Tomcat源码学习笔记
###好的习惯###
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细化你的注释，甚至可以把流程图也用ASCII的方式写在代码中。例一个接口的注释：
/* * 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.catalina; /** * Common interface for component life cycle methods. Catalina components * may implement this interface (as well as the appropriate interface(s) for * the functionality they support) in order to provide a consistent mechanism * to start and stop the component. * <br> * The valid state transitions for components that support {@link Lifecycle} * are: * <pre> * start() * ----------------------------- * | | * | init() | * NEW -»-- INITIALIZING | * | | | | ------------------«----------------------- * | | |auto | | | * | | \|/ start() \|/ \|/ auto auto stop() | * | | INITIALIZED --»-- STARTING_PREP --»- STARTING --»- STARTED --»--- | * | | | | | | * | | | | | | * | | | | | | * | |destroy()| | | | * | --»-----«-- auto auto | | | * | | ---------«----- MUST_STOP ---------------------«-- | | * | | | | | * | \|/ ---------------------------«-------------------------------- ^ * | | | | * | | \|/ auto auto start() | * | | STOPPING_PREP ------»----- STOPPING ------»----- STOPPED ----»------ * | | ^ | | ^ * | | stop() | | | | * | | -------------------------- | | | * | | | auto | | | * | | | MUST_DESTROY------«------- | | * | | | | | | * | | | |auto | | * | | | destroy() \|/ destroy() | | * | | FAILED ----»------ DESTROYING ---«----------------- | * | | ^ | | * | | destroy() | |auto | * | --------»----------------- \|/ | * | DESTROYED | * | | * | stop() | * ----»-----------------------------»------------------------------ * * Any state can transition to FAILED. * * Calling start() while a component is in states STARTING_PREP, STARTING or * STARTED has no effect. * * Calling start() while a component is in state NEW will cause init() to be * called immediately after the start() method is entered. * * Calling stop() while a component is in states STOPPING_PREP, STOPPING or * STOPPED has no effect. * * Calling stop() while a component is in state NEW transitions the component * to STOPPED. This is typically encountered when a component fails to start and * does not start all its sub-components. When the component is stopped, it will * try to stop all sub-components - even those it didn't start. * * MUST_STOP is used to indicate that the {@link #stop()} should be called on * the component as soon as {@link #start()} exits. It is typically used when a * component has failed to start. * * MUST_DESTROY is used to indicate that the {@link #destroy()} should be called on * the component as soon as {@link #stop()} exits. It is typically used when a * component is not designed to be restarted. * * Attempting any other transition will throw {@link LifecycleException}. * * </pre> * The {@link LifecycleEvent}s fired during state changes are defined in the * methods that trigger the changed. No {@link LifecycleEvent}s are fired if the * attempted transition is not valid. * * TODO: Not all components may transition from STOPPED to STARTING_PREP. These * components should use MUST_DESTROY to signal this. * * @author Craig R. McClanahan */ public interface Lifecycle { -
枚举enum可以携带多个属性。例：
/** * The list of valid states for components that implement {@link Lifecycle}. * See {@link Lifecycle} for the state transition diagram. */ public enum LifecycleState { NEW(false, null), INITIALIZING(false, Lifecycle.BEFORE_INIT_EVENT), INITIALIZED(false, Lifecycle.AFTER_INIT_EVENT), STARTING_PREP(false, Lifecycle.BEFORE_START_EVENT), STARTING(true, Lifecycle.START_EVENT), STARTED(true, Lifecycle.AFTER_START_EVENT), STOPPING_PREP(true, Lifecycle.BEFORE_STOP_EVENT), STOPPING(false, Lifecycle.STOP_EVENT), STOPPED(false, Lifecycle.AFTER_STOP_EVENT), DESTROYING(false, Lifecycle.BEFORE_DESTROY_EVENT), DESTROYED(false, Lifecycle.AFTER_DESTROY_EVENT), FAILED(false, null), MUST_STOP(true, null), MUST_DESTROY(false, null); private final boolean available; private final String lifecycleEvent; private LifecycleState(boolean available, String lifecycleEvent) { this.available = available; this.lifecycleEvent = lifecycleEvent; } /** * May the public methods other than property getters/setters and lifecycle * methods be called for a component in this state? It returns * <code>true</code> for any component in any of the following states: * <ul> * <li>{@link #STARTING}</li> * <li>{@link #STARTED}</li> * <li>{@link #STOPPING_PREP}</li> * <li>{@link #MUST_STOP}</li> * </ul> */ public boolean isAvailable() { return available; } /** * */ public String getLifecycleEvent() { return lifecycleEvent; } } -
访问外部文件时考虑增加调用耗时纪录。例：
/** * Create and configure the Digester we will be using for startup. */ protected Digester createStartDigester() { long t1=System.currentTimeMillis(); Digester digester=new Digester(); //耗时操作 long t2=System.currentTimeMillis(); if (log.isDebugEnabled()) { log.debug("Digester for server.xml created " + ( t2-t1 )); } return (digester); } -
加载文件方法
/** * Return a File object representing our configuration file. */ protected File configFile() { File file = new File(configFile); if (!file.isAbsolute()) { file = new File(Bootstrap.getCatalinaBase(), configFile); } return (file); }
###参考资料###
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