33、请求处理-【源码分析】-Servlet API参数解析原理
- WebRequest
- ServletRequest
- MultipartRequest
- HttpSession
- javax.servlet.http.PushBuilder
- Principal
- InputStream
- Reader
- HttpMethod
- Locale
- TimeZone
- ZoneId
ServletRequestMethodArgumentResolver用来处理以上的参数
public class ServletRequestMethodArgumentResolver implements HandlerMethodArgumentResolver {
@Nullable
private static Class<?> pushBuilder;
static {
try {
pushBuilder = ClassUtils.forName("javax.servlet.http.PushBuilder",
ServletRequestMethodArgumentResolver.class.getClassLoader());
}
catch (ClassNotFoundException ex) {
// Servlet 4.0 PushBuilder not found - not supported for injection
pushBuilder = null;
}
}
@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) && !parameter.hasParameterAnnotations()) ||
InputStream.class.isAssignableFrom(paramType) ||
Reader.class.isAssignableFrom(paramType) ||
HttpMethod.class == paramType ||
Locale.class == paramType ||
TimeZone.class == paramType ||
ZoneId.class == paramType);
}
@Override
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Class<?> paramType = parameter.getParameterType();
// WebRequest / NativeWebRequest / ServletWebRequest
if (WebRequest.class.isAssignableFrom(paramType)) {
if (!paramType.isInstance(webRequest)) {
throw new IllegalStateException(
"Current request is not of type [" + paramType.getName() + "]: " + webRequest);
}
return webRequest;
}
// ServletRequest / HttpServletRequest / MultipartRequest / MultipartHttpServletRequest
if (ServletRequest.class.isAssignableFrom(paramType) || MultipartRequest.class.isAssignableFrom(paramType)) {
return resolveNativeRequest(webRequest, paramType);
}
// HttpServletRequest required for all further argument types
return resolveArgument(paramType, resolveNativeRequest(webRequest, HttpServletRequest.class));
}
private <T> T resolveNativeRequest(NativeWebRequest webRequest, Class<T> requiredType) {
T nativeRequest = webRequest.getNativeRequest(requiredType);
if (nativeRequest == null) {
throw new IllegalStateException(
"Current request is not of type [" + requiredType.getName() + "]: " + webRequest);
}
return nativeRequest;
}
@Nullable
private Object resolveArgument(Class<?> paramType, HttpServletRequest request) throws IOException {
if (HttpSession.class.isAssignableFrom(paramType)) {
HttpSession session = request.getSession();
if (session != null && !paramType.isInstance(session)) {
throw new IllegalStateException(
"Current session is not of type [" + paramType.getName() + "]: " + session);
}
return session;
}
else if (pushBuilder != null && pushBuilder.isAssignableFrom(paramType)) {
return PushBuilderDelegate.resolvePushBuilder(request, paramType);
}
else if (InputStream.class.isAssignableFrom(paramType)) {
InputStream inputStream = request.getInputStream();
if (inputStream != null && !paramType.isInstance(inputStream)) {
throw new IllegalStateException(
"Request input stream is not of type [" + paramType.getName() + "]: " + inputStream);
}
return inputStream;
}
else if (Reader.class.isAssignableFrom(paramType)) {
Reader reader = request.getReader();
if (reader != null && !paramType.isInstance(reader)) {
throw new IllegalStateException(
"Request body reader is not of type [" + paramType.getName() + "]: " + reader);
}
return reader;
}
else if (Principal.class.isAssignableFrom(paramType)) {
Principal userPrincipal = request.getUserPrincipal();
if (userPrincipal != null && !paramType.isInstance(userPrincipal)) {
throw new IllegalStateException(
"Current user principal is not of type [" + paramType.getName() + "]: " + userPrincipal);
}
return userPrincipal;
}
else if (HttpMethod.class == paramType) {
return HttpMethod.resolve(request.getMethod());
}
else if (Locale.class == paramType) {
return RequestContextUtils.getLocale(request);
}
else if (TimeZone.class == paramType) {
TimeZone timeZone = RequestContextUtils.getTimeZone(request);
return (timeZone != null ? timeZone : TimeZone.getDefault());
}
else if (ZoneId.class == paramType) {
TimeZone timeZone = RequestContextUtils.getTimeZone(request);
return (timeZone != null ? timeZone.toZoneId() : ZoneId.systemDefault());
}
// Should never happen...
throw new UnsupportedOperationException("Unknown parameter type: " + paramType.getName());
}
/**
* Inner class to avoid a hard dependency on Servlet API 4.0 at runtime.
