uk.ac.ed.inf.utils.database
Class DbReader<T,U>

java.lang.Object
  uk.ac.ed.inf.utils.database.DbManaged
      uk.ac.ed.inf.utils.database.DbReader<T,U>

public class DbReader<T,U>
extends DbManaged

Class to read from a database. For queries: if a set of queries point repeatedly to the same table, or you need table specific information, get a TableReader object.

Version:

20 Feb 2009

Author:

Luna De Ferrari luna.deferrari-at-ed.ac.uk

Constructor Summary

DbReader(DbManager dbManager)

Method Summary

java.sql.ResultSet	executeQuery(java.lang.String sql) Executes an sql query returning a result set.
java.util.AbstractCollection<T>	getColumnValues(java.sql.ResultSet resultSet, int columnIndex, java.util.AbstractCollection<T> collection) Get the nth column of a ResultSet
java.sql.DatabaseMetaData	getDbMetaData()
java.util.TreeSet<java.lang.String>	getListOfDbTables() Gets the list of tables for a database
java.util.TreeMap<java.lang.String,java.lang.String>	getMap(java.lang.String sql) Converts a query resultset into a map.
OneToManyMap<T,U>	getMap(java.lang.String sql, int columnIndexOfKeys, int columnIndexOfValues) Converts a query resultset into a map.
java.sql.Statement	getStatement()
TableReader	getTableReader(java.lang.String table) Object to read from a table
java.util.AbstractCollection<T>	queryResultsColumnToCollection(java.lang.String sql, int columnIndex, java.util.AbstractCollection<T> collection)
java.util.TreeSet<java.lang.String>	queryResultsColumnToSet(java.lang.String sql, int columnIndex) Reduces a query results column to a set (beware: it eliminates duplicates!)
java.util.Vector<T>	queryResultsColumnToVector(java.lang.String sql, int columnIndex)
boolean	tableExistsInDb(java.lang.String tableName) Checks if a table exists in the database

Methods inherited from class uk.ac.ed.inf.utils.database.DbManaged

getDbConnection, getDbManager

Methods inherited from class java.lang.Object

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

Constructor Detail

DbReader

public DbReader(DbManager dbManager)

Method Detail

executeQuery

public java.sql.ResultSet executeQuery(java.lang.String sql)

Executes an sql query returning a result set.

Parameters:

sql - an SQL query

Returns:

a ResultSet with the query results

Throws:

java.sql.SQLException

getColumnValues

public java.util.AbstractCollection<T> getColumnValues(java.sql.ResultSet resultSet,
                                                       int columnIndex,
                                                       java.util.AbstractCollection<T> collection)

Get the nth column of a ResultSet

Parameters:

resultSet -

columnIndex - the column number (starting at 0)

Returns:

the column values

getDbMetaData

public java.sql.DatabaseMetaData getDbMetaData()

getListOfDbTables

public java.util.TreeSet<java.lang.String> getListOfDbTables()

Gets the list of tables for a database

Returns:

a list of table names

getMap

public java.util.TreeMap<java.lang.String,java.lang.String> getMap(java.lang.String sql)

Converts a query resultset into a map. Beware: Null values are discarded both as keys and as values.

Parameters:

sql - the sql query (the first column should be the key and the second column the value)

Returns:

the map with the resultset results

getMap

public OneToManyMap<T,U> getMap(java.lang.String sql,
                                int columnIndexOfKeys,
                                int columnIndexOfValues)

Converts a query resultset into a map. Beware: Null values are discarded both as keys and as values.

Parameters:

sql - the sql query

columnIndexOfKeys - the index for the results column which contains the keys (eg. 0)

columnIndexOfValues - the index for the results column which contains the values (eg. 1)

Returns:

the map with the resultset results

getStatement

public java.sql.Statement getStatement()

getTableReader

public TableReader getTableReader(java.lang.String table)

Object to read from a table

queryResultsColumnToCollection

public java.util.AbstractCollection<T> queryResultsColumnToCollection(java.lang.String sql,
                                                                      int columnIndex,
                                                                      java.util.AbstractCollection<T> collection)

queryResultsColumnToSet

public java.util.TreeSet<java.lang.String> queryResultsColumnToSet(java.lang.String sql,
                                                                   int columnIndex)

Reduces a query results column to a set (beware: it eliminates duplicates!)

Parameters:

sql - a query to extract the columns from database

columnIndex - the index of the column of interest

Returns:

the set of column results

queryResultsColumnToVector

public java.util.Vector<T> queryResultsColumnToVector(java.lang.String sql,
                                                      int columnIndex)

tableExistsInDb

public boolean tableExistsInDb(java.lang.String tableName)

Checks if a table exists in the database

Parameters:

tableName -

Returns:

true if a table with the given name exists in the database