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 */
017package org.apache.logging.log4j.core.appender.db.jpa.converter;
018
019import javax.persistence.AttributeConverter;
020import javax.persistence.Converter;
021
022import 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)
033public 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}