JVM在线分析-解决问题的工具一(jinfo,jmap,jstack)

2023-11-10 09:20

本文主要是介绍JVM在线分析-解决问题的工具一(jinfo,jmap,jstack),希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!

1. jinfo

(base) PS C:\Users\zishi\Desktop> jinfo
Usage:jinfo <option> <pid>(to connect to a running process)where <option> is one of:-flag <name>         to print the value of the named VM flag #输出对应名称的参数-flag [+|-]<name>    to enable or disable the named VM flag# 开启或者关闭对应名称的参数 只有被标记为 manageable 的参数才可以被动态修改-flag <name>=<value> to set the named VM flag to the given value  #设定对应名称的参数-flags               to print VM flags # 输出全部的参数-sysprops            to print Java system properties #输出系统属性<no option>          to print both VM flags and system properties -? | -h | --help | -help to print this help message
(base) PS C:\Users\zishi> jinfo 9368
Java System Properties:
#Thu Nov 09 09:05:06 CST 2023
sun.desktop=windows
awt.toolkit=sun.awt.windows.WToolkit
java.specification.version=11
sun.cpu.isalist=amd64
sun.jnu.encoding=GBK
java.class.path=.\\quality-server.jar
java.vm.vendor=Oracle Corporation
sun.arch.data.model=64
user.variant=
catalina.useNaming=false
java.vendor.url=https\://openjdk.java.net/
。。。。略去
(base) PS C:\Users\zishi> jinfo  -sysprops 9368
Java System Properties:
#Thu Nov 09 09:07:07 CST 2023
sun.desktop=windows
awt.toolkit=sun.awt.windows.WToolkit
。。。。略去
(base) PS C:\Users\zishi> jinfo  -flags 9368
VM Flags:
-XX:CICompilerCount=4 
-XX:ConcGCThreads=3 
-XX:G1ConcRefinementThreads=10 
-XX:G1HeapRegionSize=2097152 
-XX:GCDrainStackTargetSize=64 
-XX:InitialHeapSize=534773760 
-XX:MarkStackSize=4194304 
-XX:MaxHeapSize=8524922880 
-XX:MaxNewSize=5114953728 
-XX:MinHeapDeltaBytes=2097152 
-XX:NonNMethodCodeHeapSize=5836300 
-XX:NonProfiledCodeHeapSize=122910970 
-XX:ProfiledCodeHeapSize=122910970 
-XX:ReservedCodeCacheSize=251658240 
-XX:+SegmentedCodeCache 
-XX:+UseCompressedClassPointers 
-XX:+UseCompressedOops 
-XX:+UseG1GC 
-XX:-UseLargePagesIndividualAllocation
(base) PS C:\Users\zishi> jinfo  -flag MaxHeapSize 9368
-XX:MaxHeapSize=8524922880
(base) PS C:\Users\zishi> jinfo  -flag MaxHeapSize=8524922883 9368
Exception in thread "main" com.sun.tools.attach.AttachOperationFailedException: flag 'MaxHeapSize' cannot be changedat jdk.attach/sun.tools.attach.VirtualMachineImpl.execute(VirtualMachineImpl.java:130)at jdk.attach/sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:309)at jdk.attach/sun.tools.attach.HotSpotVirtualMachine.setFlag(HotSpotVirtualMachine.java:282)at jdk.jcmd/sun.tools.jinfo.JInfo.flag(JInfo.java:146)at jdk.jcmd/sun.tools.jinfo.JInfo.main(JInfo.java:127)

查看被标记为 manageable 的参数

$ java -XX:+PrintFlagsFinal -version | grep  manageableintx CMSAbortablePrecleanWaitMillis           = 100                                    {manageable} {default}intx CMSTriggerInterval                       = -1                                     {manageable} {default}intx CMSWaitDuration                          = 2000                                   {manageable} {default}bool HeapDumpAfterFullGC                      = false                                  {manageable} {default}bool HeapDumpBeforeFullGC                     = false                                  {manageable} {default}bool HeapDumpOnOutOfMemoryError               = false                                  {manageable} {default}ccstr HeapDumpPath                             =                                        {manageable} {default}uintx MaxHeapFreeRatio                         = 70                                     {manageable} {default}uintx MinHeapFreeRatio                         = 40                                     {manageable} {default}bool PrintClassHistogram                      = false                                  {manageable} {default}bool PrintConcurrentLocks                     = false                                  {manageable} {default}
java version "11.0.13" 2021-10-19 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.13+10-LTS-370)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.13+10-LTS-370, mixed mode)

