blocks|key|835963|text|您需要在应用程序的启动命令行中添加某种标识符。例如，类似：
字符串id+=+"com.app.demo"；|type|ordered-list-item|depth|inlineStyleRanges|entityRanges|data|835964|运行应用程序时，一定要包含字符串。假设您从Java内部启动它，请执行以下操作：
Runtime.getRuntime().exec("C:...\javaw.exe+-cp+.+-Dwhatever=“%2B+id+%2B”com.app.app.demo.Main")；|835965|通过id+(如$ps+aux+%7C+grep+-i+com.app.app.demo+)获取应用程序。在Java调用Runtime.getRuntime().exec("ps+aux+%7C+grep+-i+com.app.app.demo");|offset|length|style|CODE|835966|我更喜欢使用ProcessBuilder+(来自Java+8)，并通过bash运行命令：|unstyled|835967|Process+process+=+new+ProcessBuilder().command("bash",+"ps+aux+%7C+grep+com.app.app.demo").start()|code-block|syntax|javascript|835968|希望这能给你个主意。|835969|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/8/docs/api/java/lang/ProcessBuilder.html^0|0|0|2|2|7|Y|1L|1R|0|6|E|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|13|8|@$F|14|G|15|H|I]|$F|16|G|17|H|I]|$F|18|G|19|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|1A|8|@]|9|@$F|1B|G|1C|1|1D]]|A|$]]|$1|M|3|N|5|O|7|1E|8|@]|9|@]|A|$P|Q]]|$1|R|3|S|5|L|7|1F|8|@]|9|@]|A|$]]|$1|T|3|-4|5|L|7|1G|8|@]|9|@]|A|$]]]|U|$V|$5|W|X|Y|A|$Z|10]]]]

<ol>
<li>You need to put some sort of identifier into your app's startup command line. E.g. something like:

<pre><code>String id = "com.app.demo";
</code></pre></li>
<li>When you run your app, make sure to include the string. Let's say you start it from within Java, do the following:

<pre><code>Runtime.getRuntime().exec("C:\...\javaw.exe -cp ... -Dwhatever=" + id + " com.app.app.demo.Main");
</code></pre></li>
<li>Get the application by <code>id</code> like <code>$ps aux | grep -i com.app.app.demo</code>. In Java call <code>Runtime.getRuntime().exec("ps aux | grep -i com.app.app.demo");</code></li>
</ol>

I would prefer using <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/ProcessBuilder.html" rel="nofollow noreferrer">ProcessBuilder</a> instead(from Java 8), and running your command via bash:

<pre><code>Process process = new ProcessBuilder().command("bash", "ps aux | grep com.app.app.demo").start()
</code></pre>

Hope this gives an idea.

blocks|key|16358|text|快速而肮脏的方法:将静态块放入类中，并在其中将某些内容打印到日志(或system.out)中。静态块是在类加载器加载类时执行的，而不是在第一个实例实例化时执行的(这是第一次调用构造函数时)。然后，如果您的打印输出在日志中，那么类已经加载。示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|16359|public+class+Sample+{++++private+static+final+Logger+logger+=+...++++static+{+++++++logger.info("class+Sample+is+loaded");++++}+...+}|offset|length|style|CODE|16360|entityMap^0|0|0|3P|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Quick and dirty method: some static block into your class and in it print something into a log (or system.out). Static block is executed when class is loaded by class loader and not when the first instance instantiated (this is when constructor is called for the first time). Then if your printout is in the log then the class has been loaded. Example: 
<code>public class Sample {
 private static final Logger logger = ...
 static {
 logger.info("class Sample is loaded");
 }
...
}</code>

blocks|key|836091|text|假设您可以识别确定应用程序是否为springboot应用程序的特定类，则可以使用jdk中的一些工具，该工具可以输出加载的类。我已经尝试过jcmd(您可以在jre/bin/下找到它)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|836092|我不太擅长bash，所以它可能不是很有效，但这对我来说是有效的，前提是每个springboot应用程序都加载了类org.springframework.boot.logging.LoggingInitializationContext，而没有加载非assuming引导应用程序。|offset|length|style|CODE|836093|ps+aux+%7C+grep+[j]ava+%7C+awk+'{print+$2}'+%7C+xargs+-I{}+jcmd+{}+VM.class_hierarchy+%7C+grep+"org.springframework.boot.logging.LoggingInitializationContext"|code-block|syntax|javascript|836094|它找到包含java的进程，只接受PID，将它传递给jcmd，在jcmd中，您可以为特定的类实现grep。输出似乎是正确的，唯一的问题是，我失去PID在这个长管道，我不知道如何打印它。但是如果你的问题是“有多少个springboot引导应用程序”，那么它可能不是一个问题。我也不确定在使用jcmd+VM.class_hierarchy时这些类是否会出现两次，但它看起来不像。|836095|注意:这在JDK+11上有效。我首先尝试了jmap，但由于某种原因，在JDK+11上不起作用。|836096|entityMap^0|0|1K|1P|0|0|5|4|3Z|N|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@$D|Y|E|Z|F|G]|$D|10|E|11|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

Assuming you can identify some specific class which determines if the application is a springboot application, you could use some tool from the jdk, which can output loaded classes. I've tried it with jcmd(you'll find it under jre/bin/):

I'm not very good with bash so it might be not very efficient, but this works for me assuming that every springboot application has loaded class <code>org.springframework.boot.logging.LoggingInitializationContext</code> and no non-springboot app loads it. 

