Java tutorial
/* Copyright 2013 Red Hat, Inc. and/or its affiliates. This file is part of lightblue. 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 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ package com.redhat.lightblue.query; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.node.ArrayNode; import com.fasterxml.jackson.databind.node.ObjectNode; import com.redhat.lightblue.util.Error; import com.redhat.lightblue.util.Path; /** * Base class for field and array projections */ public abstract class BasicProjection extends Projection { private static final long serialVersionUID = 1L; /** * Parses a field or array projection from the given json object */ public static BasicProjection fromJson(ObjectNode node) { String field = node.get("field").asText(); if (field == null) { throw Error.get(QueryConstants.ERR_INVALID_PROJECTION, "field"); } Path path = getNonRelativePath(new Path(field)); // Processing of optional elements. We decide on the type of // the final object based on what fields this object has JsonNode x = node.get("include"); boolean include; if (x == null) { include = true; } else { include = x.asBoolean(); } Projection projection; x = node.get("project"); if (x != null) { projection = Projection.fromJson(x); } else { projection = null; } x = node.get("sort"); Sort sort; if (x != null) { sort = Sort.fromJson(x); } else { sort = null; } x = node.get("range"); if (x != null) { if (x instanceof ArrayNode && ((ArrayNode) x).size() == 2) { int from = ((ArrayNode) x).get(0).asInt(); int to = ((ArrayNode) x).get(1).asInt(); return new ArrayRangeProjection(path, include, projection, sort, from, to); } else { throw Error.get(QueryConstants.ERR_INVALID_ARRAY_RANGE_PROJECTION, node.toString()); } } x = node.get("match"); if (x != null) { return new ArrayQueryMatchProjection(path, include, projection, sort, QueryExpression.fromJson(x)); } x = node.get("recursive"); return new FieldProjection(path, include, x == null ? false : x.asBoolean()); } }