鳖摸鱼啦~

......

发表于

Lock

https://tool.4xseo.com/a/24067.html

锁分类：

对数据操作的粒度分

  1. 表锁：操作时，会锁定整个表
  2. 行锁：操作时，会锁定当前行
  3. 间隙锁：操作时，锁定范围条件内的记录

对数据的操作类型分

  1. 读锁（共享锁）：针对同一份数据，多个读操作可以同时进行不会互相影响

  2. 写锁（排他锁，也叫独占锁）：当前操作没有完成之前，会阻塞其他写锁或读锁

在开启事务的且自动提交为关闭的状态下`

select for update 和 update 会创建 排他锁,
如果带有索引查询，则会加行锁，如果查询整个表，则会加间隙锁

lock table

session 1

lock table my_table read;

select * from my_table;
unlock tables;

sessoin 2

select * from my_table;

update my_table set id = 1; -- will blocked until session 1 unlock tables

lock record

session 1

-- session  a
set autocommit = 0;
begin;
select TRX_ID from information_schema.INNODB_TRX where trx_mysql_thread_id = CONNECTION_ID();
select * from stu_teacher where teacher_id = 1 for update;
select TRX_ID from information_schema.INNODB_TRX where trx_mysql_thread_id = CONNECTION_ID();
COMMIT;

session 2

set @@autocommit=0; 
SHOW VARIABLES LIKE 'autocommit';
BEGIN;
select * from stu_teacher where teacher_id = 1 for update;
update stu_teacher set teacher_name = 'test112' where teacher_id = 1;
COMMIT;

session 1 先执行的话 session 2的查询for update 更新会被锁住

Tx

steps 


set autocommit = 0;

start transaction -- or begin;

update something set id = 1;

commit;

ISOLATION

READ_UNCOMMITED

READ_COMMITED

REPEATABLE-READ 可重复读，但会幻读（读取到新加入的行）

READ_PHANTOM

serialization

LOCK

发表于

EntryPoint


               HttpRequestHandler
                       |
                  /----------\
                 /            \
                /              \ 
 WebSocketHttpRequestHandler    SockJsHttpRequestHandler(So,text message need json format,strictly is json array)
            |                               |
SubProtocolWebSocketHandler         SockJsWebSocketHandler
            |                               |
            |                       WebSocketServerSockJsSession -> handleMessage ->  Jackson2SockJsMessageCodec -> decode 
            |                               |
StompSubProtocolHandler             StompSubProtocolHandler

发表于

AliyunVodEncryption加密分析

阿里云点播API文档地址

GetVideoPlayAuth

GetPlayInfo

预定义伪代码

covert


/**
  *  @param hexStr 16进制字符串，长度为16
  *  把16进制字符串利用base64编码，再解码，得到长度为16的字节数组
  *
  */
function convert(hexStr){
    return Base64.decode(Base64.encode(str));
}

AES

//AES加密，模式为CBC,填充方式:PKCS5Padding
function AES(){
    this.encrypt(content,KEY,IV){
    aes.encrypt(content,KEY,IV)
    }
}

返回参数说明

PlayInfoList.PlayInfo[0]

{
  "Status": "Normal",
  "StreamType": "video",
  "Rand": "NYspn8Qc220551gz62GCFGeOOU6WxF9nr9e8c64wDbE=", //存储第一段AES key
  "Size": 1368828,
  "Definition": "LD",
  "Fps": "25",
  "Duration": "10.0254",
  "ModificationTime": "2021-05-11T08:04:11Z",
  "Specification": "H264.SD",
  "Bitrate": "1092.283",
  "Encrypt": 1,//是否加密
  "PreprocessStatus": "UnPreprocess",
  "Format": "m3u8",
  "EncryptType": "AliyunVoDEncryption",//阿里云的私有加密
  "PlayURL": "https://vod.domain.com/play.m3u8",
  "NarrowBandType": "0",
  "Plaintext": "4pccpVV9LIjk9s0gZCFj4t6n85PPlwZuhrL2D4fbJJU=",//存储第二段AES key
  "CreationTime": "2021-05-11T08:04:05Z",
  "Height": 540,
  "Width": 960,
  "JobId": "a7a32209e6e3429f99128b25b34a8e40"
}

