覆盖方法SpringApplication.configureMessageConverters，使用fastJson，

@SpringBootApplication
@MapperScan("com.springboot.mapper")
public class Application implements WebMvcConfigurer {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
    /**
     * 方法一、覆盖方法configureMessageConverters，使用fastJson，
     * 此处把@Bean注释掉是为了测试方式二
     * @return
     */
    //@Bean
    public HttpMessageConverters fastJsonHttpMessageConverters() {
        //1、定义一个convert转换消息的对象
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
        //2、添加fastjson的配置信息
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
        //3、在convert中添加配置信息
        fastConverter.setFastJsonConfig(fastJsonConfig);
        //4、将convert添加到converters中
        HttpMessageConverter<?> converter = fastConverter;
        return new HttpMessageConverters(converter);
    }

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        //1、定义一个convert转换消息的对象
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
        //2、添加fastjson的配置信息
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
        //3、在convert中添加配置信息
        fastConverter.setFastJsonConfig(fastJsonConfig);
        //4、将convert添加到converters中
        converters.add(fastConverter);
    }
}