SpringBoot 配置fastjson 解决js Long类型精度丢失问题

1. 自定义消息转化器,在@Configuration的类中添加消息转化器的@bean加入到Spring容器

//此方法位于一个有@Configuration注解的类中
@Bean
public StringHttpMessageConverter stringHttpMessageConverter() {
    StringHttpMessageConverter converter = new StringHttpMessageConverter(Charset.forName("UTF-8"));
    return converter;
}
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或用如下方法

在继承WebMvcConfigurerAdapter的类中重写（覆盖）configureMessageConverters方法

// 自定义消息转化器的第二种方法
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    StringHttpMessageConverter converter  = new StringHttpMessageConverter(Charset.forName("UTF-8"));
    converters.add(converter);
}
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2.自定义fastjson转换器：

@Bean
public HttpMessageConverters fastJsonHttpMessageConverters() {
    //1.须要定义一个convert转换消息的对象;
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    //2:添加fastJson的配置信息;
    FastJsonConfig fastJsonConfig = new FastJsonConfig();
    fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
    //3处理中文乱码问题
    List<MediaType> fastMediaTypes = new ArrayList<>();
    fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
    //4.在convert中添加配置信息.
    fastJsonHttpMessageConverter.setSupportedMediaTypes(fastMediaTypes);
    fastJsonHttpMessageConverter.setFastJsonConfig(fastJsonConfig);
    HttpMessageConverter<?> converter = fastJsonHttpMessageConverter;
    return new HttpMessageConverters(converter);

}
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3. 定义一个类，实现ObjectSerializer

import java.io.IOException;
import java.lang.reflect.Type;
import com.alibaba.fastjson.serializer.JSONSerializer;
import com.alibaba.fastjson.serializer.ObjectSerializer;
import com.alibaba.fastjson.serializer.SerializeWriter;
 
public class LongToStringSerializer implements ObjectSerializer {
 
    public static final LongToStringSerializer instance = new LongToStringSerializer();
 
    @Override
    public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features)
        throws IOException {
      SerializeWriter out = serializer.out;
        if (object == null) {
            out.writeNull();
            return;
        }
        String strVal = object.toString();
        out.writeString(strVal);
    }
}
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4. 注解中使用

@JSONField(serializeUsing = LongToStringSerializer.class)
private long id;
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