工程
- 项目静态资源目录结构
testConverter.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="testConverter" method="**POST**">
<input type="text" name="test">
<input type="submit" value="submit">
</form>
</body>
</html>
- 项目说明
在不使用themleaf的情况下，通过前端以POST方式提交from表单到controller，controller处理后使用InternalResourceViewResolver进行视图解析，转发到静态资源文件夹static下的目标页面
扩展SpringMVC
@Configuration
public class MyWebMvcConfiguration implements WebMvcConfigurer {
@Override
public void addFormatters(FormatterRegistry registry) {
MyConverter myConverter = new MyConverter();
registry.addConverter(myConverter);//添加自定义Converter
}
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
//添加自定义 InternalResourceViewResolv
InternalResourceViewResolver internalResourceViewResolver = new InternalResourceViewResolver();
internalResourceViewResolver.setPrefix("/");// 给contrlloer返回值设置前后缀
internalResourceViewResolver.setSuffix(".html");
registry.viewResolver(internalResourceViewResolver);
}
自定义Converter
@Order(1)
public class MyConverter implements Converter<String, Student> {
@Override
public Student convert(String s) {
System.out.println("myconverter");//将前端提交的String转为Student对象
String[] values = s.split("-");
String lastName= values[0];
int age = Integer.parseInt(values[1]);
int departmentId = Integer.parseInt(values[2]);
String departmentName =values[3];
Department department = new Department(departmentId,departmentName,null);
return new Student(null, lastName,age,department);
}
}
Controller
@Controller
public class MyController {
//@ResponseBody
@RequestMapping("/testConverter")
public String testConverter(@RequestParam("test") Student student){
System.out.println(student);
return "testConverter2";//转发到static文件夹下的testConverter2.html页面
}
}
**
问题
**
当前端表单以POST方式提交请求时，返回405错误页面，而以GET方式则可以到目标页面
分析
从上面步骤看，控制台成功打印Student信息，证明自定义Converter有效，并成功将前端传过来的String转换为了Student，而且进一步说明Controller在前面代码执行没有问题，那么问题只能发生在return "testConverter2";，那么是什么原因呢？
-
配置的InternalResourceViewResolver解析视图有误？
难道InternalResourceViewResolver未起作用？没有将testConverter2解析为/testConverter2.html？但是如果将请求改为GET，则是可以到目标页面的，通过debug的方式发现InternalResourceViewResolver是可以成功解析视图的 -
上面的异常为不支持POST请求，那么问题出在那呢？
通过debug，进入DispatchSeverlet，执行doDispatch方法
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
try {
ModelAndView mv = null;
Object dispatchException = null;
try {
processedRequest = this.checkMultipart(request);
multipartRequestParsed = processedRequest != request;
mappedHandler = this.getHandler(processedRequest);
if (mappedHandler == null) {
this.noHandlerFound(processedRequest, response);
return;
}
//public class **RequestMappingHandlerAdapter** extends AbstractHandlerMethodAdapter implements BeanFactoryAware, InitializingBean
//请求将由RequestMappingHandlerAdapter处理
HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) { //**判断请求是否是GET或HEAD**
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
//RequestMappingHandlerAdapter（ha）处理请求，返回ModelAndView
//debug进去后，会发现问题就是在这一步发生的，具体后面详细介绍
//执行父类AbstractHandlerMethodAdapter **handle方法**
// @Nullable
//public final ModelAndView handle(HttpServletRequest request, HttpServletResponse //response, Object handler) throws Exception {
//return **this.handleInternal(request, response, (HandlerMethod)handler);**具体见下
// }
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
this.applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
} catch (Exception var20) {
dispatchException = var20;
} catch (Throwable var21) {
dispatchException = new NestedServletException("Handler dispatch failed", var21);
}
this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);
} catch (Exception var22) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);
} catch (Throwable var23) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));
}
} finally {
if (asyncManager.isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
} else if (multipartRequestParsed) {
this.cleanupMultipart(processedRequest);
}
}
}
执行handle方法，handle方法调用handleInternal方法（handle方法与hanleInternal方法均为RequestMappingHandlerAdapter父类AbstractHandlerMethodAdapter定义的方法）
protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
this.checkRequest(request);//该方法会检查请求的类型，this为RequestMappingHandlerAdapter类型
//protected final void checkRequest(HttpServletRequest request) throws ServletException {
//String method = request.getMethod();
// if (this.supportedMethods != null && !this.**supportedMethods**.contains(method)) {
// throw new HttpRequestMethodNotSupportedException(method, this.supportedMethods);
//} else if (this.requireSession && request.getSession(false) == null) {
// throw new HttpSessionRequiredException("Pre-existing session required but none found");
// }
// }
.....//省略
}
执行hanleInternal方法中的checkRequest方法
执行结果
该方法没有抛出异常，所以handleInternal方法顺序执行，返回ModelAndView
protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ServletWebRequest webRequest = new ServletWebRequest(request, response);
ModelAndView var15;
try {
WebDataBinderFactory binderFactory = this.getDataBinderFactory(handlerMethod);//数据绑定工厂
//WebDataBinder binder = binderFactory.createBinder(webRequest, (Object)null, namedValueInfo.name);获得数据绑定器
ModelFactory modelFactory = this.getModelFactory(handlerMethod, binderFactory);
.....//省略
//进行参数处理，进行转换，即使用MyConverter
invocableMethod.invokeAndHandle(webRequest, mavContainer, new Object[0]);
......//省略
}
回到DispatcherSeverlet的doDispatch方法
当前浏览器网页状况
当前后台打印信息
注意当前的mappedhandler
解析视图
将解析得到的视图放入候选视图集合中
private List<View> getCandidateViews(String viewName, Locale locale, List<MediaType> requestedMediaTypes) throws Exception {
List<View> 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);//添加候选视图
}
返回最佳视图对象
@Nullable
public View resolveViewName(String viewName, Locale locale) throws Exception {
RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");
List<MediaType> requestedMediaTypes = this.getMediaTypes(((ServletRequestAttributes)attrs).getRequest());
if (requestedMediaTypes != null) {
List<View> candidateViews = this.getCandidateViews(viewName, locale, requestedMediaTypes);
View bestView = this.getBestView(candidateViews, requestedMediaTypes, attrs);
if (bestView != null) {
return bestView;//从candidateViews获取最佳视图对象并返回
}
}
执行结果
返回到DispatcherSeverlet，执行doDispatch
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
执行该方法
执行handleRequest(HttpServletRequest request, HttpServletResponse response)
public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Resource resource = this.getResource(request);//获取资源
if (resource == null) {
logger.debug("Resource not found");
response.sendError(404);
} else if (HttpMethod.OPTIONS.matches(request.getMethod())) {
response.setHeader("Allow", this.getAllowHeader());
} else {
this.checkRequest(request);
if ((new ServletWebRequest(request, response)).checkNotModified(resource.lastModified())) {
logger.trace("Resource not modified");
} else {
this.prepareResponse(response);
MediaType mediaType = this.getMediaType(request, resource);
if ("HEAD".equals(request.getMethod())) {
找到目标资源
- 报错原因（重点）
protected final void checkRequest(HttpServletRequest request) throws ServletException {
String method = request.getMethod();
if (this.supportedMethods != null && !this.supportedMethods.contains(method)) {
throw new HttpRequestMethodNotSupportedException(method, this.supportedMethods);
} else if (this.requireSession && request.getSession(false) == null) {
throw new HttpSessionRequiredException("Pre-existing session required but none found");
}
}
从上面代码看，该方法就是判断是否满足条件，然后决定是否抛出异常
执行结果
该异常构造方法
public HttpRequestMethodNotSupportedException(String method, @Nullable String[] supportedMethods) {
//得到抛出异常的信息
this(method, supportedMethods, "Request method '" + method + "' not supported");
}
至此原因以找到，即不支持POST的方式获取静态资源
解决办法
1）使用GET方式，即表单以GET方式提交
2）进行重定向
@Controller
public class MyController {
//@ResponseBody
@RequestMapping("/testConverter")
public String testConverter(@RequestParam("test") Student student){
System.out.println(student);
return "redirect:testConverter2.html";//重定向
}
}