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[FEATURE] New class QgsJSONUtils with utilities for converting
features to and from GeoJSON strings Sponsored by Kanton of Zug, Switzerland
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,58 @@ | ||
| /** \ingroup core | ||
| * \class QgsJSONUtils | ||
| * \brief Helper utilities for working with JSON and GeoJSON conversions. | ||
| * \note Added in version 2.16 | ||
| */ | ||
|
|
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| class QgsJSONUtils | ||
| { | ||
| %TypeHeaderCode | ||
| #include <qgsjsonutils.h> | ||
| %End | ||
|
|
||
| public: | ||
|
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| /** Attempts to parse a GeoJSON string to a collection of features. | ||
| * @param string GeoJSON string to parse | ||
| * @param fields fields collection to use for parsed features | ||
| * @param encoding text encoding | ||
| * @returns list of parsed features, or an empty list if no features could be parsed | ||
| * @see stringToFields() | ||
| * @note this function is a wrapper around QgsOgrUtils::stringToFeatureList() | ||
| */ | ||
| static QgsFeatureList stringToFeatureList( const QString& string, const QgsFields& fields, QTextCodec* encoding ); | ||
|
|
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| /** Attempts to retrieve the fields from a GeoJSON string representing a collection of features. | ||
| * @param string GeoJSON string to parse | ||
| * @param encoding text encoding | ||
| * @returns retrieved fields collection, or an empty list if no fields could be determined from the string | ||
| * @see stringToFeatureList() | ||
| * @note this function is a wrapper around QgsOgrUtils::stringToFields() | ||
| */ | ||
| static QgsFields stringToFields( const QString& string, QTextCodec* encoding ); | ||
|
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| /** Returns a GeoJSON string representation of a feature. | ||
| * @param feature feature to convert | ||
| * @param precision maximum number of decimal places to use for geometry coordinates | ||
| * @param attrIndexes list of attribute indexes to include in GeoJSON, or an empty list to include | ||
| * all attributes | ||
| * @param includeGeom set to false to avoid including the geometry representation in the JSON output | ||
| * @param includeAttributes set to false to avoid including any attribute values in the JSON output | ||
| * @param id optional ID to use as GeoJSON feature's ID instead of input feature's ID. If omitted, feature's | ||
| * ID is used. | ||
| * @returns GeoJSON string | ||
| */ | ||
| static QString featureToGeoJSON( const QgsFeature& feature, | ||
| int precision = 17, | ||
| const QgsAttributeList& attrIndexes = QgsAttributeList(), | ||
| bool includeGeom = true, | ||
| bool includeAttributes = true, | ||
| const QVariant& id = QVariant() ); | ||
|
|
||
| /** Encodes a value to a JSON string representation, adding appropriate quotations and escaping | ||
| * where required. | ||
| * @param value value to encode | ||
| * @returns encoded value | ||
| */ | ||
| static QString encodeValue( const QVariant& value ); | ||
| }; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,121 @@ | ||
| /*************************************************************************** | ||
| qgsjsonutils.h | ||
| ------------- | ||
| Date : May 206 | ||
| Copyright : (C) 2016 Nyall Dawson | ||
| Email : nyall dot dawson at gmail dot com | ||
| *************************************************************************** | ||
| * * | ||
| * This program is free software; you can redistribute it and/or modify * | ||
| * it under the terms of the GNU General Public License as published by * | ||
| * the Free Software Foundation; either version 2 of the License, or * | ||
| * (at your option) any later version. * | ||
| * * | ||
| ***************************************************************************/ | ||
|
|
||
| #include "qgsjsonutils.h" | ||
| #include "qgsogrutils.h" | ||
| #include "qgsgeometry.h" | ||
|
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| QgsFeatureList QgsJSONUtils::stringToFeatureList( const QString &string, const QgsFields &fields, QTextCodec *encoding ) | ||
| { | ||
| return QgsOgrUtils::stringToFeatureList( string, fields, encoding ); | ||
| } | ||
|
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| QgsFields QgsJSONUtils::stringToFields( const QString &string, QTextCodec *encoding ) | ||
| { | ||
| return QgsOgrUtils::stringToFields( string, encoding ); | ||
| } | ||
|
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| QString QgsJSONUtils::featureToGeoJSON( const QgsFeature& feature, | ||
| int precision, | ||
| const QgsAttributeList& attrIndexes, | ||
| bool includeGeom, | ||
| bool includeAttributes, | ||
| const QVariant& id ) | ||
| { | ||
| QString s = "{\n \"type\":\"Feature\",\n"; | ||
|
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| // ID | ||
| s += QString( " \"id\":%1" ).arg( !id.isValid() ? QString::number( feature.id() ) : encodeValue( id ) ); | ||
|
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| if ( includeAttributes || includeGeom ) | ||
| s += ",\n"; | ||
| else | ||
| s += '\n'; | ||
|
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| const QgsGeometry* geom = feature.constGeometry(); | ||
| if ( geom && !geom->isEmpty() && includeGeom ) | ||
| { | ||
| QgsRectangle box = geom->boundingBox(); | ||
|
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| if ( QgsWKBTypes::flatType( geom->geometry()->wkbType() ) != QgsWKBTypes::Point ) | ||
| { | ||
| s += QString( " \"bbox\":[%1, %2, %3, %4],\n" ).arg( qgsDoubleToString( box.xMinimum(), precision ), | ||
| qgsDoubleToString( box.yMinimum(), precision ), | ||
| qgsDoubleToString( box.xMaximum(), precision ), | ||
| qgsDoubleToString( box.yMaximum(), precision ) ); | ||
| } | ||
