目录
入口
SpringApplication 部分参数初始化
SpringApplication.initialize方法
SpringApplication.run方法
StopWatch
java.awt.headless系统设定
入口
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
public static ConfigurableApplicationContext run(Object source, String... args) {
return run(new Object[] { source }, args);
}
public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
//先执行构造函数，再执行run方法
return new SpringApplication(sources).run(args);
}
/**
* 构造函数
* Create a new {@link SpringApplication} instance. The application context will load
* beans from the specified sources (see {@link SpringApplication class-level}
* documentation for details. The instance can be customized before calling
* {@link #run(String...)}.
* @param sources the bean sources
* @see #run(Object, String[])
* @see #SpringApplication(ResourceLoader, Object...)
*/
public SpringApplication(Object... sources) {
initialize(sources);
}
SpringApplication 部分参数初始化
private Banner.Mode bannerMode = Banner.Mode.CONSOLE;
private boolean logStartupInfo = true;
private boolean addCommandLineProperties = true;
private boolean headless = true;
private boolean registerShutdownHook = true;
SpringApplication.initialize方法
private void initialize(Object[] sources) {
//sources赋值为 com.example.demo.DemoApplication.class
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));
}
//webEnvironment = true
this.webEnvironment = deduceWebEnvironment();
/*
* 设置List<ApplicationContextInitializer<?>> initializers ，读取 META-
* INF/spring.factories 路径下 属性名为
* org.springframework.context.ApplicationContextInitializer的属性值，转换为类实例
* 的
* 集合
*/
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
/*
* 设置private List<ApplicationListener<?>> listeners; ，读取 META-
* INF/spring.factories 路径下 属性名为
* org.springframework.context.ApplicationListener的属性值，转换为类实例的集合
*/
setListeners((Collection)getSpringFactoriesInstances(ApplicationListener.class));
//mainApplicationClass赋值为 com.example.demo.DemoApplication.class
this.mainApplicationClass = deduceMainApplicationClass();
}
SpringApplication.run方法
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
public ConfigurableApplicationContext run(String... args) {
//StopWatch 操作耗时的日志打印类
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
//设置系统属性 java.awt.headless 为 true
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
analyzers = new FailureAnalyzers(context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
}
StopWatch
有时我们在做开发的时候需要记录每个任务执行时间，或者记录一段代码执行时间，最简单的方法就是打印当前时间与执行完时间的差值，然后这样如果执行大量测试的话就很麻烦，并且不直观，如果想对执行的时间做进一步控制，则需要在程序中很多地方修改，目前spring-framework提供了一个StopWatch类可以做类似任务执行时间控制，也就是封装了一个对开始时间，结束时间记录操作的Java类，详情查看StopWatch相关文章，StopWatch源码如下：
/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed 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.springframework.util;
import java.text.NumberFormat;
import java.util.LinkedList;
import java.util.List;
/**
* Simple stop watch, allowing for timing of a number of tasks,
* exposing total running time and running time for each named task.
*
* <p>Conceals use of {@code System.currentTimeMillis()}, improving the
* readability of application code and reducing the likelihood of calculation errors.
*
* <p>Note that this object is not designed to be thread-safe and does not
* use synchronization.
*
* <p>This class is normally used to verify performance during proof-of-concepts
* and in development, rather than as part of production applications.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Sam Brannen
* @since May 2, 2001
*/
public class StopWatch {
/**
* Identifier of this stop watch.
* Handy when we have output from multiple stop watches
* and need to distinguish between them in log or console output.
*/
private final String id;
private boolean keepTaskList = true;
private final List<TaskInfo> taskList = new LinkedList<TaskInfo>();
/** Start time of the current task */
private long startTimeMillis;
/** Is the stop watch currently running? */
private boolean running;
/** Name of the current task */
private String currentTaskName;
private TaskInfo lastTaskInfo;
private int taskCount;
/** Total running time */
private long totalTimeMillis;
/**
* Construct a new stop watch. Does not start any task.
*/
public StopWatch() {
this("");
}
/**
* Construct a new stop watch with the given id.
* Does not start any task.
* @param id identifier for this stop watch.
* Handy when we have output from multiple stop watches
* and need to distinguish between them.
*/
public StopWatch(String id) {
this.id = id;
}
/**
* Return the id of this stop watch, as specified on construction.
* @return the id (empty String by default)
* @since 4.2.2
* @see #StopWatch(String)
*/
public String getId() {
return this.id;
}
/**
* Determine whether the TaskInfo array is built over time. Set this to
* "false" when using a StopWatch for millions of intervals, or the task
* info structure will consume excessive memory. Default is "true".
*/
public void setKeepTaskList(boolean keepTaskList) {
this.keepTaskList = keepTaskList;
}
/**
* Start an unnamed task. The results are undefined if {@link #stop()}
* or timing methods are called without invoking this method.
* @see #stop()
*/
public void start() throws IllegalStateException {
start("");
}
/**
* Start a named task. The results are undefined if {@link #stop()}
* or timing methods are called without invoking this method.
* @param taskName the name of the task to start
* @see #stop()
*/
public void start(String taskName) throws IllegalStateException {
if (this.running) {
throw new IllegalStateException("Can't start StopWatch: it's already running");
}
this.running = true;
this.currentTaskName = taskName;
this.startTimeMillis = System.currentTimeMillis();
}
/**
* Stop the current task. The results are undefined if timing
* methods are called without invoking at least one pair
* {@code start()} / {@code stop()} methods.
