remkop commented on a change in pull request #284: LOG4J2-2639 - Allow logging calls to be constructed using a builder pattern URL: https://github.com/apache/logging-log4j2/pull/284#discussion_r296932718
########## File path: log4j-api/src/main/java/org/apache/logging/log4j/internal/DefaultLogBuilder.java ########## @@ -0,0 +1,179 @@ +/* + * 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.internal; + +import org.apache.logging.log4j.Level; +import org.apache.logging.log4j.Logger; +import org.apache.logging.log4j.Marker; +import org.apache.logging.log4j.message.Message; +import org.apache.logging.log4j.message.SimpleMessage; +import org.apache.logging.log4j.status.StatusLogger; +import org.apache.logging.log4j.util.StackLocatorUtil; +import org.apache.logging.log4j.util.Supplier; + + +/** + * Collects data for a log event and then logs it. + */ +public class DefaultLogBuilder implements LogBuilder { + private static Message EMPTY_MESSAGE = new SimpleMessage(""); + private static final String FQCN = DefaultLogBuilder.class.getName(); + private static final Logger LOGGER = StatusLogger.getLogger(); + + private final Logger logger; + private Level level; + private Marker marker; + private Throwable throwable; + private StackTraceElement location; + private Object object; + private Message msg; + private String textMessage; + private Supplier<Message> supplier; + private Object[] parameters; + private volatile boolean inUse; + private long threadId; + + public DefaultLogBuilder(Logger logger) { + this.logger = logger; + this.inUse = false; + this.threadId = Thread.currentThread().getId(); + } + + public LogBuilder setLevel(Level level) { + this.inUse = true; + this.level = level; + this.marker = null; + this.throwable = null; + this.location = null; + this.object = null; + this.msg = null; + this.textMessage = null; + this.supplier = null; + this.parameters = null; + return this; + } + + public LogBuilder withMarker(Marker marker) { + this.marker = marker; + return this; + } + + public LogBuilder withThrowable(Throwable throwable) { + this.throwable = throwable; + return this; + } + + public LogBuilder withLocation() { + location = StackLocatorUtil.getStackTraceElement(2); + return this; + } + + public LogBuilder withLocation(StackTraceElement location) { + this.location = location; + return this; + } + + public LogBuilder withMessage(String msg) { + this.textMessage = msg; + return this; + } + + public LogBuilder withMessage(Object msg) { + this.object = msg; + return this; + } + + public LogBuilder withMessage(Message msg) { + this.msg = msg; + return this; + } + + public LogBuilder withMessage(Supplier<Message> supplier) { + this.supplier = supplier; + return this; + } + + public LogBuilder withParameters(Object... params) { + if (params != null && params.length > 0) { + if (parameters == null) { + parameters = params; + } else { + Object[] prev = parameters; + int count = parameters.length + params.length; + parameters = new Object[count]; + System.arraycopy(prev, 0, parameters, 0, prev.length); + System.arraycopy(params, 0, parameters, prev.length, params.length); + } + } + return this; + } + + @SafeVarargs + public final LogBuilder withParameters(java.util.function.Supplier<Object>... params) { + if (params != null && params.length > 0) { + if (parameters == null) { + parameters = new Object[params.length]; + for (int i = 0; i < params.length; ++i) { + parameters[i] = params[i].get(); + } + } else { + Object[] prev = parameters; + int count = parameters.length + params.length; + parameters = new Object[count]; + System.arraycopy(prev, 0, parameters, 0, prev.length); + for (int i = 0; i < params.length; ++i) { + parameters[prev.length + i] = params[i].get(); + } + } + } + return this; + } + + public boolean isInUse() { + return inUse; + } + + public void log() { + if (!inUse) { Review comment: We can learn from [flogger](https://google.github.io/flogger/anatomy.html)'s approach. Can we avoid the call to `log()` at the end? All that this does is signal that the log statement is done, like a call to `build()` at the end of a builder chain. How about if we make the `log` method do more work? Something like this: ```java logger.atTrace().log("Hi, {}", () -> fetchWorld()); logger.atTrace().withMarker(marker).withThrowable(t).log("Found error while {}", currentTask); ``` I propose we remove the `withMessage` and `withParameters` methods and replace them with overloaded `log` methods that take these parameters: * Message * Object * Supplier<Message> * String, Object... * String, Supplier<Object>... * (potentially other...) Another benefit of this approach is that it would prevent users from doing the wrong thing, like for example: ```java // the API should not allow this: Message msg = msg(); logger.atTrace().withMessage(msg) .withMessage("It is now possible to use the API incorrectly") .withMessage(() -> differentMsg()) .withParameters("a", "b", "c") .withParameters(() -> getParams()) .withMessage("hi!") .log(); // now, which of the above should actually be logged? ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
