType) ||
Reader.class.isAssignableFrom(paramType) ||
HttpMethod.class == paramType ||
Locale.class == paramType ||
TimeZone.class == paramType ||
ZoneId.class == paramType);
}
3.1.3、复杂参数:
Map、Model(map、model里面的数据会被放在request的请求域 request.setAttribute)、Errors/BindingResult、RedirectAttributes( 重定向携带数据)、ServletResponse(response)、SessionStatus、UriComponentsBuilder、ServletUriComponentsBuilder
Map<String,Object> map, Model model, HttpServletRequest request 都是可以给request域中放数据,
request.getAttribute();
Map、Model类型的参数,会返回 mavContainer.getModel();
—> BindingAwareModelMap 是Model 也是Map
mavContainer.getModel(); 获取到值的
3.1.4、自定义对象参数:
可以自动类型转换与格式化,可以级联封装。
/**
* 姓名: <input name="userName"/> <br/>
* 年龄: <input name="age"/> <br/>
* 生日: <input name="birth"/> <br/>
* 宠物姓名:<input name="pet.name"/><br/>
* 宠物年龄:<input name="pet.age"/>
*/
@Data
public class Person {
private String userName;
private Integer age;
private Date birth;
private Pet pet;
}
@Data
public class Pet {
private String name;
private String age;
}
result
3.2POJO封装过程
- ServletModelAttributeMethodProcessor
3.3、参数处理原理
- HandlerMapping中找到能处理请求的Handler(Controller.method())
- 为当前Handler 找一个适配器 HandlerAdapter; RequestMappingHandlerAdapter
- 适配器执行目标方法并确定方法参数的每一个值
3.3.1、HandlerAdapter
0 - 支持方法上标注@RequestMapping
1 - 支持函数式编程的
3.3.2、执行目标方法
// Actually invoke the handler.
//DispatcherServlet -- doDispatch
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
mav = invokeHandlerMethod(request, response, handlerMethod); //执行目标方法
//ServletInvocableHandlerMethod
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
//获取方法的参数值
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
3.3.3、参数解析器-HandlerMethodArgumentResolver
确定将要执行的目标方法的每一个参数的值是什么;
SpringMVC目标方法能写多少种参数类型。取决于参数解析器。
- 当前解析器是否支持解析这种参数
- 支持就调用 resolveArgument
3.3.4、返回值处理器
3.3.5、如何确定目标方法每一个参数的值
============InvocableHandlerMethod==========================
protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
MethodParameter[] parameters = getMethodParameters();
if (ObjectUtils.isEmpty(parameters)) {
return EMPTY_ARGS;
}
Object[] args = new Object[parameters.length];
for (int i = 0; i < parameters.length; i++) {
MethodParameter parameter = parameters[i];
parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
args[i] = findProvidedArgument(parameter, providedArgs);
if (args[i] != null) {
continue;
}
if (!this.resolvers.supportsParameter(parameter)) {
throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
}
try {
args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
}
catch (Exception ex) {
// Leave stack trace for later, exception may actually be resolved and handled...
if (logger.isDebugEnabled()) {
String exMsg = ex.getMessage();
if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {
logger.debug(formatArgumentError(parameter, exMsg));
}
}
throw ex;
}
}
return args;
}
3.3.5.1、挨个判断所有参数解析器那个支持解析这个参数
@Nullable
private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
if (result == null) {
for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
if (resolver.supportsParameter(parameter)) {
result = resolver;
this.argumentResolverCache.put(parameter, result);
break;
}
}
}
return result;
}
3.5.5.2、解析这个参数的值
调用各自 HandlerMethodArgumentResolver 的 resolveArgument 方法即可.
