1. Java SpringMVC框架源碼分析
目錄
1. 使用
1.1. 新建項目
1.1.1. 第一種方式
1.1.1.1. 新建web項目
1.1.1.2. 導入jar包依賴
在WEB-INF下新建lib目錄，導入如下依賴。并且add as library
1.1.2. 第二種方式
1.1.2.1. 新建maven工程
1.1.2.2. 添加web框架支持
1.1.2.3. maven pom 依賴
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.zsk</groupId>
<artifactId>springmvc_test</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>1.8</java.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.1.8.RELEASE</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
</plugin>
</plugins>
<!--配置資源目錄-->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.*</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.*</include>
</includes>
</resource>
<!-- 打包時將jsp文件拷貝到META-INF目錄下 -->
<resource>
<!-- 指定resources插件處理哪個目錄下的資源文件 -->
<directory>src/main/webapp</directory>
<!--注意此次必須要放在此目錄下才能被訪問到 -->
<targetPath>META-INF/resources</targetPath>
<includes>
<include>**/*.*</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
</project>
1.1.2.4. 修改project配置lib包
1.2. 配置spring mvc
- WEB-INF/web.xml
配置DispatcherServlet和springmvc.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<servlet>
<servlet-name>dispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>springmvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
- springmvc.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd">
<context:component-scan base-package="com.zsk.controller"/>
<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
<!--尋找RequestMapping-->
<mvc:annotation-driven/>
<!--尋找靜態資源-->
<mvc:default-servlet-handler/>
</beans>
1.3. 新建controller
- com.zsk.controller.TestController
package com.zsk.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
/**
* @description:
* @author: zsk
* @create: 2019-11-27 23:43
**/
@Controller
public class TestController
{
@RequestMapping("/test")
public String test()
{
return "test";
}
}
- com.zsk.controller.TestController2
package com.zsk.controller;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* @description:
* @author: zsk
* @create: 2019-11-30 21:28
**/
@Component("/test2")
public class TestController2 implements Controller
{
@Override
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception
{
ModelAndView test2 = new ModelAndView("test2");
return test2;
}
}
1.4. 新建jsp
- WEB-INF/jsp/test.jsp
<%--
User: zsk
Date: 2019/11/29
Time: 20:45
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Test</title>
</head>
<body>
Hello World
</body>
</html>
- WEB-INF/jsp/test2.jsp
<%--
User: zsk
Date: 2019/11/27
Time: 23:24
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Test2</title>
</head>
<body>
Hello2
</body>
</html>
1.5. 新建html文件
- web/abc.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>abc</title>
</head>
<body>
abc
</body>
</html>
1.6. 配置tomcat
1.7. 項目結構
- 第一種
![]()
- 第二種
![]()
1.8. 啟動并訪問
2. 源碼分析
2.1. 打斷點
我們在com.zsk.controller.TestController#test的方法上打上斷點，查看調用棧如下
test:17, TestController (com.zsk.controller)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
doInvoke:190, InvocableHandlerMethod (org.springframework.web.method.support)
invokeForRequest:138, InvocableHandlerMethod (org.springframework.web.method.support)
invokeAndHandle:104, ServletInvocableHandlerMethod (org.springframework.web.servlet.mvc.method.annotation)
invokeHandlerMethod:892, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handleInternal:797, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handle:87, AbstractHandlerMethodAdapter (org.springframework.web.servlet.mvc.method)
doDispatch:1039, DispatcherServlet (org.springframework.web.servlet)
doService:942, DispatcherServlet (org.springframework.web.servlet)
processRequest:1005, FrameworkServlet (org.springframework.web.servlet)
doGet:897, FrameworkServlet (org.springframework.web.servlet)
service:634, HttpServlet (javax.servlet.http)
service:882, FrameworkServlet (org.springframework.web.servlet)
service:741, HttpServlet (javax.servlet.http)
internalDoFilter:231, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilter:52, WsFilter (org.apache.tomcat.websocket.server)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
invoke:199, StandardWrapperValve (org.apache.catalina.core)
invoke:96, StandardContextValve (org.apache.catalina.core)
invoke:528, AuthenticatorBase (org.apache.catalina.authenticator)
invoke:139, StandardHostValve (org.apache.catalina.core)
invoke:81, ErrorReportValve (org.apache.catalina.valves)
invoke:678, AbstractAccessLogValve (org.apache.catalina.valves)
invoke:87, StandardEngineValve (org.apache.catalina.core)
service:343, CoyoteAdapter (org.apache.catalina.connector)
service:609, Http11Processor (org.apache.coyote.http11)
process:65, AbstractProcessorLight (org.apache.coyote)
process:810, AbstractProtocol$ConnectionHandler (org.apache.coyote)
doRun:1506, NioEndpoint$SocketProcessor (org.apache.tomcat.util.net)
run:49, SocketProcessorBase (org.apache.tomcat.util.net)
runWorker:1149, ThreadPoolExecutor (java.util.concurrent)
run:624, ThreadPoolExecutor$Worker (java.util.concurrent)
run:61, TaskThread$WrappingRunnable (org.apache.tomcat.util.threads)