在这里插入图片描述
修改参数的值

(base) PS C:\Users\zishi> jinfo  -flag MaxHeapFreeRatio 9368
-XX:MaxHeapFreeRatio=70
(base) PS C:\Users\zishi> jinfo  -flag MaxHeapFreeRatio=80 9368
(base) PS C:\Users\zishi> jinfo  -flag MaxHeapFreeRatio 9368
-XX:MaxHeapFreeRatio=80

开启参数:

(base) PS C:\Users\zishi> jinfo -flag HeapDumpBeforeFullGC 9368
-XX:-HeapDumpBeforeFullGC
(base) PS C:\Users\zishi> jinfo -flag +HeapDumpBeforeFullGC 9368
(base) PS C:\Users\zishi> jinfo -flag HeapDumpBeforeFullGC 9368
-XX:+HeapDumpBeforeFullGC

扩展
java -XX:+PrintFlagsInitial 查看所有 JVM 参数启动的初始值
java -XX:+PrintFlagsFinal 查看所有 JVM 参数的最终值
java -XX:+PrintCommandLineFlags 查看哪些已经被用户或者 JVM 设置过的详细的 XX 参数的名称和值

2. jmap

(base) PS C:\Users\zishi> jmap
Usage:jmap -clstats <pid>to connect to running process and print class loader statisticsjmap -finalizerinfo <pid>to connect to running process and print information on objects awaiting finalizationjmap -histo[:live] <pid>to connect to running process and print histogram of java object heapif the "live" suboption is specified, only count live objectsjmap -dump:<dump-options> <pid>to connect to running process and dump java heapjmap -? -h --helpto print this help messagedump-options:live         dump only live objects; if not specified,all objects in the heap are dumped.format=b     binary formatfile=<file>  dump heap to <file>Example: jmap -dump:live,format=b,file=heap.bin <pid>
$ jmap -clstats 9368 > a.txt
$ cat a.txt | head -n 10
Index Super InstBytes KlassBytes annotations    CpAll MethodCount Bytecodes MethodAll    ROAll    RWAll    Total ClassName1    -1  10510264        504           0        0           0         0         0       24      616      640 [B2  8286   5545320       1112           0     6816          47      1117     27912     6480    30104    36584 java.lang.reflect.Method3    18   4025232        616         128    14264         109      4576     71992    18640    69664    88304 java.lang.String4    18   2461504        592           0     1360           9       213      2720     1488     3520     5008 java.util.concurrent.ConcurrentHashMap$Node5    -1   2286832        504           0        0           0         0         0       24      616      640 [Ljava.lang.Object;6    -1   2075104        504           0        0           0         0         0       32      616      648 [Ljava.util.HashMap$Node;7    18   2013216        584           0     1384           7       149      1816     1152     2952     4104 java.util.HashMap$Node8     7   1977960        584           0      504           1        10       624      304     1640     1944 java.util.LinkedHashMap$Entry9    18   1720280        672           0    22112         139      5679     85040    24632    85104   109736 java.lang.Class$ jmap -clstats 9368 | grep com.zishi.docuvate.exception4077    18        16        552          56     2568           6       282      1576     1448     3504     4952 com.zishi.docuvate.exception.GlobalExceptionHandler7429  7856         0        624           0      440           3        54       568      464     1368     1832 com.zishi.docuvate.exception.BadRequestException7430  7856         0        640           0      624           8       105      1472     1072     1952     3024 com.zishi.docuvate.exception.GlobalException

说明:

Index
Super
InstBytes
KlassBytes
annotations
CpAll
MethodCount
Bytecodes
MethodAll
ROAll
RWAll
Total
ClassName: 类的完全限定名

