SpringMvc
【源码仓库】【本文仓库】
三层结构
表现层
MVC 模型
业务层
service
持久层
dao
工作流程
用户 -> 前端控制器: 用户发送请求
前端控制器 -> 后端控制器: 根据用户请求查询具体控制器
后端控制器 –> 前端控制器: 处理后结果
前端控制器 –> 视图: 视图渲染
视图 –> 前端控制器: 返回视图
前端控制器 –> 用户: 响应结果
简单案例
依赖
<?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.huifer</groupId>
<artifactId>mySpringMvcBook</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring.version>5.1.5.RELEASE</spring.version>
<junit.version>4.12</junit.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>aopalliance</groupId>
<artifactId>aopalliance</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<!– https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl –>
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.4</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.3</version>
</dependency>
<!– https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core –>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.3</version>
</dependency>
<!– https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations –>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.9.3</version>
</dependency>
</dependencies>
<build>
<resources>
<!– 千千万万别忘记 –>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
spring-config
<?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: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.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd”>
<context:component-scan base-package=”com.huifer.springmvc”/>
<!– 配置注解的适配器和映射器，同时还注入了很多其他的 bean –>
<mvc:annotation-driven/>
</beans>
web.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>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc-config.xml</param-value>
</init-param>
<!– 跟随 tomcat 启动 –>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
controller
@Controller
@RequestMapping(“item”)
public class ItemController {
@ResponseBody
@GetMapping(“/query”)
public ModelAndView query() throws Exception {
List<Item> itemList = new ArrayList<>();
itemList.add(new Item(“ 吃的 ”, 3.3, new Date()));
itemList.add(new Item(“ 玩的 ”, 3.3, new Date()));
ModelAndView modelAndView = new ModelAndView();
modelAndView.addObject(“itemList”, itemList);
modelAndView.setViewName(“/WEB-INF/jsp/item.jsp”);
return modelAndView;
}
}
item.JSP
<%–
Created by IntelliJ IDEA.
User: huifer
Date: 2019/3/10
Time: 11:26
To change this template use File | Settings | File Templates.
–%>
<%@ page language=”java” contentType=”text/html; charset=UTF-8″
pageEncoding=”UTF-8″ isELIgnored=”false” %>
<!DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “http://www.w3.org/TR/html4/loose.dtd”>
<html>
<head>
<title>ItemList</title>
</head>
<body>
<h1>ITEM</h1>
<p>${itemList}</p>
</body>
</html>
web.xml 中的加载顺序
context-param->listener->filter->servlet
url-parttern 匹配顺序
精确匹配，如 /baidu
目录匹配，如 /*
拓展名匹配，如 *.jpg
默认匹配，如 /
tomcat 中的 url-parttern
文件在 ${tomcatHome}/conf/web.xml 中
发布到 tomcat 的 web 应用共享下面两个配置
<!– The mapping for the default servlet –>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!– The mappings for the JSP servlet –>
<servlet-mapping>
<servlet-name>jsp</servlet-name>
<url-pattern>*.jsp</url-pattern>
<url-pattern>*.jspx</url-pattern>
</servlet-mapping>
此处面试题
为什么在自己的项目中 web.xml 配置 /* 报错。如图
根据 tomcat 的 web.xml 配置可以看到 / 和 jsp 的拦截是分开的，而我们直接用一个 /* 来拦截那么 tomcat 将不知道用什么来处理
spring-mvc 大致流程源码翻阅
从配置文件中知道前端控制器 DispatcherServlet
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc-config.xml</param-value>
</init-param>
<!– 跟随 tomcat 启动 –>
<load-on-startup>2</load-on-startup>
</servlet>
在 org.springframework.web.servlet.DispatcherServlet 看下面两个方法
doService 将访问的数据接收到交给 doDispatch
doDispatch 具体调度
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;
// 加载 handler
mappedHandler = this.getHandler(processedRequest);
if (mappedHandler == null) {
this.noHandlerFound(processedRequest, response);
return;
}
// handler 适配器
HandlerAdapter ha = this.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;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// 适配器执行操作
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
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);
}
// 操作结果返回
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);
}
}
}
handler 怎么来
initHandlerMappings(context)
protected void initStrategies(ApplicationContext context) {
this.initMultipartResolver(context);
this.initLocaleResolver(context);
this.initThemeResolver(context);
this.initHandlerMappings(context);
this.initHandlerAdapters(context);
this.initHandlerExceptionResolvers(context);
this.initRequestToViewNameTranslator(context);
this.initViewResolvers(context);
this.initFlashMapManager(context);
}
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
