tap.formatter

Class JSONFormat

java.lang.Object

tap.formatter.JSONFormat

All Implemented Interfaces:

OutputFormat

public class JSONFormat
extends java.lang.Object
implements OutputFormat

Format any given query (table) result into JSON.

Version:

2.1 (08/2015)

Author:

Grégory Mantelet (CDS;ARI)

Field Summary

Fields

Modifier and Type	Field and Description
protected ServiceConnection	service The ServiceConnection to use (for the log and to have some information about the service (particularly: name, description).

Constructor Summary

Constructors

Constructor and Description
JSONFormat(ServiceConnection service) Build a JSON formatter.

Method Summary

Modifier and Type	Method and Description
java.lang.String	getDescription() Gets a description of this format.
java.lang.String	getFileExtension() Gets a file extension for this format.
java.lang.String	getMimeType() Gets the MIME type corresponding to this format.
java.lang.String	getShortMimeType() Gets a short expression of its MIME type.
protected TAPColumn	getValidColMeta(DBColumn typeFromQuery, TAPColumn typeFromResult) Try to get or otherwise to build appropriate metadata using those extracted from the ADQL query and those extracted from the result.
protected void	writeData(TableIterator result, DBColumn[] selectedColumns, org.json.JSONWriter out, TAPExecutionReport execReport, java.lang.Thread thread) Write the whole data part of the JSON file.
protected void	writeFieldMeta(TAPColumn tapCol, org.json.JSONWriter out) Formats in JSON and writes the given TAPColumn in the given output.
protected void	writeFieldValue(java.lang.Object value, DBColumn column, org.json.JSONWriter out) Writes the given field value in JSON and into the given output.
protected DBColumn[]	writeMetadata(TableIterator result, org.json.JSONWriter out, TAPExecutionReport execReport, java.lang.Thread thread) Write the whole metadata part of the JSON file.
void	writeResult(TableIterator result, java.io.OutputStream output, TAPExecutionReport execReport, java.lang.Thread thread) Formats the given query result and writes it in the given output stream.

Methods inherited from class java.lang.Object

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

Field Detail

service

protected final ServiceConnection service

The ServiceConnection to use (for the log and to have some information about the service (particularly: name, description).

Constructor Detail

JSONFormat

public JSONFormat(ServiceConnection service)
           throws java.lang.NullPointerException

Build a JSON formatter.

Parameters:

service - Description of the TAP service.

Throws:

java.lang.NullPointerException - If the given service connection is null.

Method Detail

getMimeType

public java.lang.String getMimeType()

Description copied from interface: OutputFormat

Gets the MIME type corresponding to this format.

Specified by:

getMimeType in interface OutputFormat

Returns:

Its MIME type (MUST BE DIFFERENT FROM NULL).

getShortMimeType

public java.lang.String getShortMimeType()

Description copied from interface: OutputFormat

Gets a short expression of its MIME type.

Specified by:

getShortMimeType in interface OutputFormat

Returns:

Its short MIME type.

getDescription

public java.lang.String getDescription()

Description copied from interface: OutputFormat

Gets a description of this format.

Specified by:

getDescription in interface OutputFormat

Returns:

Its description.

getFileExtension

public java.lang.String getFileExtension()

Description copied from interface: OutputFormat

Gets a file extension for this format.

Specified by:

getFileExtension in interface OutputFormat

Returns:

Its file extension.

writeResult

public void writeResult(TableIterator result,
                        java.io.OutputStream output,
                        TAPExecutionReport execReport,
                        java.lang.Thread thread)
                 throws TAPException,
                        java.io.IOException,
                        java.lang.InterruptedException

Description copied from interface: OutputFormat

Formats the given query result and writes it in the given output stream.

Note: the given output stream should not be closed at the end of this function. It is up to the called to do it.