(base) PS C:\Users\zishi> jmap -histo 23152num     #instances         #bytes  class name (module)
-------------------------------------------------------1:       1164144      152211432  [B (java.base@11.0.13)2:        147373       44824568  [I (java.base@11.0.13)3:        694738       16673712  java.lang.String (java.base@11.0.13)4:        601819       12621496  [Ljava.lang.Class; (java.base@11.0.13)5:        107422        9453136  java.lang.reflect.Method (java.base@11.0.13)6:        113936        7291904  java.net.URL (java.base@11.0.13)7:        141772        4536704  org.springframework.boot.loader.jar.StringSequence8:         75593        4434728  [Ljava.lang.Object; (java.base@11.0.13)9:        178622        4286928  java.lang.StringBuilder (java.base@11.0.13)10:        102026        4081040  org.springframework.core.annotation.TypeMappedAnnotations11:         36093        2871384  [Ljava.util.HashMap$Node; (java.base@11.0.13)12:         88017        2816544  java.util.concurrent.ConcurrentHashMap$Node (java.base@11.0.13)13:         84459        2702688  org.springframework.core.annotation.TypeMappedAnnotations$MergedAnnotationFinder14:         82805        2649760  java.util.HashMap$Node (java.base@11.0.13)15:         64740        2589600  java.util.LinkedHashMap$Entry (java.base@11.0.13)16:         49166        2359968  java.util.HashMap (java.base@11.0.13)17:         92807        2227368  org.springframework.boot.loader.jar.JarURLConnection$JarEntryName18:         12370        2153808  [C (java.base@11.0.13)

说明:

#instances:对象数量
#bytes: 占用内存大小(单位:字节)
class name (module): 类的完全限定名

3. jstack

(base) PS C:\Users\zishi> jstack
Usage:jstack [-l][-e] <pid>(to connect to running process)Options:-l  long listing. Prints additional information about locks-e  extended listing. Prints additional information about threads-? -h --help -help to print this help message

代码示例:

/*** 当DeadLock类的对象flag==1时(td1),先锁定o1,睡眠500毫秒* 而td1在睡眠的时候另一个flag==0的对象(td2)线程启动,先锁定o2,睡眠500毫秒* td1睡眠结束后需要锁定o2才能继续执行,而此时o2已被td2锁定;* td2睡眠结束后需要锁定o1才能继续执行,而此时o1已被td1锁定;* td1、td2相互等待,都需要得到对方锁定的资源才能继续执行,从而死锁。*/
public class DeadLockTest implements Runnable{public int flag = 1;//静态对象是类的所有对象共享的private static Object o1 = new Object(), o2 = new Object();@Overridepublic void run() {System.out.println("flag=" + flag);if (flag == 1) {synchronized (o1) {try {Thread.sleep(500);} catch (Exception e) {e.printStackTrace();}synchronized (o2) {System.out.println("1");}}}if (flag == 0) {synchronized (o2) {try {Thread.sleep(500);} catch (Exception e) {e.printStackTrace();}synchronized (o1) {System.out.println("0");}}}}public static void main(String[] args) {DeadLockTest td1 = new DeadLockTest();DeadLockTest td2 = new DeadLockTest();td1.flag = 1;td2.flag = 0;//td1,td2都处于可执行状态,但JVM线程调度先执行哪个线程是不确定的。//td2的run()可能在td1的run()之前运行new Thread(td1).start();new Thread(td2).start();}
}

