CachedRowSet
, FilteredRowSet
, JdbcRowSet
, JoinRowSet
, WebRowSet
public interface Joinable
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 implemented 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.
Modifier and Type | Method | Description |
---|---|---|
int[] |
getMatchColumnIndexes() |
Retrieves the indexes of the match columns that were set for this RowSet object with the method setMatchColumn(int[] columnIdxes) . |
String[] |
getMatchColumnNames() |
Retrieves the names of the match columns that were set for this RowSet object with the method setMatchColumn(String [] columnNames) . |
void |
setMatchColumn |
Sets the designated column as the match column for this RowSet object. |
void |
setMatchColumn |
Sets the designated columns as the match column for this RowSet object. |
void |
setMatchColumn |
Sets the designated column as the match column for this RowSet object. |
void |
setMatchColumn |
Sets the designated columns as the match column for this RowSet object. |
void |
unsetMatchColumn |
Unsets the designated column as the match column for this RowSet object. |
void |
unsetMatchColumn |
Unsets the designated columns as the match column for this RowSet object. |
void |
unsetMatchColumn |
Unsets the designated column as the match column for this RowSet object. |
void |
unsetMatchColumn |
Unsets the designated columns as the match columns for this RowSet object. |
void setMatchColumn(int columnIdx) throws SQLException
RowSet
object. A JoinRowSet
object can now add this RowSet
object based on the match column. Sub-interfaces 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(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.
columnIdx
- an int
identifying the index of the column to be set as the match columnSQLException
- if an invalid column index is setvoid setMatchColumn(int[] columnIdxes) throws SQLException
RowSet
object. A JoinRowSet
object can now add this RowSet
object based on the match column.columnIdxes
- an array of int
identifying the indexes of the columns to be set as the match columnsSQLException
- if an invalid column index is setvoid setMatchColumn(String columnName) throws SQLException
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.
columnName
- a String
object giving the name of the column to be set as the match columnSQLException
- if an invalid column name is set, the column name is a null, or the column name is an empty stringvoid setMatchColumn(String[] columnNames) throws SQLException
RowSet
object. A JoinRowSet
object can now add this RowSet
object based on the match column.columnNames
- an array of String
objects giving the names of the column to be set as the match columnsSQLException
- if an invalid column name is set, the column name is a null, or the column name is an empty stringint[] getMatchColumnIndexes() throws SQLException
RowSet
object with the method setMatchColumn(int[] columnIdxes)
.int
array identifying the indexes of the columns that were set as the match columns for this RowSet
objectSQLException
- if no match column has been setString[] getMatchColumnNames() throws SQLException
RowSet
object with the method setMatchColumn(String [] columnNames)
.String
objects giving the names of the columns set as the match columns for this RowSet
objectSQLException
- if no match column has been setvoid unsetMatchColumn(int columnIdx) throws SQLException
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.
columnIdx
- an int
that identifies the index of the column that is to be unset as a match columnSQLException
- if an invalid column index is designated or if the designated column was not previously set as a match columnvoid unsetMatchColumn(int[] columnIdxes) throws SQLException
RowSet
object.columnIdxes
- an array of int
that identifies the indexes of the columns that are to be unset as match columnsSQLException
- if an invalid column index is designated or if the designated column was not previously set as a match columnvoid unsetMatchColumn(String columnName) throws SQLException
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.
columnName
- a String
object giving the name of the column that is to be unset as a match columnSQLException
- if an invalid column name is designated or the designated column was not previously set as a match columnvoid unsetMatchColumn(String[] columnName) throws SQLException
RowSet
object.columnName
- an array of String
objects giving the names of the columns that are to be unset as the match columnsSQLException
- if an invalid column name is designated or the designated column was not previously set as a match column
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https://docs.oracle.com/en/java/javase/21/docs/api/java.sql.rowset/javax/sql/rowset/Joinable.html