    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    }