Joinable interface provides the methods for getting and
* setting a match column, which is the basis for forming the SQL JOIN
* formed by adding RowSet objects to a JoinRowSet
* object.
*
* Any standard RowSet implementation may implement
* the Joinable interface in order to be
* added to a JoinRowSet object. Implementing this interface gives
* a RowSet object the ability to use Joinable methods,
* which set, retrieve, and get information about match columns. An
* application may add a
* RowSet object that has not implemented the Joinable
* interface to a JoinRowSet object, but to do so it must use one
* of the JoinRowSet.addRowSet methods that takes both a
* RowSet object and a match column or an array of RowSet
* objects and an array of match columns.
*
* To get access to the methods in the Joinable interface, a
* RowSet object implements at least one of the
* five standard RowSet interfaces and also implements the
* Joinable interface. In addition, most RowSet
* objects extend the BaseRowSet class. For example:
*
* class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
* :
* :
* }
*
* *
* The methods in the Joinable interface allow a RowSet object
* to set a match column, retrieve a match column, or unset a match column, which is
* the column upon which an SQL JOIN can be based.
* An instance of a class that implements these methods can be added to a
* JoinRowSet object to allow an SQL JOIN relationship to
* be established.
*
*
* CachedRowSet crs = new MyRowSetImpl(); * crs.populate((ResultSet)rs); * (Joinable)crs.setMatchColumnIndex(1); * * JoinRowSet jrs = new JoinRowSetImpl(); * jrs.addRowSet(crs); ** In the previous example, crs is a
CachedRowSet object that
* has emplemented the Joinable interface. In the following example,
* crs2 has not, so it must supply the match column as an argument to the
* addRowSet method. This example assumes that column 1 is the match
* column.
* * CachedRowSet crs2 = new MyRowSetImpl(); * crs2.populate((ResultSet)rs); * * JoinRowSet jrs2 = new JoinRowSetImpl(); * jrs2.addRowSet(crs2, 1); **
* The JoinRowSet interface makes it possible to get data from one or
* more RowSet objects consolidated into one table without having to incur
* the expense of creating a connection to a database. It is therefore ideally suited
* for use by disconnected RowSet objects. Nevertheless, any
* RowSet object may implement this interface
* regardless of whether it is connected or disconnected. Note that a
* JdbcRowSet object, being always connected to its data source, can
* become part of an SQL JOIN directly without having to become part
* of a JoinRowSet object.
*
*
setMatchColumn methods indicates
* how many match columns are being set (the length of the array) in addition to
* which columns will be used for the match. For example:
*
* int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
* // indexes 1, 2, 4, 7 participating in the JOIN.
* Joinable.setMatchColumn(i);
*
* Subsequent match columns may be added as follows to a different Joinable
* object (a RowSet object that has implemented the Joinable
* interface).
*
* int[] w = {3, 2, 5, 3};
* Joinable2.setMatchColumn(w);
*
* When an application adds two or more RowSet objects to a
* JoinRowSet object, the order of the indexes in the array is
* particularly important. Each index of
* the array maps directly to the corresponding index of the previously added
* RowSet object. If overlap or underlap occurs, the match column
* data is maintained in the event an additional Joinable RowSet is
* added and needs to relate to the match column data. Therefore, applications
* can set multiple match columns in any order, but
* this order has a direct effect on the outcome of the SQL JOIN.
*
* This assertion applies in exactly the same manner when column names are used
* rather than column indexes to indicate match columns.
*
* @see JoinRowSet
* @author Jonathan Bruce
*/
public interface Joinable {
/**
* Sets the designated column as the match column for this RowSet
* object. A JoinRowSet object can now add this RowSet
* object based on the match column.
*
* Sub-interfaces such as the CachedRowSetTM
* interface define the method CachedRowSet.setKeyColumns, which allows
* primary key semantics to be enforced on specific columns.
* Implementations of the setMatchColumn(int columnIdx) method
* should ensure that the constraints on the key columns are maintained when
* a CachedRowSet object sets a primary key column as a match column.
*
* @param columnIdx an int identifying the index of the column to be
* set as the match column
* @throws SQLException if an invalid column index is set
* @see #setMatchColumn(int[])
* @see #unsetMatchColumn(int)
*
*/
public void setMatchColumn(int columnIdx) throws SQLException;
/**
* Sets the designated columns as the match column for this RowSet
* object. A JoinRowSet object can now add this RowSet
* object based on the match column.