编译运行,执行jstack

(base) PS C:\Users\zishi> jstack 21744
2023-11-09 18:47:14
Full thread dump Java HotSpot(TM) 64-Bit Server VM (11.0.13+10-LTS-370 mixed mode):Threads class SMR info:
_java_thread_list=0x000001d91fca51a0, length=12, elements={
0x000001d91fa90800, 0x000001d91fab5800, 0x000001d91fb2b800, 0x000001d91fb2c800,
0x000001d91fb2e000, 0x000001d91fb31000, 0x000001d91fb32800, 0x000001d91fb35800,
0x000001d91fcb6800, 0x000001d91fcbc000, 0x000001d91fcbc800, 0x000001d972982000
}"Reference Handler" #2 daemon prio=10 os_prio=2 cpu=0.00ms elapsed=18.72s tid=0x000001d91fa90800 nid=0x2aac waiting on condition  [0x000000aacf8ff000]java.lang.Thread.State: RUNNABLEat java.lang.ref.Reference.waitForReferencePendingList(java.base@11.0.13/Native Method)at java.lang.ref.Reference.processPendingReferences(java.base@11.0.13/Reference.java:241)at java.lang.ref.Reference$ReferenceHandler.run(java.base@11.0.13/Reference.java:213)"Finalizer" #3 daemon prio=8 os_prio=1 cpu=0.00ms elapsed=18.72s tid=0x000001d91fab5800 nid=0x2224 in Object.wait()  [0x000000aacf9fe000]java.lang.Thread.State: WAITING (on object monitor)at java.lang.Object.wait(java.base@11.0.13/Native Method)- waiting on <0x0000000623a08fa8> (a java.lang.ref.ReferenceQueue$Lock)at java.lang.ref.ReferenceQueue.remove(java.base@11.0.13/ReferenceQueue.java:155)- waiting to re-lock in wait() <0x0000000623a08fa8> (a java.lang.ref.ReferenceQueue$Lock)at java.lang.ref.ReferenceQueue.remove(java.base@11.0.13/ReferenceQueue.java:176)at java.lang.ref.Finalizer$FinalizerThread.run(java.base@11.0.13/Finalizer.java:170)"Signal Dispatcher" #4 daemon prio=9 os_prio=2 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb2b800 nid=0x3bcc runnable  [0x0000000000000000]java.lang.Thread.State: RUNNABLE"Attach Listener" #5 daemon prio=5 os_prio=2 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb2c800 nid=0x3740 waiting on condition  [0x0000000000000000]java.lang.Thread.State: RUNNABLE"Service Thread" #6 daemon prio=9 os_prio=0 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb2e000 nid=0xd0c runnable  [0x0000000000000000]java.lang.Thread.State: RUNNABLE"C2 CompilerThread0" #7 daemon prio=9 os_prio=2 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb31000 nid=0x1620 waiting on condition  [0x0000000000000000]java.lang.Thread.State: RUNNABLENo compile task"C1 CompilerThread0" #10 daemon prio=9 os_prio=2 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb32800 nid=0x133c waiting on condition  [0x0000000000000000]java.lang.Thread.State: RUNNABLENo compile task"Sweeper thread" #11 daemon prio=9 os_prio=2 cpu=0.00ms elapsed=18.70s tid=0x000001d91fb35800 nid=0x1368 runnable  [0x0000000000000000]java.lang.Thread.State: RUNNABLE"Common-Cleaner" #12 daemon prio=8 os_prio=1 cpu=0.00ms elapsed=18.67s tid=0x000001d91fcb6800 nid=0x1df8 in Object.wait()  [0x000000aad01fe000]java.lang.Thread.State: TIMED_WAITING (on object monitor)at java.lang.Object.wait(java.base@11.0.13/Native Method)- waiting on <0x0000000623bf37f8> (a java.lang.ref.ReferenceQueue$Lock)at java.lang.ref.ReferenceQueue.remove(java.base@11.0.13/ReferenceQueue.java:155)- waiting to re-lock in wait() <0x0000000623bf37f8> (a java.lang.ref.ReferenceQueue$Lock)at jdk.internal.ref.CleanerImpl.run(java.base@11.0.13/CleanerImpl.java:148)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)at jdk.internal.misc.InnocuousThread.run(java.base@11.0.13/InnocuousThread.java:134)"Thread-0" #13 prio=5 os_prio=0 cpu=0.00ms elapsed=18.67s tid=0x000001d91fcbc000 nid=0x39d4 waiting for monitor entry  [0x000000aad02ff000]java.lang.Thread.State: BLOCKED (on object monitor)at DeadLockTest.run(DeadLockTest.java:25)- waiting to lock <0x0000000623bf7078> (a java.lang.Object)- locked <0x0000000623bf7068> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)"Thread-1" #14 prio=5 os_prio=0 cpu=0.00ms elapsed=18.67s tid=0x000001d91fcbc800 nid=0x7f8 waiting for monitor entry  [0x000000aad03ff000]java.lang.Thread.State: BLOCKED (on object monitor)at DeadLockTest.run(DeadLockTest.java:37)- waiting to lock <0x0000000623bf7068> (a java.lang.Object)- locked <0x0000000623bf7078> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)"DestroyJavaVM" #15 prio=5 os_prio=0 cpu=15.63ms elapsed=18.67s tid=0x000001d972982000 nid=0x5744 waiting on condition  [0x0000000000000000]java.lang.Thread.State: RUNNABLE"VM Thread" os_prio=2 cpu=0.00ms elapsed=18.73s tid=0x000001d91fa8f800 nid=0x222c runnable"GC Thread#0" os_prio=2 cpu=0.00ms elapsed=18.77s tid=0x000001d972996800 nid=0x5144 runnable"G1 Main Marker" os_prio=2 cpu=0.00ms elapsed=18.77s tid=0x000001d972a17800 nid=0x4180 runnable"G1 Conc#0" os_prio=2 cpu=0.00ms elapsed=18.77s tid=0x000001d972a19000 nid=0x3380 runnable"G1 Refine#0" os_prio=2 cpu=0.00ms elapsed=18.75s tid=0x000001d97fde5800 nid=0x2ba4 runnable"G1 Young RemSet Sampling" os_prio=2 cpu=0.00ms elapsed=18.75s tid=0x000001d97fde6800 nid=0x2f8c runnable
"VM Periodic Task Thread" os_prio=2 cpu=0.00ms elapsed=18.67s tid=0x000001d91fcb6000 nid=0x2990 waiting on conditionJNI global refs: 6, weak refs: 0Found one Java-level deadlock:
=============================
"Thread-0":waiting to lock monitor 0x000001d91fabff80 (object 0x0000000623bf7078, a java.lang.Object),which is held by "Thread-1"
"Thread-1":waiting to lock monitor 0x000001d91fabcc80 (object 0x0000000623bf7068, a java.lang.Object),which is held by "Thread-0"Java stack information for the threads listed above:
===================================================
"Thread-0":at DeadLockTest.run(DeadLockTest.java:25)- waiting to lock <0x0000000623bf7078> (a java.lang.Object)- locked <0x0000000623bf7068> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)
"Thread-1":at DeadLockTest.run(DeadLockTest.java:37)- waiting to lock <0x0000000623bf7068> (a java.lang.Object)- locked <0x0000000623bf7078> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)Found 1 deadlock.