* @see #start()
*/
public void stop() throws IllegalStateException {
if (!this.running) {
throw new IllegalStateException("Can't stop StopWatch: it's not running");
}
long lastTime = System.currentTimeMillis() - this.startTimeMillis;
this.totalTimeMillis += lastTime;
this.lastTaskInfo = new TaskInfo(this.currentTaskName, lastTime);
if (this.keepTaskList) {
this.taskList.add(lastTaskInfo);
}
++this.taskCount;
this.running = false;
this.currentTaskName = null;
}
/**
* Return whether the stop watch is currently running.
* @see #currentTaskName()
*/
public boolean isRunning() {
return this.running;
}
/**
* Return the name of the currently running task, if any.
* @since 4.2.2
* @see #isRunning()
*/
public String currentTaskName() {
return this.currentTaskName;
}
/**
* Return the time taken by the last task.
*/
public long getLastTaskTimeMillis() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task interval");
}
return this.lastTaskInfo.getTimeMillis();
}
/**
* Return the name of the last task.
*/
public String getLastTaskName() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task name");
}
return this.lastTaskInfo.getTaskName();
}
/**
* Return the last task as a TaskInfo object.
*/
public TaskInfo getLastTaskInfo() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task info");
}
return this.lastTaskInfo;
}
/**
* Return the total time in milliseconds for all tasks.
*/
public long getTotalTimeMillis() {
return this.totalTimeMillis;
}
/**
* Return the total time in seconds for all tasks.
*/
public double getTotalTimeSeconds() {
return this.totalTimeMillis / 1000.0;
}
/**
* Return the number of tasks timed.
*/
public int getTaskCount() {
return this.taskCount;
}
/**
* Return an array of the data for tasks performed.
*/
public TaskInfo[] getTaskInfo() {
if (!this.keepTaskList) {
throw new UnsupportedOperationException("Task info is not being kept!");
}
return this.taskList.toArray(new TaskInfo[this.taskList.size()]);
}
/**
* Return a short description of the total running time.
*/
public String shortSummary() {
return "StopWatch '" + getId() + "': running time (millis) = " + getTotalTimeMillis();
}
/**
* Return a string with a table describing all tasks performed.
* For custom reporting, call getTaskInfo() and use the task info directly.
*/
public String prettyPrint() {
StringBuilder sb = new StringBuilder(shortSummary());
sb.append('\n');
if (!this.keepTaskList) {
sb.append("No task info kept");
}
else {
sb.append("-----------------------------------------\n");
sb.append("ms % Task name\n");
sb.append("-----------------------------------------\n");
NumberFormat nf = NumberFormat.getNumberInstance();
nf.setMinimumIntegerDigits(5);
nf.setGroupingUsed(false);
NumberFormat pf = NumberFormat.getPercentInstance();
pf.setMinimumIntegerDigits(3);
pf.setGroupingUsed(false);
for (TaskInfo task : getTaskInfo()) {
sb.append(nf.format(task.getTimeMillis())).append(" ");
sb.append(pf.format(task.getTimeSeconds() / getTotalTimeSeconds())).append(" ");
sb.append(task.getTaskName()).append("\n");
}
}
return sb.toString();
}
/**
* Return an informative string describing all tasks performed
* For custom reporting, call {@code getTaskInfo()} and use the task info directly.
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder(shortSummary());
if (this.keepTaskList) {
for (TaskInfo task : getTaskInfo()) {
sb.append("; [").append(task.getTaskName()).append("] took ").append(task.getTimeMillis());
long percent = Math.round((100.0 * task.getTimeSeconds()) / getTotalTimeSeconds());
sb.append(" = ").append(percent).append("%");
}
}
else {
sb.append("; no task info kept");
}
return sb.toString();
}
/**
* Inner class to hold data about one task executed within the stop watch.
*/
public static final class TaskInfo {
private final String taskName;
private final long timeMillis;
TaskInfo(String taskName, long timeMillis) {
this.taskName = taskName;
this.timeMillis = timeMillis;
}
/**
* Return the name of this task.
*/
public String getTaskName() {
return this.taskName;
}
/**
* Return the time in milliseconds this task took.
*/
public long getTimeMillis() {
return this.timeMillis;
}
/**
* Return the time in seconds this task took.
*/
public double getTimeSeconds() {
return (this.timeMillis / 1000.0);
}
}
}
java.awt.headless系统设定
Headless模式是在缺少显示屏、键盘或者鼠标时的系统配置。在java.awt.toolkit和java.awt.graphicsenvironment类中有许多方法，除了对字体、图形和打印的操作外还可以调用显示器、键盘和鼠标的方法。但是有一些类中，比如Canvas和Panel，可以在headless模式下执行。
系统属性配置
①为了启用headless模式，需要使用setProperty方法去设置相应的系统属性。
System.setProperty("java.awt.headless","true")
②如果想在一个相同的程序 中使用headless和传统环境，你可以使用下面的命令行来完成：
java -Djava.awt.headless=true
③通过反射设置java.awt.GraphicsEnvironment中这个属性的值为true
如果名字为java.awt.headless的系统属性被设置true，那么headless工具包就会被使用。应用程序可以执行如下操作：
（1）创建轻量级组件。
（2）收集关于可用的字体、字体指标和字体设置的信息。
（3）设置颜色来渲染准备图片。
（4）创造和获取图像，为渲染准备图片。
（5）使用java.awt.PrintJob,java.awt.print.*,和javax.print.*类里的打印。
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