Java tutorial
/* * The MIT License (MIT) * * Copyright (c) 2016 Jon Peterson * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ package com.github.jonpeterson.jackson.module.versioning; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.SerializerProvider; import com.fasterxml.jackson.databind.introspect.BeanPropertyDefinition; import com.fasterxml.jackson.databind.jsontype.TypeSerializer; import com.fasterxml.jackson.databind.node.JsonNodeFactory; import com.fasterxml.jackson.databind.node.ObjectNode; import com.fasterxml.jackson.databind.ser.ResolvableSerializer; import com.fasterxml.jackson.databind.ser.std.StdSerializer; import java.io.ByteArrayOutputStream; import java.io.IOException; public class VersionedModelSerializer<T> extends StdSerializer<T> implements ResolvableSerializer { private final StdSerializer<T> delegate; private final JsonVersionedModel jsonVersionedModel; private final VersionedModelConverter converter; private final BeanPropertyDefinition serializeToVersionProperty; public VersionedModelSerializer(StdSerializer<T> delegate, JsonVersionedModel jsonVersionedModel, BeanPropertyDefinition serializeToVersionProperty) { super(delegate.handledType()); this.delegate = delegate; this.jsonVersionedModel = jsonVersionedModel; this.serializeToVersionProperty = serializeToVersionProperty; Class<? extends VersionedModelConverter> converterClass = jsonVersionedModel.toPastConverterClass(); if (converterClass != VersionedModelConverter.class) try { this.converter = converterClass.newInstance(); } catch (Exception e) { throw new RuntimeException( "unable to create instance of converter '" + converterClass.getName() + "'", e); } else converter = null; } @Override public void resolve(SerializerProvider provider) throws JsonMappingException { if (delegate instanceof ResolvableSerializer) ((ResolvableSerializer) delegate).resolve(provider); } @Override public void serialize(T value, JsonGenerator generator, SerializerProvider provider) throws IOException { doSerialize(value, generator, provider, null); } @Override public void serializeWithType(T value, JsonGenerator generator, SerializerProvider provider, TypeSerializer typeSerializer) throws IOException { doSerialize(value, generator, provider, typeSerializer); } private void doSerialize(T value, JsonGenerator generator, SerializerProvider provider, TypeSerializer typeSerializer) throws IOException { // serialize the value into a byte array buffer then parse it back out into a JsonNode tree // TODO: find a better way to convert the value into a tree JsonFactory factory = generator.getCodec().getFactory(); ByteArrayOutputStream buffer = new ByteArrayOutputStream(4096); JsonGenerator bufferGenerator = factory.createGenerator(buffer); try { if (typeSerializer != null) delegate.serializeWithType(value, bufferGenerator, provider, typeSerializer); else delegate.serialize(value, bufferGenerator, provider); } finally { bufferGenerator.close(); } ObjectNode modelData = factory.createParser(buffer.toByteArray()).readValueAsTree(); // set target version to @SerializeToVersion's value, @JsonVersionModel's defaultSerializeToVersion, or // @JsonVersionModel's currentVersion in that order String targetVersion = null; if (serializeToVersionProperty != null) { targetVersion = (String) serializeToVersionProperty.getAccessor().getValue(value); modelData.remove(serializeToVersionProperty.getName()); } if (targetVersion == null) targetVersion = jsonVersionedModel.defaultSerializeToVersion(); if (targetVersion.isEmpty()) targetVersion = jsonVersionedModel.currentVersion(); // convert model data if there is a converter and targetVersion is different than the currentVersion or if // alwaysConvert is true if (converter != null && (jsonVersionedModel.alwaysConvert() || !targetVersion.equals(jsonVersionedModel.currentVersion()))) modelData = converter.convert(modelData, jsonVersionedModel.currentVersion(), targetVersion, JsonNodeFactory.instance); // add target version to model data if it wasn't the version to suppress if (!targetVersion.equals(jsonVersionedModel.versionToSuppressPropertySerialization())) modelData.put(jsonVersionedModel.propertyName(), targetVersion); // write node generator.writeTree(modelData); } }