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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  package org.apache.logging.log4j.core.appender.db.jpa.converter;
18  
19  import java.io.IOException;
20  import java.util.List;
21  
22  import javax.persistence.AttributeConverter;
23  import javax.persistence.Converter;
24  import javax.persistence.PersistenceException;
25  
26  import org.apache.logging.log4j.ThreadContext;
27  import org.apache.logging.log4j.spi.DefaultThreadContextStack;
28  import org.apache.logging.log4j.util.Strings;
29  
30  import com.fasterxml.jackson.core.type.TypeReference;
31  
32  /**
33   * A JPA 2.1 attribute converter for 
34   * {@link org.apache.logging.log4j.ThreadContext.ContextStack ThreadContext.ContextStack}s in
35   * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is capable of converting both to and from
36   * {@link String}s.
37   *
38   * In addition to other optional dependencies required by the JPA appender, this converter requires the Jackson Data
39   * Processor.
40   */
41  @Converter(autoApply = false)
42  public class ContextStackJsonAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
43      @Override
44      public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
45          if (contextStack == null) {
46              return null;
47          }
48  
49          try {
50              return ContextMapJsonAttributeConverter.OBJECT_MAPPER.writeValueAsString(contextStack.asList());
51          } catch (final IOException e) {
52              throw new PersistenceException("Failed to convert stack list to JSON string.", e);
53          }
54      }
55  
56      @Override
57      public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
58          if (Strings.isEmpty(s)) {
59              return null;
60          }
61  
62          List<String> list;
63          try {
64              list = ContextMapJsonAttributeConverter.OBJECT_MAPPER.readValue(s, new TypeReference<List<String>>() { });
65          } catch (final IOException e) {
66              throw new PersistenceException("Failed to convert JSON string to list for stack.", e);
67          }
68  
69          final DefaultThreadContextStack result = new DefaultThreadContextStack(true);
70          result.addAll(list);
71          return result;
72      }
73  }