| s += " \"geometry\":\n "; | ||
| s += geom->exportToGeoJSON( precision ); | ||
| if ( includeAttributes ) | ||
| s += ",\n"; | ||
| else | ||
| s += '\n'; | ||
| } | ||
|
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| if ( includeAttributes ) | ||
| { | ||
| //read all attribute values from the feature | ||
| s += " \"properties\":{\n"; | ||
|
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| const QgsFields* fields = feature.fields(); | ||
| int attributeCounter = 0; | ||
|
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| for ( int i = 0; i < fields->count(); ++i ) | ||
| { | ||
| if ( !attrIndexes.isEmpty() && !attrIndexes.contains( i ) ) | ||
| continue; | ||
|
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| if ( attributeCounter > 0 ) | ||
| s += ",\n"; | ||
| QVariant val = feature.attributes().at( i ); | ||
|
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| s += QString( " \"%1\":%2" ).arg( fields->at( i ).name(), encodeValue( val ) ); | ||
|
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| ++attributeCounter; | ||
| } | ||
|
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| s += "\n }\n"; | ||
| } | ||
|
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| s += "}"; | ||
|
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| return s; | ||
| } | ||
|
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| QString QgsJSONUtils::encodeValue( const QVariant &value ) | ||
| { | ||
| if ( value.isNull() ) | ||
| return "null"; | ||
|
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| switch ( value.type() ) | ||
| { | ||
| case QVariant::Int: | ||
| case QVariant::UInt: | ||
| case QVariant::LongLong: | ||
| case QVariant::ULongLong: | ||
| case QVariant::Double: | ||
| return value.toString(); | ||
|
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| case QVariant::Bool: | ||
| return value.toBool() ? "true" : "false"; | ||
|
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| default: | ||
| case QVariant::String: | ||
| QString v = value.toString().replace( '"', "\\\"" ) | ||
| .replace( '\r', "\\r" ) | ||
| .replace( '\n', "\\n" ); | ||
| return v.prepend( '"' ).append( '"' ); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| /*************************************************************************** | ||
| qgsjsonutils.h | ||
| ------------- | ||
| Date : May 206 | ||
| Copyright : (C) 2016 Nyall Dawson | ||
| Email : nyall dot dawson at gmail dot com | ||
| *************************************************************************** | ||
| * * | ||
| * This program is free software; you can redistribute it and/or modify * | ||
| * it under the terms of the GNU General Public License as published by * | ||
| * the Free Software Foundation; either version 2 of the License, or * | ||
| * (at your option) any later version. * | ||
| * * | ||
| ***************************************************************************/ | ||
|
|
||
| #ifndef QGSJSONUTILS_H | ||
| #define QGSJSONUTILS_H | ||
|
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| #include "qgsfeature.h" | ||
|
|
||
| class QTextCodec; | ||
|
|
||
| /** \ingroup core | ||
| * \class QgsJSONUtils | ||
| * \brief Helper utilities for working with JSON and GeoJSON conversions. | ||
| * \note Added in version 2.16 | ||
| */ | ||
|
|
||
| class CORE_EXPORT QgsJSONUtils | ||
| { | ||
| public: | ||
|
|
||
| /** Attempts to parse a GeoJSON string to a collection of features. | ||
| * @param string GeoJSON string to parse | ||
| * @param fields fields collection to use for parsed features | ||
| * @param encoding text encoding | ||
| * @returns list of parsed features, or an empty list if no features could be parsed | ||
| * @see stringToFields() | ||
| * @note this function is a wrapper around QgsOgrUtils::stringToFeatureList() | ||
| */ | ||
| static QgsFeatureList stringToFeatureList( const QString& string, const QgsFields& fields, QTextCodec* encoding ); | ||
|
|
||
| /** Attempts to retrieve the fields from a GeoJSON string representing a collection of features. | ||
| * @param string GeoJSON string to parse | ||
| * @param encoding text encoding | ||
| * @returns retrieved fields collection, or an empty list if no fields could be determined from the string | ||
| * @see stringToFeatureList() | ||
| * @note this function is a wrapper around QgsOgrUtils::stringToFields() | ||
| */ | ||
| static QgsFields stringToFields( const QString& string, QTextCodec* encoding ); | ||
|
|
||
| /** Returns a GeoJSON string representation of a feature. | ||
| * @param feature feature to convert | ||
| * @param precision maximum number of decimal places to use for geometry coordinates | ||
| * @param attrIndexes list of attribute indexes to include in GeoJSON, or an empty list to include | ||
| * all attributes | ||
| * @param includeGeom set to false to avoid including the geometry representation in the JSON output | ||
| * @param includeAttributes set to false to avoid including any attribute values in the JSON output | ||
| * @param id optional ID to use as GeoJSON feature's ID instead of input feature's ID. If omitted, feature's | ||
| * ID is used. | ||
| * @returns GeoJSON string | ||
| */ | ||
| static QString featureToGeoJSON( const QgsFeature& feature, | ||
| int precision = 17, | ||
| const QgsAttributeList& attrIndexes = QgsAttributeList(), | ||
| bool includeGeom = true, | ||
| bool includeAttributes = true, | ||
| const QVariant& id = QVariant() ); | ||
|
|
||
| /** Encodes a value to a JSON string representation, adding appropriate quotations and escaping | ||
| * where required. | ||
| * @param value value to encode | ||
| * @returns encoded value | ||
| */ | ||
| static QString encodeValue( const QVariant& value ); | ||
|
|
||
| }; | ||
|
|
||
| #endif // QGSJSONUTILS_H |
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