说明:

Thread-1:线程名
prio:优先级
os_prio:操作系统级别的线程优先级
tid:线程id
nid:线程对应本地线程id
java.lang.Thread.State:线程状态

可以看到有一个 dead lock
Found one Java-level deadlock:
jstack还帮我们打印了死锁产生的原因
打印了死锁产生的原因之外,还帮我们定位到了java的代码行数:

Found one Java-level deadlock:
=============================
"Thread-0":waiting to lock monitor 0x000001d91fabff80 (object 0x0000000623bf7078, a java.lang.Object),which is held by "Thread-1"
"Thread-1":waiting to lock monitor 0x000001d91fabcc80 (object 0x0000000623bf7068, a java.lang.Object),which is held by "Thread-0"Java stack information for the threads listed above:
===================================================
"Thread-0":at DeadLockTest.run(DeadLockTest.java:25)- waiting to lock <0x0000000623bf7078> (a java.lang.Object)- locked <0x0000000623bf7068> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)
"Thread-1":at DeadLockTest.run(DeadLockTest.java:37)- waiting to lock <0x0000000623bf7068> (a java.lang.Object)- locked <0x0000000623bf7078> (a java.lang.Object)at java.lang.Thread.run(java.base@11.0.13/Thread.java:834)Found 1 deadlock.

