content: package com.alibaba.excel.converters;
  
  import com.alibaba.excel.enums.CellDataTypeEnum;
  import com.alibaba.excel.metadata.GlobalConfiguration;
  import com.alibaba.excel.metadata.data.ReadCellData;
  import com.alibaba.excel.metadata.data.WriteCellData;
  import com.alibaba.excel.metadata.property.ExcelContentProperty;
  
  /**
   * Convert between Java objects and excel objects
   *
   * @param <T>
   * @author Dan Zheng
   */
  public interface Converter<T> {
  
      /**
       * Back to object types in Java
       *
       * @return Support for Java class
       */
      default Class<?> supportJavaTypeKey() {
          throw new UnsupportedOperationException("The current operation is not supported by the current converter.");
      }
  
      /**
       * Back to object enum in excel
       *
       * @return Support for {@link CellDataTypeEnum}
       */
      default CellDataTypeEnum supportExcelTypeKey() {
          throw new UnsupportedOperationException("The current operation is not supported by the current converter.");
      }
  
      /**
       * Convert excel objects to Java objects
       *
       * @param cellData            Excel cell data.NotNull.
       * @param contentProperty     Content property.Nullable.
       * @param globalConfiguration Global configuration.NotNull.
       * @return Data to put into a Java object
       * @throws Exception Exception.
       */
      default T convertToJavaData(ReadCellData<?> cellData, ExcelContentProperty contentProperty,
          GlobalConfiguration globalConfiguration) throws Exception {
          throw new UnsupportedOperationException("The current operation is not supported by the current converter.");
      }
  
      /**
       * Convert excel objects to Java objects
       *
       * @param context read converter context
       * @return Data to put into a Java object
       * @throws Exception Exception.
       */
      default T convertToJavaData(ReadConverterContext<?> context) throws Exception {
          return convertToJavaData(context.getReadCellData(), context.getContentProperty(),
              context.getAnalysisContext().currentReadHolder().globalConfiguration());
      }
  
      /**
       * Convert Java objects to excel objects
       *
       * @param value               Java Data.NotNull.
       * @param contentProperty     Content property.Nullable.
       * @param globalConfiguration Global configuration.NotNull.
       * @return Data to put into a Excel
       * @throws Exception Exception.
       */
      default WriteCellData<?> convertToExcelData(T value, ExcelContentProperty contentProperty,
          GlobalConfiguration globalConfiguration) throws Exception {
          throw new UnsupportedOperationException("The current operation is not supported by the current converter.");
      }
  
      /**
       * Convert Java objects to excel objects
       *
       * @param context write context
       * @return Data to put into a Excel
       * @throws Exception Exception.
       */
      default WriteCellData<?> convertToExcelData(WriteConverterContext<T> context) throws Exception {
          return convertToExcelData(context.getValue(), context.getContentProperty(),
              context.getWriteContext().currentWriteHolder().globalConfiguration());
      }
  }
  