*
* @param columnIdxes an array of int identifying the indexes of the
* columns to be set as the match columns
* @throws SQLException if an invalid column index is set
* @see #setMatchColumn(int[])
* @see #unsetMatchColumn(int[])
*/
public void setMatchColumn(int[] columnIdxes) throws SQLException;
/**
* Sets the designated column as the match column for this RowSet
* object. A JoinRowSet object can now add this RowSet
* object based on the match column.
*
* Subinterfaces such as the CachedRowSet interface define
* the method CachedRowSet.setKeyColumns, which allows
* primary key semantics to be enforced on specific columns.
* Implementations of the setMatchColumn(String columnIdx) method
* should ensure that the constraints on the key columns are maintained when
* a CachedRowSet object sets a primary key column as a match column.
*
* @param columnName a String object giving the name of the column
* to be set as the match column
* @throws SQLException if an invalid column name is set, the column name
* is a null, or the column name is an empty string
* @see #unsetMatchColumn
* @see #setMatchColumn(int[])
*/
public void setMatchColumn(String columnName) throws SQLException;
/**
* Sets the designated columns as the match column for this RowSet
* object. A JoinRowSet object can now add this RowSet
* object based on the match column.
*
* @param columnNames an array of String objects giving the names
* of the column to be set as the match columns
* @throws SQLException if an invalid column name is set, the column name
* is a null, or the column name is an empty string
* @see #unsetMatchColumn
* @see #setMatchColumn(int[])
*/
public void setMatchColumn(String[] columnNames) throws SQLException;
/**
* Retrieves the indexes of the match columns that were set for this
* RowSet object with the method
* setMatchColumn(int[] columnIdxes).
*
* @return an int array identifying the indexes of the columns
* that were set as the match columns for this RowSet object
* @throws SQLException if no match column has been set
* @see #setMatchColumn
* @see #unsetMatchColumn
*/
public int[] getMatchColumnIndexes() throws SQLException;
/**
* Retrieves the names of the match columns that were set for this
* RowSet object with the method
* setMatchColumn(String [] columnNames).
*
* @return an array of String objects giving the names of the columns
* set as the match columns for this RowSet object
* @throws SQLException if no match column has been set
* @see #setMatchColumn
* @see #unsetMatchColumn
*
*/
public String[] getMatchColumnNames() throws SQLException;
/**
* Unsets the designated column as the match column for this RowSet
* object.
*
* RowSet objects that implement the Joinable interface
* must ensure that a key-like constraint continues to be enforced until the
* method CachedRowSet.unsetKeyColumns has been called on the
* designated column.
*
* @param columnIdx an int that identifies the index of the column
* that is to be unset as a match column
* @throws SQLException if an invalid column index is designated or if
* the designated column was not previously set as a match
* column
* @see #setMatchColumn
*/
public void unsetMatchColumn(int columnIdx) throws SQLException;
/**
* Unsets the designated columns as the match column for this RowSet
* object.
*
* @param columnIdxes an arrary of int that identifies the indexes
* of the columns that are to be unset as match columns
* @throws SQLException if an invalid column index is designated or if
* the designated column was not previously set as a match
* column
* @see #setMatchColumn
*/
public void unsetMatchColumn(int[] columnIdxes) throws SQLException;
/**
* Unsets the designated column as the match column for this RowSet
* object.
*
* RowSet objects that implement the Joinable interface
* must ensure that a key-like constraint continues to be enforced until the
* method CachedRowSet.unsetKeyColumns has been called on the
* designated column.
*
* @param columnName a String object giving the name of the column
* that is to be unset as a match column
* @throws SQLException if an invalid column name is designated or
* the designated column was not previously set as a match
* column
* @see #setMatchColumn
*/
public void unsetMatchColumn(String columnName) throws SQLException;
/**
* Unsets the designated columns as the match columns for this RowSet
* object.
*
* @param columnName an array of String objects giving the names of
* the columns that are to be unset as the match columns
* @throws SQLException if an invalid column name is designated or the
* designated column was not previously set as a match column
* @see #setMatchColumn
*/
public void unsetMatchColumn(String[] columnName) throws SQLException;
}