3.5.5.3、自定义类型参数 封装POJO
ServletModelAttributeMethodProcessor
这个参数处理器支持
是否为简单类型。
public static boolean isSimpleValueType(Class<?> type) {
return (Void.class != type && void.class != type &&
(ClassUtils.isPrimitiveOrWrapper(type) ||
Enum.class.isAssignableFrom(type) ||
CharSequence.class.isAssignableFrom(type) ||
Number.class.isAssignableFrom(type) ||
Date.class.isAssignableFrom(type) ||
Temporal.class.isAssignableFrom(type) ||
URI.class == type ||
URL.class == type ||
Locale.class == type ||
Class.class == type));
}
@Override
@Nullable
public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Assert.state(mavContainer != null, "ModelAttributeMethodProcessor requires ModelAndViewContainer");
Assert.state(binderFactory != null, "ModelAttributeMethodProcessor requires WebDataBinderFactory");
String name = ModelFactory.getNameForParameter(parameter);
ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
if (ann != null) {
mavContainer.setBinding(name, ann.binding());
}
Object attribute = null;
BindingResult bindingResult = null;
if (mavContainer.containsAttribute(name)) {
attribute = mavContainer.getModel().get(name);
}
else {
// Create attribute instance
try {
attribute = createAttribute(name, parameter, binderFactory, webRequest);
}
catch (BindException ex) {
if (isBindExceptionRequired(parameter)) {
// No BindingResult parameter -> fail with BindException
throw ex;
}
// Otherwise, expose null/empty value and associated BindingResult
if (parameter.getParameterType() == Optional.class) {
attribute = Optional.empty();
}
bindingResult = ex.getBindingResult();
}
}
if (bindingResult == null) {
// Bean property binding and validation;
// skipped in case of binding failure on construction.
WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
if (binder.getTarget() != null) {
if (!mavContainer.isBindingDisabled(name)) {
bindRequestParameters(binder, webRequest);
}
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
throw new BindException(binder.getBindingResult());
}
}
// Value type adaptation, also covering java.util.Optional
if (!parameter.getParameterType().isInstance(attribute)) {
attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
}
bindingResult = binder.getBindingResult();
}
// Add resolved attribute and BindingResult at the end of the model
Map<String, Object> bindingResultModel = bindingResult.getModel();
mavContainer.removeAttributes(bindingResultModel);
mavContainer.addAllAttributes(bindingResultModel);
return attribute;
}
WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
WebDataBinder :web数据绑定器,将请求参数的值绑定到指定的JavaBean里面
WebDataBinder 利用它里面的 Converters 将请求数据转成指定的数据类型。再次封装到JavaBean中
GenericConversionService:在设置每一个值的时候,找它里面的所有converter那个可以将这个数据类型(request带来参数的字符串)转换到指定的类型(JavaBean – Integer)
byte – > file
@FunctionalInterfacepublic
interface Converter<S, T> ** 只针对于form表单提交的数据**
未来我们可以给WebDataBinder里面放自己的Converter;
private static final class StringToNumber implements Converter<String, T>
自定义 Converter
//1、WebMvcConfigurer定制化SpringMVC的功能
@Bean
public WebMvcConfigurer webMvcConfigurer(){
return new WebMvcConfigurer() {
@Override
public void configurePathMatch(PathMatchConfigurer configurer) {
UrlPathHelper urlPathHelper = new UrlPathHelper();
// 不移除;后面的内容。矩阵变量功能就可以生效
urlPathHelper.setRemoveSemicolonContent(false);
configurer.setUrlPathHelper(urlPathHelper);
}
@Override
public void addFormatters(FormatterRegistry registry) {
registry.addConverter(new Converter<String, Pet>() {
@Override
public Pet convert(String source) {
// 啊猫,3
if(!StringUtils.isEmpty(source)){
Pet pet = new Pet();
String[] split = source.split(",");
pet.setName(split[0]);
pet.setAge(Integer.parseInt(split[1]));
return pet;
}
return null;
}
});
}
};
}
3.3.6、目标方法执行完成
将所有的数据都放在 ModelAndViewContainer;包含要去的页面地址View。还包含Model数据。
3.3.7、处理派发结果
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);
InternalResourceView:
@Override
protected void renderMergedOutputModel(
Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Expose the model object as request attributes.
exposeModelAsRequestAttributes(model, request);
// Expose helpers as request attributes, if any.
exposeHelpers(request);
// Determine the path for the request dispatcher.
String dispatcherPath = prepareForRendering(request, response);
// Obtain a RequestDispatcher for the target resource (typically a JSP).
