[Liquibase]先從一個簡單的示例開始

原創 不曾听说 2020-02-21 14:02

對於開發者，代碼層級，有git幫你管理版本。
但是運維時，常常會遇到有些地方忘記執行某些SQL導致程序無法使用的問題。SQL的版本管理就成爲運維時候的一個痛點。
Liquibase就是爲解決這件事情而生的。

文章目錄


比較方便的是，Springboot對於Liquibase進行了整合，這篇文章先從最簡單的一個示例說起。這篇文章以實戰爲主，概念性知識最多稍提一嘴，主要留到後面章節去介紹。

1.引入相關依賴

liquibase的核心，主要引入的是

<dependency>
      <groupId>org.liquibase</groupId>
      <artifactId>liquibase-core</artifactId>
      <version>3.8.5</version>
    </dependency>

我把完整的pom.xml貼一下：

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.powersi</groupId>
  <artifactId>LiquibaseTest</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>LiquibaseTest Maven Webapp</name>
  <url>http://www.example.com</url>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.2.4.RELEASE</version>
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>
  <dependencies>
    <!-- liquibase 依賴-->
    <dependency>
      <groupId>org.liquibase</groupId>
      <artifactId>liquibase-core</artifactId>
      <version>3.8.5</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jpa</artifactId>
      <exclusions>
        <exclusion>
          <groupId>org.hibernate</groupId>
          <artifactId>hibernate-core</artifactId>
        </exclusion>
      </exclusions>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
    </dependency>
    <dependency>
      <groupId> org.springframework.boot </groupId >
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>6.0.6</version>
    </dependency>
  </dependencies>
</project>

2.配置

（1）application.yml配置

spring:
  liquibase:
    change-log: classpath:liquibase/master.xml
    user: pcloud
    password: pcloud
    enabled: true
    drop-first: true
    url: jdbc:mysql://192.168.133.15:3306/webchat
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://192.168.133.15:3306/webchat
    username: pcloud
    password: pcloud

（2）master.xml

<?xml version="1.0" encoding="utf-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.4.xsd">

    <include file="classpath:liquibase/change_log/2020-02-06-init-schema.xml" relativeToChangelogFile="false"/>

</databaseChangeLog>

（3）2020-02-06-init-schema.xml

<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.4.xsd">
    <property name="autoIncrement" value="true" dbms="mysql"/>
    <changeSet id="init-schema" author="Young" >
        <comment>init schema</comment>
        <createTable tableName="user">
            <column name="id" type="bigint" autoIncrement="${autoIncrement}">
                <constraints primaryKey="true" nullable="false"/>
            </column>
            <column name="nick_name" type="varchar(255)">
                <constraints  nullable="false"/>
            </column>
            <column name="email" type="varchar(255)">
                <constraints  nullable="false"/>
            </column>
            <column name="register_time" type="timestamp"  defaultValueComputed="CURRENT_TIMESTAMP">
                <constraints nullable="false"/>
            </column>
        </createTable>

        <modifySql dbms="mysql">
            <append value="ENGINE=INNODB DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_general_ci"/>
        </modifySql>
    </changeSet>
</databaseChangeLog>

3.驗證執行

這裏基本不涉及任何代碼的書寫，springboot的約定大於配置自動幫我們構建好了一個可以運行的環境，只需要在寫一個main方法，將springboot應用運行起來即可。
附上現在我創建的工程目錄結構：
在這裏插入圖片描述

第一探 初體驗，xml方式初始化數據庫表

（1）程序運行前
首先檢查數據庫：
在這裏插入圖片描述
可見數據庫中並無任何表。

（2）程序執行後
運行main方法後，logback在控制檯輸出瞭如下內容:

