uk.ac.starlink.vo

Class DalQuery

java.lang.Object

uk.ac.starlink.vo.DalQuery

public class DalQuery
extends Object

Represents a particular query to a DAL-like service. DAL refers to the the Data Access Layer family of protocols defined by the IVOA.

Since:

2 Feb 2009

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
DalQuery(RegResource resource, RegCapabilityInterface capability, String serviceType, double raPos, double decPos, double size) Constructs a DAL query based on a resource from a registry.
DalQuery(String baseURL, String serviceType, double raPos, double decPos, double size, ContentCoding coding) Constructs a DAL query based on a service URL.

Method Summary

Modifier and Type	Method and Description
void	addArgument(String name, String value) Adds an argument to the query.
String	doubleToString(double value) Encodes a floating point value as a string for use in a DAL query.
StarTable	execute(StarTableFactory tfact) Executes this query synchronously, returning a StarTable which represents the results.
static StarTable	executeQuery(URL qurl, StarTableFactory tfact, ContentCoding coding) Submits a synchronous query to a URL and retrieves the result as a StarTable following standard DAL conventions.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

DalQuery

public DalQuery(RegResource resource,
                RegCapabilityInterface capability,
                String serviceType,
                double raPos,
                double decPos,
                double size)

Constructs a DAL query based on a resource from a registry.

Parameters:

resource - resource describing the DAL service

capability - DAL capability from resource

serviceType - short name for service type; informative, used for error messages etc

raPos - right ascension of ROI center in degrees

decPos - declination of ROI center in degrees

size - ROI size in degrees

DalQuery

public DalQuery(String baseURL,
                String serviceType,
                double raPos,
                double decPos,
                double size,
                ContentCoding coding)

Constructs a DAL query based on a service URL.

Parameters:

baseURL - URL forming basis of CGI query for the DAL service

serviceType - short name for service type; informative, used for error messages etc

raPos - right ascension of ROI center in degrees

decPos - declination of ROI center in degrees

size - size in degrees

coding - controls HTTP-level byte-stream compression

Method Detail

addArgument

public void addArgument(String name,
                        String value)

Adds an argument to the query. No validation is performed to check it is one of the ones that the DAL service knows about.

Parameters:

name - service argument name

value - argument value

execute

public StarTable execute(StarTableFactory tfact)
                  throws IOException

Executes this query synchronously, returning a StarTable which represents the results. If the query resulted in a QUERY_STATUS of ERROR, or if the returned VOTable document is not comprehensible according to the DAL rules, an IOException will be thrown.

Parameters:

tfact - factory which may be used to influence how the table is built

Throws:

IOException - in absence of good data

toString

public String toString()

Overrides:

toString in class Object

doubleToString

public String doubleToString(double value)

Encodes a floating point value as a string for use in a DAL query. There ought to be a definition within the DAL protocols of how to do this. At time of writing there is not, so the current implementation defers to the ad-hoc implementation in CgiQuery.formatDouble(double), which avoids exponential notation except for very large/small values.

Parameters:

value - numeric value

Returns:

string equivalent

executeQuery

public static StarTable executeQuery(URL qurl,
                                     StarTableFactory tfact,
                                     ContentCoding coding)
                              throws IOException

Submits a synchronous query to a URL and retrieves the result as a StarTable following standard DAL conventions.

Parameters:

qurl - query URL

tfact - table factory

coding - encoding to use for communications

Returns:

table included in DAL result resource

Throws:

IOException