Note.md

issues found & skills learnt

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issue.1 synchronized and @Transactional co-exist

@Transactional will add transaction begin and commit or rollback before and after the method, so adding synchronizedand @Transactional doesn't mean the whole block is synchronized， refer to the method register in user-service org.shop.service.UserServiceImpl class. example:

void proxy(obj,method){
    transaction.begin();
    synchronized{
        obj.invoke(method);
    }
    transaction.commit();
}

issue.2 new thread running inside a method annotated with @Transactional & @Rollback

@Transactional & Rollback doesn't work for the new thread created inside the annotated method. example:

@Transactional
@Rollback
void testNewThread(){
    new Thread(()->{
        mapper.insert(obj);
    }).start();
}

issue.3 dyingThread.join(). the calling thread such as main thread will wait for this dyingThread to die.

source code:

while(thread.isAlive()){ //dying thread is alive
    object.wait();// calling thread wait();
}

example:

Thread dying = new Thread(()->{
    sout("dying begin");
    Thread.sleep(3000);
    sout("died")
});
dying.start();
dying.join(); //blocking until the dying thread is finished
sout("main\calling thread finished");

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###issue4.

• PreAuthorize() on a controller doesn't work because PreAuthorize is based on AOP which in this case uses jdk proxy, and proxy needs interface to work properly and controller generally doesn't implement interface.

redis

1. import jedis and spring-boot-starter-data-redis
2. by default, there will be two default redisTemplates: redisTemplate and StringRedisTemplate configured in RedisAutoConfiguration class
3. config a new redisTemplate, it needs to be renamed: @Bean(name = "redisTemplate") and new serializers need to be configured.

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#img server ###nearly all the following dfs are based on Google File System paper.

1. minIO seems to be a good choice but mac m1 not supported
2. fastDFS outdated.
3. mongodb GridFS cannot retrive img directly from mongodb. have to you use spring as a server to process.
4. aliyun OSS, too expensive, and takes time to learn.
5. yupoo.com '又拍云图片管家' seems a good idea.
6. amazon s3 bucket cannot get access from mainland china.
7. TFS(taobao filesystem) the community is basically dead. nobody maintain it.

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#Shiro

• permission:

  • Resource Level A user can edit customer(any) records or open(any) doors.
  • Instance Level A user can edit a certain type of customer(i.e : IBM) or open a specific type of door such as kitchen door.
  • Attribute Level A user can edit Address field on the IBM Customer Record.

• roles:

  • Implicit Roles : admin can do whatever he wants, but no idea what permissions admin have.
  • Explicit Roles(better): admin can do whatever he wants, because admin have all the permission under admin role (*)

• users:

  • Users can have multiple roles, roles have different permission. therefore, users are granted with different permissions.

• Principals: Username, email, phone number anything that is unique

• Credentials: passwords, biometric data such as fingerprints and retina scans, and X.509 certificates