Specified by:

writeResult in interface OutputFormat

Parameters:

result - The raw (table) result to format.

output - The output stream (a ServletOutputStream or a stream on a file) in which the formatted result must be written.

execReport - The report of the execution of the TAP query whose the result must be now written.

thread - The thread which has asked the result writing.

Throws:

TAPException - If there is an error while formatting the query result.

java.io.IOException - If any error occurs while writing into the given stream.

java.lang.InterruptedException - If the query has been interrupted/aborted.

writeMetadata

protected DBColumn[] writeMetadata(TableIterator result,
                                   org.json.JSONWriter out,
                                   TAPExecutionReport execReport,
                                   java.lang.Thread thread)
                            throws java.io.IOException,
                                   TAPException,
                                   java.lang.InterruptedException,
                                   org.json.JSONException

Write the whole metadata part of the JSON file.

Parameters:

result - Result to write later (but it contains also metadata that was extracted from the result itself).

out - Output stream in which the metadata must be written.

execReport - Execution report (which contains the metadata extracted/guessed from the ADQL query).

thread - Thread which has asked for this formatting (it must be used in order to test the Thread.isInterrupted() flag and so interrupt everything if need).

Returns:

All the written metadata.

Throws:

java.io.IOException - If there is an error while writing something in the output stream.

java.lang.InterruptedException - If the thread has been interrupted.

org.json.JSONException - If there is an error while formatting something in JSON.

TAPException - If any other error occurs.

See Also:

getValidColMeta(DBColumn, TAPColumn)

getValidColMeta

protected TAPColumn getValidColMeta(DBColumn typeFromQuery,
                                    TAPColumn typeFromResult)

Try to get or otherwise to build appropriate metadata using those extracted from the ADQL query and those extracted from the result.

Parameters:

typeFromQuery - Metadata extracted/guessed from the ADQL query.

typeFromResult - Metadata extracted/guessed from the result.

Returns:

The most appropriate metadata.

writeFieldMeta

protected void writeFieldMeta(TAPColumn tapCol,
                              org.json.JSONWriter out)
                       throws java.io.IOException,
                              TAPException,
                              org.json.JSONException

Formats in JSON and writes the given TAPColumn in the given output.

Parameters:

tapCol - The column metadata to format/write in JSON.

out - The stream in which the formatted column metadata must be written.

Throws:

java.io.IOException - If there is an error while writing the field metadata.

org.json.JSONException - If there is an error while formatting something in JSON format.

TAPException - If there is any other error (by default: never happen).

writeData

protected void writeData(TableIterator result,
                         DBColumn[] selectedColumns,
                         org.json.JSONWriter out,
                         TAPExecutionReport execReport,
                         java.lang.Thread thread)
                  throws java.io.IOException,
                         TAPException,
                         java.lang.InterruptedException,
                         org.json.JSONException

Write the whole data part of the JSON file.

Parameters:

result - Result to write.

selectedColumns - All columns' metadata.

out - Output stream in which the data must be written.

execReport - Execution report (which contains the maximum allowed number of records to output).

thread - Thread which has asked for this formatting (it must be used in order to test the Thread.isInterrupted() flag and so interrupt everything if need).

Throws:

java.io.IOException - If there is an error while writing something in the output stream.

java.lang.InterruptedException - If the thread has been interrupted.

org.json.JSONException - If there is an error while formatting something in JSON.

TAPException - If any other error occurs.

writeFieldValue

protected void writeFieldValue(java.lang.Object value,
                               DBColumn column,
                               org.json.JSONWriter out)
                        throws java.io.IOException,
                               TAPException,
                               org.json.JSONException

Writes the given field value in JSON and into the given output.

note: special numeric values NaN and Inf (double or float) will be written as NULL values.

Parameters:

value - The value to write.

column - The corresponding column metadata.

out - The stream in which the field value must be written.

Throws:

java.io.IOException - If there is an error while writing the given field value in the given stream.

TAPException - If there is any other error (by default: never happen).

org.json.JSONException