SpringApplicationBuilder 作用，以及设置跨域请求过滤器

springboot 项目，若打成 war 包，使用外置的 tomcat 启动

1. 需要继承 **org.springframework.boot.context.web.SpringBootServletInitializer** 类
2. 然后重写 **configure(SpringApplicationBuilder application)** 方法

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.core.annotation.Order;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;
import com.upincar.dms.filter.CharacterEncodingFilter;
/**
 * 
 * @Description:启动类
 */
@SpringBootApplication
@EnableAsync
@MapperScan(basePackages = "com.upincar.dms.user.dao", sqlSessionFactoryRef = "sqlSessionFactory")
public class DmsApplication extends SpringBootServletInitializer {
    public static void main(String[] args) {
        try{
            SpringApplication.run(DmsApplication.class, args);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 如此配置打包后可以war包才可在tomcat下使用
     * @param application
     * @return
     */
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
      return application.sources(DmsApplication.class);
    }
    /**
     * 设置全局UTF-8编码过滤器
     * @return
     */
    @Bean
    @Order(Integer.MAX_VALUE)//设置执行先后顺序
    public FilterRegistrationBean<CharacterEncodingFilter> characterFilterRegistration() {
      FilterRegistrationBean<CharacterEncodingFilter> registration = new FilterRegistrationBean<CharacterEncodingFilter>();
      registration.setFilter(new CharacterEncodingFilter());
      registration.addUrlPatterns("/*");
      registration.addInitParameter("paramName", "paramValue");
      registration.setName("characterEncodingFilter");
      return registration;
    }
    /**
     * 跨域过滤器
     *
     * @return
     */
    @Bean
    public CorsFilter corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", buildConfig()); 
        return new CorsFilter(source);
    }
    private CorsConfiguration buildConfig() {
        CorsConfiguration corsConfiguration = new CorsConfiguration();
        corsConfiguration.addAllowedOrigin("*");
        corsConfiguration.addAllowedHeader("*");
        corsConfiguration.addAllowedMethod("*");
        corsConfiguration.setMaxAge(3600L);
        corsConfiguration.addExposedHeader("x-requested-with");
        return corsConfiguration;
    }    
}