*/
private static class PushBuilderDelegate {
@Nullable
public static Object resolvePushBuilder(HttpServletRequest request, Class<?> paramType) {
PushBuilder pushBuilder = request.newPushBuilder();
if (pushBuilder != null && !paramType.isInstance(pushBuilder)) {
throw new IllegalStateException(
"Current push builder is not of type [" + paramType.getName() + "]: " + pushBuilder);
}
return pushBuilder;
}
}
}
用例：
@Controller
public class RequestController {
@GetMapping("/goto")
public String goToPage(HttpServletRequest request){
request.setAttribute("msg","成功了...");
request.setAttribute("code",200);
return "forward:/success"; //转发到 /success请求
}
}
34、请求处理-【源码分析】-Model、Map原理
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
用例：
@GetMapping("/params")
public String testParam(Map<String,Object> map,
Model model,
HttpServletRequest request,
HttpServletResponse response){
//下面三位都是可以给request域中放数据
map.put("hello","world666");
model.addAttribute("world","hello666");
request.setAttribute("message","HelloWorld");
Cookie cookie = new Cookie("c1","v1");
response.addCookie(cookie);
return "forward:/success";
}
@ResponseBody
@GetMapping("/success")
public Map success(@RequestAttribute(value = "msg",required = false) String msg,
@RequestAttribute(value = "code",required = false)Integer code,
HttpServletRequest request){
Object msg1 = request.getAttribute("msg");
Map<String,Object> map = new HashMap<>();
Object hello = request.getAttribute("hello");//得出testParam方法赋予的值 world666
Object world = request.getAttribute("world");//得出testParam方法赋予的值 hello666
Object message = request.getAttribute("message");//得出testParam方法赋予的值 HelloWorld
map.put("reqMethod_msg",msg1);
map.put("annotation_msg",msg);
map.put("hello",hello);
map.put("world",world);
map.put("message",message);
return map;
}
Map<String,Object> mapModel modelHttpServletRequest request
上面三位都是可以给request域中放数据，用request.getAttribute()获取
接下来我们看看，Map<String,Object> map与Model model用什么参数处理器。
Map<String,Object> map参数用MapMethodProcessor处理：
public class MapMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
@Override
public boolean supportsParameter(MethodParameter parameter) {
return (Map.class.isAssignableFrom(parameter.getParameterType()) &&
parameter.getParameterAnnotations().length == 0);
}
@Override
@Nullable
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");
return mavContainer.getModel();
}
...
}
mavContainer.getModel()如下：
public class ModelAndViewContainer {
...
private final ModelMap defaultModel = new BindingAwareModelMap();
@Nullable
private ModelMap redirectModel;
...
public ModelMap getModel() {
if (useDefaultModel()) {
return this.defaultModel;
}
else {
if (this.redirectModel == null) {
this.redirectModel = new ModelMap();
}
return this.redirectModel;
}
}
private boolean useDefaultModel() {
return (!this.redirectModelScenario || (this.redirectModel == null && !this.ignoreDefaultModelOnRedirect));
}
...
}
Model model用ModelMethodProcessor处理：
public class ModelMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
@Override
public boolean supportsParameter(MethodParameter parameter) {
return Model.class.isAssignableFrom(parameter.getParameterType());
}
@Override
@Nullable
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");
return mavContainer.getModel();
}
...
}
return mavContainer.getModel();这跟MapMethodProcessor的一致
Model也是另一种意义的Map。
接下来看看Map<String,Object> map与Model model值是如何做到用request.getAttribute()获取的。
众所周知，所有的数据都放在 ModelAndView包含要去的页面地址View，还包含Model数据。
先看ModelAndView接下来是如何处理的？
public class DispatcherServlet extends FrameworkServlet {
...
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
...
try {
ModelAndView mv = null;
...
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
...
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
//处理分发结果
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
...
}
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
@Nullable Exception exception) throws Exception {
...
// Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
render(mv, request, response);
...
}
...
}
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
...
View view;
String viewName = mv.getViewName();
if (viewName != null) {
// We need to resolve the view name.
view = resolveViewName(viewName, mv.getModelInternal(), locale, request);
if (view == null) {
throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
"' in servlet with name '" + getServletName() + "'");
}
}
else {
// No need to lookup: the ModelAndView object contains the actual View object.
view = mv.getView();
if (view == null) {
throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
"View object in servlet with name '" + getServletName() + "'");
}
}
view.render(mv.getModelInternal(), request, response);
...
}
}
在Debug模式下，view属为InternalResourceView类。
public class InternalResourceView extends AbstractUrlBasedView {
@Override//该方法在AbstractView，AbstractUrlBasedView继承了AbstractView
public void render(@Nullable Map<String, ?> model, HttpServletRequest request,
HttpServletResponse response) throws Exception {
...
Map<String, Object> mergedModel = createMergedOutputModel(model, request, response);
prepareResponse(request, response);
//看下一个方法实现
renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);
}
@Override
protected void renderMergedOutputModel(
Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Expose the model object as request attributes.
// 暴露模型作为请求域属性
exposeModelAsRequestAttributes(model, request);//<---重点
// 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);
...
}
//该方法在AbstractView，AbstractUrlBasedView继承了AbstractView
protected void exposeModelAsRequestAttributes(Map<String, Object> model,
HttpServletRequest request) throws Exception {
model.forEach((name, value) -> {
if (value != null) {
request.setAttribute(name, value);
}
else {
request.removeAttribute(name);
}
});
}
}
exposeModelAsRequestAttributes方法看出，Map<String,Object> map，Model model这两种类型数据可以给request域中放数据，用request.getAttribute()获取。
35、请求处理-【源码分析】-自定义参数绑定原理
@RestController
public class ParameterTestController {
/**
* 数据绑定：页面提交的请求数据（GET、POST）都可以和对象属性进行绑定
* @param person
* @return
*/
@PostMapping("/saveuser")
public Person saveuser(Person person){
return person;
}
}
/**
* 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;
}
封装过程用到ServletModelAttributeMethodProcessor
public class ServletModelAttributeMethodProcessor extends ModelAttributeMethodProcessor {
@Override//本方法在ModelAttributeMethodProcessor类，
public boolean supportsParameter(MethodParameter parameter) {
return (parameter.hasParameterAnnotation(ModelAttribute.class) ||
(this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType())));
}
@Override
@Nullable//本方法在ModelAttributeMethodProcessor类，
public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
...
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 (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)) {
//web数据绑定器，将请求参数的值绑定到指定的JavaBean里面**
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 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
在过程当中，用到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
