org.springframework.batch.item

## Interface PeekableItemReader<T>

- All Superinterfaces:
    ItemReader<T>
  All Known Implementing Classes:
    SingleItemPeekableItemReader

      public interface PeekableItemReader<T>
      extends ItemReader<T>

  A specialisation of `ItemReader` that allows the user to look ahead into the stream of items. This is useful, for instance, when reading flat file data that contains record separator lines which are actually part of the next record.

  The detailed contract for `peek()` has to be defined by the implementation because there is no general way to define it in a concurrent environment. The definition of "the next read()" operation is tenuous if multiple clients are reading concurrently, and the ability to peek implies that some state is likely to be stored, so implementations of `PeekableItemReader` may well be restricted to single threaded use.

  Author:
    Dave Syer, Mahmoud Ben Hassine

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `T` | `peek()` Get the next item that would be returned by `ItemReader.read()`, without affecting the result of `ItemReader.read()`.

    - ### Methods inherited from interface org.springframework.batch.item.ItemReader

      `read`

- - ### Method Detail

    - #### peek

          @Nullable
          T peek()
                    throws java.lang.Exception,
                           UnexpectedInputException,
                           ParseException

      Get the next item that would be returned by `ItemReader.read()`, without affecting the result of `ItemReader.read()`.
      Returns:
        the next item or `null` if the data source is exhausted
      Throws:
        `java.lang.Exception` - if there is a problem
        `UnexpectedInputException`
        `ParseException`