Tag Archives: solution

A simple method of generating secret key by GIT and configuring SSH public key

First install git, then right-click in any blank space on the desktop and select git base here, as shown in the following figure:
① mode 1: input command: Cd ~ and then input: SSH- keygen.exe Then press enter, press enter again, and press enter three times at enter:
② mode 2: input: SSH keygen – O – t RSA – B 4096 – C “ [email protected] ”Then press enter, press enter again, at enter, press enter three times (same as mode one)

Then find the ID corresponding to the directory above_ rsa.pub You can open the public key file, open it in Notepad or other ways, copy the contents
, find the settings in your remote warehouse, and configure SSH to succeed
, reprint address (detailed steps address:

https://blog.csdn.net/xiayiye5/article/details/79652296https :// blog.csdn.net/r8hzgemq/article/details/49897905

Solution to node sass installation failure

When NPM installs the node sass dependency, the github.com Download the. Node file from the. Due to the problems of domestic network environment, the download time may be very long, even leading to timeout failure.

Method 1:

Use Taobao image:

npm install -g cnpm --registry=https://registry.npm.taobao.org

Method 2: if the use of Taobao mirror still failed

Delete the entire dependent node_ Use cnpm I to download the modules file again

Method 3:

npm uninstall node-sass

cnpm install node-sass

After that, start the Vue project again.

NPM and Node.js Version incompatibility

Today, when Xiaobian was installing dependency, he suddenly reported the following error:
. Well, although Xiaobian passed CET-4, he didn’t know which ocean to throw him into, so he went to Baidu to translate.
The result of translation is: the possible node tar or NPM version is the same as node.js This version of is not compatible. Then Xiaobian searches for answers on Baidu, saying that NPM will be downgraded, and the error prompt also says that Xiaobian should mention the version of NPM to be greater than 5.5.1 or less than 5.4.0. However, goose, Xiaobian according to it said downgrade or upgrade operation a wave as fierce as a tiger, the result, ha ha.
So, Xiaobian saw another article on Du Niang. Well, it solved the problem perfectly, so I shared it with you. Xiaobian also took notes.
NPM error

WARNING: You are likely using a version of node-tar or npm that is incompatible with this version of Node.js.
Please use either the version of npm that is bundled with Node.js, or a version of npm (> 5.5.1 or < 5.4.0) or node-tar (> 4.0.1) that is compatible with Node.js 9 and above.
npm[12696]: c:\ws\src\node_zlib.cc:568: Assertion `args.Length() == 7 && "init(windowBits, level, memLevel, strategy, writeResult, writeCallback," " dictionary)"' failed. 
 1: 00007FF7EA10363F napi_wrap+128063
 2: 00007FF7EA0A2836 v8::base::CPU::has_sse+35142
 3: 00007FF7EA0A2B53 v8::base::CPU::has_sse+35939
 4: 00007FF7EA021197 v8::internal::Debug::break_frame_id+84983
 5: 00007FF7EA86DBE0 v8::internal::Builtins::builtin_handle+323456
 6: 00007FF7EA86D127 v8::internal::Builtins::builtin_handle+320711
 7: 00007FF7EA86D468 v8::internal::Builtins::builtin_handle+321544
 8: 00007FF7EA86D26E v8::internal::Builtins::builtin_handle+321038
 9: 00007FF7EAD04EDD v8::internal::SetupIsolateDelegate::SetupHeap+546893
10: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748
11: 00007FF7EAC85320 v8::internal::SetupIsolateDelegate::SetupHeap+23696
12: 00007FF7EAD695C0 v8::internal::SetupIsolateDelegate::SetupHeap+958256
15: 00007FF7EAC852F7 v8::internal::SetupIsolateDelegate::SetupHeap+23655
16: 00007FF7EAD695C0 v8::internal::SetupIsolateDelegate::SetupHeap+958256
17: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748
18: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748
19: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748
20: 00007FF7EAC830BC v8::internal::SetupIsolateDelegate::SetupHeap+14892
21: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748
22: 00007FF7EAC89D8C v8::internal::SetupIsolateDelegate::SetupHeap+42748

Solution:
1. Uninstall node.js2 Delete the NPM and NPM cache (this step can’t be omitted) under C:: (users/administrator/appdata/roaming)
3. Re install nodejs. Please download the installation files from the official website and click here.
Official website address: https://nodejs.org/zh-cn/download/

4. Open the small blackboard and enter node – V and NPM – V respectively to see the corresponding version number

However, the version of nodejs installed by Xiaobian is 12.16.3, and the corresponding version of NPM is 6.14.4. Ah, in this way, Xiaobian reported another error when running NPMI in other projects: exceeding the maximum stack

Maximum call stack size exceeded

Xiaobian asked Du Niang again that the solution is to go back to a lower version of NMP, that is, to downgrade it. Ah, as a result, only the node corresponding to the lower version of NPM can be installed.

