Examples of org.geotools.data.Query

org.geotools.data.Query
Encapsulates a request for data, typically as:
```
 Query query = ... myFeatureSource.getFeatures(query); 
```
The query class is based on the Web Feature Server specification and offers a few interesting capabilities such as the ability to sort results and use a filter (similar to the WHERE clause in SQL).
Additional capabilities:
- {@linkplain #setMaxFeatures(int)} and {@linkplain #setStartIndex(Integer)} can be usedimplement 'paging' through the data source's content. This is useful if, for example, the FeatureSource has an upper limit on the number of features it can return in a single request or you are working with limited memory.
- {@linkplain #setHandle(String)} can be used to give the query a mnemonic namewhich will appear in error reporing and logs.
- {@linkplain #setCoordinateSystem(CoordinateReferenceSystem)} is used to to specify thecoordinate system that retrieved features will be "forced" into. This is often used to correct a feature source when the application and the data format have different ideas about the coordinate system (for example, the "axis order" issue).
- {@linkplain #setCoordinateSystemReproject(CoordinateReferenceSystem)} is used to ask forthe retrieved features to be reproejcted.
Vendor specific:
- {@linkplain setHints(Hints)} is used to specify venfor specific capabilitiesprovided by a feature source implementation.
Joins:
The Query class supports the concepts of joins in that a query can result in a join of the feature type to other feature types in the same datastore. For example, the following would be a spatial join that selected the country that contain a particular city.
```
 Query query = new Query("countries"); Join join = new Join("cities", CQL.toFilter("CONTAINS(geometry, b.geometry)")); join.setAlias("b"); join.setFilter(CQL.toFilter("CITY_NAME = 'Canmore'")) query.getJoins().add(join); 
```
Example:
```
 Filter filter = CQL.toFilter("NAME like '%land'"); Query query = new Query( "countries", filter ); FeatureCollection features = featureSource.getFeatures( query ); 
```
@author Chris Holmes @source $URL$ @version $Id$

            SimpleFeatureSource featureSource = store.getFeatureSource();


            CoordinateReferenceSystem sourceCRS = featureSource.getInfo().getCRS();
            CoordinateReferenceSystem WGS84 = CRS.decode("EPSG:4326", true);


            Query query = new Query();
            query.setCoordinateSystem(sourceCRS);
            query.setCoordinateSystemReproject(WGS84);
            SimpleFeatureCollection featureCollection = featureSource.getFeatures(query);


            SimpleFeatureIterator it = featureCollection.features();
            int i = 0;
            while (it.hasNext()) {

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        }
        final String defaultGeomAttName = geometryDescriptor.getLocalName();


        // we're calculating the bounds, so we'd better be sure and add the
        // spatial column to the query's propertynames
        final Query realQuery = new Query(query);
        realQuery.setPropertyNames(new String[] { defaultGeomAttName });


        final ArcSDEQuery boundsQuery;


        if (typeInfo.isInProcessView()) {
            final SeQueryInfo definitionQuery = typeInfo.getSdeDefinitionQuery();

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        log("Testing feature source");
        final SimpleFeatureType schema = fs.getSchema();
        final String typeName = schema.getTypeName();
        final String spatialColName = schema.getGeometryDescriptor().getLocalName();


        Query query = new Query(typeName, Filter.INCLUDE, new String[] { spatialColName });
        long runTime = 0;
        for (int run = 0; run < numRuns; run++) {
            runTime += iterate(fs, query);
        }
        double avg = runTime / numRuns;

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        log("-----------------------------------------------------");
        log("Testing feature source without geometry");
        DataStore ds = testData.getDataStore();
        SimpleFeatureSource fs = ds.getFeatureSource(typeName);
        try {
            Query query = new Query(typeName, Filter.INCLUDE, new String[] { "TOWN_ID" });
            long runTime = 0;
            for (int run = 0; run < numRuns; run++) {
                runTime += iterate(fs, query);
            }
            double avg = runTime / numRuns;

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        for (int i = 0; i < queryAtts.length; i++) {
            queryAtts[i] = schema.getDescriptor(i).getLocalName();
        }


        // build the query asking for a subset of attributes
        final Query query = new Query(typeName, Filter.INCLUDE, queryAtts);


        FeatureReader<SimpleFeatureType, SimpleFeature> reader;
        reader = ds.getFeatureReader(query, Transaction.AUTO_COMMIT);
        SimpleFeatureType resultSchema;
        try {

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            --i;
            queryAtts[j] = schema.getDescriptor(i).getLocalName();
        }


        // build the query asking for a subset of attributes
        final Query query = new Query(typeName, Filter.INCLUDE, queryAtts);


        FeatureReader<SimpleFeatureType, SimpleFeature> reader;
        reader = ds.getFeatureReader(query, Transaction.AUTO_COMMIT);
        try {

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        final String[] queryAtts = { "SHAPE" };
        final Filter filter = CQL.toFilter("INT32_COL = 1");


        // build the query asking for a subset of attributes
        final Query query = new Query(typeName, filter, queryAtts);


        SimpleFeatureCollection features = fs.getFeatures(query);
        SimpleFeatureType resultSchema = features.getSchema();


        assertEquals(1, resultSchema.getAttributeCount());

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        return false;
    }


    private FeatureReader<SimpleFeatureType, SimpleFeature> getReader(String typeName)
            throws IOException {
        Query q = new Query(typeName, Filter.INCLUDE);
        FeatureReader<SimpleFeatureType, SimpleFeature> reader = store.getFeatureReader(q,
                Transaction.AUTO_COMMIT);
        SimpleFeatureType retType = reader.getFeatureType();
        assertNotNull(retType.getGeometryDescriptor());
        assertTrue(reader.hasNext());

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    @Test
    public void testAttributeOnlyQuery() throws Exception {
        DataStore ds = testData.getDataStore();
        SimpleFeatureSource fSource = ds.getFeatureSource(testData.getTempTableName());
        SimpleFeatureType type = fSource.getSchema();
        Query attOnlyQuery = new Query(type.getTypeName());
        List<String> propNames = new ArrayList<String>(type.getAttributeCount() - 1);


        for (int i = 0; i < type.getAttributeCount(); i++) {
            if (type.getDescriptor(i) instanceof GeometryDescriptor) {
                continue;
            }


            propNames.add(type.getDescriptor(i).getLocalName());
        }


        attOnlyQuery.setPropertyNames(propNames);


        SimpleFeatureCollection results = fSource.getFeatures(attOnlyQuery);
        SimpleFeatureType resultSchema = results.getSchema();
        assertEquals(propNames.size(), resultSchema.getAttributeCount());

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    public void testFidFilters() throws Exception {
        final DataStore ds = testData.getDataStore();
        final String typeName = testData.getTempTableName();


        // grab some fids
        FeatureReader<SimpleFeatureType, SimpleFeature> reader = ds.getFeatureReader(new Query(
                typeName), Transaction.AUTO_COMMIT);
        List<FeatureId> fids = new ArrayList<FeatureId>();


        while (reader.hasNext()) {
            fids.add(ff.featureId(reader.next().getID()));


            // skip one
            if (reader.hasNext()) {
                reader.next();
            }
        }


        reader.close();


        Id filter = ff.id(new HashSet<FeatureId>(fids));


        SimpleFeatureSource source = ds.getFeatureSource(typeName);
        Query query = new Query(typeName, filter);
        SimpleFeatureCollection results = source.getFeatures(query);


        assertEquals(fids.size(), results.size());
        SimpleFeatureIterator iterator = results.features();
        try {

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