uk.ac.starlink.vo

Class TapSchemaInterrogator

java.lang.Object

uk.ac.starlink.vo.TapSchemaInterrogator

public class TapSchemaInterrogator
extends Object

Interrogates the TAP_SCHEMA tables from a TAP service to acquire table metadata information. In the current implementation, synchronous queries are used.

Since:

6 Jun 2011

Author:

Mark Taylor

See Also:

TAP standard

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TapSchemaInterrogator.MetaQuerier<T> Object that can read a certain type of TAP metadata object from a table of a TAP_SCHEMA database table.

Field Summary

Fields

Modifier and Type	Field and Description
static TapSchemaInterrogator.MetaQuerier<ColumnMeta>	COLUMN_QUERIER Acquires ColumnMeta objects from TAP_SCHEMA.columns.
static TapSchemaInterrogator.MetaQuerier<ForeignMeta>	FKEY_QUERIER Acquires ForeignMeta objects from TAP_SCHEMA.keys.
static TapSchemaInterrogator.MetaQuerier<ForeignMeta.Link>	LINK_QUERIER Acquires ForeignMeta.Link objects from TAP_SCHEMA.key_columns.
static TapSchemaInterrogator.MetaQuerier<SchemaMeta>	SCHEMA_QUERIER Acquires SchemaMeta objects from TAP_SCHEMA.schemas.
static TapSchemaInterrogator.MetaQuerier<TableMeta>	TABLE_QUERIER Acquires TableMeta objects from TAP_SCHEMA.tables.

Constructor Summary

Constructors

Constructor and Description
TapSchemaInterrogator(TapService service, int maxrec, ContentCoding coding) Constructs an interrogator with explicit configuration.

Method Summary

Modifier and Type	Method and Description
protected TapQuery	createTapQuery(String adql) Constructs a TAP query for a given ADQL string.
protected StarTable	executeQuery(TapQuery tq) Performs an ADQL TAP query to this interrogator's service.
TapService	getTapService() Returns the TAP service used by this interrogator.
static void	main(String[] args) Prints out metadata content of a given TAP service.
void	populateForeignKey(ForeignMeta fmeta, Map<String,List<ForeignMeta.Link>> lMap) Fills in link information for a ForeignMeta object.
void	populateSchema(SchemaMeta smeta, Map<String,List<TableMeta>> tMap) Fills in table information for a SchemaMeta object.
void	populateTable(TableMeta tmeta, Map<String,List<ForeignMeta>> fMap, Map<String,List<ColumnMeta>> cMap) Fills in foreign key and column information for a TableMeta object, Any relevant entries are removed from the supplied maps.
SchemaMeta[]	queryMetadata() This convenience method returns an array of fully filled in SchemaMeta objects describing the tables available from the service.
<T> List<T>	readList(TapSchemaInterrogator.MetaQuerier<T> mq, String moreAdql) Reads a list of metadata items using a given MetaQuerier object.
<T> Map<String,List<T>>	readMap(TapSchemaInterrogator.MetaQuerier<T> mq, String moreAdql) Reads a map of metadata items using a given MetaQuerier object.
SchemaMeta[]	readSchemas(boolean populateSchemas, boolean populateTables, boolean addOrphanTables) Reads all schemas.

Methods inherited from class java.lang.Object

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

Field Detail

LINK_QUERIER

public static final TapSchemaInterrogator.MetaQuerier<ForeignMeta.Link> LINK_QUERIER

Acquires ForeignMeta.Link objects from TAP_SCHEMA.key_columns. When reading a map, it is keyed by key_id.

FKEY_QUERIER

public static final TapSchemaInterrogator.MetaQuerier<ForeignMeta> FKEY_QUERIER

Acquires ForeignMeta objects from TAP_SCHEMA.keys. When reading a map, it is keyed by from_table.

COLUMN_QUERIER

public static final TapSchemaInterrogator.MetaQuerier<ColumnMeta> COLUMN_QUERIER

Acquires ColumnMeta objects from TAP_SCHEMA.columns. When reading a map, it is keyed by table_name.

TABLE_QUERIER

public static final TapSchemaInterrogator.MetaQuerier<TableMeta> TABLE_QUERIER

Acquires TableMeta objects from TAP_SCHEMA.tables. When reading a map, it is keyed by schema_name.

SCHEMA_QUERIER

public static final TapSchemaInterrogator.MetaQuerier<SchemaMeta> SCHEMA_QUERIER

Acquires SchemaMeta objects from TAP_SCHEMA.schemas. It doesn't read maps.