Reprint address: https://blog.csdn.net/qq_ 41241767/article/details/89465508

Lock mechanism in Oracle

In order to explore lock, I set up a test table test, the structure and test data are as follows:
sql & gt; select * from test;

        ID NAME
———- ———-
         6 yoxi
         2 robinson
         2 tttt
         3 david
         4 jason
         5 lucy
         1 test

7 rows selected.

Row share if row share locking is performed on a table, other sessions cannot perform exclusive locking on the table, but they can perform any other locking. That is to say, if a session performs row share lock on the table, other sessions can be executed except drop command.
In session 1:
sql & gt; lock table test in row share mode;
the table is locked.
Session 2:
sql & gt; lock table test in row share mode;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in row exclusive mode;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in share mode;
the table is locked.
SQL & gt; commit;
submit complete
sql & gt; lock table test in exclusive mode nowait;
lock table test in exclusive mode nowait
*
error in line 1:
ora-00054: the resource is busy, but the specified nowait method is used to obtain the resource
sql & gt; update test set id = 10;
7 lines have been updated.
SQL & gt; rollback;
rollback completed.
SQL & gt; drop table test;
drop table test
*
error in line 1:
ora-00054: the resource is busy, but it is specified to obtain the resource by nowait// in fact, the drop table command will perform exclusive locking on the table
row exclusive when executing insert, update, Delete will obtain a row exclusive lock, which has all the characteristics of row share. If a session obtains a row exclusive lock, then other sessions cannot perform exclusive lock on the table or share lock on the table. DML operation can be performed on the table, but drop is not allowed;

In session 1, the
sql & gt; lock table test in row exclusive mode;
table is locked.
Session 2:
sql & gt; lock table test in row share mode;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in row exclusive mode;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in share mode nowait;
lock table test in share mode nowait
*
error in line 1:
ora-00054: the resource is busy, but it is specified to get the resource in nowait mode
sql & gt; lock table test in exclusive mode nowait;
Lock table test in exclusive mode nowait
*
error in line 1:
ora-00054: the resource is busy, but the nowait mode is specified to obtain the resource

Share (shared lock) when a session has a share lock on a table, other sessions cannot lock the table in exclusive, row exclusive mode. In other words, if row exclusive is not available, insert, update, delete and drop operations cannot be performed.
In session 1, the
sql & gt; lock table test in share mode;
table is locked.
In session 2, the
sql & gt; lock table test in row share mode;
table is locked.
SQL & gt; lock table test in row exclusive mode nowait;
error in line 1:
ora-00054: the resource is busy, but the specified nowait method is used to get the resource
sql & gt; lock table test in share mode;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in exclusive mode nowait;
lock table test in exclusive mode nowait
*
error in line 1:
ora-00054: the resource is busy, but it is specified to get the resource in nowait mode

Exclusive (exclusive lock) when the drop command is executed, an exclusive lock is generated. As the name suggests, as long as a session has an exclusive lock on a table, other sessions cannot lock the table.
In session 1, the
sql & gt; lock table test in exclusive mode;
table is locked.
In session 2,
sql & gt; lock table test in row share mode nowait;
lock table test in row share mode nowait
*
there is an error in line 1:
ora-00054: the resource is busy, but the specified nowait method is used to obtain the resource
other locks do not need to be tested, because row share cannot obtain other locks, let alone other locks

Share row exclusive: if a session obtains a share row exclusive lock, other sessions can only obtain the row share lock on the table, that is to say, other sessions can’t perform insert, update, delete or drop operations on the table. Row share locking is good for nothing except preventing drop…
sql & gt; lock table test in share in session 1 Row exclusive mode;
the table is locked.
In session 2
sql & gt; lock table test in row share mode nowait;
the table is locked.
SQL & gt; commit;
commit completed.
SQL & gt; lock table test in row exclusive mode nowait;
lock table test in row exclusive mode nowait
*
error in line 1:
ora-00054: the resource is busy, but it is specified to get the resource in nowait mode
sql & gt; lock table test in share mode nowait;
Error in lock table test in share mode nowait
*
line 1:
ora-00054: the resource is busy, but the specified nowait method is used to obtain the resource
sql & gt; lock table test in exclusive mode nowait;
error in lock table test in exclusive mode nowait
*
line 1:
ora-00054: the resource is busy, However, it is specified to obtain resources in nowait mode

