Package org.springframework.batch.item.support

# Class SynchronizedItemStreamReader<T>

java.lang.Object
org.springframework.batch.item.support.SynchronizedItemStreamReader<T>

Type Parameters:
  `T` - type of object being read

All Implemented Interfaces:
  `ItemReader<T>`, `ItemStream`, `ItemStreamReader<T>`, `org.springframework.beans.factory.InitializingBean`

public class SynchronizedItemStreamReader<T> extends Object implements ItemStreamReader<T>, org.springframework.beans.factory.InitializingBean
This is a simple ItemStreamReader decorator with a synchronized ItemReader.read() method - which makes a non-thread-safe ItemReader thread-safe. However, if reprocessing an item is problematic then using this will make a job not restartable. Here are some links about the motivation behind this class: - https://projects.spring.io/spring-batch/faq.html#threading-reader} - https://stackoverflow.com/a/20002493/2910265}

Since:
  3.0.4
Author:
  Matthew Ouyang

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `SynchronizedItemStreamReader()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `afterPropertiesSet()`
  `void`
  `close()`
  If any resources are needed for the stream to operate they need to be destroyed here.
  `void`
  `open(ExecutionContext executionContext)`
  Open the stream for the provided `ExecutionContext`.
  `T`
  `read()`
  This delegates to the read method of the `delegate`
  `void`
  `setDelegate(ItemStreamReader<T> delegate)`
  `void`
  `update(ExecutionContext executionContext)`
  Indicates that the execution context provided during open is about to be saved.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### SynchronizedItemStreamReader

    public SynchronizedItemStreamReader()

- ## Method Details

  - ### setDelegate

    public void setDelegate(ItemStreamReader<T> delegate)

  - ### read

    @Nullable public T read() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException
    This delegates to the read method of the `delegate`
    Specified by:
      `read` in interface `ItemReader<T>`
    Returns:
      T the item to be processed or `null` if the data source is exhausted
    Throws:
      `ParseException` - if there is a problem parsing the current record (but the next one may still be valid)
      `NonTransientResourceException` - if there is a fatal exception in the underlying resource. After throwing this exception implementations should endeavour to return null from subsequent calls to read.
      `UnexpectedInputException` - if there is an uncategorised problem with the input data. Assume potentially transient, so subsequent calls to read might succeed.
      `Exception` - if an there is a non-specific error.

  - ### close

    public void close()
    Description copied from interface: `ItemStream`
    If any resources are needed for the stream to operate they need to be destroyed here. Once this method has been called all other methods (except open) may throw an exception.
    Specified by:
      `close` in interface `ItemStream`

  - ### open

    public void open(ExecutionContext executionContext)
    Description copied from interface: `ItemStream`
    Open the stream for the provided `ExecutionContext`.
    Specified by:
      `open` in interface `ItemStream`
    Parameters:
      `executionContext` - current step's `ExecutionContext`. Will be the executionContext from the last run of the step on a restart.

  - ### update

    public void update(ExecutionContext executionContext)
    Description copied from interface: `ItemStream`
    Indicates that the execution context provided during open is about to be saved. If any state is remaining, but has not been put in the context, it should be added here.
    Specified by:
      `update` in interface `ItemStream`
    Parameters:
      `executionContext` - to be updated

  - ### afterPropertiesSet

    public void afterPropertiesSet() throws Exception
    Specified by:
      `afterPropertiesSet` in interface `org.springframework.beans.factory.InitializingBean`
    Throws:
      `Exception`