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 java.io.IOException;
020    import java.util.List;
021    
022    import javax.persistence.AttributeConverter;
023    import javax.persistence.PersistenceException;
024    
025    import org.apache.logging.log4j.ThreadContext;
026    import org.apache.logging.log4j.spi.DefaultThreadContextStack;
027    
028    import com.fasterxml.jackson.core.type.TypeReference;
029    
030    /**
031     * A JPA 2.1 attribute converter for {@link ThreadContext.ContextStack}s in
032     * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is capable of converting both to and from
033     * {@link String}s.
034     *
035     * In addition to other optional dependencies required by the JPA appender, this converter requires the Jackson Data
036     * Processor.
037     */
038    public class ContextStackJsonAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
039        @Override
040        public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
041            try {
042                return ContextMapJsonAttributeConverter.OBJECT_MAPPER.writeValueAsString(contextStack.asList());
043            } catch (IOException e) {
044                throw new PersistenceException("Failed to convert stack list to JSON string.", e);
045            }
046        }
047    
048        @Override
049        public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
050            if (s == null || s.length() == 0) {
051                return null;
052            }
053    
054            List<String> list;
055            try {
056                list = ContextMapJsonAttributeConverter.OBJECT_MAPPER.readValue(s, new TypeReference<List<String>>() { });
057            } catch (IOException e) {
058                throw new PersistenceException("Failed to convert JSON string to list for stack.", e);
059            }
060    
061            DefaultThreadContextStack result = new DefaultThreadContextStack(true);
062            result.addAll(list);
063            return result;
064        }
065    }