Package org.springframework.batch.item.database

Class AbstractCursorItemReader<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.AbstractCursorItemReader<T>
All Implemented Interfaces:
ItemReader<T>, ItemStream, ItemStreamReader<T>, org.springframework.beans.factory.InitializingBean
Direct Known Subclasses:
JdbcCursorItemReader, StoredProcedureItemReader
public abstract class AbstractCursorItemReader<T> extends AbstractItemCountingItemStreamItemReader<T> implements org.springframework.beans.factory.InitializingBean

Abstract base class for any simple item reader that opens a database cursor and continually retrieves the next row in the ResultSet.

By default the cursor will be opened using a separate connection. The ResultSet for the cursor is held open regardless of commits or roll backs in a surrounding transaction. Clients of this reader are responsible for buffering the items in the case that they need to be re-presented on a rollback. This buffering is handled by the step implementations provided and is only a concern for anyone writing their own step implementations.

There is an option (setUseSharedExtendedConnection(boolean) that will share the connection used for the cursor with the rest of the step processing. If you set this flag to true then you must wrap the DataSource in a ExtendedConnectionDataSourceProxy to prevent the connection from being closed and released after each commit performed as part of the step processing. You must also use a JDBC driver supporting JDBC 3.0 or later since the cursor will be opened with the additional option of 'HOLD_CURSORS_OVER_COMMIT' enabled.

Each call to AbstractItemCountingItemStreamItemReader.read() will attempt to map the row at the current position in the ResultSet. There is currently no wrapping of the ResultSet to suppress calls to next(). However, if the RowMapper (mistakenly) increments the current row, the next call to read will verify that the current row is at the expected position and throw a DataAccessException if it is not. The reason for such strictness on the ResultSet is due to the need to maintain control for transactions and restartability. This ensures that each call to AbstractItemCountingItemStreamItemReader.read() returns the ResultSet at the correct row, regardless of rollbacks or restarts.

ExecutionContext: The current row is returned as restart data, and when restored from that same data, the cursor is opened and the current row set to the value within the restart data. See setDriverSupportsAbsolute(boolean) for improving restart performance.

Calling close on this ItemStream will cause all resources it is currently using to be freed. (Connection, ResultSet, etc). It is then illegal to call AbstractItemCountingItemStreamItemReader.read() again until it has been re-opened.

Known limitation: when used with Derby setVerifyCursorPosition(boolean) needs to be false because ResultSet.getRow() call used for cursor position verification is not available for 'TYPE_FORWARD_ONLY' result sets.

Subclasses are inherently not thread-safe.

Author:
Lucas Ward, Peter Zozom, Robert Kasanicky, Thomas Risberg, Michael Minella, Mahmoud Ben Hassine

  • Field Details

    • log

      protected final org.apache.commons.logging.Log log
      Logger available to subclasses

    • VALUE_NOT_SET

      public static final int VALUE_NOT_SET
      See Also:

    • rs

      protected ResultSet rs

  • Constructor Details

    • AbstractCursorItemReader

      public AbstractCursorItemReader()

  • Method Details

    • afterPropertiesSet

      public void afterPropertiesSet() throws Exception
      Assert that mandatory properties are set.
      Specified by:
      afterPropertiesSet in interface org.springframework.beans.factory.InitializingBean
      Throws:
      IllegalArgumentException - if either data source or SQL properties not set.
      Exception

    • setDataSource

      public void setDataSource(DataSource dataSource)
      Public setter for the data source for injection purposes.
      Parameters:
      dataSource - DataSource to be used

    • getDataSource

      public DataSource getDataSource()
      Public getter for the data source.
      Returns:
      the dataSource

    • applyStatementSettings

      protected void applyStatementSettings(PreparedStatement stmt) throws SQLException
      Prepare the given JDBC Statement (or PreparedStatement or CallableStatement), applying statement settings such as fetch size, max rows, and query timeout. @param stmt the JDBC Statement to prepare
      Parameters:
      stmt - PreparedStatement to be configured
      Throws:
      SQLException - if interactions with provided stmt fail
      See Also:

    • getExceptionTranslator

      protected org.springframework.jdbc.support.SQLExceptionTranslator getExceptionTranslator()
      Creates a default SQLErrorCodeSQLExceptionTranslator for the specified DataSource if none is set.
      Returns:
      the exception translator for this instance.

