log4j-layout-jackson-yaml/src/main/java/org/apache/logging/log4j/jackson/yaml/layout/YamlLayout.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */

package org.apache.logging.log4j.jackson.yaml.layout;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.DefaultConfiguration;
import org.apache.logging.log4j.core.config.Node;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.core.util.KeyValuePair;
import org.apache.logging.log4j.jackson.AbstractJacksonLayout;
import org.apache.logging.log4j.util.Strings;

import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonRootName;
import com.fasterxml.jackson.annotation.JsonUnwrapped;

/**
 * Appends a series of YAML events as strings serialized as bytes.
 *
 * <h3>Encoding</h3>
 * <p>
 * Appenders using this layout should have their {@code charset} set to {@code UTF-8} or {@code UTF-16}, otherwise
 * events containing non ASCII characters could result in corrupted log files.
 * </p>
 * <h3>Additional Fields</h3>
 * <p>
 * This property allows addition of custom fields into generated JSON.
 * {@code <YamlLayout><KeyValuePair key="foo" value="bar"/></YamlLayout>} inserts {@code foo: "bar"} directly into YAML
 * output. Supports Lookup expressions.
 * </p>
 */
@Plugin(name = "YamlLayout", category = Node.CATEGORY, elementType = Layout.ELEMENT_TYPE, printObject = true)
public final class YamlLayout extends AbstractJacksonLayout {

    public static class Builder<B extends Builder<B>> extends AbstractJacksonLayout.Builder<B>
            implements org.apache.logging.log4j.core.util.Builder<YamlLayout> {

        public Builder() {
            super();
            setCharset(StandardCharsets.UTF_8);
        }

        @Override
        public YamlLayout build() {
            final String headerPattern = toStringOrNull(getHeader());
            final String footerPattern = toStringOrNull(getFooter());
            return new YamlLayout(getConfiguration(), isLocationInfo(), isProperties(), isComplete(), isCompact(),
                    getEventEol(), headerPattern, footerPattern, getCharset(), isIncludeStacktrace(),
                    isStacktraceAsString(), isIncludeNullDelimiter(), getAdditionalFields());
        }
    }

    @JsonRootName(YamlConstants.EVENT)
    public static class YamlLogEventWithAdditionalFields extends LogEventWithAdditionalFields {

        public YamlLogEventWithAdditionalFields(final Object logEvent, final Map<String, String> additionalFields) {
            super(logEvent, additionalFields);
        }

        @Override
        @JsonAnyGetter
        public Map<String, String> getAdditionalFields() {
            return super.getAdditionalFields();
        }

        @Override
        @JsonUnwrapped
        public Object getLogEvent() {
            return super.getLogEvent();
        }

    }

    private static final String DEFAULT_FOOTER = Strings.EMPTY;

    private static final String DEFAULT_HEADER = Strings.EMPTY;

    static final String CONTENT_TYPE = "application/yaml";

    /**
     * Creates a YAML Layout using the default settings. Useful for testing.
     *
     * @return A YAML Layout.
     */
    public static AbstractJacksonLayout createDefaultLayout() {
        return new YamlLayout(new DefaultConfiguration(), false, false, false, false, false, DEFAULT_HEADER,
                DEFAULT_FOOTER, StandardCharsets.UTF_8, true, false, false, null);
    }

    /**
     * Creates a YAML Layout.
     *
     * @param config
     *            The plugin configuration.
     * @param locationInfo
     *            If "true", includes the location information in the generated YAML.
     * @param properties
     *            If "true", includes the thread context map in the generated YAML.
     * @param headerPattern
     *            The header pattern, defaults to {@code ""} if null.
     * @param footerPattern
     *            The header pattern, defaults to {@code ""} if null.
     * @param charset
     *            The character set to use, if {@code null}, uses "UTF-8".
     * @param includeStacktrace
     *            If "true", includes the stacktrace of any Throwable in the generated YAML, defaults to "true".
     * @return A YAML Layout.
     *
     * @deprecated Use {@link #newBuilder()} instead
     */
    @Deprecated
    public static AbstractJacksonLayout createLayout(final Configuration config, final boolean locationInfo,
            final boolean properties, final String headerPattern, final String footerPattern, final Charset charset,
            final boolean includeStacktrace) {
        return new YamlLayout(config, locationInfo, properties, false, false, true, headerPattern, footerPattern,
                charset, includeStacktrace, false, false, null);
    }

