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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  }