<pre><code>ps aux | grep [j]ava | awk '{print $2}' | xargs -I{} jcmd {} VM.class_hierarchy | grep "org.springframework.boot.logging.LoggingInitializationContext"
</code></pre>

It finds processes containing <code>java</code>, takes only the PID, passes it to the jcmd where you grep for the specific class. The output seems to be correct, the only problem is that I loose the PID in this long pipe and I'm not sure how to print it. 
But if your problem is "how many springboot apps", then it might not be an issue. I'm also not sure if the classes may appear twice when using <code>jcmd VM.class_hierarchy</code>, but it doesn't look like it. 

Note: This works on JDK 11. I tried jmap first, but that doesn't work for me on JDK 11 for some reason.

blocks|key|836127|text|我来到这个页面，寻找“如何找到是否加载了一个jar”的食谱(这与最初的问题有点不同)。但也许它会对某些人有用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|836128|我发现jcmd是获取这些信息的最佳方法，例如：|offset|length|style|CODE|836129|我有一个具有PID+1的JVM正在运行(它是一个在K8s中启动的CN应用程序)：|ordered-list-item|836130|$+jps+
1+MyAppLauncher
529+Jps|code-block|syntax|javascript|836131|了解jcmd为这个JVM提供了哪些选项：|836132|[eceuser@ecs1-0+temp]$+jcmd+1+help
1:
The+following+commands+are+available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
VM.classloader_stats
GC.rotate_log
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.finalizer_info
GC.heap_info
GC.run_finalization
GC.run
VM.uptime
VM.dynlibs
VM.flags
VM.system_properties
VM.command_line
VM.version
help|836133|经过一些尝试和错误，我发现VM.dynlibs做了我需要的事情：|836134|$+jcmd+1+VM.dynlibs+%7C+grep+custom
7f59a4b3b000-7f59a4b3d000+r--s+00000000+fd:00+1116085962+++++++++++++++++/home/app/lib/custom-fi-extensions-0.0.1-SNAPSHOT.jar|836135|所以是的，这个罐子已经装好了。|836136|entityMap^0|0|3|4|0|0|0|2|4|0|0|D|A|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@$D|13|E|14|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|15|8|@]|9|@]|A|$]]|$1|K|3|L|5|M|7|16|8|@]|9|@]|A|$N|O]]|$1|P|3|Q|5|J|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|R|3|S|5|M|7|1A|8|@]|9|@]|A|$N|O]]|$1|T|3|U|5|J|7|1B|8|@$D|1C|E|1D|F|G]]|9|@]|A|$]]|$1|V|3|W|5|M|7|1E|8|@]|9|@]|A|$N|O]]|$1|X|3|Y|5|6|7|1F|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|10|$]]

I came to this page searching for a recipe &quot;how to find if a jar has been loaded&quot; (which is a bit different than the original question). But perhaps it will be useful for somebody:
I found <code>jcmd</code> as best way to get this info, for example:
<ol>
<li>I have a running JVM with PID 1 (it's a CN application started in K8s):</li>
</ol>
<pre><code>$ jps 
1 MyAppLauncher
529 Jps
</code></pre>
<ol start="2">
<li>Figure out what options <code>jcmd</code> provides for this JVM:</li>
</ol>
<pre><code>[eceuser@ecs1-0 temp]$ jcmd 1 help
1:
The following commands are available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
VM.classloader_stats
GC.rotate_log
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.finalizer_info
GC.heap_info
GC.run_finalization
GC.run
VM.uptime
VM.dynlibs
VM.flags
VM.system_properties
VM.command_line
VM.version
help
</code></pre>
<ol start="3">
<li>With a bit of try and error, I found that <code>VM.dynlibs</code> does what I needed:</li>
</ol>
<pre><code>$ jcmd 1 VM.dynlibs | grep custom
7f59a4b3b000-7f59a4b3d000 r--s 00000000 fd:00 1116085962 /home/app/lib/custom-fi-extensions-0.0.1-SNAPSHOT.jar
</code></pre>
So yes, this jar has been loaded.

My task is to find out how many springboot app are running on a Linux system.
So What I am planning to do is,

1. to get all the java process IDs 

<pre><code>$ ps -aux|grep java
</code></pre>

2. Then somehow get the loaded classes from the IDs. 

I don't know if it is possible or not. Someone please kind enough to guide me to the right direction? 
P.S. : I am using java to run the above command by the help of Process class, something like this :

<pre><code>Process process = Runtime.getRuntime().exec("ps -ef");
</code></pre>

So I want to do it from a java project.

How to check if a class is loaded or not in a Java process

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我的任务是找出在Linux系统上运行的springboot应用程序的数量。所以我打算做的是，1.获取所有java进程ID的$ ps -aux|grep java然后，2.以某种方式从ID中获取加载的类。我不知道这是否可能。P.S.：我正在使用java在Process类的帮助下运行上述命令，如下所示：Process pr...

问如何检查类是否加载在Java进程中
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问如何检查类是否加载在Java进程中EN