    • translateSqlException

      protected org.springframework.dao.DataAccessException translateSqlException(String task, String sql, SQLException ex)

    • handleWarnings

      protected void handleWarnings(Statement statement) throws org.springframework.jdbc.SQLWarningException, SQLException
      Throw a SQLWarningException if we're not ignoring warnings, else log the warnings (at debug level).
      Parameters:
      statement - the current statement to obtain the warnings from, if there are any.
      Throws:
      SQLException - if interaction with provided statement fails.
      org.springframework.jdbc.SQLWarningException
      See Also:
      • SQLWarningException

    • 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:

    • setMaxRows

      public void setMaxRows(int maxRows)
      Sets the limit for the maximum number of rows that any ResultSet object can contain to the given number.
      Parameters:
      maxRows - the new max rows limit; zero means there is no limit
      See Also:

    • setQueryTimeout

      public void setQueryTimeout(int queryTimeout)
      Sets the number of seconds the driver will wait for a Statement object to execute to the given number of seconds. If the limit is exceeded, an SQLException is thrown.
      Parameters:
      queryTimeout - seconds the new query timeout limit in seconds; zero means there is no limit
      See Also:

    • setIgnoreWarnings

      public void setIgnoreWarnings(boolean ignoreWarnings)
      Set whether SQLWarnings should be ignored (only logged) or exception should be thrown.
      Parameters:
      ignoreWarnings - if TRUE, warnings are ignored

    • setVerifyCursorPosition

      public void setVerifyCursorPosition(boolean verifyCursorPosition)
      Allow verification of cursor position after current row is processed by RowMapper or RowCallbackHandler. Default value is TRUE.
      Parameters:
      verifyCursorPosition - if true, cursor position is verified

    • setDriverSupportsAbsolute

      public void setDriverSupportsAbsolute(boolean driverSupportsAbsolute)
      Indicate whether the JDBC driver supports setting the absolute row on a ResultSet. It is recommended that this is set to true for JDBC drivers that supports ResultSet.absolute() as it may improve performance, especially if a step fails while working with a large data set.
      Parameters:
      driverSupportsAbsolute - false by default
      See Also:

    • setUseSharedExtendedConnection

      public void setUseSharedExtendedConnection(boolean useSharedExtendedConnection)
      Indicate whether the connection used for the cursor should be used by all other processing thus sharing the same transaction. If this is set to false, which is the default, then the cursor will be opened using in its connection and will not participate in any transactions started for the rest of the step processing. If you set this flag to true then you must wrap the DataSource in a ExtendedConnectionDataSourceProxy to prevent the connection from being closed and released after each commit.

      When you set this option to true then the statement used to open the cursor will be created with both 'READ_ONLY' and 'HOLD_CURSORS_OVER_COMMIT' options. This allows holding the cursor open over transaction start and commits performed in the step processing. To use this feature you need a database that supports this and a JDBC driver supporting JDBC 3.0 or later.

      Parameters:
      useSharedExtendedConnection - false by default

    • isUseSharedExtendedConnection

      public boolean isUseSharedExtendedConnection()

    • setConnectionAutoCommit

      public void setConnectionAutoCommit(boolean autoCommit)
      Set whether "autoCommit" should be overridden for the connection used by the cursor. If not set, defaults to Connection / Datasource default configuration.
      Parameters:
      autoCommit - value used for Connection.setAutoCommit(boolean).
      Since:
      4.0

    • getSql

      public abstract String getSql()

    • doClose

      protected void doClose() throws Exception
      Close the cursor and database connection. Make call to cleanupOnClose so sub classes can cleanup any resources they have allocated.
      Specified by:
      doClose in class AbstractItemCountingItemStreamItemReader<T>
      Throws:
      Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

    • cleanupOnClose

      protected abstract void cleanupOnClose(Connection connection) throws Exception
      Clean up resources.
      Parameters:
      connection - to the database
      Throws:
      Exception - If unable to clean up resources

    • doOpen

      protected void doOpen() throws Exception
      Execute the statement to open the cursor.
      Specified by:
      doOpen in class AbstractItemCountingItemStreamItemReader<T>
      Throws:
      Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

    • initializeConnection

      protected void initializeConnection()

    • openCursor

      protected abstract void openCursor(Connection con)

    • doRead

      @Nullable protected T doRead() throws Exception
      Read next row and map it to item, verify cursor position if setVerifyCursorPosition(boolean) is true.
      Specified by:
      doRead in class AbstractItemCountingItemStreamItemReader<T>
      Returns:
      an item or null if the data source is exhausted
      Throws:
      Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

    • readCursor

      @Nullable protected abstract T readCursor(ResultSet rs, int currentRow) throws SQLException
      Read the cursor and map to the type of object this reader should return. This method must be overridden by subclasses.
      Parameters:
      rs - The current result set
      currentRow - Current position of the result set
      Returns:
      the mapped object at the cursor position
      Throws:
      SQLException - if interactions with the current result set fail

    • jumpToItem

      protected void jumpToItem(int itemIndex) throws Exception
      Use ResultSet.absolute(int) if possible, otherwise scroll by calling ResultSet.next().
      Overrides:
      jumpToItem in class AbstractItemCountingItemStreamItemReader<T>
      Parameters:
      itemIndex - index of item (0 based) to jump to.
      Throws:
      Exception - Allows subclasses to throw checked exceptions for interpretation by the framework