To sum up:

1. If a table is locked by a session, no matter what the lock is, the other session will not be able to obtain the exclusive lock for the table, that is, the table cannot be deleted. In fact, it is very easy to be the same. If someone is using that table, you must delete it

2. If row exclusive locking can be performed on a table, DML operation can certainly be performed

3. Share lock can be understood in this way. As the name suggests, share lock is used for sharing. Since it is shared, other users can only view it and cannot change it.

4. We can understand exclusive lock in this way. As the name suggests, exclusive lock is exclusive. Other users can only view it and cannot modify it.

Note: the lock command above can only get TM (table) lock

There are two kinds of locks generated by update, delete and insert. One is TM lock, the other is TX lock. TX lock means transaction lock

Select….. For update will also get a TX lock and a row exclusive lock
as well

Reprint address: http://blog.csdn.net/robinson1988/article/details/4675371

How can Oracle query tables of other users without adding a table user name

Question: how can Oracle access other users’ tables without adding a table user name

Reasons: 1. Convenient access to common tables

2. Hide the users of the table

3. Limit authority

Solution:

1、 Create consent word

CREATE [PUBLIC] SYNONYM synonym_ name FOR [schema.] object[@db_ link];

2、 Create view

create view DF_ YHJB_ BZ as select * from MIS.DF_ YHJB_ BZ

3、 Modify current_ Schema parameter

The schema used to switch the current session. When parsing the object name, if there is no qualified schema name before the object name, Oracle will automatically query the matching objects under this schema.

for example, when the “Scott” user executes the “select * from EMPs;” statement, Oracle will query the “EMPs” table under the “Scott” architecture by default; however, if the “alter session set” current_ Schema = XX; the current schema of the session is changed. When this statement is executed, Oracle will query the EMPs table under XX schema.

Oracle stops a job

1. Related tables and views

　dba_ jobs 　　all_ jobs 　　user_ Jobs contains all the job information DBA of the login user_ jobs_ Running contains information about running jobs. Note that you must use the sys user of Oracle to log in to the database to view the DBA_ jobs_ Running, V $process, V $session table. At the same time, when logging in to the operating system, the Oracle user should be used.

2. Problem description

Solve a problem for colleagues, when the network connection is poor, execute a very long time SQL insert operation.

Since the network condition is not good, we choose to use disposable job to complete the insertion operation. After the job was executed for a period of time, I found that there was something wrong with the inserted table (I’m sorry, I didn’t check it first at that time). I’m going to stop job, because when job is running, all my modifications will report the error that system resources are busy.

It is not feasible to forcibly kill session, because the job will be restarted later. If the executed SQL is also killed, the restarted job will be executed again.

3. Solutions

The better way to do it is to do it;

1. First determine the job number to stop

In 10g, it can pass DBA_ Jobs_ Running to confirm.

Find running job:

select sid from dba_ jobs_ running;

Find the SPID of the running job:

select a.spid from v$process a ,v$session b where a.addr=b.paddr and b.sid in (select sid from dba_ jobs_ running);

2. Break your confirmed job

Pay attention to DBMS_ Job package to identify your job as broken.

SQL> EXEC DBMS_ JOB.BROKEN (job#,TRUE);

Note: after executing the command, the job you selected is still running.

3. Oracle session corresponding to kill

If the job is required to stop immediately, you need to find the corresponding session (SID, serial #) of the job, and then execute the following command:

ALTER SYSTEM KILL SESSION ‘sid,serial#’;

Or directly kill the session of the corresponding operating system. If you use alter system kill session to execute for a long time, you can use the OS command to quickly kill the session

For Windows, at the DOS Prompt: orakill sid spid

For UNIX at the command line> kill –9 spid

4. Check if your job is still running

Check whether the job you want to stop is still running. In most cases, it should have stopped. In particular, the execution of the third step of the “killer” command. If it really doesn’t stop, we have to do it again from the first step and the third step.

5. Change the number of job queue processes to 0

First, confirm the current number of job queue processes

SQL> col value for a10

SQL> select name,value from v$parameter where name =’job_ queue_ processes’;

Then change the number of job queue processes to 0

SQL> ALTER SYSTEM SET job_ queue_ processes = 0;

Make sure all jobs stop.

