org.mmbase.storage.search.implementation.database
Class ChainedSqlHandler

java.lang.Object
  org.mmbase.storage.search.implementation.database.ChainedSqlHandler

All Implemented Interfaces:

SqlHandler

Direct Known Subclasses:

EtxSqlHandler

public class ChainedSqlHandler

extends java.lang.Object

implements SqlHandler

Baseclass for chained sql handlers, these are SqlHandler implementations that wrap SqlHandler objects to create a chain of handlers, following the Chain Of Responsibility design pattern.

This class is provided as a baseclass to for chained handlers. It implements all SqlHandler methods by delegating to its successor, i.e. the next handler in the chain.

Since:

MMBase-1.7

Version:

$Id: ChainedSqlHandler.java,v 1.4 2003/03/10 11:50:59 pierre Exp $

Author:

Rob van Maris

See Also:

SqlHandler

Constructor Summary

ChainedSqlHandler(SqlHandler successor)
Creates a new instance of ChainedSqlHandler.

Method Summary

void	appendConstraintToSql(java.lang.StringBuffer sb, Constraint constraint, SearchQuery query, boolean inverse, boolean inComposite) Represents Constraint object, that is not a CompositeConstraint, as a constraint in SQL format, appending the result to a stringbuffer.
void	appendQueryBodyToSql(java.lang.StringBuffer sb, SearchQuery query, SqlHandler firstInChain) Represents body of a SearchQuery object as a string in SQL format, using the database configuration.
java.lang.String	getAllowedValue(java.lang.String value) Maps string to value that is allowed as table or field name.
protected SqlHandler	getSuccessor() Accessor to successor in chain of responsibility.
int	getSupportLevel(Constraint constraint, SearchQuery query) Gets the level at which a constraint is supported for a query by this handler.
int	getSupportLevel(int feature, SearchQuery query) Gets the level at which a feature is supported for a query by this handler.
java.lang.String	toSql(SearchQuery query, SqlHandler firstInChain) Represents a SearchQuery object as a string in SQL format, using the database configuration.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ChainedSqlHandler

public ChainedSqlHandler(SqlHandler successor)

Creates a new instance of ChainedSqlHandler.

Parameters:

successor - Successor in chain of responsibility.

Method Detail

toSql

public java.lang.String toSql(SearchQuery query,
                              SqlHandler firstInChain)
                       throws SearchQueryException

Description copied from interface: SqlHandler

Represents a SearchQuery object as a string in SQL format, using the database configuration.

Specified by:

toSql in interface SqlHandler

Parameters:

query - The searchquery.

firstInChain - The first element in the chain of handlers. At some point appendQueryBodyToSql() will have to be called on this handler, to generate the body of the query.

Returns:

SQL string representation of the query.

Throws:

SearchQueryException

appendQueryBodyToSql

public void appendQueryBodyToSql(java.lang.StringBuffer sb,
                                 SearchQuery query,
                                 SqlHandler firstInChain)
                          throws SearchQueryException

Description copied from interface: SqlHandler

Represents body of a SearchQuery object as a string in SQL format, using the database configuration. Appends this to a stringbuffer.
The body of the SQL query string is defined as the substring containing fields, tables, constraints and orders.

Specified by:

appendQueryBodyToSql in interface SqlHandler

Parameters:

sb - The stringbuffer to append to.

query - The searchquery.

firstInChain - The first element in the chain of handlers. At some point appendConstraintToSql() will have to be called on this handler, to generate the constraints in the query.

Returns:

SQL string representation of the query.

Throws:

SearchQueryException

appendConstraintToSql

public void appendConstraintToSql(java.lang.StringBuffer sb,
                                  Constraint constraint,
                                  SearchQuery query,
                                  boolean inverse,
                                  boolean inComposite)
                           throws SearchQueryException

Description copied from interface: SqlHandler

Represents Constraint object, that is not a CompositeConstraint, as a constraint in SQL format, appending the result to a stringbuffer. When it is part of a composite expression, it will be surrounded by parenthesis when needed.

Specified by:

appendConstraintToSql in interface SqlHandler

Parameters:

sb - The stringbuffer to append to.

constraint - The (non-composite) constraint.

query - The searchquery containing the constraint.

inverse - True when the inverse constraint must be represented, false otherwise.

inComposite - True when the constraint is part of a composite expression.

Throws:

SearchQueryException

getSupportLevel

public int getSupportLevel(int feature,
                           SearchQuery query)
                    throws SearchQueryException

Description copied from interface: SqlHandler

Gets the level at which a feature is supported for a query by this handler. This is one of either:

• SUPPORT_NONE
• SUPPORT_WEAK
• SUPPORT_NORMAL
• SUPPORT_OPTIMAL

Given the choice, the query handler with the highest level of support is prefered.

Specified by:

getSupportLevel in interface SqlHandler

Throws:

SearchQueryException

getSupportLevel

public int getSupportLevel(Constraint constraint,
                           SearchQuery query)
                    throws SearchQueryException

Description copied from interface: SqlHandler

Gets the level at which a constraint is supported for a query by this handler. This is one of either:

• SUPPORT_NONE
• SUPPORT_WEAK
• SUPPORT_NORMAL
• SUPPORT_OPTIMAL

Given the choice, the query handler with the highest level of support is prefered.

Specified by:

getSupportLevel in interface SqlHandler

Throws:

SearchQueryException

getAllowedValue

public java.lang.String getAllowedValue(java.lang.String value)

Description copied from interface: SqlHandler

Maps string to value that is allowed as table or field name.

Specified by:

getAllowedValue in interface SqlHandler

Returns:

The mapped value.

getSuccessor

protected SqlHandler getSuccessor()

Accessor to successor in chain of responsibility.

Returns:

The successor.