log4j-layout-json-template/src/main/java/org/apache/logging/log4j/layout/json/template/resolver/ExceptionResolver.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.layout.json.template.resolver;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.layout.json.template.util.JsonWriter;

/**
 * Exception resolver.
 *
 * Note that this resolver is toggled by {@link
 * org.apache.logging.log4j.layout.json.template.JsonTemplateLayout.Builder#setStackTraceEnabled(boolean)}.
 *
 * @see ExceptionInternalResolverFactory
 */
class ExceptionResolver implements EventResolver {

    private static final ExceptionInternalResolverFactory INTERNAL_RESOLVER_FACTORY =
            new ExceptionInternalResolverFactory() {

                @Override
                EventResolver createClassNameResolver() {
                    return (final LogEvent logEvent, final JsonWriter jsonWriter) -> {
                        final Throwable exception = logEvent.getThrown();
                        if (exception == null) {
                            jsonWriter.writeNull();
                        } else {
                            String exceptionClassName = exception.getClass().getCanonicalName();
                            jsonWriter.writeString(exceptionClassName);
                        }
                    };
                }

                @Override
                EventResolver createMessageResolver(final EventResolverContext context) {
                    return (final LogEvent logEvent, final JsonWriter jsonWriter) -> {
                        final Throwable exception = logEvent.getThrown();
                        if (exception == null) {
                            jsonWriter.writeNull();
                        } else {
                            String exceptionMessage = exception.getMessage();
                            jsonWriter.writeString(exceptionMessage);
                        }
                    };
                }

                @Override
                EventResolver createStackTraceStringResolver(final EventResolverContext context) {
                    StackTraceStringResolver stackTraceStringResolver =
                            new StackTraceStringResolver(context);
                    return (final LogEvent logEvent, final JsonWriter jsonWriter) -> {
                        final Throwable exception = logEvent.getThrown();
                        if (exception == null) {
                            jsonWriter.writeNull();
                        } else {
                            stackTraceStringResolver.resolve(exception, jsonWriter);
                        }
                    };
                }

                @Override
                EventResolver createStackTraceObjectResolver(final EventResolverContext context) {
                    return (final LogEvent logEvent, final JsonWriter jsonWriter) -> {
                        final Throwable exception = logEvent.getThrown();
                        if (exception == null) {
                            jsonWriter.writeNull();
                        } else {
                            context.getStackTraceObjectResolver().resolve(exception, jsonWriter);
                        }
                    };
                }

            };

    private final boolean stackTraceEnabled;

    private final EventResolver internalResolver;

    ExceptionResolver(
            final EventResolverContext context,
            final TemplateResolverConfig config) {
        this.stackTraceEnabled = context.isStackTraceEnabled();
        this.internalResolver = INTERNAL_RESOLVER_FACTORY
                .createInternalResolver(context, config);
    }

    static String getName() {
        return "exception";
    }

    @Override
    public boolean isResolvable() {
        return stackTraceEnabled;
    }

    @Override
    public boolean isResolvable(final LogEvent logEvent) {
        return stackTraceEnabled && logEvent.getThrown() != null;
    }

    @Override
    public void resolve(
            final LogEvent logEvent,
            final JsonWriter jsonWriter) {
        internalResolver.resolve(logEvent, jsonWriter);
    }

}