6. Modify anything you want to modify, even the content in the job.

7. After the modification is completed, stop the broken state of the job.

SQL>EXEC DBMS_ JOB.BROKEN (job#,FALSE):

8. Resume job_ queue_ The original value of processes

ALTER SYSTEM SET job_ queue_ processes = original_ value;

At this point, the entire stop and modify job completed

However, it should be noted that when mark is in a broken state, it may take a while for job to execute SQL internally. Therefore, you must consider it carefully when creating a job. At the same time, if possible, you can add some parts to judge the “stop signal” in your PL/SQL code. To perform the above steps.

After all, Oracle is very stubborn when executing jobs

4. Annex: usage of orakill

Oracle’s lock table solution “ora-00031: session marked for kill” often encounters a session that is always active, making the CPU always in use. Although it kills, it can’t make the thread end. Kill session is just to kill the process, but the thread is always active. It needs a real kill thread to solve the problem of high CPU utilization. OS: Windows 2003 orakill uses orakill Sid SPID, where sid is the instance name and SPID is the thread number. How to get this SPID?The following is a statement to find SPID. Select SPID, osuser, s.program from V $process P, V $session s where p.addr = s.paddr and s.sid = XXX; — Note: XXX is the SID of session (not database SID). You can input it yourself.
orakill instance_ Name SPID can successfully solve the problem of high CPU utilization in this way

MySQL forgot the root password

1. Start the task manager and end the MySQL process

2. Enter the command line, enter the bin directory of MySQL (& lt; environment change & gt; path, you can find the bin directory) and start the MySQL service

mysqld -nt –skip-grant-tables

(start without checking permissions);

(it may appear: 120705 17:41:14 [warning] option ‘new’: Boolean value’t ‘wasn’t recognized. Set to off. )

3. Reopen a command prompt window

Input: MySQL – uroot

4. Change the root password:

update mysql.user set password=PASSWORD(‘newpass’) where User=’root’;

5, flush privileges;

6, quit

Reconnecting MySQL

Reprint address:

http://blog.sina.com.cn/s/blog_ a3695da601010 mrs.html

MySQL modify character set

First of all, there are two main concepts about MySQL character set, one is character sets, the other is collations, the former is character content
and encoding, and the latter is some rules for comparing the former. These two parameter sets can be specified at four levels: database instance, single database, table and column.

For users, utf8 encoding is generally recommended to store data. To solve the problem of garbled code, it is not only the storage of MySQL data, but also related to the coding mode of user program files and the connection mode between user program and MySQL database.

first of all, MySQL has a default character set, which is determined during installation. When compiling mysql, you can use default_ Charset =
utf8 and default_ COLLATION=utf8_ general_ CI (MySQL version 5.5, version 5.1 uses — with charset =
utf8 — with collation = utf8)_ general_ The default character set is utf8, which is also the most once and for all method. After this is specified,
the coding mode of client connecting to database is utf8 by default, and the application does not need any processing.

unfortunately, many people don’t specify these two parameters when compiling and installing mysql, and most people install it through binary programs.
at this time, the default character set of MySQL is Latin1. At this time, we can still specify the default character set of MySQL by my.cnf Add two parameters to the file:
1. Add
default character set = utf8 under [mysqld]
2. Add
default character set = utf8 under [Client]
2 In this way, we don’t need to specify utf8 character set when we build database and table. This writing method in the configuration file solves the problem of data storage and comparison
, but it has no effect on the connection of the client. At this time, the client usually needs to specify utf8 connection to avoid garbled code. This is the general set
Names command. In fact, the set names utf8 command corresponds to the following server-side commands:
set character_ set_ client = utf8;
SET character_ set_ results = utf8;
SET character_ set_ Connection = xutf8;
but these three parameters cannot be written in the configuration file my.cnf It’s in the library. It can only be modified dynamically by the set command. What we need is to write a way to
Yongyi in the configuration file. At this time, is there a way to solve the problem on the server?The feasible idea is in init_ Set in connect. This command will be triggered every time an ordinary user connects. You can add the following line in the [mysqld] section to set the connection character set:
Add under [mysqld]:
init_ Connect =’set names utf8 ‘
summary:
1. It is preferred to specify two parameters to use utf8 encoding when compiling and installing mysql.
2. Select in the configuration file my.cnf or my.ini Set two parameters and init at the same time_ Connect parameter.
3. The third is in the configuration file my.cnf or my.ini Set two parameters, and specify the set names command for the client connection.
4. In the configuration file my.cnf The default character set parameter is added to the client and server in to facilitate management.

Using common file upload to upload files in SSH project

Today, the project used to upload. What I store in my database is the URL of the file, so I have to do some processing in the background. I have written several times before uploading, and I feel that the amount of code is too large. Today, I searched the Internet, and it will be much easier to upload with common file upload. After groping for an afternoon, I finally got it done. The background code is as follows

//The uploaded file
private File upload;
//file name and type
private String uploadContentType;
private String uploadFileName;
/*This is the variable to be written in the action, you must write it, otherwise it will be very troublesome, Struts2 will automatically assign the file to be uploaded, the file name, type, etc.*/

/// The following is the processing method
public String uploadStaffImage() throws Exception{
	//Take the file name and path, rename the file name with uuid to prevent Chinese mess
	String fileName = UUID.randomUUID().toString();
        //intercept file type
        String fileType = this.uploadFileName.substring(this.uploadFileName.lastIndexOf("."), this.uploadFileName.length());
        //New file name
        String file = fileName + fileType;
        // My directory is under "StaffImg" folder
        String path = request.getSession().getServletContext().getRealPath("/StaffImg");
	InputStream is = new FileInputStream(getUpload());  
        //Create an output stream to generate a new file  
        OutputStream os = new FileOutputStream(path + "//" + file);  
        //write disk 
        IOUtils.copy(is, os);
        os.flush();  
        IOUtils.closeQuietly(is);
        IOUtils.closeQuietly(os);
        //Update the URL in the database
        String imgURL = "StaffImg/"+file;
        this.staffFileUpLoadService.updataStaffImgURL(this.staffId, imgURL);
	return SUCCESS;
}

A total of 13 lines of code, compared to the previous written to be a lot more concise, method use is relatively simple.

This method can only upload a single file. If you upload in batches, the idea is the same, and you should add a loop in the outer layer
instead

Nginx, which is suitable for front-end H5 requests, routes and forwards according to the URL and cuts the URL

1. Ruqirement
nginx accepts the request url uniformly and forwards it
http://172.16.51.91:9000/api/order/create/44010000
http://172.16.51.91:9000/api/order/create/44060000
目标：
http://172.15.10.13:9001/api/order/create
http://172.15.10.13:9002/api/order/create
2. nginx Settings

server {
        listen      9000;
        server_name  172.16.51.91;

		location ~*(44010000)$ {
                rewrite ^/(.*)/44010000$ http://172.15.10.13:9001/$1 permanent;
        }
		 location ~*(44060000)$ {
                 rewrite ^/(.*)/44060000$ http://172.15.10.13:9002/$1 permanent;
        }	

}

Nginx routes and forwards according to the URL and cuts the URL

1. Ruqirement
nginx accepts the request url uniformly and forwards it
http://172.16.51.91:9000/44010000/api/order/create
http://172.16.51.91:9000/44060000/api/order/create
goal:
http://172.15.10.13:9001/api/order/create
http://172.15.10.13:9002/api/order/create
2. nginx Setting

server {
    listen   9000;
    server_name 172.16.51.91;

	location /44010000/ {
		    proxy_pass http://172.15.10.13:9001/;
    }
		 location /44060000/ {
         proxy_pass http://172.15.10.13:10002/;
    }
}

Java uses single thread pool to realize multi thread sequential execution (non alternating, non synchronous)

1. Principle and mechanism

Use one-way pool to ensure orderly submission and execution.

explain:

1) Alternate execution between threads is not supported.

2) Multithreading is not synchronous, only to ensure the order of execution, multithreading is concurrent execution.

2. Code examples

package com.thread;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class TasksWithoutLockTest extends Thread {

    private static int num = 0;
    private int id;

    public TasksWithoutLockTest(int id) {
        this.id = id;
    }


    @Override
    public void run() {
        System.out.println("Thread" + id + "output num:" + num++);
        try {
            Thread.sleep(3);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        //ExecutorService exec = Executors.newFixedThreadPool(1);
        ExecutorService exec = Executors.newSingleThreadScheduledExecutor();
        for (int i = 0; i < 12; i++) {
            exec.submit(new TasksWithoutLockTest(i));
        }

        exec.shutdown();

    }
}

3. Output results

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