1. 改造成maven项目

IDEA如何将普通项目改成maven项目

2. 增加pom依赖

统一Springboot版本

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.1</version>
    </parent>

增加对SpringBoot的依赖

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

增加对jsp的支持

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
            <scope>7.0.59</scope>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>

增加对静态资源的过滤

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.*</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/WebContent</directory>
                <targetPath>META-INF/resources</targetPath>
                <includes>
                    <include>**/*.*</include>
                </includes>
            </resource>
        </resources>

    </build>

3. 增加主启动类

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;


@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        new SpringApplicationBuilder(Application.class).run(args);    }
}

4. 注册Servlet、Filter、Listener

若项目通过@WebServlet、@WebFilter、@WebListener注册Servlet、Filter、Listener
则可以通过在主启动类上增加注解@ServletComponentScan，自动注册Servlet、Filter、Listener

否则则需要通过spring的ServletRegistrationBean注册，这个bean是由springboot提供专门来注册servlet的，可以像注册bean一样去配置servlet。

@Configuration
public class ServletRegist {

    /**
     * 1、通过@Bean注解注册实例
     * 2、返回类型为ServletRegistrationBean
     * 3、new KaptchaServlet() 第三方依赖包的对象，对应web.xml 中的<servlet-class>
     * 4、设置相关拦截器参数initParams，对应web.xml 中的<init-param>
     * 5、必须指定一个别名，如果不指定则会覆盖springboot提供的DispatcherServlet，对应web.xml 中的<servlet-name>
     * 5、设置映射的url;setUrlMappings,多个url的话可以放到list，对应web.xml中的<url-pattern>
     * 6、setLoadOnStartup 设置启动级别，对应web.xml 中的<load-on-startup>
     * @return
     */
    @Bean
    public ServletRegistrationBean kaptchaServletBean(){
        ServletRegistrationBean bean = new ServletRegistrationBean(new KaptchaServlet());
        Map<String,String> initParams = new HashMap<>();
        initParams.put("kaptcha.textproducer.font.names","Arial");
        bean.setInitParameters(initParams);
        bean.setName("Kaptcha");
        ArrayList urlList = new ArrayList();
        urlList.add("/Kaptcha");
        bean.setUrlMappings(urlList);
        bean.setLoadOnStartup(1);
        return bean;
    }
}

注册Filter

通过FilterRegistrationBean 注册

@Bean
public FilterRegistrationBean myFilter(){
     FilterRegistrationBean registrationBean = new FilterRegistrationBean();
     registrationBean.setFilter(new MyFilter());
     registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
     return registrationBean;
 }

注册Listener

通过ServletListenerRegistrationBean 注册

 @Bean
    public ServletListenerRegistrationBean myListener(){
        ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
        return registrationBean;
    }

5. 根目录映射index.jsp

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {

    /**
     * 拦截某个请求跳转固定位置
     *
     * @param registry
     */
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("index.jsp");
//        registry.addViewController("/index").setViewName("index.jsp");
    }
}