仓库源文，站点原文

layout: post title: "解决fastJson循环引用的问题" categories: Java tags: json

author: 张乘辉

• content {:toc} 最近发现返回给前段的json串出现了循环引用的问题，这是由于在json串中存在相同的属性信息，对象的属性之间存在相互引用导致循环，而fastjson支持循环引用/重复引用，并且是缺省打开的。所以会出现以下现象：

解决方式是关闭fastJson的循环引用：

String listJsonStr = JSON.toJSONString(list, SerializerFeature.DisableCircularReferenceDetect);

但通常不这么写，我们直接让其项目启动的时候就生效，所以我们直接配置bean：

@Configuration
@ConditionalOnClass({FastJsonHttpMessageConverter.class}) //1
@ConditionalOnProperty(//2
  name = {"spring.http.converters.preferred-json-mapper"},
  havingValue = "fastjson",
  matchIfMissing = true
)
protected static class FastJson2HttpMessageConverterConfiguration {
  protected FastJson2HttpMessageConverterConfiguration() {
  }

  @Bean
  @ConditionalOnMissingBean({FastJsonHttpMessageConverter.class})//3
  public FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
    FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
    FastJsonConfig fastJsonConfig = new FastJsonConfig();//4
    fastJsonConfig.setSerializerFeatures(SerializerFeature.WriteNullBooleanAsFalse,
                                         SerializerFeature.WriteNullStringAsEmpty,
                                         SerializerFeature.WriteNullNumberAsZero,
                                         SerializerFeature.DisableCircularReferenceDetect
                                        );

    ValueFilter valueFilter = (o, s, o1) -> {
      //5
      //o 是class
      //s 是key值
      //o1 是value值
      if (null == o1) {
        return null;
      }
      return o1;
    };


    fastJsonConfig.setSerializeFilters(valueFilter);

    converter.setFastJsonConfig(fastJsonConfig);

    return converter;
  }
}