} else {
try {
HandlerMapping hm = (HandlerMapping)context.getBean(“handlerMapping”, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
} catch (NoSuchBeanDefinitionException var3) {
}
}
if (this.handlerMappings == null) {
// 读取默认配置文件
this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class);
if (this.logger.isTraceEnabled()) {
this.logger.trace(“No HandlerMappings declared for servlet ‘” + this.getServletName() + “‘: using default strategies from DispatcherServlet.properties”);
}
}
}
默认配置文件
handler 适配器也在配置文件中
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
if (this.handlerAdapters != null) {
Iterator var2 = this.handlerAdapters.iterator();
while(var2.hasNext()) {
HandlerAdapter adapter = (HandlerAdapter)var2.next();
// 是否能够适配
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”);
}
HttpRequestHandlerAdapter
public class HttpRequestHandlerAdapter implements HandlerAdapter {
public HttpRequestHandlerAdapter() {
}
// 判断是否是当前类支持的适配器
public boolean supports(Object handler) {
return handler instanceof HttpRequestHandler;
}
// 适配器执行操作
@Nullable
public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
((HttpRequestHandler)handler).handleRequest(request, response);
return null;
}
public long getLastModified(HttpServletRequest request, Object handler) {
return handler instanceof LastModified ? ((LastModified)handler).getLastModified(request) : -1L;
}
}
视图解析
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) {
this.logger.debug(“ModelAndViewDefiningException encountered”, exception);
mv = ((ModelAndViewDefiningException)exception).getModelAndView();
} else {
Object handler = mappedHandler != null ? mappedHandler.getHandler() : null;
mv = this.processHandlerException(request, response, handler, exception);
errorView = mv != null;
}
}
if (mv != null && !mv.wasCleared()) {
// 这个地方在做渲染
this.render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
} else if (this.logger.isTraceEnabled()) {
this.logger.trace(“No view rendering, null ModelAndView returned.”);
}
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, (Exception)null);
}
}
}
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
Locale locale = this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale();
response.setLocale(locale);
String viewName = mv.getViewName();
View view;
if (viewName != null) {
// 视图解析器
view = this.resolveViewName(viewName, mv.getModelInternal(), locale, request);
if (view == null) {
throw new ServletException(“Could not resolve view with name ‘” + mv.getViewName() + “‘ in servlet with name ‘” + this.getServletName() + “‘”);
}
} else {
view = mv.getView();
if (view == null) {
throw new ServletException(“ModelAndView [” + mv + “] neither contains a view name nor a View object in servlet with name ‘” + this.getServletName() + “‘”);
}
}
if (this.logger.isTraceEnabled()) {
this.logger.trace(“Rendering view [” + view + “] “);
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
// 视图的渲染函数渲染到页面上
view.render(mv.getModelInternal(), request, response);
} catch (Exception var8) {
if (this.logger.isDebugEnabled()) {
this.logger.debug(“Error rendering view [” + view + “]”, var8);
}
throw var8;
}
}
@Nullable
protected View resolveViewName(String viewName, @Nullable Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception {
if (this.viewResolvers != null) {
Iterator var5 = this.viewResolvers.iterator();
while(var5.hasNext()) {
// 视图解析器
ViewResolver viewResolver = (ViewResolver)var5.next();
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
return view;
}
}
}
return null;
}
spring-mvc 请求具体流程图
用户 -> 前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:1. 用户发送请求
前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> HandlerMapper : 2. 根据 url 进行处理
HandlerMapper -> 前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:3. 将 handlerMapper 处理结果给前端控制器
前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> HandlerAdapter:4. 给适配器确认具体的适配器，比如我们这里给了 HttpRequestHandlerAdapter
HandlerAdapter ->ModelAndView:5. 用来执行业务操作
ModelAndView ->HandlerAdapter: 6. 执行完成给 HandlerAdapter 返回
HandlerAdapter-> 前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:7. 返回一个 modelAndView
前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> ViewResolver 视图解析器 :8. 将第 7 步中的 view 进行解析
ViewResolver 视图解析器 -> 前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:9. 解析结果返回
前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> View : 9. 将 model 渲染到 view 中
View-> 前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果: 10.view 结果返回给前端控制器
前端控制器 \n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 –> 用户: 查看到完整的网页