org.apache.torque.adapter
Class AbstractAdapter

java.lang.Object
  extended by org.apache.torque.adapter.AbstractAdapter
All Implemented Interfaces:
Serializable, Adapter
Direct Known Subclasses:
DerbyAdapter, HsqldbAdapter, MssqlAdapter, MysqlAdapter, NoneAdapter, OracleAdapter, PostgresAdapter

public abstract class AbstractAdapter
extends Object
implements Adapter

This class is the abstract base for any database adapter Support for new databases is added by subclassing this class and implementing its abstract methods, and by registering the new database adapter and its corresponding JDBC driver in the service configuration file.

The Torque database adapters exist to present a uniform interface to database access across all available databases. Once the necessary adapters have been written and configured, transparent swapping of databases is theoretically supported with zero code changes and minimal configuration file modifications.

Version:
$Id: AbstractAdapter.java 1450486 2013-02-26 22:18:00Z tfischer $
Author:
Jon S. Stevens, Brett McLaughlin, Daniel Rall, Augustin Vidovic, Greg Monroe
See Also:
Serialized Form

Field Summary
 
Fields inherited from interface org.apache.torque.adapter.Adapter
ADAPTER_KEY, AUTODETECT_ADAPTER, DRIVER_KEY
 
Constructor Summary
protected AbstractAdapter()
          Empty constructor.
 
Method Summary
 boolean escapeText()
          This method is for the SqlExpression.quoteAndEscape rules.
 void generateLimits(Query query, long offset, int limit)
          This method is used to generate the database specific query extension to limit the number of record returned.
abstract  String getIDMethodSQL(Object obj)
          Returns SQL used to get the most recently inserted primary key.
abstract  IDMethod getIDMethodType()
          Returns the constant from the IDMethod interface denoting which type of primary key generation method this type of RDBMS uses.
 char getStringDelimiter()
          Returns the character used to indicate the beginning and end of a piece of text used in a SQL statement (generally a single quote).
 String getUpdateLockClause()
          Returns the clause which acquires a write lock on a row when doing a select.
abstract  String ignoreCase(String in)
          Wraps the input string in a database function to change it to a case-insensitive representation.
 String ignoreCaseInOrderBy(String in)
          This method is used to ignore case in an ORDER BY clause.
abstract  void lockTable(Connection con, String table)
          Locks the specified table.
 boolean supportsNativeLimit()
          Returns whether the database can natively limit the size of the ResultSet of a query.
 boolean supportsNativeOffset()
          Returns whether the database natively supports returning results starting at an offset position other than 0.
abstract  String toUpperCase(String in)
          Wraps the input string in a database function to change it to upper case.
abstract  void unlockTable(Connection con, String table)
          Unlocks the specified table.
 boolean useEscapeClauseForLike()
          Whether an escape clause in like should be used.
 boolean useIlike()
          Whether ILIKE should be used for case insensitive like clauses.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

AbstractAdapter

protected AbstractAdapter()
Empty constructor.

Method Detail

toUpperCase

public abstract String toUpperCase(String in)
Wraps the input string in a database function to change it to upper case.

Specified by:
toUpperCase in interface Adapter
Parameters:
in - The string to transform to upper case, may be a literal string, a prepared statement replacement placeholder(*) or any other database expression.
Returns:
The wrapped input string, so that the database evaluates the returned expression to the upper case of the input.

getStringDelimiter

public char getStringDelimiter()
Returns the character used to indicate the beginning and end of a piece of text used in a SQL statement (generally a single quote).

Specified by:
getStringDelimiter in interface Adapter
Returns:
The text delimiter.

getIDMethodType

public abstract IDMethod getIDMethodType()
Returns the constant from the IDMethod interface denoting which type of primary key generation method this type of RDBMS uses.

Specified by:
getIDMethodType in interface Adapter
Returns:
IDMethod constant

getIDMethodSQL

public abstract String getIDMethodSQL(Object obj)
Returns SQL used to get the most recently inserted primary key. Databases which have no support for this return null.