2020-02-06 18:38:25.033  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:25.049  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : CREATE TABLE webchat.DATABASECHANGELOGLOCK (ID INT NOT NULL, `LOCKED` BIT(1) NOT NULL, LOCKGRANTED datetime NULL, LOCKEDBY VARCHAR(255) NULL, CONSTRAINT PK_DATABASECHANGELOGLOCK PRIMARY KEY (ID))
2020-02-06 18:38:25.066  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:25.072  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : DELETE FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:25.074  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : INSERT INTO webchat.DATABASECHANGELOGLOCK (ID, `LOCKED`) VALUES (1, 0)
2020-02-06 18:38:25.078  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT `LOCKED` FROM webchat.DATABASECHANGELOGLOCK WHERE ID=1
2020-02-06 18:38:25.086  INFO 11356 --- [           main] l.lockservice.StandardLockService        : Successfully acquired change log lock
2020-02-06 18:38:25.086  INFO 11356 --- [           main] liquibase.command.core.DropAllCommand    : Dropping Database Objects in schema: webchat.webchat
2020-02-06 18:38:25.094  INFO 11356 --- [           main] l.c.StandardChangeLogHistoryService      : Creating database history table with name: webchat.DATABASECHANGELOG
2020-02-06 18:38:25.095  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : CREATE TABLE webchat.DATABASECHANGELOG (ID VARCHAR(255) NOT NULL, AUTHOR VARCHAR(255) NOT NULL, FILENAME VARCHAR(255) NOT NULL, DATEEXECUTED datetime NOT NULL, ORDEREXECUTED INT NOT NULL, EXECTYPE VARCHAR(10) NOT NULL, MD5SUM VARCHAR(35) NULL, `DESCRIPTION` VARCHAR(255) NULL, COMMENTS VARCHAR(255) NULL, TAG VARCHAR(255) NULL, LIQUIBASE VARCHAR(20) NULL, CONTEXTS VARCHAR(255) NULL, LABELS VARCHAR(255) NULL, DEPLOYMENT_ID VARCHAR(10) NULL)
2020-02-06 18:38:25.107  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:25.196  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT @@FOREIGN_KEY_CHECKS
2020-02-06 18:38:25.197  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SET FOREIGN_KEY_CHECKS=0
2020-02-06 18:38:25.198  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SET FOREIGN_KEY_CHECKS=1
2020-02-06 18:38:25.199  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM `webchat`.`DATABASECHANGELOG`
2020-02-06 18:38:26.549  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : DROP TABLE `webchat`.`databasechangelog`
2020-02-06 18:38:26.560  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM `webchat`.`DATABASECHANGELOGLOCK`
2020-02-06 18:38:26.588  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : DROP TABLE `webchat`.`databasechangeloglock`
2020-02-06 18:38:26.593  INFO 11356 --- [           main] liquibase.database.core.MySQLDatabase    : Successfully deleted all supported object types in schema webchat.webchat.
2020-02-06 18:38:26.595  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.596  INFO 11356 --- [           main] l.lockservice.StandardLockService        : Successfully released change log lock
2020-02-06 18:38:26.597  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.600  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.602  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : CREATE TABLE webchat.DATABASECHANGELOGLOCK (ID INT NOT NULL, `LOCKED` BIT(1) NOT NULL, LOCKGRANTED datetime NULL, LOCKEDBY VARCHAR(255) NULL, CONSTRAINT PK_DATABASECHANGELOGLOCK PRIMARY KEY (ID))
2020-02-06 18:38:26.613  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.615  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : DELETE FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.617  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : INSERT INTO webchat.DATABASECHANGELOGLOCK (ID, `LOCKED`) VALUES (1, 0)
2020-02-06 18:38:26.620  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT `LOCKED` FROM webchat.DATABASECHANGELOGLOCK WHERE ID=1
2020-02-06 18:38:26.623  INFO 11356 --- [           main] l.lockservice.StandardLockService        : Successfully acquired change log lock
2020-02-06 18:38:26.795  INFO 11356 --- [           main] l.c.StandardChangeLogHistoryService      : Creating database history table with name: webchat.DATABASECHANGELOG
2020-02-06 18:38:26.797  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : CREATE TABLE webchat.DATABASECHANGELOG (ID VARCHAR(255) NOT NULL, AUTHOR VARCHAR(255) NOT NULL, FILENAME VARCHAR(255) NOT NULL, DATEEXECUTED datetime NOT NULL, ORDEREXECUTED INT NOT NULL, EXECTYPE VARCHAR(10) NOT NULL, MD5SUM VARCHAR(35) NULL, `DESCRIPTION` VARCHAR(255) NULL, COMMENTS VARCHAR(255) NULL, TAG VARCHAR(255) NULL, LIQUIBASE VARCHAR(20) NULL, CONTEXTS VARCHAR(255) NULL, LABELS VARCHAR(255) NULL, DEPLOYMENT_ID VARCHAR(10) NULL)
2020-02-06 18:38:26.809  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOG
2020-02-06 18:38:26.812  INFO 11356 --- [           main] l.c.StandardChangeLogHistoryService      : Reading from webchat.DATABASECHANGELOG
2020-02-06 18:38:26.813  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT * FROM webchat.DATABASECHANGELOG ORDER BY DATEEXECUTED ASC, ORDEREXECUTED ASC
2020-02-06 18:38:26.815  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 18:38:26.831  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : CREATE TABLE webchat.user (id BIGINT AUTO_INCREMENT NOT NULL, nick_name VARCHAR(255) NOT NULL, email VARCHAR(255) NOT NULL, register_time timestamp DEFAULT NOW() NOT NULL, CONSTRAINT PK_USER PRIMARY KEY (id))ENGINE=INNODB DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_general_ci
2020-02-06 18:38:26.841  INFO 11356 --- [           main] liquibase.changelog.ChangeSet            : Table user created
2020-02-06 18:38:26.843  INFO 11356 --- [           main] liquibase.changelog.ChangeSet            : ChangeSet classpath:liquibase/change_log/2020-02-06-init-schema.xml::init-schema::Young ran successfully in 17ms
2020-02-06 18:38:26.846  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT MAX(ORDEREXECUTED) FROM webchat.DATABASECHANGELOG
2020-02-06 18:38:26.848  INFO 11356 --- [           main] liquibase.executor.jvm.JdbcExecutor      : INSERT INTO webchat.DATABASECHANGELOG (ID, AUTHOR, FILENAME, DATEEXECUTED, ORDEREXECUTED, MD5SUM, `DESCRIPTION`, COMMENTS, EXECTYPE, CONTEXTS, LABELS, LIQUIBASE, DEPLOYMENT_ID) VALUES ('init-schema', 'Young', 'classpath:liquibase/change_log/2020-02-06-init-schema.xml', NOW(), 1, '8:90aeeb431c3781579d93afd4280e6066', 'createTable tableName=user', 'init schema', 'EXECUTED', NULL, NULL, '3.8.5', '0985506816')
2020-02-06 18:38:26.859  INFO 11356 --- [           main] l.lockservice.StandardLockService        : Successfully released change log lock
2020-02-06 18:38:26.864  INFO 11356 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2020-02-06 18:38:26.884  INFO 11356 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
2020-02-06 18:38:26.994  INFO 11356 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-02-06 18:38:26.997  INFO 11356 --- [           main] com.powersi.MainClass                    : Started MainClass in 8.028 seconds (JVM running for 10.31)

