The Joinable.java Java example source code
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package javax.sql.rowset;
import java.sql.SQLException;
/**
* <h3>1.0 Background
* The <code>Joinable interface provides the methods for getting and
* setting a match column, which is the basis for forming the SQL <code>JOIN
* formed by adding <code>RowSet objects to a JoinRowSet
* object.
* <P>
* Any standard <code>RowSet implementation may implement
* the <code>Joinable interface in order to be
* added to a <code>JoinRowSet object. Implementing this interface gives
* a <code>RowSet object the ability to use Joinable methods,
* which set, retrieve, and get information about match columns. An
* application may add a
* <code>RowSet object that has not implemented the Joinable
* interface to a <code>JoinRowSet object, but to do so it must use one
* of the <code>JoinRowSet.addRowSet methods that takes both a
* <code>RowSet object and a match column or an array of RowSet
* objects and an array of match columns.
* <P>
* To get access to the methods in the <code>Joinable interface, a
* <code>RowSet object implements at least one of the
* five standard <code>RowSet interfaces and also implements the
* <code>Joinable interface. In addition, most RowSet
* objects extend the <code>BaseRowSet class. For example:
* <pre>
* class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
* :
* :
* }
* </pre>
*
* <h3>2.0 Usage Guidelines
* <P>
* The methods in the <code>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 <code>JOIN can be based.
* An instance of a class that implements these methods can be added to a
* <code>JoinRowSet object to allow an SQL JOIN relationship to
* be established.
*
* <pre>
* CachedRowSet crs = new MyRowSetImpl();
* crs.populate((ResultSet)rs);
* (Joinable)crs.setMatchColumnIndex(1);
*
* JoinRowSet jrs = new JoinRowSetImpl();
* jrs.addRowSet(crs);
* </pre>
* In the previous example, <i>crs is a CachedRowSet object that
* has implemented the <code>Joinable interface. In the following example,
* <i>crs2 has not, so it must supply the match column as an argument to the
* <code>addRowSet method. This example assumes that column 1 is the match
* column.
* <PRE>
* CachedRowSet crs2 = new MyRowSetImpl();
* crs2.populate((ResultSet)rs);
*
* JoinRowSet jrs2 = new JoinRowSetImpl();
* jrs2.addRowSet(crs2, 1);
* </PRE>
* <p>
* The <code>JoinRowSet interface makes it possible to get data from one or
* more <code>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 <code>RowSet objects. Nevertheless, any
* <code>RowSet object may implement this interface
* regardless of whether it is connected or disconnected. Note that a
* <code>JdbcRowSet object, being always connected to its data source, can
* become part of an SQL <code>JOIN directly without having to become part
* of a <code>JoinRowSet object.
*
* <h3>3.0 Managing Multiple Match Columns
* The index array passed into the <code>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:
* <pre>
* int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
* // indexes 1, 2, 4, 7 participating in the JOIN.
* Joinable.setMatchColumn(i);
* </pre>
* Subsequent match columns may be added as follows to a different <code>Joinable
* object (a <code>RowSet object that has implemented the Joinable
* interface).
* <pre>
* int[] w = {3, 2, 5, 3};
* Joinable2.setMatchColumn(w);
* </pre>
* When an application adds two or more <code>RowSet objects to a
* <code>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
* <code>RowSet object. If overlap or underlap occurs, the match column
* data is maintained in the event an additional <code>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 <code>SQL JOIN.
* <p>
* 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 <code>RowSet
* object. A <code>JoinRowSet object can now add this RowSet
* object based on the match column.
* <p>
* Sub-interfaces such as the <code>CachedRowSet™
* interface define the method <code>CachedRowSet.setKeyColumns, which allows
* primary key semantics to be enforced on specific columns.
* Implementations of the <code>setMatchColumn(int columnIdx) method
* should ensure that the constraints on the key columns are maintained when
* a <code>CachedRowSet object sets a primary key column as a match column.
*
* @param columnIdx an <code>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 <code>RowSet
* object. A <code>JoinRowSet object can now add this RowSet
* object based on the match column.
*
* @param columnIdxes an array of <code>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 <code>RowSet
* object. A <code>JoinRowSet object can now add this RowSet
* object based on the match column.
* <p>
* Subinterfaces such as the <code>CachedRowSet interface define
* the method <code>CachedRowSet.setKeyColumns, which allows
* primary key semantics to be enforced on specific columns.
* Implementations of the <code>setMatchColumn(String columnIdx) method
* should ensure that the constraints on the key columns are maintained when
* a <code>CachedRowSet object sets a primary key column as a match column.
*
* @param columnName a <code>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 <code>RowSet
* object. A <code>JoinRowSet object can now add this RowSet
* object based on the match column.
*
* @param columnNames an array of <code>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
* <code>RowSet object with the method
* <code>setMatchColumn(int[] columnIdxes).
*
* @return an <code>int array identifying the indexes of the columns
* that were set as the match columns for this <code>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
* <code>RowSet object with the method
* <code>setMatchColumn(String [] columnNames).
*
* @return an array of <code>String objects giving the names of the columns
* set as the match columns for this <code>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 <code>RowSet
* object.
* <P>
* <code>RowSet objects that implement the Joinable interface
* must ensure that a key-like constraint continues to be enforced until the
* method <code>CachedRowSet.unsetKeyColumns has been called on the
* designated column.
*
* @param columnIdx an <code>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 <code>RowSet
* object.
*
* @param columnIdxes an array of <code>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 <code>RowSet
* object.
* <P>
* <code>RowSet objects that implement the Joinable interface
* must ensure that a key-like constraint continues to be enforced until the
* method <code>CachedRowSet.unsetKeyColumns has been called on the
* designated column.
*
* @param columnName a <code>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 <code>RowSet
* object.
*
* @param columnName an array of <code>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;
}
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