Java tutorial
/** * Copyright (C) 2012 Ness Computing, Inc. * * Licensed 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 com.nesscomputing.jackson.datatype; import java.io.IOException; import java.util.Map; import java.util.Map.Entry; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonToken; import com.fasterxml.jackson.core.Version; import com.fasterxml.jackson.databind.BeanDescription; import com.fasterxml.jackson.databind.DeserializationConfig; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JavaType; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.Module; import com.fasterxml.jackson.databind.deser.Deserializers; import com.google.common.base.Preconditions; import com.google.common.collect.Maps; class MapEntryModule extends Module { @Override public String getModuleName() { return "Map.Entry module"; } @Override public Version version() { return Version.unknownVersion(); } @Override public void setupModule(SetupContext context) { context.addDeserializers(new MapEntryDeserializers()); } private static class MapEntryDeserializers extends Deserializers.Base { @Override public JsonDeserializer<?> findBeanDeserializer(JavaType type, DeserializationConfig config, BeanDescription beanDesc) throws JsonMappingException { if (type.getRawClass().equals(Map.Entry.class)) { return new MapEntryDeserializer(type); } return null; } } private static class MapEntryDeserializer extends JsonDeserializer<Map.Entry<?, ?>> { private final JavaType type; MapEntryDeserializer(JavaType type) { this.type = type; Preconditions.checkArgument(type.containedTypeCount() == 2, "Map.Entry has exactly 2 child types"); } @Override public Entry<?, ?> deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException { JsonDeserializer<Object> deserK = ctxt.findContextualValueDeserializer(type.containedType(0), null); JsonDeserializer<Object> deserV = ctxt.findContextualValueDeserializer(type.containedType(1), null); Object k = null, v = null; if (!(jp.hasCurrentToken() && jp.getCurrentToken() == JsonToken.START_OBJECT)) { expect(jp.nextToken(), JsonToken.START_OBJECT, jp, ctxt); } while (true) { JsonToken nextToken = jp.nextToken(); if (nextToken == JsonToken.END_OBJECT) { break; } expect(nextToken, JsonToken.FIELD_NAME, jp, ctxt); jp.nextToken(); if ("key".equals(jp.getCurrentName())) { k = deserK.deserialize(jp, ctxt); } else if ("value".equals(jp.getCurrentName())) { v = deserV.deserialize(jp, ctxt); } else { if (!ctxt.handleUnknownProperty(jp, this, Map.Entry.class, jp.getCurrentName())) { throw new JsonMappingException("Unknown Map.Entry property " + jp.getCurrentName(), jp.getCurrentLocation()); } } } return Maps.immutableEntry(k, v); } private void expect(JsonToken actual, JsonToken expected, JsonParser jp, DeserializationContext ctxt) throws JsonMappingException { if (actual != expected) { throw ctxt.wrongTokenException(jp, expected, "Wrong token"); } } } }