上面的日誌打印的比較直觀，從以下這行看出來它似乎成功幫我們建好了表:
CREATE TABLE webchat.user
我們連接到這個庫，驗證一下是不是真的建好了數據表：
在這裏插入圖片描述
這裏可以看到，除了我們配置的user表以外，還幫我們創建了兩個表：databasechangelog表和databasechangeloglock表。

databasechangelog表結構爲：

CREATE TABLE `databasechangelog`  (
  `ID` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `AUTHOR` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `FILENAME` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `DATEEXECUTED` datetime(0) NOT NULL,
  `ORDEREXECUTED` int(11) NOT NULL,
  `EXECTYPE` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `MD5SUM` varchar(35) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `DESCRIPTION` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `COMMENTS` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `TAG` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `LIQUIBASE` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `CONTEXTS` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `LABELS` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `DEPLOYMENT_ID` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

databasechangeloglock表結構爲：

CREATE TABLE `databasechangeloglock`  (
  `ID` int(11) NOT NULL,
  `LOCKED` bit(1) NOT NULL,
  `LOCKGRANTED` datetime(0) NULL DEFAULT NULL,
  `LOCKEDBY` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`ID`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

databasechangelog中有這麼一條記錄：
在這裏插入圖片描述
databasechangeloglock表中有這麼一條數據：
在這裏插入圖片描述

第二探 利用SQL腳本維護數據

網上說liquibase版本從2.0開始，增加了SQL的支持，接下來寫個簡單的腳本進行測試（這裏爲什麼是這個寫法先不糾結，後面再去深究）：

2020-02-06-add-user.sql

--liquibase formatted sql
--changeset luyang:1
insert into user(nick_name,email,register_time) values('young','[email protected]',now());

同樣，要將這個文件include到master.xml中：

<include file="classpath:liquibase/change_log/2020-02-06-add-user.sql"/>

運行後，日誌打印如下圖：
在這裏插入圖片描述
看起來執行成功了，到數據庫端驗證：
在這裏插入圖片描述
另外值得一提的是，databasechangelog表中，有以下兩條記錄：
在這裏插入圖片描述

