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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 javax.persistence.AttributeConverter;
20  import javax.persistence.Converter;
21  
22  import org.apache.logging.log4j.ThreadContext;
23  
24  /**
25   * A JPA 2.1 attribute converter for
26   * {@link org.apache.logging.log4j.ThreadContext.ContextStack ThreadContext.ContextStack}s in
27   * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is only capable of converting to {@link String}s. The
28   * {@link #convertToEntityAttribute(String)} method throws an {@link UnsupportedOperationException}. If you need to
29   * support converting to an entity attribute, you should use the {@link ContextStackJsonAttributeConverter} for
30   * conversion both ways.
31   */
32  @Converter(autoApply = false)
33  public class ContextStackAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
34      @Override
35      public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
36          if (contextStack == null) {
37              return null;
38          }
39  
40          final StringBuilder builder = new StringBuilder();
41          for (final String value : contextStack.asList()) {
42              if (builder.length() > 0) {
43                  builder.append('\n');
44              }
45              builder.append(value);
46          }
47          return builder.toString();
48      }
49  
50      @Override
51      public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
52          throw new UnsupportedOperationException("Log events can only be persisted, not extracted.");
53      }
54  }