org.springframework.jdbc.core

## Class RowCountCallbackHandler

- java.lang.Object
- - org.springframework.jdbc.core.RowCountCallbackHandler

- All Implemented Interfaces:
    RowCallbackHandler

      public class RowCountCallbackHandler
      extends Object
      implements RowCallbackHandler

  Implementation of RowCallbackHandler. Convenient superclass for callback handlers. An instance can only be used once.

  We can either use this on its own (for example, in a test case, to ensure that our result sets have valid dimensions), or use it as a superclass for callback handlers that actually do something, and will benefit from the dimension information it provides.

  A usage example with JdbcTemplate:

      JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);  // reusable object

       RowCountCallbackHandler countCallback = new RowCountCallbackHandler();  // not reusable
       jdbcTemplate.query("select * from user", countCallback);
       int rowCount = countCallback.getRowCount();

  Since:
    May 3, 2001
  Author:
    Rod Johnson

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `RowCountCallbackHandler()`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `getColumnCount()` Return the number of columns in this result set.
    `String[]` | `getColumnNames()` Return the names of the columns.
    `int[]` | `getColumnTypes()` Return the types of the columns as java.sql.Types constants Valid after processRow is invoked the first time.
    `int` | `getRowCount()` Return the row count of this ResultSet Only valid after processing is complete
    `void` | `processRow(ResultSet rs)` Implementation of ResultSetCallbackHandler.
    `protected void` | `processRow(ResultSet rs, int rowNum)` Subclasses may override this to perform custom extraction or processing.

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

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

- - ### Constructor Detail

    - #### RowCountCallbackHandler

          public RowCountCallbackHandler()

  - ### Method Detail

    - #### processRow

          public final void processRow(ResultSet rs)
                                throws SQLException

      Implementation of ResultSetCallbackHandler. Work out column size if this is the first row, otherwise just count rows.

      Subclasses can perform custom extraction or processing by overriding the `processRow(ResultSet, int)` method.

      Specified by:
        `processRow` in interface `RowCallbackHandler`
      Parameters:
        `rs` - the ResultSet to process (pre-initialized for the current row)
      Throws:
        `SQLException` - if a SQLException is encountered getting column values (that is, there's no need to catch SQLException)
      See Also:
        `processRow(java.sql.ResultSet, int)`

    - #### processRow

          protected void processRow(ResultSet rs,
                                    int rowNum)
                             throws SQLException

      Subclasses may override this to perform custom extraction or processing. This class's implementation does nothing.
      Parameters:
        `rs` - ResultSet to extract data from. This method is invoked for each row
        `rowNum` - number of the current row (starting from 0)
      Throws:
        `SQLException`

    - #### getColumnTypes

          public final int[] getColumnTypes()

      Return the types of the columns as java.sql.Types constants Valid after processRow is invoked the first time.
      Returns:
        the types of the columns as java.sql.Types constants. Indexed from 0 to n-1.

    - #### getColumnNames

          public final String[] getColumnNames()

      Return the names of the columns. Valid after processRow is invoked the first time.
      Returns:
        the names of the columns. Indexed from 0 to n-1.

    - #### getRowCount

          public final int getRowCount()

      Return the row count of this ResultSet Only valid after processing is complete
      Returns:
        the number of rows in this ResultSet

    - #### getColumnCount

          public final int getColumnCount()

      Return the number of columns in this result set. Valid once we've seen the first row, so subclasses can use it during processing
      Returns:
        the number of columns in this result set