1 /*
2 * Copyright (c) 2001-2017, Zoltan Farkas All Rights Reserved.
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Additionally licensed with:
19 *
20 * Licensed under the Apache License, Version 2.0 (the "License");
21 * you may not use this file except in compliance with the License.
22 * You may obtain a copy of the License at
23 *
24 * http://www.apache.org/licenses/LICENSE-2.0
25 *
26 * Unless required by applicable law or agreed to in writing, software
27 * distributed under the License is distributed on an "AS IS" BASIS,
28 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
29 * See the License for the specific language governing permissions and
30 * limitations under the License.
31 */
32 package org.spf4j.avro;
33
34
35 import com.fasterxml.jackson.core.JsonGenerator;
36 import com.fasterxml.jackson.databind.JsonNode;
37 import java.io.IOException;
38 import java.util.function.Function;
39 import javax.annotation.Nonnull;
40 import javax.annotation.Nullable;
41 import org.apache.avro.Schema;
42
43 /**
44 * @author Zoltan Farkas
45 */
46 public interface SchemaResolver {
47
48 /**
49 * Lower level resolver implementation, that will write a schema in a "custom way"
50 * @param schema
51 * @param gen
52 * @return
53 * @throws IOException
54 */
55 default boolean customWrite(Schema schema, JsonGenerator gen) throws IOException {
56 String ref = getId(schema);
57 if (ref != null) {
58 gen.writeStartObject();
59 gen.writeFieldName(getJsonAttrName());
60 gen.writeString(ref);
61 gen.writeEndObject();
62 return true;
63 } else {
64 return false;
65 }
66 }
67
68 /**
69 * Lowere level resolver implementation that will read a schema from a "custom way"
70 * @param object
71 * @return the resolved schema, or null if nothing to resolve.
72 */
73 @Nullable
74 default Schema customRead(Function<String, JsonNode> object) {
75 JsonNode refVal = object.apply(getJsonAttrName());
76 if (refVal != null) {
77 return resolveSchema(refVal.asText());
78 } else {
79 return null;
80 }
81 }
82
83 SchemaResolver NONE = new SchemaResolver() {
84 @Override
85 public boolean customWrite(final Schema schema, final JsonGenerator gen) {
86 return false;
87 }
88
89 @Override
90 public Schema customRead(final Function<String, JsonNode> object) {
91 return null;
92 }
93
94 @Override
95 public Schema resolveSchema(final String id) {
96 throw new UnsupportedOperationException();
97 }
98
99 @Override
100 public String getId(final Schema schema) {
101 return null;
102 }
103 };
104
105 default String getJsonAttrName() {
106 return "$ref";
107 }
108
109 @Nonnull
110 Schema resolveSchema(String id);
111
112 @Nullable
113 String getId(Schema schema);
114
115
116 }