Spring自定义解析的集中方式

springMVC 、springboot中返回前端JSON 时候，经常需要不同的格式 实现方式有几种

一 、自己实现JSON序列化器  

序列化对象上使用
public class TopSymbolVo implements Serializable {
     @JsonSerialize(using = BigDecimalSerializer.class)
    private BigDecimal price;
  }

JSON 序列化器实现
public class BigDecimalSerializer extends JsonSerializer<BigDecimal> {
    @Override
    public void serialize(BigDecimal value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        jgen.writeString(value.stripTrailingZeros().toPlainString());
    }
}

二、 自定义注释  

定义注释

@Target({ElementType.METHOD,ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DateFormatter {
    String pattern() default "yyyy-MM-dd HH:mm:ss";
}

//定义序列化器

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.util.Date;

public class DateSerializer extends JsonSerializer<Date> {

    private final String pattern;

    public DateSerializer(String pattern) {
        super()
        this.pattern = pattern;
    }

    @Override
    public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        String output = StringUtils.EMPTY;
        if (date != null) {
            output = new SimpleDateFormat(pattern).format(date);
        }
        jsonGenerator.writeString(output);
    }
}

// JacksonAnnotationIntrospector

import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;

public class DateFormatterAnnotationIntrospector extends JacksonAnnotationIntrospector {

    
    @Override
    public Object findSerializer(Annotated annotated) {
        DateFormatter formatter = annotated.getAnnotation(DateFormatter.class);
        if (formatter != null) {
            return new DateSerializer(formatter.pattern());
        }
        return super.findSerializer(annotated);
    }
}

//加入配置  或者在上一步中@bean 自动扫描加入
@Configuration
public class WebServerConfig {

    @Bean
    public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
        // Config the Json convert Chinese garbled.
        // 这里的配置可能会导致application.properties文件中spring.jackson.time-zone=GMT+8失效
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();

        // 不设置Utf-8格式,可能会导致Mock测试输出信息乱码
        converter.setDefaultCharset(StandardCharsets.UTF_8);

        ObjectMapper objectMapper = converter.getObjectMapper();
        objectMapper.setTimeZone(TimeZone.getDefault());
        objectMapper.setAnnotationIntrospector(new DateFormatterAnnotationIntrospector());
        return converter;
    }
}