|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
Joinable
interface provides the methods any standard
RowSet
implementation must implement in order to be
added to a JoinRowSet
object. Therefore, in order for a
RowSet
implementation to become 'joinable', it will implement
this interface in addition to extending the BaseRowSet
class
and implementing any of the other standard RowSet
interfaces
described in this package. For example:
class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable { : : }
NOTE: It is not mandatory requirement for all standard RowSet
objects
to implement the Joinable
interface. This is only necessary
when an RowSet
object wishes to be consumed by a
JoinRowSet
to participate in a SQL JOIN
.
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);
Any RowSet
object may implement this interface
regardless of whether it is connected or disconnected. 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. However, both connected and disconnected
RowSet
objects have to implement the Joinable
interface to be eligible for becoming part of an SQL JOIN
through
being added to a JoinRowSet
object.
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.
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
int[] w = {3, 2, 5, 3}; Joinable2.setMatchColumn(w);When adding the two
Joinable
RowSets to a JoinRowSet
,
the order of the array index plays particular importance here. Each index of
the array maps directly to the corresponding index of the previously added
Joinable
RowSet. If over-lap or under-lap 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 affect on the outcome of the SQL
JOIN.
Ths assertion applies in exactly the same manner when column names are used rather than column indexes.
JoinRowSet
Method Summary | |
int[] |
getMatchColumnIndexes()
Retrieves the index of the match column that was set for this RowSet object with the method
setMatchColumn(int columnIdx) . |
java.lang.String[] |
getMatchColumnNames()
Retrieves the name of the match column that was set for this RowSet object with the method
setMatchColumn(String columnName) . |
void |
setMatchColumn(int columnIdx)
Sets the designated column as the match column for this RowSet
object. |
void |
setMatchColumn(int[] columnIdxes)
Sets the designated columns as the match column for this RowSet
object. |
void |
setMatchColumn(java.lang.String columnName)
Sets the designated column as the match column for this RowSet
object. |
void |
setMatchColumn(java.lang.String[] columnNames)
Sets the designated columns as the match column for this RowSet
object. |
void |
unsetMatchColumn(int columnIdx)
Unsets the designated column as the match column for this RowSet
object. |
void |
unsetMatchColumn(int[] columnIdxes)
Unsets the designated columns as the match column for this RowSet
object. |
void |
unsetMatchColumn(java.lang.String columnName)
Unsets the designated column as the match column for this RowSet
object. |
void |
unsetMatchColumn(java.lang.String[] columnName)
Unsets the designated columns as the match column for this RowSet
object. |
Method Detail |
public void setMatchColumn(int columnIdx) throws java.sql.SQLException
RowSet
object. A JoinRowSet
object can now add this RowSet
object based on the match column.
Sub-interfaces such as the CachedRowSet
TM
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 column
java.sql.SQLException
- if an invalid column index is setsetMatchColumn(int[])
,
unsetMatchColumn(int)
public void setMatchColumn(int[] columnIdxes) throws java.sql.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 columns
java.sql.SQLException
- if an invalid column index is setsetMatchColumn(int[])
,
unsetMatchColumn(int[])
public void setMatchColumn(java.lang.String columnName) throws java.sql.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(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 column
java.sql.SQLException
- if in invalid column name is set; if the column name
is a null or an empty stringunsetMatchColumn(int)
,
setMatchColumn(int[])
public void setMatchColumn(java.lang.String[] columnNames) throws java.sql.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 columns
java.sql.SQLException
- if in invalid column name is set; if the column name
is a null or an empty stringunsetMatchColumn(int)
,
setMatchColumn(int[])
public int[] getMatchColumnIndexes() throws java.sql.SQLException
RowSet
object with the method
setMatchColumn(int columnIdx)
.
int
identifying the index of the column that was set
as the match column for this RowSet
object
java.sql.SQLException
- if no match column has been setsetMatchColumn(int)
,
unsetMatchColumn(int)
public java.lang.String[] getMatchColumnNames() throws java.sql.SQLException
RowSet
object with the method
setMatchColumn(String columnName)
.
String
object giving the name of the column
set as the match column for this RowSet
object
java.sql.SQLException
- if no match column has been setsetMatchColumn(int)
,
unsetMatchColumn(int)
public void unsetMatchColumn(int columnIdx) throws java.sql.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 column
java.sql.SQLException
- if an invalid column index is designated or if
the designated column was not previously set as a match
columnsetMatchColumn(int)
public void unsetMatchColumn(int[] columnIdxes) throws java.sql.SQLException
RowSet
object.
columnIdxes
- an arrary of int
that identifies the indexes
of the column that are to be unset as a match column
java.sql.SQLException
- if an invalid column index is designated or if
the designated column was not previously set as a match
columnsetMatchColumn(int)
public void unsetMatchColumn(java.lang.String columnName) throws java.sql.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 column
java.sql.SQLException
- if an invalid column name is designated or
the designated column was not previously set as a match
columnsetMatchColumn(int)
public void unsetMatchColumn(java.lang.String[] columnName) throws java.sql.SQLException
RowSet
object.
columnName
- a array String
objects giving the name of
the columns that are to be unset as a match columns
java.sql.SQLException
- if an invalid column name is designated or the
designated column was not previously set as a match columnsetMatchColumn(int)
|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |