# 云胡的编程周报第 006 期

时间：2023/9/18 - 2023/9/24

# 一、点滴记录

# 1

给「云胡图书馆」添加用户可以选择的高亮颜色，没什么技术难度，就是把高亮的颜色变为一个响应式变量即可。

# 2

更改器方法与访问器方法的区别

# 2.1 访问器方法

只访问对象而不更改对象的方法称为访问器方法。

ray-so-export (5).png

# 2.2 更新器方法

访问对象并且更改对象的方法称为更新器方法。

# 3

Node.js ``18 的版本在运行 vuepress 的时候会报错：

i ｢wds｣: Project is running at http://0.0.0.0:8080/
i ｢wds｣: webpack output is served from /yunhu-library-doc/
    at F:\CodeProject\ProjectDocs\yunhu-library-docs\node_modules\enhanced-resolve\lib\CachedInputFileSystem.js:91:9
    at F:\CodeProject\ProjectDocs\yunhu-library-docs\node_modules\graceful-fs\graceful-fs.js:123:16
    at FSReqCallback.readFileAfterClose [as oncomplete] (node:internal/fs/read_file_context:68:3) {
  opensslErrorStack: [ 'error:03000086:digital envelope routines::initialization error' ],
  library: 'digital envelope routines',
  reason: 'unsupported',
  code: 'ERR_OSSL_EVP_UNSUPPORTED'
}

1
2
3
4
5
6
7
8
9
10

解决方法：在原来的 package.json 文件的 scripts的vuepress 命令前加上 set NODE_OPTIONS=--openssl-legacy-provider &

原来的：

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "docs:dev": "vuepress dev docs",
    "docs:build": "vuepress build docs"
  }

1
2
3
4
5

改为：

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "docs:dev": "set NODE_OPTIONS=--openssl-legacy-provider & vuepress dev docs",
    "docs:build": "set NODE_OPTIONS=--openssl-legacy-provider & vuepress build docs"
  }

1
2
3
4
5

# 4

MyBatis Plus 批量插入数据的三种方式

# 4.1 for 循环中 insert 或者 save

在 for 循环中一条一条插入数据到数据库中。

 void testInsert() {
        Date sdate = new Date();
        for (int i = 0;i < 10; i++) {
            ProjectRemarkTableEntity projectRemarkTableEntity = new ProjectRemarkTableEntity();
            projectRemarkTableEntity.setUserName("yunhu");
            projectRemarkTableEntity.setEssayTitle("优化一下阅读体验");
            projectRemarkTableEntity.setEssayContent("比如切换主题");
            projectRemarkTableEntity.setSubmitDate(LocalDateTime.now());
            projectRemarkMapper.insert(projectRemarkTableEntity);
        }
        Date edate = new Date();
        System.out.printf("执行时长：%d 毫秒." , (edate.getTime() - sdate.getTime()));
    }

1
2
3
4
5
6
7
8
9
10
11
12
13

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1253b822] was not registered for synchronization because synchronization is not active
2023-09-25 13:58:40.026  WARN 62628 --- [           main] com.zaxxer.hikari.HikariConfig           : HikariPool-1 - idleTimeout is close to or more than maxLifetime, disabling it.
2023-09-25 13:58:40.026  INFO 62628 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2023-09-25 13:58:40.592  INFO 62628 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1244869566 wrapping com.mysql.cj.jdbc.ConnectionImpl@13b4ee4e] will not be managed by Spring
==>  Preparing: INSERT INTO t_project_remark ( user_name, essay_title, essay_content, submit_date ) VALUES ( ?, ?, ?, ? )
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T13:58:40.004879(LocalDateTime)
<==    Updates: 1
Committing JDBC Connection [HikariProxyConnection@1244869566 wrapping com.mysql.cj.jdbc.ConnectionImpl@13b4ee4e]
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1253b822]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@619854a3] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1191123629 wrapping com.mysql.cj.jdbc.ConnectionImpl@13b4ee4e] will not be managed by Spring
==>  Preparing: INSERT INTO t_project_remark ( user_name, essay_title, essay_content, submit_date ) VALUES ( ?, ?, ?, ? )
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T13:58:40.717177100(LocalDateTime)
<==    Updates: 1
Committing JDBC Connection [HikariProxyConnection@1191123629 wrapping com.mysql.cj.jdbc.ConnectionImpl@13b4ee4e]
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@619854a3]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@4d4600fb] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1934770572 wrapping com.mysql.cj.jdbc.ConnectionImpl@13b4ee4e] will not be managed by Spring
==>  Preparing: INSERT INTO t_project_remark ( user_name, essay_title, essay_content, submit_date ) VALUES ( ?, ?, ?, ? )
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T13:58:40.796141300(LocalDateTime)
<==    Updates: 1

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

可以看到每次插入一条数据都要创建一个 SqlSession，效率很低。执行时长：1430 毫秒.

# 4.2 saveBatch() 批量插入

@Test
    void testSaveBatch() {
        Date sdate = new Date();
        List<ProjectRemarkTableEntity> insertList = new ArrayList<>();
        for (int i = 0;i < 10; i++) {
            ProjectRemarkTableEntity projectRemarkTableEntity = new ProjectRemarkTableEntity();
            projectRemarkTableEntity.setUserName("yunhu");
            projectRemarkTableEntity.setEssayTitle("优化一下阅读体验");
            projectRemarkTableEntity.setEssayContent("比如切换主题");
            projectRemarkTableEntity.setSubmitDate(LocalDateTime.now());
            insertList.add(projectRemarkTableEntity);
        }
        appProjectRemarkService.saveBatch(insertList);
        Date edate = new Date();
        System.out.printf("执行时长：%d 毫秒." , (edate.getTime() - sdate.getTime()));
    }

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

2023-09-25 14:09:20.900  WARN 51348 --- [           main] com.zaxxer.hikari.HikariConfig           : HikariPool-1 - idleTimeout is close to or more than maxLifetime, disabling it.
2023-09-25 14:09:20.900  INFO 51348 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2023-09-25 14:09:21.480  INFO 51348 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@405881980 wrapping com.mysql.cj.jdbc.ConnectionImpl@7741507c] will be managed by Spring
==>  Preparing: INSERT INTO t_project_remark ( user_name, essay_title, essay_content, submit_date ) VALUES ( ?, ?, ?, ? )
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
==> Parameters: yunhu(String), 优化一下阅读体验(String), 比如切换主题(String), 2023-09-25T14:09:20.897110700(LocalDateTime)
执行时长：962 毫秒.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

执行时长：962 毫秒。实际上也是一条一条 insert，但是减少了很多创建SqlSession的消耗，提高了效率。

# 4.3 手动拼接 SQL

手动拼接，可以达到真正的批量插入，效率最高。

# 5

在两张表或者多张表插入或者更新数据的时候，我们希望保持数据的一致性，因此我们需要用到数据库的事务。现在重新复习一下事务的四个特性：

原子性（Atomicity）：事务作为一个整体被执行，包含在其中的对数据库的操作要么全部被执行，要么都不执行。

比如一个事务中插入了五条数据，这五条数据要么全部全部插入成功，要么全部插入失败，没有其他情况。
一致性（Consistency）：事务应确保数据库的状态从一个一致状态转变为另一个一致状态。

比如小云向小胡转账 100 块钱，那么小云的账户余额 -100，小胡的账户余额 +100，这就保持了一致性，如果小云的账户 -100，而小胡的账户没有 +100，这就不符合一致性。
隔离性（Isolation）：多个事务并发执行时，一个事务的执行不应影响其他事务的执行。
持久性（Durability）：已被提交的事务对数据库的修改应该永久保存在数据库中