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.Converter;
024    import javax.persistence.PersistenceException;
025    
026    import org.apache.logging.log4j.ThreadContext;
027    import org.apache.logging.log4j.spi.DefaultThreadContextStack;
028    import org.apache.logging.log4j.util.Strings;
029    
030    import com.fasterxml.jackson.core.type.TypeReference;
031    
032    /**
033     * A JPA 2.1 attribute converter for 
034     * {@link org.apache.logging.log4j.ThreadContext.ContextStack ThreadContext.ContextStack}s in
035     * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is capable of converting both to and from
036     * {@link String}s.
037     *
038     * In addition to other optional dependencies required by the JPA appender, this converter requires the Jackson Data
039     * Processor.
040     */
041    @Converter(autoApply = false)
042    public class ContextStackJsonAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
043        @Override
044        public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
045            if (contextStack == null) {
046                return null;
047            }
048    
049            try {
050                return ContextMapJsonAttributeConverter.OBJECT_MAPPER.writeValueAsString(contextStack.asList());
051            } catch (final IOException e) {
052                throw new PersistenceException("Failed to convert stack list to JSON string.", e);
053            }
054        }
055    
056        @Override
057        public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
058            if (Strings.isEmpty(s)) {
059                return null;
060            }
061    
062            List<String> list;
063            try {
064                list = ContextMapJsonAttributeConverter.OBJECT_MAPPER.readValue(s, new TypeReference<List<String>>() { });
065            } catch (final IOException e) {
066                throw new PersistenceException("Failed to convert JSON string to list for stack.", e);
067            }
068    
069            final DefaultThreadContextStack result = new DefaultThreadContextStack(true);
070            result.addAll(list);
071            return result;
072        }
073    }