徹底解決Jmap在mac版本無法使用的問題
看了網上很多文章，都說一半，說的都是大家說過的，根本沒有解決問題。說jdk8不行，換成jdk9或者jdk11，我都試了，還是不行，最後說是mac的問題。換成linux，崩潰！！！
一、在mac運作Jmap的問題
1. 我們運作jps查詢剛剛啟動的項目
然後執行Jmap查詢堆記憶體使用情況
Jmap -heap 1518
執行後報錯：
Attaching to process ID 1518, please wait...
ERROR: attach: task_for_pid(1518) failed: '(os/kern) failure' (5)
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$BsdDebuggerLocalWorkerThread.execute(BsdDebuggerLocal.java:169)
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.attach(BsdDebuggerLocal.java:287)
at sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:671)
at sun.jvm.hotspot.HotSpotAgent.setupDebuggerDarwin(HotSpotAgent.java:659)
at sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:341)
at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:304)
at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:140)
at sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.tools.jmap.JMap.runTool(JMap.java:201)
at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.attach0(Native Method)
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.access$100(BsdDebuggerLocal.java:65)
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$1AttachTask.doit(BsdDebuggerLocal.java:278)
at sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$BsdDebuggerLocalWorkerThread.run(BsdDebuggerLocal.java:144)
2. 百度這個異常
說mac環境jdk8不支援Jmap，需要替換成jdk11。于是在mac上安裝了jdk11。安裝的時候讓jdk8和jdk11共存，原因是，機關項目使用的是jdk8，是以不能删。
二、Jmap在JDK11的問題
如何配置jdk8和jdk11共存切換，參考這篇文章：cnblogs.com/ITPower/p/15527478.html
1. 檢查目前jdk版本
我已經替換成了jdk11版本，需要注意的是，需要看一下我們啟動的項目的jdk版本是不是11。
2. 檢查idea項目中JDK版本
這裡需要注意的是，修改目前項目的jdk版本即可。不要修改系統的。修改目前項目，右擊項目名稱-->Open Module Settings-->SDKs。
3.執行Jmap指令
Error: -heap option used
Cannot connect to core dump or remote debug server. Use jhsdb jmap instead
看錯誤提示說讓替換Jamp為jhsdb jmap，百度其用法
jhsdb jmap --heap --pid 程序号
詳細jhsdb相關資訊檢視文檔：https://www.jianshu.com/p/92931e6466b3
可是依然報錯
Attaching to process ID 1525, please wait...
ERROR: attach: task_for_pid(1525) failed: '(os/kern) failure' (5)
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$BsdDebuggerLocalWorkerThread.execute(BsdDebuggerLocal.java:169)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.attach(BsdDebuggerLocal.java:283)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:672)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebuggerDarwin(HotSpotAgent.java:660)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:342)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:141)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.JMap.main(JMap.java:176)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runJMAP(SALauncher.java:326)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:455)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process. Could be caused by an incorrect pid or lack of privileges.
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.attach0(Native Method)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$1AttachTask.doit(BsdDebuggerLocal.java:274)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal$BsdDebuggerLocalWorkerThread.run(BsdDebuggerLocal.java:144)
很鬧心。又折騰了半天，最後又說是權限問題的，有說是項目使用jdk和jmap運作jdk版本不一緻的。我兩個都試了。
權限問題解決辦法，執行如下指令：
jhsdb jmap --heap --pid 2139
jdk版本問題，我們上面都設定了使用jdk11， idea也是jdk11. 但是沒有編譯，這裡重新編譯一下，再試。
最終運作項目，檢視到結果
Attaching to process ID 2139, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 11.0.2+9
using thread-local object allocation.
Garbage-First (G1) GC with 8 thread(s)
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 4294967296 (4096.0MB)
NewSize = 1363144 (1.2999954223632812MB)
MaxNewSize = 2576351232 (2457.0MB)
OldSize = 5452592 (5.1999969482421875MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 21807104 (20.796875MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 17592186044415 MB
G1HeapRegionSize = 1048576 (1.0MB)
Heap Usage:
G1 Heap:
regions = 4096
capacity = 4294967296 (4096.0MB)
used = 21654560 (20.651397705078125MB)
free = 4273312736 (4075.348602294922MB)
0.5041845142841339% used
G1 Young Generation:
Eden Space:
regions = 15
capacity = 52428800 (50.0MB)
used = 15728640 (15.0MB)
free = 36700160 (35.0MB)
30.0% used
Survivor Space:
regions = 5
capacity = 5242880 (5.0MB)
used = 5242880 (5.0MB)
free = 0 (0.0MB)
100.0% used
G1 Old Generation:
regions = 1
capacity = 210763776 (201.0MB)
used = 0 (0.0MB)
free = 210763776 (201.0MB)
0.0% used
成功！