逻辑分析

假设视频文件的AES key 为 realKey

浏览器生成一个随机串 r1 利用RSA公钥加密，结果为randStr

服务器接受到randStr，利用私钥解密出随机串 r1

把r1利用MD5生成数字摘要，再截取(8,24)位的字符串 记为rs1

convert(rs1)得到第一段加密的IV和KEY,记为KEY1,IV1

再生成一段随机字符串记为r2,利用AES.encrypt(r2,KEY1,IV1) 得到上面返回结果中的 Rand

拼接r1 + r2，利用MD5生成数字摘要，再截取(8,24)为的字符串，记为rs2

convert(rs2)得到第二段加密的KEY，记为KEY2

利用AES.encrypt(realKey,KEY2,IV1) 得到上面返回的结果Plaintext

至此，整个加密逻辑分析完毕

解密TS文件

MPEG-TS文件结构

用到的工具EasyICE,DVB Inspector,tsduck

ts-header(32byte)

字段名 位数 说明
sync_byte 4bit TS package 标识,固定值0x47
transport_error_indicator 1bit 传输错误标识
payload_unit_start_indicator 1bit PES包开始标识,可以用掩码0x40 判断
transport_priority 1bit 传输优先级
PID 13bit TS package identity 0x100:视频数据,0x101:音频数据, -1:id3Track，应该从PMT表中查找
transport_scrambling_control 2bit 是否有干扰码
adaptation_field_control 2bit 是否有扩展字段，0x01:payload only,0x02:adaptation field only,0x03:adaptation field follow payload
continuity_counter 4bit pack seq 
var data = []
//当遇到`PUSI(Payload unit start indicator )`标识时，获取每个ts包的payload
data.push(payload)
//遇到下一个`pusi`标识时，
//合并data中的payload，作为一个PES单元
//解密PES数据段,再把解密后的payload回写到TSPacket

reference

AES五种加密模式

aliplayer-vod.js

aes-js

jsencrypt

https://gist.github.com/manyuanrong/39f151181a193b454c3b11dac1b60e15#file-jsencrypt-js

https://g.alicdn.com/de/prismplayer/2.9.0/hls/aliplayer-hls-min.js

https://stackoverflow.com/questions/28562894/how-to-loop-an-mpeg-ts-stream

https://github.com/fy-create/TSParser

发表于

只构建parent pom

cd your-project
mvn install -N

note:

-N,--non-recursive Do not recurse into sub-projects

构建多模块

     p
     |
     |
-----------
|         |
a  -----> b

````

mvn install -pl a -am -amd


note:

-pl, –projects
构建指定的模块，模块间用逗号分隔；适合无依赖的项目
-am, –also-make (常用)
同时构建所列模块的依赖模块，比如A依赖B，B依赖C，构建B，同时构建C
-amd, –also-make-dependents
同时构建依赖于所列模块的模块，比如A依赖B，B依赖C,构建B，同时构建A

```

reference

Maven 单独构建多模块项目中的子模块

Install parent POM without building Child modules

发表于

how it works

// create worker
new SharedWorkder("https://socialclub.rockstargames.com/Home/SocketWorker") // 
// self.importScripts('https://s.rsg.sc/sc/js/20201212bfdb/build/socketWorker.js');

how to debug

  1. Type chrome://inspect/#workers in chrome location bar;

  2. You can find https://socialclub.rockstargames.com/Home/SocketWorker in the Shared workers

  3. Click inpect as you can debug like debug normal session;

conclusion

//https://www.right.com.cn/forum/thread-4052504-1-1.html
//https://www.jianshu.com/p/01262e314eab
//http://alisdk-api-doc.oss-cn-hangzhou.aliyuncs.com/player/5.1.6/android/index.html?com/aliyun/player/VidPlayerConfigGen.EncryptType.html

  1. hidden the network request detail;

  2. increase debugging difficulty;

发表于 分类于

AOP

PointCut

切入点

用于匹配符合某些特征的方法.

JoinPoint

连接点

程序执行过程中的一个点，如方法的执行或异常的处理。在Spring AOP中，连接点总是表示方法执行。

advice

before

beofore

目标JoinPoint执行之前执行

afterReturing

目标JoinPoint正常执行返回.

afterThrowing

目标JoinPoint 执行时抛出异常

after(finnaly)

目标JoinPoint方法执行结束

around

需要手动的调用目标JoinPoint执行.

该通知的第一个参数是ProceedingJoinPoint类型.

