Package org.springframework.batch.item.database

Class JdbcPagingItemReader<T>

java.lang.Object
org.springframework.batch.item.ItemStreamSupport
org.springframework.batch.item.support.AbstractItemStreamItemReader<T>
org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader<T>
org.springframework.batch.item.database.AbstractPagingItemReader<T>
org.springframework.batch.item.database.JdbcPagingItemReader<T>
All Implemented Interfaces:
ItemReader<T>, ItemStream, ItemStreamReader<T>, org.springframework.beans.factory.InitializingBean
public class JdbcPagingItemReader<T> extends AbstractPagingItemReader<T> implements org.springframework.beans.factory.InitializingBean

ItemReader for reading database records using JDBC in a paging fashion.

It executes the SQL built by the PagingQueryProvider to retrieve requested data. The query is executed using paged requests of a size specified in AbstractPagingItemReader.setPageSize(int). Additional pages are requested when needed as AbstractItemCountingItemStreamItemReader.read() method is called, returning an object corresponding to current position. On restart it uses the last sort key value to locate the first page to read (so it doesn't matter if the successfully processed items have been removed or modified). It is important to have a unique key constraint on the sort key to guarantee that no data is lost between executions.

The performance of the paging depends on the database specific features available to limit the number of returned rows. Setting a fairly large page size and using a commit interval that matches the page size should provide better performance.

The implementation is thread-safe in between calls to open(ExecutionContext), but remember to use saveState=false if used in a multi-threaded client (no restart available).

Since:
2.0
Author:
Thomas Risberg, Dave Syer, Michael Minella, Mahmoud Ben Hassine

  • Field Details

  • Constructor Details

    • JdbcPagingItemReader

      public JdbcPagingItemReader()

  • Method Details

    • setDataSource

      public void setDataSource(DataSource dataSource)

    • setFetchSize

      public void setFetchSize(int fetchSize)
      Gives the JDBC driver a hint as to the number of rows that should be fetched from the database when more rows are needed for this ResultSet object. If the fetch size specified is zero, the JDBC driver ignores the value.
      Parameters:
      fetchSize - the number of rows to fetch
      See Also:

    • setQueryProvider

      public void setQueryProvider(PagingQueryProvider queryProvider)
      A PagingQueryProvider. Supplies all the platform dependent query generation capabilities needed by the reader.
      Parameters:
      queryProvider - the PagingQueryProvider to use

    • setRowMapper

      public void setRowMapper(org.springframework.jdbc.core.RowMapper<T> rowMapper)
      The row mapper implementation to be used by this reader. The row mapper is used to convert result set rows into objects, which are then returned by the reader.
      Parameters:
      rowMapper - a RowMapper implementation

    • setParameterValues

      public void setParameterValues(Map<String,Object> parameterValues)
      The parameter values to be used for the query execution. If you use named parameters then the key should be the name used in the query clause. If you use "?" placeholders then the key should be the relative index that the parameter appears in the query string built using the select, from and where clauses specified.
      Parameters:
      parameterValues - the values keyed by the parameter named/index used in the query string.

    • afterPropertiesSet

      public void afterPropertiesSet() throws Exception
      Check mandatory properties.
      Specified by:
      afterPropertiesSet in interface org.springframework.beans.factory.InitializingBean
      Overrides:
      afterPropertiesSet in class AbstractPagingItemReader<T>
      Throws:
      Exception
      See Also:
      • InitializingBean.afterPropertiesSet()

    • doReadPage

      protected void doReadPage()
      Specified by:
      doReadPage in class AbstractPagingItemReader<T>

    • update

      public void update(ExecutionContext executionContext) throws ItemStreamException
      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
      Overrides:
      update in class AbstractItemCountingItemStreamItemReader<T>
      Parameters:
      executionContext - to be updated
      Throws:
      ItemStreamException

    • open

      public void open(ExecutionContext executionContext)
      Description copied from interface: ItemStream
      Open the stream for the provided ExecutionContext.
      Specified by:
      open in interface ItemStream
      Overrides:
      open in class AbstractItemCountingItemStreamItemReader<T>
      Parameters:
      executionContext - current step's ExecutionContext. Will be the executionContext from the last run of the step on a restart.