uk.ac.starlink.vo.datalink

Class ServiceInvoker

java.lang.Object

uk.ac.starlink.vo.datalink.ServiceInvoker

public class ServiceInvoker
extends Object

Provides functionality related to invoking a service defined by a DataLink document. It is based on a ServiceDescriptor.

This class divides the input ServiceParams defined by the ServiceDescriptor into three different categories according to how their values are acquired at service invocation time:

• row parameters: the value is acquired from a cell of the result table; a table row object must be supplied to obtain the value
• fixed parameters: the value is provided by the parameter definition and fixed for all invocations
• user parameters: the value must be supplied for each invocation by the user

The DataLink-1.0 standard is not very explicit about this distinction, but the above division appears(?) to be the consensus of the standard authors. This does not however prevent service invocations filling these parameter values differently than according to the above outline. For instance, users may be given the option to change the values of fixed or row parameters for a given invocation.

Since:

22 Nov 2017

Author:

Mark Taylor

See Also:

DataLink-1.0, sec 4

Constructor Summary

Constructors

Constructor and Description
ServiceInvoker(ServiceDescriptor descriptor, StarTable resultTable) Attempts to construct an invoker based on a service descriptor and an associated results table.

Method Summary

Modifier and Type	Method and Description
URL	completeUrl(Map<ServiceParam,String> paramMap) Assembles an invocation URL from the base URL of this service and any name-value pairs supplied in a given map.
Map<ServiceParam,String>	getFixedParamMap() Returns a parameter-value map for the fixed parameters.
ServiceParam[]	getFixedParams() Returns the 'fixed' parameters of this service.
Map<ServiceParam,String>	getRowParamMap(Object[] row) Constructs a parameter-value map for the row parameters at a given table row.
ServiceParam[]	getRowParams() Returns the 'row' parameters of this service.
ServiceDescriptor	getServiceDescriptor() Returns this invoker's service descriptor.
URL	getUrl(Object[] row, Map<ServiceParam,String> userParamMap) Assembles an invocation URL from the base URL of this service, the values of any row parameters corresponding to a supplied table row, and any additional parameters supplied explicitly.
ServiceParam[]	getUserParams() Returns the 'user' parameters of this service.

Methods inherited from class java.lang.Object

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

Constructor Detail

ServiceInvoker

public ServiceInvoker(ServiceDescriptor descriptor,
                      StarTable resultTable)
               throws MalformedURLException,
                      IOException

Attempts to construct an invoker based on a service descriptor and an associated results table.

Parameters:

descriptor - service descriptor

resultTable - result table corresponding to the descriptor

Throws:

MalformedURLException - if the descriptor's accessUrl is no good

IOException - if the descriptor references a column that is not present in the result table

Method Detail

getServiceDescriptor

public ServiceDescriptor getServiceDescriptor()

Returns this invoker's service descriptor.

Returns:

service descriptor

getRowParams

public ServiceParam[] getRowParams()

Returns the 'row' parameters of this service. These take their values from one of the columns in the results table.

Returns:

list of 'row' parameters

getFixedParams

public ServiceParam[] getFixedParams()

Returns the 'fixed' parameters of this service. These have fixed values supplied in the parameter definitions.

Returns:

list of 'fixed' parameters

getUserParams

public ServiceParam[] getUserParams()

Returns the 'user' parameters of this service. The values for these must to be supplied externally in some unspecified way (for instance by user action). They may have some hints in the form of options or min/max values.

Returns:

list of 'user' parameters

getFixedParamMap

public Map<ServiceParam,String> getFixedParamMap()

Returns a parameter-value map for the fixed parameters.

Returns:

map containing fixed parameter-value pairs

getRowParamMap

public Map<ServiceParam,String> getRowParamMap(Object[] row)

Constructs a parameter-value map for the row parameters at a given table row.

Parameters:

row - a row of cell values from this invoker's table

Returns:

map containing row parameter-value pairs

completeUrl

public URL completeUrl(Map<ServiceParam,String> paramMap)

Assembles an invocation URL from the base URL of this service and any name-value pairs supplied in a given map. Values are appended in the form "?n1=v1&n2=v2".

Parameters:

paramMap - map representing parameter values to be appended to this service's base URL

Returns:

base URL with supplied parameter name-value pairs appended

getUrl

public URL getUrl(Object[] row,
                  Map<ServiceParam,String> userParamMap)

Assembles an invocation URL from the base URL of this service, the values of any row parameters corresponding to a supplied table row, and any additional parameters supplied explicitly.

This utility method calls the methods getRowParamMap, getFixedParamMap and completeUrl.

Parameters:

row - table row

userParamMap - additional non-'row' parameter-value pairs, usually corresponding to the 'user' parameters

Returns:

base URL with row and user name-value pairs appended