• auto-gen TOC: {:toc}

SpringMVC

官方文档：https://docs.spring.io/spring-framework/docs/5.3.x/reference/html/web.html

辅助资料：https://www.w3cschool.cn/spring_mvc_documentation_linesh_translation

教程：http://c.biancheng.net/spring_mvc/

https://www.cnblogs.com/wormday/p/8435617.html

SpringMVC是基于ServletAPI的Web框架

DispatcherServlet

所有的请求都由DispatcherServlet管理并分发到各个具体的控制器中。因此，需要在web.xml中注册该Servlet，或通过ServletRegistration.Dynamic动态注册。

支持的Bean类型

Bean 类型	备注
HandlerMapping	Map a request to a handler along with a list of interceptors (opens new window) for pre- and post-processing. The mapping is based on some criteria, the details of which vary by HandlerMapping implementation.The two main HandlerMapping implementations are RequestMappingHandlerMapping (which supports @RequestMapping annotated methods) and SimpleUrlHandlerMapping (which maintains explicit registrations of URI path patterns to handlers).
HandlerAdapter	Help the DispatcherServlet to invoke a handler mapped to a request, regardless of how the handler is actually invoked. For example, invoking an annotated controller requires resolving annotations. The main purpose of a HandlerAdapter is to shield the DispatcherServlet from such details.
HandlerExceptionResolver	Strategy to resolve exceptions, possibly mapping them to handlers, to HTML error views, or other targets. See Exceptions (opens new window).
ViewResolver	Resolve logical String-based view names returned from a handler to an actual View with which to render to the response. See View Resolution (opens new window) and View Technologies (opens new window).
LocaleResolver, LocaleContextResolver	Resolve the Locale a client is using and possibly their time zone, in order to be able to offer internationalized views. See Locale (opens new window).
ThemeResolver	Resolve themes your web application can use — for example, to offer personalized layouts. See Themes (opens new window).
MultipartResolver	Abstraction for parsing a multi-part request (for example, browser form file upload) with the help of some multipart parsing library. See Multipart Resolver (opens new window).
FlashMapManager	Store and retrieve the “input” and the “output” FlashMap that can be used to pass attributes from one request to another, usually across a redirect. See Flash Attributes (opens new window).

如果WebApplicationContext中未声明对应类型的bean，那么将会使用 DispatcherServlet.properties (opens new window)中的默认实现。

请求处理流程 (文档1.1.5) *

Controller允许的返回值

https://www.cnblogs.com/guo-rong/p/9199511.html

https://blog.csdn.net/u011001084/article/details/52846791

零散笔记

• Spring围绕DispatcherServlet设计
• ContextLoaderListener会负责实例化ApplicationContext容器

问题

• SpringMVC启动流程？

跟着教程走

创建简单Controller

创建一个bean，继承Controller接口，其id设置为路径

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;

@Component("/plain")
public class PlainController implements Controller {

    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
        return new ModelAndView("plain");
    }
}

内部视图解析器

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/jsp/"/>
    <property name="suffix" value=".jsp"/>
</bean>

请求处理方法

对于@RequestMapping注释的方法，若要使用Servlet API类型，可以将其作为方法的参数类型。

@GetMapping("/hello")
public String hello(HttpSession session, HttpServletRequest request){
    return "hello";
}

可以从HttpServletRequest中得到参数

还可以添加org.springframework.ui.Model类型

@GetMapping("/hello")
public String hello(Model model){
    /*在视图中可以使用EL表达式${success}取出model中的值*/
    model.addAttribute("a", "b");
    return "hello";
}

可以使用参数来接受post/get的数据，相当于使用@RequestParam(required = false)注解

@RequestMapping("/login")
public String hello(String attr){
    logger.warn(attr);
    return "login";
}

访问http://localhost:8080/hello?=123输出日志"123"，访问http://localhost:8080/hello则attr为null

甚至可以使用POJO接收参数

public class User {
    private String username;
    private String password;

	// getter/setter/toString省略
}

@RequestMapping("/login")
public String hello(User attr, String username){
    logger.warn(attr);
    logger.warn(username);
    return "login";
}

当访问login?username=123&password=456时，attr.username与username的值都为"123"

还可以使用@PathVariable/@ModelAttribute注解

Service 与 Controller 的区别 *

@ModelAttribute

被 @ModelAttribute 注解的方法将在每次调用该控制器类的请求处理方法前被调用。

@ModelAttribute("timestamp")
public Long isPermitted(Model model){
    return System.currentTimeMillis();
}

@RequestMapping("/login")
public String hello(Model model, String timestamp){
    logger.warn(timestamp);
    logger.warn(model.getAttribute("timestamp"));
    return "login";
}

访问http://localhost:8080/login?timestamp=12580时，得到日志

top.chgtaxihe.springmvc.HelloController.hello 12580
top.chgtaxihe.springmvc.HelloController.hello 1612859868434