Specified by:
getIDMethodSQL in interface Adapter
Parameters:
obj - Information used for key generation.
Returns:
The most recently inserted database key.

getUpdateLockClause

public String getUpdateLockClause()
Returns the clause which acquires a write lock on a row when doing a select.

Specified by:
getUpdateLockClause in interface Adapter
Returns:
the SQL clause to acquire a write lock. This implementation returns "FOR UPDATE";

lockTable

public abstract void lockTable(Connection con,
                               String table)
                        throws SQLException
Locks the specified table.

Specified by:
lockTable in interface Adapter
Parameters:
con - The JDBC connection to use.
table - The name of the table to lock.
Throws:
SQLException - No Statement could be created or executed.

unlockTable

public abstract void unlockTable(Connection con,
                                 String table)
                          throws SQLException
Unlocks the specified table.

Specified by:
unlockTable in interface Adapter
Parameters:
con - The JDBC connection to use.
table - The name of the table to unlock.
Throws:
SQLException - No Statement could be created or executed.

ignoreCase

public abstract String ignoreCase(String in)
Wraps the input string in a database function to change it to a case-insensitive representation.

Specified by:
ignoreCase in interface Adapter
Parameters:
in - The string to transform to a case-insensitive representation, may be a literal string, a prepared statement replacement placeholder(*) or any other database expression.
Returns:
The wrapped input string, so that the database evaluates the returned expression to a case-insensitive representation of the input.

ignoreCaseInOrderBy

public String ignoreCaseInOrderBy(String in)
This method is used to ignore case in an ORDER BY clause. Usually it is the same as ignoreCase, but some databases (hsqldb for example) do not use the same SQL in ORDER BY and other clauses.

Specified by:
ignoreCaseInOrderBy in interface Adapter
Parameters:
in - The string whose case to ignore.
Returns:
The string in a case that can be ignored.

supportsNativeLimit

public boolean supportsNativeLimit()
Returns whether the database can natively limit the size of the ResultSet of a query.

Specified by:
supportsNativeLimit in interface Adapter
Returns:
true if the database natively supports limiting the size of the resultset.

supportsNativeOffset

public boolean supportsNativeOffset()
Returns whether the database natively supports returning results starting at an offset position other than 0.

Specified by:
supportsNativeOffset in interface Adapter
Returns:
true if the database natively supports returning results starting at an offset position other than 0.

generateLimits

public void generateLimits(Query query,
                           long offset,
                           int limit)
                    throws TorqueException
This method is used to generate the database specific query extension to limit the number of record returned.

Specified by:
generateLimits in interface Adapter
Parameters:
query - The query to modify
offset - the offset Value
limit - the limit Value
Throws:
TorqueException - if any error occurs when building the query

escapeText

public boolean escapeText()
This method is for the SqlExpression.quoteAndEscape rules. The rule is, any string in a SqlExpression with a BACKSLASH will either be changed to "\\" or left as "\".

Specified by:
escapeText in interface Adapter
Returns:
true if the database needs to escape text in SqlExpressions.

useIlike

public boolean useIlike()
Whether ILIKE should be used for case insensitive like clauses. As most databases do not use ILIKE, this implementation returns false. This behaviour may be overwritten in subclasses.

Specified by:
useIlike in interface Adapter
Returns:
true if ilike should be used for case insensitive likes, false if ignoreCase should be applied to the compared strings.

useEscapeClauseForLike

public boolean useEscapeClauseForLike()
Whether an escape clause in like should be used. Example : select * from AUTHOR where AUTHOR.NAME like '\_%' ESCAPE '\'; As most databases do not need the escape clause, this implementation always returns false. This behaviour can be overwritten in subclasses.

Specified by:
useEscapeClauseForLike in interface Adapter
Returns:
whether the escape clause should be appended or not.


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