Constructor Detail

TapSchemaInterrogator

public TapSchemaInterrogator(TapService service,
                             int maxrec,
                             ContentCoding coding)

Constructs an interrogator with explicit configuration.

Parameters:

service - TAP service description

maxrec - maximum number of records to retrieve per query

coding - configures HTTP compression

Method Detail

getTapService

public TapService getTapService()

Returns the TAP service used by this interrogator.

Returns:

TAP service description

queryMetadata

public SchemaMeta[] queryMetadata()
                           throws IOException

This convenience method returns an array of fully filled in SchemaMeta objects describing the tables available from the service.

Returns:

fully populated array of known schemas

Throws:

IOException

readSchemas

public SchemaMeta[] readSchemas(boolean populateSchemas,
                                boolean populateTables,
                                boolean addOrphanTables)
                         throws IOException

Reads all schemas. According to the options, the schemas may or may not have their tables filled in, and those tables may or may not have their columns and foreign key information filled in.

Parameters:

populateSchemas - if true, schemas will contain non-null table lists

populateTables - if true, tables will contain non-null column/key lists (ignored if populateSchemas is false)

addOrphanTables - if true include tables whose schemas are not explicitly declared

Returns:

schema list

Throws:

IOException

readMap

public <T> Map<String,List<T>> readMap(TapSchemaInterrogator.MetaQuerier<T> mq,
                                       String moreAdql)
                                throws IOException

Reads a map of metadata items using a given MetaQuerier object. The key of the map is the name of the parent object of the map value list type. See the documentation of the specific querier object for details.

The form of the basic SELECT statement generated by this call is "SELECT <columns> FROM <table>". If non-null the text of the moreAdql parameter is appended (after a space), so it may be used to qualify the query further.

Parameters:

mq - type-specific querier

moreAdql - additional ADQL text to append after the FROM clause (for example a WHERE clause); may be null

Returns:

map from parent metadata item name to list of metadata items

Throws:

IOException

readList

public <T> List<T> readList(TapSchemaInterrogator.MetaQuerier<T> mq,
                            String moreAdql)
                     throws IOException

Reads a list of metadata items using a given MetaQuerier object.

The form of the basic SELECT statement generated by this call is "SELECT <columns> FROM <table>". If non-null the text of the moreAdql parameter is appended (after a space), so it may be used to qualify the query further.

Parameters:

mq - type-specific querier

moreAdql - additional ADQL text to append after the FROM clause (for example a WHERE clause); may be null

Returns:

list of metadata items

Throws:

IOException

populateForeignKey

public void populateForeignKey(ForeignMeta fmeta,
                               Map<String,List<ForeignMeta.Link>> lMap)

Fills in link information for a ForeignMeta object. Any relevant entries are removed from the supplied map. If the map contains no relevant entries, an empty list is filled in.

Parameters:

fmeta - unpopulated foreign key item

lMap - map acquired using LINK_QUERIER

populateTable

public void populateTable(TableMeta tmeta,
                          Map<String,List<ForeignMeta>> fMap,
                          Map<String,List<ColumnMeta>> cMap)

Fills in foreign key and column information for a TableMeta object, Any relevant entries are removed from the supplied maps. Where the maps contain no relevant entries, an empty list is filled in.

Parameters:

tmeta - unpopulated table metadata item

fMap - map acquired using FKEY_QUERIER

cMap - map acquired using COLUMN_QUERIER

populateSchema

public void populateSchema(SchemaMeta smeta,
                           Map<String,List<TableMeta>> tMap)

Fills in table information for a SchemaMeta object. Any relevant entries are removed from the supplied map. If the map contains no relevant entries, an empty list is filled in.

Parameters:

smeta - unpopulated schema metadata item

tMap - map acquired using TABLE_QUERIER

createTapQuery

protected TapQuery createTapQuery(String adql)

Constructs a TAP query for a given ADQL string. May be overridden.

Parameters:

adql - query text

Returns:

query to execute

executeQuery

protected StarTable executeQuery(TapQuery tq)
                          throws IOException

Performs an ADQL TAP query to this interrogator's service. May be overridden.

Parameters:

tq - tap query

Returns:

output table

Throws:

IOException

main

public static void main(String[] args)
                 throws IOException

Prints out metadata content of a given TAP service.

Parameters:

args - first element is TAP service URL

Throws:

IOException