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

13.1、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。

package pers.tianyu.config;

import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.filter.HiddenHttpMethodFilter;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

import javax.servlet.Filter;

/**
 * 用来代替web.xml
 */
public class WebInit extends AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    //设置一个配置类，代替spring的配置类
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{SpringConfig.class};
    }

    @Override
    //设置一个配置类，代替SpringMVC的配置类
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{WebConfig.class};
    }

    @Override
    //设置springmvc的前端控制器DispatcherServlet的url-pattern
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }


    @Override
    //设置当前过滤器
    protected Filter[] getServletFilters() {
        //创建编码过滤器
        CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();
        characterEncodingFilter.setEncoding("UTF-8");
        characterEncodingFilter.setForceRequestEncoding(true);
        //创建处理请求方式的过滤器
        HiddenHttpMethodFilter hiddenHttpMethodFilter = new HiddenHttpMethodFilter();
        return new Filter[]{characterEncodingFilter, hiddenHttpMethodFilter};
    }
}

13.2、创建SpringConfig配置类，代替spring的配置文件

package pers.tianyu.config;

import org.springframework.context.annotation.Configuration;

@Configuration //将类标识为配置类，代替spring的配置文件
public class SpringConfig {
    //ssm整合之后，spring的配置信息写在此类中

}

13.3、创建WebConfig配置类，代替SpringMVC的配置文件

package pers.tianyu.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.*;
import org.springframework.web.servlet.handler.SimpleMappingExceptionResolver;
import org.thymeleaf.spring5.SpringTemplateEngine;
import org.thymeleaf.spring5.view.ThymeleafViewResolver;
import org.thymeleaf.templatemode.TemplateMode;
import org.thymeleaf.templateresolver.ITemplateResolver;
import org.thymeleaf.templateresolver.ServletContextTemplateResolver;
import pers.tianyu.interceptor.FirstInterceptor;

import java.util.List;
import java.util.Properties;

@Configuration //将类标识为配置类，代替springmvc的配置文件
@ComponentScan("pers.tianyu.controller") //扫面组件
@EnableWebMvc//开启MVC的注解驱动
public class WebConfig implements WebMvcConfigurer {


    @Override
    //使用默认的servlet处理静态资源
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

    @Override
    //配置视图控制
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("index");
    }

    @Bean //@Bean注解可以将标识的方法的返回值作为bean进行管理，bean的id为方法的方法名
    //配置文件上传解析器
    public CommonsMultipartResolver multipartResolver() {
        return new CommonsMultipartResolver();
    }

    @Override
    //配置拦截器
    public void addInterceptors(InterceptorRegistry registry) {
        FirstInterceptor firstInterceptor = new FirstInterceptor();
        registry.addInterceptor(firstInterceptor).addPathPatterns("/**");
    }


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

    //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;
    }

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

    //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;
    }
}

13.4、测试功能

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
	<head>
	    <meta charset="UTF-8">
	    <title>首页</title>
	</head>
	<body>
	欢迎欢迎
	</body>
</html>