Java tutorial
/******************************************************************************* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. ******************************************************************************/ package org.apache.drill.common.logical.data; import java.io.IOException; import org.apache.drill.common.logical.data.Sequence.De; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.fasterxml.jackson.annotation.JsonProperty; import com.fasterxml.jackson.annotation.JsonTypeName; import com.fasterxml.jackson.annotation.ObjectIdGenerator; import com.fasterxml.jackson.annotation.ObjectIdGenerators; import com.fasterxml.jackson.core.JsonLocation; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.core.JsonToken; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JavaType; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.annotation.JsonDeserialize; import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId; import com.fasterxml.jackson.databind.deser.std.StdDeserializer; /** * Describes a list of operators where each operator only has one input and that * input is the operator that came before. * */ @JsonDeserialize(using = De.class) @JsonTypeName("sequence") public class Sequence extends LogicalOperatorBase { static final Logger logger = LoggerFactory.getLogger(Sequence.class); private Sequence() { } public boolean openTop; public LogicalOperator input; @JsonProperty("do") public LogicalOperator[] stream; public static class De extends StdDeserializer<LogicalOperator> { protected De() { super(Sequence.class); } @Override public LogicalOperator deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException { ObjectIdGenerator<Integer> idGenerator = new ObjectIdGenerators.IntSequenceGenerator(); JsonLocation start = jp.getCurrentLocation(); JsonToken t = jp.getCurrentToken(); LogicalOperator parent = null; LogicalOperator first = null; LogicalOperator prev = null; Integer id = null; while (true) { String fieldName = jp.getText(); t = jp.nextToken(); switch (fieldName) { // switch on field names. case "@id": id = _parseIntPrimitive(jp, ctxt); break; case "input": JavaType tp = ctxt.constructType(LogicalOperator.class); JsonDeserializer<Object> d = ctxt.findRootValueDeserializer(tp); parent = (LogicalOperator) d.deserialize(jp, ctxt); break; case "do": if (!jp.isExpectedStartArrayToken()) throwE(jp, "The do parameter of sequence should be an array of SimpleOperators. Expected a JsonToken.START_ARRAY token but received a " + t.name() + "token."); int pos = 0; while ((t = jp.nextToken()) != JsonToken.END_ARRAY) { // logger.debug("Reading sequence child {}.", pos); JsonLocation l = jp.getCurrentLocation(); // get current location // first so we can // correctly reference the // start of the object in // the case that the type // is wrong. LogicalOperator o = jp.readValueAs(LogicalOperator.class); if (pos == 0) { if (!(o instanceof SingleInputOperator) && !(o instanceof SourceOperator)) throwE(l, "The first operator in a sequence must be either a ZeroInput or SingleInput operator. The provided first operator was not. It was of type " + o.getClass().getName()); first = o; } else { if (!(o instanceof SingleInputOperator)) throwE(l, "All operators after the first must be single input operators. The operator at position " + pos + " was not. It was of type " + o.getClass().getName()); SingleInputOperator now = (SingleInputOperator) o; now.setInput(prev); } prev = o; pos++; } break; default: throwE(jp, "Unknown field name provided for Sequence: " + jp.getText()); } t = jp.nextToken(); if (t == JsonToken.END_OBJECT) { break; } } if (first == null) throwE(start, "A sequence must include at least one operator."); if ((parent == null && first instanceof SingleInputOperator) || (parent != null && first instanceof SourceOperator)) throwE(start, "A sequence must either start with a ZeroInputOperator or have a provided input. It cannot have both or neither."); if (parent != null && first instanceof SingleInputOperator) { ((SingleInputOperator) first).setInput(parent); } // set input reference. if (id != null) { ReadableObjectId rid = ctxt.findObjectId(id, idGenerator); rid.bindItem(prev); // logger.debug("Binding id {} to item {}.", rid.id, rid.item); } return first; } } private static void throwE(JsonLocation l, String e) throws JsonParseException { throw new JsonParseException(e, l); } private static void throwE(JsonParser jp, String e) throws JsonParseException { throw new JsonParseException(e, jp.getCurrentLocation()); } }