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.atlas.services; import com.google.gson.FieldNamingPolicy; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.JsonDeserializationContext; import com.google.gson.JsonDeserializer; import com.google.gson.JsonElement; import com.google.gson.JsonParseException; import com.google.gson.JsonSyntaxException; import org.apache.atlas.services.AtlasTypePatch.PatchContent; import org.apache.atlas.services.AtlasTypePatch.PatchData; import org.apache.atlas.services.AtlasTypePatch.PatchResult; import org.apache.atlas.services.AtlasTypePatch.PatchStatus; import org.apache.atlas.typesystem.types.Multiplicity; import org.apache.atlas.typesystem.types.TypeSystem; import org.apache.atlas.typesystem.types.TypeUpdateException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.File; import java.io.IOException; import java.lang.reflect.Type; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.util.ArrayList; import java.util.Arrays; import java.util.Comparator; import java.util.HashMap; import java.util.List; import java.util.Map; public class AtlasPatchHandler { private static final Logger LOG = LoggerFactory.getLogger(AtlasPatchHandler.class); public static void handlePatches(DefaultMetadataService metadataService, TypeSystem typeSystem) throws TypeUpdateException { Map<String, AtlasTypePatch> patchHandlerMap = initializePatchHandlerMap(metadataService, typeSystem); if (patchHandlerMap == null || patchHandlerMap.isEmpty()) return; String patchDirName = ReservedTypesRegistrar.getTypesDir() + File.separator + "patches"; LOG.info("Checking for any patches to be applied to the type system in " + patchDirName); File patchDir = new File(patchDirName); if (!patchDir.exists()) { LOG.info("Patch directory {} doesn't exist, not applying any patches", patchDirName); return; } File[] patchFiles = patchDir.listFiles(); if (patchFiles == null || patchFiles.length == 0) { LOG.info("No patch files found in {}, not applying any patches", patchDirName); return; } // Sort the patch files based on file name. Arrays.sort(patchFiles, new Comparator<File>() { public int compare(File f1, File f2) { return String.valueOf(f1.getName()).compareTo(f2.getName()); } }); LOG.info("Found " + patchFiles.length + " patch files to process."); int patchNumber = 0; Gson gson = initializeGson(); AtlasTypePatch typePatch; for (File patchFile : patchFiles) { try { LOG.info("Processing patch file " + (++patchNumber) + " - " + patchFile.getAbsolutePath()); String content = new String(Files.readAllBytes(patchFile.toPath()), StandardCharsets.UTF_8); PatchContent patchContent = gson.fromJson(content, PatchContent.class); PatchData[] patchDatas = patchContent.getPatches(); PatchResult result; int patchCounter = 0; for (PatchData patch : patchDatas) { typePatch = patchHandlerMap.get(patch.getAction()); if (typePatch != null) { result = typePatch.applyPatch(patch); if (result != null) { LOG.info(result.getMessage() + " Patch " + (++patchCounter) + " out of " + patchDatas.length + " processed in : " + patchFile.toPath()); if (result.getStatus().equals(PatchStatus.FAILED)) { throw new TypeUpdateException(result.getMessage() + " patch " + patchNumber + " failed in :" + patchFile.getAbsolutePath()); } } } } } catch (IOException e) { throw new TypeUpdateException("Unable to read patch file from " + patchFile.getAbsolutePath()); } catch (JsonSyntaxException e) { throw new TypeUpdateException( "Invalid non-parseable JSON patch file in " + patchFile.getAbsolutePath()); } } LOG.info("Processed " + patchFiles.length + " patch files."); } private static Map<String, AtlasTypePatch> initializePatchHandlerMap(DefaultMetadataService metadataService, TypeSystem typeSystem) { Map<String, AtlasTypePatch> patchHandlerMap = new HashMap<String, AtlasTypePatch>(); List<AtlasTypePatch> patchers = new ArrayList<AtlasTypePatch>(); // Register new patch classes here patchers.add(new AtlasTypeAttributePatch(metadataService, typeSystem)); for (AtlasTypePatch patcher : patchers) { for (String action : patcher.getSupportedActions()) { patchHandlerMap.put(action, patcher); } } return patchHandlerMap; } public static Gson initializeGson() { GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.registerTypeAdapter(Multiplicity.class, new MultiplicityDeserializer()); gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.IDENTITY); Gson gson = gsonBuilder.create(); return gson; } static class MultiplicityDeserializer implements JsonDeserializer<Multiplicity> { @Override public Multiplicity deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { String multiplicityString = json.getAsString().toLowerCase(); Multiplicity m = null; switch (multiplicityString) { case "optional": m = Multiplicity.OPTIONAL; break; case "required": m = Multiplicity.REQUIRED; break; case "collection": m = Multiplicity.COLLECTION; break; case "set": m = Multiplicity.SET; break; default: break; } return m; } } }