Java tutorial
/* * Copyright 2016 Proofpoint, 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.proofpoint.tracetoken; import com.fasterxml.jackson.annotation.JsonCreator; import com.fasterxml.jackson.annotation.JsonValue; import com.google.common.collect.ForwardingMap; import com.google.common.collect.ImmutableMap; import com.google.common.collect.Maps; import java.util.Map; import static java.util.Objects.requireNonNull; public class TraceToken extends ForwardingMap<String, String> { private final Map<String, String> delegate; TraceToken(Map<String, String> map) { requireNonNull(map, "map is null"); requireNonNull(map.get("id"), "map{id} is null"); delegate = ImmutableMap.copyOf(map); } @JsonCreator static TraceToken createJson(Map<String, String> map) { return new TraceToken(Maps.filterKeys(map, key -> !key.startsWith("_"))); } @JsonValue Map<String, String> getJson() { return Maps.filterKeys(this, key -> !key.startsWith("_")); } @Override protected Map<String, String> delegate() { return delegate; } @Override public String toString() { if (delegate.size() == 1) { return delegate.get("id"); } return super.toString(); } }