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.ProceedingJoinPoint;

@Aspect
public class AroundExample {

    @Around("com.xyz.myapp.CommonPointcuts.businessService()")
    public Object doBasicProfiling(ProceedingJoinPoint pjp) throws Throwable {
        // start stopwatch
        Object retVal = pjp.proceed();
        // stop stopwatch
        return retVal;
    }

}

访问当前JoinPoint

任何通知可以定义该方法的第一个参数类型为（org.aspectj.lang.JoinPoint)类型，除@around通知外

  • getArgs() 返回方法参数

  • getThis() 返回代理对象

  • getTarget 返回目标对象

  • getSignature() 返回被通知的方法的描述

  • toString() 打印被通知的方法的有用描述

传递参数给Advice


@Before("com.xyz.myapp.CommonPointcuts.dataAccessOperation() && args(account,..)")
public void validateAccount(Account account) {
    // ...
}

Advice的顺序

从高到底

@Around, @Before, @After, @AfterReturning, @AfterThrowing

发表于

Method.invoke

调用链

method.invoke()
    ->
        MethodAccessor.invoke()
            -> ReflectionFactory.newMethodAccessor() -> DelegatingMethodAccessorImpl
            -> invoke
            -> DelegatingMethodAccessorImpl.invoke
                -- delegate = NativeMethodAccessorImpl
                                    -> invoke
                                        if(numInvocations > ReflectionFactory.inflationThreshold())
                                            -> acc = MethodAccessorGenerator.generateMethod
                                            -> parent.setDelegate(acc) 
                                        invoke0()//native invoke
                -- deletegate = sun.reflect.GeneratedMethodAccessor1@101df177

补充说明

  • 下文中代理类皆为MethodAccessor的子类

  • 当ReflectionFactory.noInflation = true 会直接生成代理类

  • 反射调用方法执行次数大于ReflectionFactory.inflationThreshold(默认15)时，会生成代理类，用于提高反射执行效率,代理类反编译后源码大致如下(以String#toCharArray为例)

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package sun.reflect;

import java.lang.reflect.InvocationTargetException;

public class GeneratedMethodAccessor1 extends MethodAccessorImpl {
    public GeneratedMethodAccessor1() {
    }

    //var1 为原object对象，var为方法参数数组
    public Object invoke(Object var1, Object[] var2) throws InvocationTargetException {
        if (var1 == null) {
            throw new NullPointerException();
        } else {
            //生成字节码时已经自动处理了对象类型
            String var10000;
            try {
                var10000 = (String)var1;
                if (var2 != null && var2.length != 0) {
                    throw new IllegalArgumentException();
                }
            } catch (NullPointerException | ClassCastException var4) {
                throw new IllegalArgumentException(var4.toString());
            }

            try {
                //实际调用 等价于 strObj.toCharArray();所以开销很小
                return var10000.toCharArray();
            } catch (Throwable var3) {
                throw new InvocationTargetException(var3);
            }
        }
    }
}

  • 当系统中反射调用过多时会导致metaspace溢出，因为生成了过多的代理类

  • noInflation可通过sun.reflect.noInflation配置

  • inflationThreshold可通过sun.reflect.inflationThreshold配置

Constructor.newInstance

调用链

和上文大致类似

补充说明

  • 生成代理类的代理类反编译后源码大致如下(以new String(String)为例)
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package sun.reflect;

import java.lang.reflect.InvocationTargetException;

public class GeneratedConstructorAccessor2 extends ConstructorAccessorImpl {
    public GeneratedConstructorAccessor2() {
    }

    public Object newInstance(Object[] var1) throws InvocationTargetException {
        String var10000;
        String var10001;
        String var10002;
        try {
            var10000 = new String;
            var10001 = var10000;
            if (var1.length != 1) {
                throw new IllegalArgumentException();
            }

            var10002 = (String)var1[0];
        } catch (NullPointerException | ClassCastException var3) {
            throw new IllegalArgumentException(var3.toString());
        }

        try {
            var10001.<init>(var10002);
            return var10000;
        } catch (Throwable var2) {
            throw new InvocationTargetException(var2);
        }
    }
}

发表于 
<profiles>
       <profile>
           <id>docker-build-local</id>
           <properties>
               <docker-maven-plugin.host>http://192.168.2.210:2374</docker-maven-plugin.host>
               <docker-maven-plugin.registry.url>registry.cn-hangzhou.aliyuncs.com</docker-maven-plugin.registry.url>
               <docker-maven-plugin.image.tag>snapshot</docker-maven-plugin.image.tag>
               <docker-maven-plugin.skip.build>false</docker-maven-plugin.skip.build>
               <docker-maven-plugin.skip.docker>false</docker-maven-plugin.skip.docker>
           </properties>
           <activation>
               <property>
                   <name>dockerBuild</name>
                   <value>local</value>
               </property>
           </activation>
       </profile>
   </profiles>
   <build>
       <plugins>
           <plugin>
               <groupId>com.spotify</groupId>
               <artifactId>docker-maven-plugin</artifactId>
               <configuration>
                   <env>
                       <LANG>zh_CH.UTF-8</LANG>
                   </env>
                   <runs>
                       <run>
                           echo "test something"
                       </run>
                   </runs>
               </configuration>
           </plugin>
       </plugins>
   </build>
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