    @PluginBuilderFactory
    public static <B extends Builder<B>> B newBuilder() {
        return new Builder<B>().asBuilder();
    }

    /**
     * @deprecated Use {@link #newBuilder()} instead
     */
    @Deprecated
    protected YamlLayout(final Configuration config, final boolean locationInfo, final boolean properties,
            final boolean complete, final boolean compact, final boolean eventEol, final String headerPattern,
            final String footerPattern, final Charset charset, final boolean includeStacktrace) {
        super(config, new YamlJacksonFactory(includeStacktrace, false).newWriter(locationInfo, properties, compact),
                charset, compact, complete, eventEol,
                PatternLayout.newSerializerBuilder().setConfiguration(config).setPattern(headerPattern)
                        .setDefaultPattern(DEFAULT_HEADER).build(),
                PatternLayout.newSerializerBuilder().setConfiguration(config).setPattern(footerPattern)
                        .setDefaultPattern(DEFAULT_FOOTER).build(),
                false, null);
    }

    private YamlLayout(final Configuration config, final boolean locationInfo, final boolean properties,
            final boolean complete, final boolean compact, final boolean eventEol, final String headerPattern,
            final String footerPattern, final Charset charset, final boolean includeStacktrace,
            final boolean stacktraceAsString, final boolean includeNullDelimiter,
            final KeyValuePair[] additionalFields) {
        super(config,
                new YamlJacksonFactory(includeStacktrace, stacktraceAsString).newWriter(locationInfo, properties,
                        compact),
                charset, compact, complete, eventEol,
                PatternLayout.newSerializerBuilder().setConfiguration(config).setPattern(headerPattern)
                        .setDefaultPattern(DEFAULT_HEADER).build(),
                PatternLayout.newSerializerBuilder().setConfiguration(config).setPattern(footerPattern)
                        .setDefaultPattern(DEFAULT_FOOTER).build(),
                includeNullDelimiter, additionalFields);
    }

    @Override
    protected LogEventWithAdditionalFields createLogEventWithAdditionalFields(final LogEvent event,
            final Map<String, String> additionalFieldsMap) {
        return new YamlLogEventWithAdditionalFields(event, additionalFieldsMap);
    }

    @Override
    public Map<String, String> getContentFormat() {
        final Map<String, String> result = new HashMap<>();
        result.put("version", "3.0");
        return result;
    }

    /**
     * @return The content type.
     */
    @Override
    public String getContentType() {
        return CONTENT_TYPE + "; charset=" + this.getCharset();
    }

    /**
     * Returns appropriate YAML footer.
     *
     * @return a byte array containing the footer, closing the YAML array.
     */
    @Override
    public byte[] getFooter() {
        if (!this.complete) {
            return null;
        }
        final StringBuilder buf = new StringBuilder();
        buf.append(this.eol);
        final String str = serializeToString(getFooterSerializer());
        if (str != null) {
            buf.append(str);
        }
        buf.append(this.eol);
        return getBytes(buf.toString());
    }

    /**
     * Returns appropriate YAML header.
     *
     * @return a byte array containing the header, opening the YAML array.
     */
    @Override
    public byte[] getHeader() {
        if (!this.complete) {
            return null;
        }
        final StringBuilder buf = new StringBuilder();
        final String str = serializeToString(getHeaderSerializer());
        if (str != null) {
            buf.append(str);
        }
        buf.append(this.eol);
        return getBytes(buf.toString());
    }
}