Jackson自定义序列化注解之 保留小数位数 (默认2位小数 四舍五入)

目录

1. 注解类

2. 注解处理类DecimalPrecisionHandler

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        此文章需要先看Jackson自定义序列化注解 (支持同时使用多个自定义序列化注解)

1. 注解类

   import com.fasterxml.jackson.annotation.JacksonAnnotationsInside;
   
   import java.lang.annotation.Documented;
   import java.lang.annotation.ElementType;
   import java.lang.annotation.Retention;
   import java.lang.annotation.RetentionPolicy;
   import java.lang.annotation.Target;
   import java.math.RoundingMode;
   
   /**
    * 保留小数位数 (默认2位小数 四舍五入)
    *
    * @author ds
    */
   @Target({ElementType.FIELD})
   @Retention(RetentionPolicy.RUNTIME)
   @Documented
   @JacksonAnnotationsInside
   @JacksonBaseSerialize(handlerClazz = DecimalPrecisionHandler.class)
   public @interface DecimalPrecision {
   
       /**
        * 保留小数位数 (默认2位小数)
        */
       int precision() default 2;
   
       /**
        * 舍入模式 (默认四舍五入)
        */
       RoundingMode roundingMode() default RoundingMode.HALF_UP;
   
       /**
        * 是否单独返回 (默认否)
        */
       boolean isSeparately() default false;
   
       /**
        * 是否去除末尾的0 (默认是)
        */
       boolean isStripTrailingZeros() default true;
   }
   

2. 注解处理类DecimalPrecisionHandler

   import com.fasterxml.jackson.core.JsonGenerator;
   import com.fasterxml.jackson.databind.BeanProperty;
   import com.fasterxml.jackson.databind.SerializerProvider;
   
   import java.io.IOException;
   import java.math.BigDecimal;
   import java.math.BigInteger;
   import java.math.RoundingMode;
   
   /**
    * Jackson 序列化处理类
    * 保留小数位数 (默认2位小数 四舍五入)
    *
    * @author ds
    */
   public class DecimalPrecisionHandler implements IJacksonBaseSerializeHandler<DecimalPrecision, Object> {
   
       /**
        * Method that can be called to ask implementation to serialize
        * values of type this serializer handles.
        *
        * @param value       Value to serialize; can <b>not</b> be null.
        * @param gen         Generator used to output resulting Json content
        * @param serializers Provider that can be used to get serializers for
        *                    serializing Objects value contains, if any.
        */
       @Override
       public void serializeHandler(BeanProperty beanProperty, DecimalPrecision annotation, Object value, JsonGenerator gen, SerializerProvider serializers)
               throws IOException {
   
           // 为空直接跳过
           if (beanProperty == null) {
               return;
           }
           BigDecimal temp = this.handlerBigDecimal(value);
   
           int precision = annotation.precision();
           RoundingMode roundingMode = annotation.roundingMode();
   
           temp = temp.setScale(precision, roundingMode);
   
           // 是否去除末尾的0 (默认是)
           if (annotation.isStripTrailingZeros()) {
               temp = temp.stripTrailingZeros();
           }
   
           String valueStr = temp.toPlainString();
           if (annotation.isSeparately()) {
               // 单独返回
               gen.writeStringField(beanProperty.getName() + "DecimalPrecision", valueStr);
           } else {
               // 当前字段中返回
               gen.writeStringField(beanProperty.getName(), valueStr);
           }
       }
   
       /**
        * 处理成BigDecimal类型
        *
        * @param value Value to serialize; can <b>not</b> be null.
        * @return 对应的BigDecimal类型实例
        */
       private BigDecimal handlerBigDecimal(Object value) {
           BigDecimal temp;
           if (value instanceof BigDecimal) {
               temp = (BigDecimal) value;
           } else if (value instanceof Integer) {
               temp = BigDecimal.valueOf((Integer) value);
           } else if (value instanceof Long) {
               temp = BigDecimal.valueOf((Long) value);
           } else if (value instanceof BigInteger) {
               temp = new BigDecimal((BigInteger) value);
           } else if (value instanceof String) {
               temp = new BigDecimal((String) value);
           } else {
               throw new NumberFormatException("No digits found.");
           }
           return temp;
       }
   }