001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache license, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the license for the specific language governing permissions and
015     * limitations under the license.
016     */
017    package org.apache.logging.log4j.core.appender.db.jpa.converter;
018    
019    import javax.persistence.AttributeConverter;
020    import javax.persistence.Converter;
021    
022    import org.apache.logging.log4j.ThreadContext;
023    
024    /**
025     * A JPA 2.1 attribute converter for 
026     * {@link org.apache.logging.log4j.ThreadContext.ContextStack ThreadContext.ContextStack}s in
027     * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is only capable of converting to {@link String}s. The
028     * {@link #convertToEntityAttribute(String)} method throws an {@link UnsupportedOperationException}. If you need to
029     * support converting to an entity attribute, you should use the {@link ContextStackJsonAttributeConverter} for
030     * conversion both ways.
031     */
032    @Converter(autoApply = false)
033    public class ContextStackAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
034        @Override
035        public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
036            if (contextStack == null) {
037                return null;
038            }
039    
040            final StringBuilder builder = new StringBuilder();
041            for (final String value : contextStack.asList()) {
042                if (builder.length() > 0) {
043                    builder.append('\n');
044                }
045                builder.append(value);
046            }
047            return builder.toString();
048        }
049    
050        @Override
051        public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
052            throw new UnsupportedOperationException("Log events can only be persisted, not extracted.");
053        }
054    }