Spring MVC 环境搭建

XML 搭建

<web-app>
    <display-name>Archetype Created Web Application</display-name>
    <listener>
      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <context-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>WEB-INF/spring.xml</param-value>
    </context-param>
    <servlet>
        <servlet-name>mvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>WEB-INF/web.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>mvc</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>
</web-app>

注解配置

使用接口 WebApplicationInitializer 来实例化 Spring 容器 和 DispathServlet

public class MyWebApplicationInitializer implements WebApplicationInitializer {
// public class MyWebApplicationInitializer implements TestWebApplicationInitializer {
    /**
     * Spring MVC 0-XML 配置的原理：
     *
     * 因为 servlet 3.0 的一个新规范（ServletContainerInitializer），
     * 而 tomcat 也遵守了了这个规范，所以会调用 实现了 WebApplicationInitializer 的 onStartup 方法
     *
     * Spring 定义了一个 org.springframework.web.SpringServletContainerInitializer 类，实现了 servlet 3.0 的这个新规范
     *
     * Spring 实现方式
     * spring-web\META-INF\services\javax.servlet.ServletContainerInitializer，是指需要实现的接口
     * javax.servlet.ServletContainerInitializer 文件里面的 org.springframework.web.SpringServletContainerInitializer 是实现类
     * @HandlesTypes(WebApplicationInitializer.class) 会由容器进行解析里面定义的接口，找出所有实现类，并回调给 Set<Class<?>> webAppInitializerClasses
     * Spring 再对 webAppInitializerClasses 的子类进行遍历，分别调用其 onStartup 的方法
     *
     * @param servletContext Web上下文对象
     * @throws ServletException
     */
    public void onStartup(ServletContext servletContext) throws ServletException {
        System.out.println("-------onStartup-------");
        // Load Spring web application configuration
        AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext();
        ac.register(AppConfig.class);
        // ac.refresh();
        // Create and register the DispatcherServlet
        // DispatcherServlet 的 init 方法
        DispatcherServlet servlet = new DispatcherServlet(ac);
        ServletRegistration.Dynamic registration = servletContext.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
        registration.addMapping("*.do");
        // registration.addMapping("/*");
    }
}

使用 WebMvcConfigurer 来配置 Spring MVC 环境

@Configuration
@ComponentScan("org.wesoft.mvc")
@EnableWebMvc // 相当于 XML 中的 <mvc:annotation-driven/>
public class AppConfig implements WebMvcConfigurer {
// public class AppConfig extends WebMvcConfigurationSupport {
    /*
    Apache Commons FileUpload
    To use Apache Commons FileUpload,
    you can configure a bean of type CommonsMultipartResolver with a name of multipartResolver.
    You also need to have commons-fileupload as a dependency on your classpath.
     */
    @Bean
    public CommonsMultipartResolver multipartResolver() {
        CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
        return commonsMultipartResolver;
    }
    // 会在 Spring mvc 环境初始化完成之后，加载这个方法
    @Autowired
    public void iniArgumentsResolvers(RequestMappingHandlerAdapter requestMappingHandlerAdapter) {
        List<HandlerMethodArgumentResolver> argumentResolvers = new ArrayList<>(requestMappingHandlerAdapter.getArgumentResolvers());
        // 获取自定义的参数解析器
        List<HandlerMethodArgumentResolver> customArgumentResolvers = requestMappingHandlerAdapter.getCustomArgumentResolvers();
        // 删除原来集合中的自定义参数解析器
        argumentResolvers.removeAll(customArgumentResolvers);
        // 重新加入到最前面
        argumentResolvers.addAll(0, customArgumentResolvers);
        // 重新设置参数解析器
        requestMappingHandlerAdapter.setArgumentResolvers(argumentResolvers);
    }
    /**
     * 视图处理
     *
     * @param registry
     */
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.jsp("/page/", ".html");
    }
    /**
     * 添加消息解析器
     *
     * @param converters
     */
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter jsonHttpMessageConverter = new FastJsonHttpMessageConverter();
        converters.add(jsonHttpMessageConverter);
    }
    /**
     * 添加参数解析器
     *
     * @param resolvers initially an empty list
     */
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        // 这里其实是传过来一个空集合，对应着 customArgumentResolvers
        // 也就是我们其实是在 customArgumentResolvers 里添加自定义方法
        // 然后 spring mvc 会将这个集合合并到 argumentResolvers 中，所以并不能保证执行顺序
        resolvers.add(new LoginUserResolver());
    }
}