run:748, Thread (java.lang)
從中間一段調用棧看出主要經過HttpServlet、FrameworkServlet、DispatcherServlet這幾個類的方法，我們從搞清楚這幾個類的關系
2.2. servlet類圖
由圖可以看出這幾類都是servlet，我們記得servlet的生命周期Servlet.md
所以從HttpServlet的service方法開始追蹤源碼
2.3. DispatcherServlet是怎么加載的
-
如果是web.xml配置的
這是我們自己在web.xml中配置的，在tomcat啟動的時候會加載<load-on-startup>1</load-on-startup>的Servlet，同時傳入<init-param></init-param>的參數 -
如果是servlet3.0的配置方式
2.4. 關鍵方法是哪個
2.4.1. HttpServlet service
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException
{
HttpServletRequest request;
HttpServletResponse response;
if (!(req instanceof HttpServletRequest &&
res instanceof HttpServletResponse)) {
throw new ServletException("non-HTTP request or response");
}
request = (HttpServletRequest) req;
response = (HttpServletResponse) res;
//只是將request、resposne對象封裝成HttpServletRequest和HttpServletResponse
//調用子類的方法
//org.springframework.web.servlet.FrameworkServlet#service
service(request, response);
}
2.4.2. FrameworkServlet service
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());
if (httpMethod == HttpMethod.PATCH || httpMethod == null) {
processRequest(request, response);
}
else {
//調用父類的另一個service方法
//javax.servlet.http.HttpServlet#service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
super.service(request, response);
}
}
2.4.3. HttpServlet 另一個service
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
//根據http方法調用doXXX方法
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
//get方法
//org.springframework.web.servlet.FrameworkServlet#doGet
doGet(req, resp);
} else {
long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
if (ifModifiedSince < lastModified) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
2.4.4. FrameworkServlet doGet
protected final void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//調用FrameworkServlet#processRequest
processRequest(request, response);
}
2.4.5. FrameworkServlet processRequest
protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//...
try {
//調用DispatcherServlet#doService
doService(request, response);
}
catch (ServletException | IOException ex) {
failureCause = ex;
throw ex;
}
catch (Throwable ex) {
failureCause = ex;
throw new NestedServletException("Request processing failed", ex);
}
finally {
resetContextHolders(request, previousLocaleContext, previousAttributes);
if (requestAttributes != null) {
requestAttributes.requestCompleted();
}
logResult(request, response, failureCause, asyncManager);
publishRequestHandledEvent(request, response, startTime, failureCause);
}
}
2.4.6. DispatcherServlet doService
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
//...
try {
//調用DispatcherServlet#doDispatch
doDispatch(request, response);
}
finally {
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Restore the original attribute snapshot, in case of an include.
if (attributesSnapshot != null) {
restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
}
2.4.7. DispatcherServlet doDispatch【關鍵】
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 {
//處理文件二進制流的請求
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
//1.獲取相應的HandlerExecutionChain【包括handler和interceptor】處理請求
//handler是我們自己的處理類
//intercepter是攔截器
mappedHandler = getHandler(processedRequest);
//沒找到handler，那么控制臺打印not found，跳轉到404
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
//2.將Handler封裝成HandlerAdapter【adpater的作用是適配不同的handler
//比如有@Controller、implement Controller、implement RequestHandler等】
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
//3.調用interceptor的preHandle處理
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
//4.真正調用handler的方法
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
//5.調用interceptor的postHandle處理
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
//6.渲染視圖
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
2.5. Handler是怎么找到的
2.5.1. 獲取所有HandlerMapping一個個試
- getHandler
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//查找合適的HandlerExecutionChain【包括handler和interceptor】
if (this.handlerMappings != null) {
//不同的Handler有不同的HandlerMapping處理
//如果是xml配置或者implements Controller的那么使用BeanNameUrlHandlerMapping
//如果是注解@Controller配置的那么使用RequestMappingHandlerMapping
//如果是靜態資源映射且開啟了<mvc:default-servlet-handler/>，使用的是SimpleUrlHandlerMapping
//HandlerMapping已經提前定義好了：C:/Users/zsk/.m2/repository/org/springframework/spring-webmvc/5.1.8.RELEASE/spring-webmvc-5.1.8.RELEASE.jar!/org/springframework/web/servlet/DispatcherServlet.properties
for (HandlerMappig mapping : this.handlerMappings) {
//只要找到一個能處理的就返回
HandlerExecutionChain handler = mapping.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
2.5.1.1. HandlerMapping類型
2.5.1.1.1. 如果是xml配置或者implements Controller的那么使用BeanNameUrlHandlerMapping
2.5.1.1.2. 如果是注解@Controller配置的那么使用RequestMappingHandlerMapping
2.5.1.1.3. 如果是靜態資源映射且開啟了mvc:default-servlet-handler/，使用的是SimpleUrlHandlerMapping
2.5.1.2. 通過HandlerMapping獲取Handler和攔截器鏈
- AbstractHandlerMapping#getHandler
@Override
@Nullable
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
//嘗試靜態資源
