net.cds
Class CDSParser

java.lang.Object
  net.cds.CDSParser

Direct Known Subclasses:

NameResolver, Vizier

public abstract class CDSParser
extends Object

A base class for all xml-cds retrieval queries. Provides a common dom-parser and a simple caching mechansim. The interaction with the daughter classes is a little bit confusing, therefore here is the path of a query.

• The main entry point is any of the daughters get... methods, like the NameResolver.getResolver(java.lang.String) class.
• To ease access, the daughter class checks, if the arguments supplied to the get... method equal the last retrieval. As the number and format of these arguments is daughter-specific, normally the checkCache(java.util.List) method will not be called directly, but via a (private) method like Vizier.checkArguments(java.lang.String, double, java.lang.String, java.lang.String).
• This daughter class method will convert the arguments into a List and pass this on to checkCache(java.util.List).
• If the cache needs an update, the main CDS-parser class calls the abstract query(java.util.List) method with the List of arguments supplied to the checkCache(java.util.List) method.
• Now, control is again transfered to the daughter class that implements the query(java.util.List) method. The daughter class calls the remote CDS service and returns the result (which is in XML-format) to the CDS-parser class.
• The CDS-parser now converts the XML-string into a parsed DOM using its dom parser reference.
• Daughter classes may now retrieve the parsed DOM with the getParsed() method. Interpretation of the DOM is again transfered to the daughter class, e.g. the NameResolver.getResolver(java.lang.String) returns the CDSConstants.RESOLVERNAME attribute to the CDSConstants.RESOLVER element.

This software uses source code created at the Centre de Donn�es astronomiques de Strasbourg, France.

Field Summary

private static DocumentBuilder	dom The document builder for parsing the sesam output into a DOM.
private static boolean	EXPAND The entity-expanding flag.
private List<Object>	lastquery The last query performed, for simple caching.
private Document	parsed The dom parsed out of the last query.
private static boolean	VALIDATE The validating flag.
private static boolean	WHITESPACE The whitespace-ignoring flag.

Constructor Summary

CDSParser()

Method Summary

protected boolean	checkCache(List<Object> target) Checks, if the actual query was already processed.
protected Document	getParsed() Returns the parsed result.
protected abstract boolean	isRetrievable() Returns false if the remote service is not available.
protected abstract String	query(List<Object> args) This is the generic method to access a CDS service.

Methods inherited from class java.lang.Object

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

Field Detail

dom

private static DocumentBuilder dom

The document builder for parsing the sesam output into a DOM.

VALIDATE

private static final boolean VALIDATE

The validating flag.

See Also:

Constant Field Values

WHITESPACE

private static final boolean WHITESPACE

The whitespace-ignoring flag.

See Also:

Constant Field Values

EXPAND

private static final boolean EXPAND

The entity-expanding flag.

See Also:

Constant Field Values

lastquery

private List<Object> lastquery

The last query performed, for simple caching.

parsed

private Document parsed

The dom parsed out of the last query.

Constructor Detail

CDSParser

public CDSParser()

Method Detail

query

protected abstract String query(List<Object> args)

This is the generic method to access a CDS service. The implementing class must know how to convert the argument list to the specific AXIS call.
Note that this implementation only work with single query calls.

isRetrievable

protected abstract boolean isRetrievable()

Returns false if the remote service is not available.

getParsed

protected Document getParsed()

Returns the parsed result.

checkCache

protected boolean checkCache(List<Object> target)

Checks, if the actual query was already processed. If not, the newly returned DOM is parsed into parsed.

Returns:

True, if parsed is ready for retrieval.