13、注解配置SpringMVC

使用配置类和注解代替web.xml和SpringMVC配置文件的功能

1、创建初始化类，代替web.xml

在Servlet3.0环境中，容器会在类路径中查找实现javax.servlet.ServletContainerInitializer接口的类， 如果找到的话就用它来配置Servlet容器。 Spring提供了这个接口的实现，名为SpringServletContainerInitializer，这个类反过来又会查找实现WebApplicationInitializer的类并将配置的任务交给它们来完成。Spring3.2引入了一个便利的WebApplicationInitializer基础实现，名为 AbstractAnnotationConfigDispatcherServletInitializer，当我们的类扩展了 AbstractAnnotationConfigDispatcherServletInitializer并将其部署到Servlet3.0容器的时候，容器会自动发现它，并用它来配置Servlet上下文。

【WebInit.java】

//web工程的初始化类，用来代替web.xml
public class WebInit extends AbstractAnnotationConfigDispatcherServletInitializer {

    /**
     * 指定 spring的配置类
     * @return
     */
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{SpringConfig.class};
    }

    /**
     * 指定 SpringMVC的配置类
     * @return
     */
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{WebConfig.class};
    }

    /**
     * 指定 DispatcherServlet的映射规则，即url-pattern
     * @return
     */
    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }

    /**
     * 注册过滤器
     * @return
     */
    @Override
    protected Filter[] getServletFilters() {
        CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();
        characterEncodingFilter.setEncoding("UTF-8");
        characterEncodingFilter.setForceResponseEncoding(true);
        HiddenHttpMethodFilter hiddenHttpMethodFilter = new HiddenHttpMethodFilter();
        return new Filter[]{characterEncodingFilter, hiddenHttpMethodFilter};
    }
}
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2、创建SpringConfig配置类，代替spring的配置文件

【SpringConfig.java】

@Configuration
public class SpringConfig {
}
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3、创建WebConfig配置类，代替SpringMVC的配置文件

【WebConfig.java】

/**
 * 代替SpringMVC的配置文件:
 * 1.扫描组件  2.视图解析器  3.view-controller  4.default-servlet-handler
 * 5.mvc注解驱动  6.文件上传解析器  7.异常处理   8.拦截器
 */
//将当前类标识为一个配置类
@Configuration
//1.扫描组件
@ComponentScan("com.ssm.mvc.controller")
//5.mvc注解驱动
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {

    //4.default-servlet-handler
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

    //8.拦截器
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        TestInterceptor testInterceptor = new TestInterceptor();
        registry.addInterceptor(testInterceptor).addPathPatterns("/**");
    }

    //3.view-controller
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/hello").setViewName("hello");
    }

    //6.文件上传解析器
    @Bean
    public MultipartResolver multipartResolver() {
        CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
        return commonsMultipartResolver;
    }

    //7.异常处理
    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
        SimpleMappingExceptionResolver exceptionResolver = new SimpleMappingExceptionResolver();
        Properties properties = new Properties();
        properties.setProperty("java.lang.ArithmeticException","error");
        //设置异常映射
        exceptionResolver.setExceptionMappings(properties);
        //设置共享异常信息的键
        exceptionResolver.setExceptionAttribute("exception");
        resolvers.add(exceptionResolver);
    }

    //2.视图解析器
    //2-1.配置生成模板解析器
    @Bean
    public ITemplateResolver templateResolver() {
        WebApplicationContext webApplicationContext = ContextLoader.getCurrentWebApplicationContext();
        //ServletContextTemplateResolver需要一个ServletContext作为构造参数，可通过webApplicationContext的方法获得
        ServletContextTemplateResolver templateResolver = new ServletContextTemplateResolver(webApplicationContext.getServletContext());
        templateResolver.setPrefix("/WEB-INF/templates/");
        templateResolver.setSuffix(".html");
        templateResolver.setCharacterEncoding("UTF-8");
        templateResolver.setTemplateMode(TemplateMode.HTML);
        return templateResolver;
    }

    //2-2.生成模板引擎并为模板引擎引入模板解析器
    @Bean
    public SpringTemplateEngine templateEngine(ITemplateResolver templateResolver) {
        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.setTemplateResolver(templateResolver);
        return templateEngine;
    }

    //2-3.生成视图解析器并为解析器注入模板引擎
    @Bean
    public ViewResolver viewResolver(SpringTemplateEngine templateEngine) {
        ThymeleafViewResolver viewResolver = new ThymeleafViewResolver();
        viewResolver.setCharacterEncoding("UTF-8");
        viewResolver.setTemplateEngine(templateEngine);
        return viewResolver;
    }
}
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4、测试功能——访问首页

@Controller
public class TestController {
    @RequestMapping("/")
    public String index() {
        return "index";
    }
}
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