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
//加上攔截器
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (logger.isTraceEnabled()) {
logger.trace("Mapped to " + handler);
}
else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
logger.debug("Mapped to " + executionChain.getHandler());
}
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
2.5.1.2.1. 拿到url對應的Handler
- AbstractHandlerMethodMapping#getHandlerInternal
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
//拿到url路徑
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
this.mappingRegistry.acquireReadLock();
try {
//通過url路徑從map中查找
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
this.mappingRegistry.releaseReadLock();
}
}
2.6. Handler Adapter是怎么適配的
2.6.1. 遍歷所有HandlerMappingAdapter一個個試
- getHandlerAdapter
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
//如果是注解@Controller配置的那么使用RequestMappingHandlerMappingAdapter【AbstractHandlerMethodAdapter】
//如果是靜態資源或者implements Controller使用的是SimpleControllerHandlerAdapter
//如果是implements HttpRequestHandler那么HttpRequestHandlerAdapter
//如果是Servlet那么SimpleServletHandlerAdapter
if (this.handlerAdapters != null) {
for (HandlerAdapter adapter : this.handlerAdapters) {
//適配器是否匹配當前handler
if (adapter.supports(handler)) {
return adapter;
}
}
}
throw new ServletException("No adapter for handler [" + handler +
"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
}
2.6.1.1. HandlerAdapter類型
2.6.1.1.1. 如果是靜態資源或者implements Controller使用的是SimpleControllerHandlerAdapter
- SimpleControllerHandlerAdapter#supports
public boolean supports(Object handler) {
return (handler instanceof Controller);
}
2.6.1.1.2. 如果是implements HttpRequestHandler那么HttpRequestHandlerAdapter
- HttpRequestHandlerAdapter#supports
public boolean supports(Object handler) {
return (handler instanceof HttpRequestHandler);
}
2.6.1.1.3. 如果是Servlet那么SimpleServletHandlerAdapter
- SimpleServletHandlerAdapter#supports
public boolean supports(Object handler) {
return (handler instanceof Servlet);
}
2.6.1.1.4. 如果是注解@Controller配置的那么使用RequestMappingHandlerMappingAdapter
- AbstractHandlerMethodAdapter#supports
public final boolean supports(Object handler) {
return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
}
2.7. handler的方法是怎么調用的
2.7.1. 如果是implements Controller的強轉直接調用
public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
//強轉直接調用
return ((Controller) handler).handleRequest(request, response);
}
2.7.2. @Controller的反射調用
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
return handleInternal(request, response, (HandlerMethod) handler);
}
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ModelAndView mav;
//這個
mav = invokeHandlerMethod(request, response, handlerMethod);
return mav;
}
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
//這個
invocableMethod.invokeAndHandle(webRequest, mavContainer);
}
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
//這個
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
}
public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
//解析調用參數
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
logger.trace("Arguments: " + Arrays.toString(args));
}
//反射調用
return doInvoke(args);
}
2.8. 視圖是怎么渲染的
- processDispatchResult
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
@Nullable Exception exception) throws Exception {
boolean errorView = false;
if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException) exception).getModelAndView();
}
else {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(request, response, handler, exception);
errorView = (mv != null);
}
}
// Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
//渲染handler返回的ModelAndView
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("No view rendering, null ModelAndView returned.");
}
}
if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Concurrent handling started during a forward
return;
}
if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, null);
}
}
2.8.1. 獲取合適的view并渲染
- DispatcherServlet#render
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Determine locale for request and apply it to the response.
Locale locale =
(this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
response.setLocale(locale);
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.
//通過視圖名和ViewResolver獲取相應的view
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() + "'");
}
}
// Delegate to the View object for rendering.
if (logger.isTraceEnabled()) {
logger.trace("Rendering view [" + view + "] ");
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
//使用view渲染
view.render(mv.getModelInternal(), request, response);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "]", ex);
}
throw ex;
}
}
protected View resolveViewName(String viewName, @Nullable Map<String, Object> model,
Locale locale, HttpServletRequest request) throws Exception {
if (this.viewResolvers != null) {
//通過視圖解析器獲取的
for (ViewResolver viewResolver : this.viewResolvers) {
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
return view;
}
}
}
return null;
}
浙公網安備 33010602011771號