RequestDispatcher rd = getRequestDispatcher(request, dispatcherPath);
if (rd == null) {
throw new ServletException("Could not get RequestDispatcher for [" + getUrl() +
"]: Check that the corresponding file exists within your web application archive!");
}
// If already included or response already committed, perform include, else forward.
if (useInclude(request, response)) {
response.setContentType(getContentType());
if (logger.isDebugEnabled()) {
logger.debug("Including [" + getUrl() + "]");
}
rd.include(request, response);
}
else {
// Note: The forwarded resource is supposed to determine the content type itself.
if (logger.isDebugEnabled()) {
logger.debug("Forwarding to [" + getUrl() + "]");
}
rd.forward(request, response);
}
}
protected void exposeModelAsRequestAttributes(Map<String, Object> model,
HttpServletRequest request) throws Exception {
//model中的所有数据遍历挨个放在请求域中
model.forEach((name, value) -> {
if (value != null) {
request.setAttribute(name, value);
}
else {
request.removeAttribute(name);
}
});
}
四、数据响应与内容协商
4.1、响应JSON
4.1.1、jackson.jar+@ResponseBody
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
web场景自动引入了json场景
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-json</artifactId>
<version>2.3.4.RELEASE</version>
<scope>compile</scope>
</dependency>
给前端自动返回json数据;
4.1.1.1、返回值解析器
try {
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);
if (handler == null) {
throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
}
handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
}
RequestResponseBodyMethodProcessor
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
mavContainer.setRequestHandled(true);
ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
ServletServerHttpResponse outputMessage = createOutputMessage(webRequest);
// Try even with null return value. ResponseBodyAdvice could get involved.
// 使用消息转换器进行写出操作
writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
}
4.1.1.2、返回值解析器原理
- 1、返回值处理器判断是否支持这种类型返回值 supportsReturnType
- 2、返回值处理器调用 handleReturnValue 进行处理
- 3、RequestResponseBodyMethodProcessor 可以处理返回值标了@ResponseBody 注解的。
- 1.利用 MessageConverters 进行处理 将数据写为json
- 1、内容协商(浏览器默认会以请求头的方式告诉服务器他能接受什么样的内容类型)
- 2、服务器最终根据自己自身的能力,决定服务器能生产出什么样内容类型的数据,
- 3、SpringMVC会挨个遍历所有容器底层的 HttpMessageConverter ,看谁能处理?
- 1、得到MappingJackson2HttpMessageConverter可以将对象写为json
- 2、利用MappingJackson2HttpMessageConverter将对象转为json再写出去。
- 1.利用 MessageConverters 进行处理 将数据写为json
4.1.2、SpringMVC到底支持哪些返回值
ModelAndView
Model
View
ResponseEntity
ResponseBodyEmitter
StreamingResponseBody
HttpEntity
HttpHeaders
Callable
DeferredResult
ListenableFuture
CompletionStage
WebAsyncTask
有 @ModelAttribute 且为对象类型的
@ResponseBody 注解 ---> RequestResponseBodyMethodProcessor;
4.1.3、HTTPMessageConverter原理
4.1.3.1、MessageConverter规范
HttpMessageConverter: 看是否支持将 此 Class类型的对象,转为MediaType类型的数据。
例子:Person对象转为JSON。或者 JSON转为Person
4.1.3.2、默认的MessageConverter
0 - 只支持Byte类型的
1 - String
2 - String
3 - Resource
4 - ResourceRegion
5 - DOMSource.class \ SAXSource.class) \ StAXSource.class \StreamSource.class \Source.class
6 - MultiValueMap
7 - true
8 - true
9 - 支持注解方式xml处理的。
最终 MappingJackson2HttpMessageConverter 把对象转为JSON(利用底层的jackson的objectMapper转换的)
总结
接上篇文章的SpringBoot的介绍,本文开始为SpringBoot中MVC的配置及底层原理进行学习。
下篇文章是关于内容协商和上传文件、异常处理等进行学习。
文章来自于博主自学B站雷神SpringBoot2的笔记如有侵权或其他问题请直接私信。