第三探 drop-first探究

之前在配置application.yml的時候，把這個參數drop-first: true設置爲了true，根據日誌顯示，每次程序運行時它都會把相關的表全部刪掉。而在實際的業務上面，這個操作完全不可取。改爲false，再去啓動，會有什麼情況發生？
在這裏插入圖片描述
在這裏插入圖片描述
記錄並沒有發生什麼變化。

第四探 版本問題

猜想，如果在保持drop-first: false前提下，我對數據庫表進行了一些修改，會發生什麼？

2020-02-06-update-user.sql

--liquibase formatted sql
--changeset luyang:2
update user set nick_name = 'LuYang' where id = 1;

同時記得在master.xml中要include進去：

    <include file="classpath:liquibase/change_log/2020-02-06-update-user.sql"/>

再運行程序，可以看到日誌輸出：

2020-02-06 19:00:28.099  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 19:00:28.112  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOGLOCK
2020-02-06 19:00:28.114  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT `LOCKED` FROM webchat.DATABASECHANGELOGLOCK WHERE ID=1
2020-02-06 19:00:28.125  INFO 13068 --- [           main] l.lockservice.StandardLockService        : Successfully acquired change log lock
2020-02-06 19:00:29.735  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT MD5SUM FROM webchat.DATABASECHANGELOG WHERE MD5SUM IS NOT NULL LIMIT 1
2020-02-06 19:00:29.736  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT COUNT(*) FROM webchat.DATABASECHANGELOG
2020-02-06 19:00:29.737  INFO 13068 --- [           main] l.c.StandardChangeLogHistoryService      : Reading from webchat.DATABASECHANGELOG
2020-02-06 19:00:29.738  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT * FROM webchat.DATABASECHANGELOG ORDER BY DATEEXECUTED ASC, ORDEREXECUTED ASC
2020-02-06 19:00:29.749  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : update user set nick_name = 'LuYang' where id = 1
2020-02-06 19:00:29.751  INFO 13068 --- [           main] liquibase.changelog.ChangeSet            : Custom SQL executed
2020-02-06 19:00:29.752  INFO 13068 --- [           main] liquibase.changelog.ChangeSet            : ChangeSet classpath:liquibase/change_log/2020-02-06-update-user.sql::2::luyang ran successfully in 5ms
2020-02-06 19:00:29.753  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : SELECT MAX(ORDEREXECUTED) FROM webchat.DATABASECHANGELOG
2020-02-06 19:00:29.755  INFO 13068 --- [           main] liquibase.executor.jvm.JdbcExecutor      : INSERT INTO webchat.DATABASECHANGELOG (ID, AUTHOR, FILENAME, DATEEXECUTED, ORDEREXECUTED, MD5SUM, `DESCRIPTION`, COMMENTS, EXECTYPE, CONTEXTS, LABELS, LIQUIBASE, DEPLOYMENT_ID) VALUES ('2', 'luyang', 'classpath:liquibase/change_log/2020-02-06-update-user.sql', NOW(), 3, '8:5882f164036521bc55d78eaf7eb475d4', 'sql', '', 'EXECUTED', NULL, NULL, '3.8.5', '0986829741')
2020-02-06 19:00:29.761  INFO 13068 --- [           main] l.lockservice.StandardLockService        : Successfully released change log lock
2020-02-06 19:00:29.762  INFO 13068 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2020-02-06 19:00:29.774  INFO 13068 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
2020-02-06 19:00:29.853  INFO 13068 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-02-06 19:00:29.856  INFO 13068 --- [           main] com.powersi.MainClass                    : Started MainClass in 9.701 seconds (JVM running for 12.267)

user表的記錄也被成功修改：
在這裏插入圖片描述
另外，日誌記錄多了一行：
在這裏插入圖片描述

第五探 錯誤的版本跳躍？

這裏版本直接指定爲4，看會不會發生把這條記錄刪掉的情況：
在這裏插入圖片描述
在這裏插入圖片描述
在這裏插入圖片描述
記錄被刪掉了。

第六探 那如果寫出了重複的版本號呢？

在這裏插入圖片描述
日誌上看依舊被執行成功：
在這裏插入圖片描述
數據庫也有相應的記錄：
在這裏插入圖片描述
在這裏插入圖片描述

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