参考:
https://juejin.cn/post/6957903936657293319#heading-3

这篇关于JVM在线分析-解决问题的工具一(jinfo,jmap,jstack)的文章就介绍到这儿,希望我们推荐的文章对编程师们有所帮助!



http://www.chinasem.cn/article/381789

相关文章

Java NoClassDefFoundError运行时错误分析解决

《JavaNoClassDefFoundError运行时错误分析解决》在Java开发中,NoClassDefFoundError是一种常见的运行时错误,它通常表明Java虚拟机在尝试加载一个类时未能... 目录前言一、问题分析二、报错原因三、解决思路检查类路径配置检查依赖库检查类文件调试类加载器问题四、常见

Java注解之超越Javadoc的元数据利器详解

《Java注解之超越Javadoc的元数据利器详解》本文将深入探讨Java注解的定义、类型、内置注解、自定义注解、保留策略、实际应用场景及最佳实践,无论是初学者还是资深开发者,都能通过本文了解如何利用... 目录什么是注解?注解的类型内置注编程解自定义注解注解的保留策略实际用例最佳实践总结在 Java 编程

Java 实用工具类Spring 的 AnnotationUtils详解

《Java实用工具类Spring的AnnotationUtils详解》Spring框架提供了一个强大的注解工具类org.springframework.core.annotation.Annot... 目录前言一、AnnotationUtils 的常用方法二、常见应用场景三、与 JDK 原生注解 API 的

Java controller接口出入参时间序列化转换操作方法(两种)

《Javacontroller接口出入参时间序列化转换操作方法(两种)》:本文主要介绍Javacontroller接口出入参时间序列化转换操作方法,本文给大家列举两种简单方法,感兴趣的朋友一起看... 目录方式一、使用注解方式二、统一配置场景:在controller编写的接口,在前后端交互过程中一般都会涉及

Java中的StringBuilder之如何高效构建字符串

《Java中的StringBuilder之如何高效构建字符串》本文将深入浅出地介绍StringBuilder的使用方法、性能优势以及相关字符串处理技术,结合代码示例帮助读者更好地理解和应用,希望对大家... 目录关键点什么是 StringBuilder?为什么需要 StringBuilder?如何使用 St

Python实现微信自动锁定工具

《Python实现微信自动锁定工具》在数字化办公时代,微信已成为职场沟通的重要工具,但临时离开时忘记锁屏可能导致敏感信息泄露,下面我们就来看看如何使用Python打造一个微信自动锁定工具吧... 目录引言:当微信隐私遇到自动化守护效果展示核心功能全景图技术亮点深度解析1. 无操作检测引擎2. 微信路径智能获

使用Java将各种数据写入Excel表格的操作示例

《使用Java将各种数据写入Excel表格的操作示例》在数据处理与管理领域,Excel凭借其强大的功能和广泛的应用,成为了数据存储与展示的重要工具,在Java开发过程中,常常需要将不同类型的数据,本文... 目录前言安装免费Java库1. 写入文本、或数值到 Excel单元格2. 写入数组到 Excel表格

Java并发编程之如何优雅关闭钩子Shutdown Hook

《Java并发编程之如何优雅关闭钩子ShutdownHook》这篇文章主要为大家详细介绍了Java如何实现优雅关闭钩子ShutdownHook,文中的示例代码讲解详细,感兴趣的小伙伴可以跟随小编一起... 目录关闭钩子简介关闭钩子应用场景数据库连接实战演示使用关闭钩子的注意事项开源框架中的关闭钩子机制1.

Maven中引入 springboot 相关依赖的方式(最新推荐)

《Maven中引入springboot相关依赖的方式(最新推荐)》:本文主要介绍Maven中引入springboot相关依赖的方式(最新推荐),本文给大家介绍的非常详细,对大家的学习或工作具有... 目录Maven中引入 springboot 相关依赖的方式1. 不使用版本管理(不推荐)2、使用版本管理(推

Java 中的 @SneakyThrows 注解使用方法(简化异常处理的利与弊)

《Java中的@SneakyThrows注解使用方法(简化异常处理的利与弊)》为了简化异常处理,Lombok提供了一个强大的注解@SneakyThrows,本文将详细介绍@SneakyThro... 目录1. @SneakyThrows 简介 1.1 什么是 Lombok?2. @SneakyThrows