mybatis逆向工程之一鍵生成數(shù)據(jù)庫(kù)表對(duì)應(yīng)的實(shí)體對(duì)象和mapper.xml映射文件

Mybatis簡(jiǎn)述一下其優(yōu)缺點(diǎn)

mybatis是一種持久層框架，也屬于ORM映射。前身是ibatis。
相比于hibernatehibernate為全自動(dòng)化，配置文件書(shū)寫之后不需要書(shū)寫sql語(yǔ)句，但是欠缺靈活，很多時(shí)候需要優(yōu)化；
mybatis為半自動(dòng)化，需要自己書(shū)寫sql語(yǔ)句，需要自己定義映射。增加了程序員的一些操作，但是帶來(lái)了設(shè)計(jì)上的靈活，并且也是支持hibernate的一些特性，如延遲加載，緩存和映射等；對(duì)數(shù)據(jù)庫(kù)的兼容性比hibernate差。移植性不好，但是可編寫靈活和高性能的sql語(yǔ)句。

1.sql語(yǔ)句與代碼分離，存放于xml配置文件中：
優(yōu)點(diǎn)：便于維護(hù)管理，不用在java代碼中找這些語(yǔ)句；

缺點(diǎn)： JDBC方式可以用用打斷點(diǎn)的方式調(diào)試，但是Mybatis不能，需要通過(guò)log4j日志輸出日志信息幫助調(diào)試，然后在配置文件中修改。

2.用邏輯標(biāo)簽控制動(dòng)態(tài)SQL的拼接：
優(yōu)點(diǎn)：用標(biāo)簽代替編寫邏輯代碼；

缺點(diǎn)：拼接復(fù)雜SQL語(yǔ)句時(shí)，沒(méi)有代碼靈活，拼寫比較復(fù)雜。不要使用變通的手段來(lái)應(yīng)對(duì)這種復(fù)雜的語(yǔ)句。

3.查詢的結(jié)果集與java對(duì)象自動(dòng)映射：
優(yōu)點(diǎn)：保證名稱相同，配置好映射關(guān)系即可自動(dòng)映射或者，不配置映射關(guān)系，通過(guò)配置列名=字段名也可完成自動(dòng)映射。

缺點(diǎn)：對(duì)開(kāi)發(fā)人員所寫的SQL依賴很強(qiáng)。

4.編寫原聲SQL：
優(yōu)點(diǎn)：接近JDBC，比較靈活。

缺點(diǎn)：對(duì)SQL語(yǔ)句依賴程度很高；并且屬于半自動(dòng)，數(shù)據(jù)庫(kù)移植比較麻煩，比如mysql數(shù)據(jù)庫(kù)編程Oracle數(shù)據(jù)庫(kù)，部分的sql語(yǔ)句需要調(diào)整。

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至此結(jié)束，介紹就到這里了，小編今日給大家介紹如何使用 Mybatis的逆向工程一鍵生成由數(shù)據(jù)庫(kù)表——>實(shí)體，mapper.xml，mapper.java 一站式生成策略

從 pom 文件開(kāi)始

添加 mybatis-generator-maven-plugin 依賴插件以及相關(guān)配置文件插件 resource (用于掃描配置文件)

<plugin>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-maven-plugin</artifactId>
    <version>1.3.2</version>
    <configuration>
        <verbose>true</verbose>
        <overwrite>true</overwrite>
    </configuration>
</plugin>

在resource 目錄下（也可以自定義目錄，配置相關(guān)路徑需要更改）創(chuàng)建 generatorConfig.xml 其內(nèi)容為：相關(guān)注釋已經(jīng)加上

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
"http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">

<generatorConfiguration>

<!--導(dǎo)入屬性配置 在同級(jí)的目錄下創(chuàng)建 generator.properties-->
<properties resource="generator.properties"></properties>

<!--指定特定數(shù)據(jù)庫(kù)的jdbc驅(qū)動(dòng)jar包的位置(絕對(duì)路徑)-->
<classPathEntry location="${jdbc.driverLocation}"/>

<context id="default" targetRuntime="MyBatis3">

<!-- optional，旨在創(chuàng)建class時(shí)，對(duì)注釋進(jìn)行控制 -->
<commentGenerator>
<!--是否去掉自動(dòng)生成的注釋 true:是-->
<property name="suppressDate" value="true"/>
<property name="suppressAllComments" value="true"/>
</commentGenerator>

<!--jdbc的數(shù)據(jù)庫(kù)連接：驅(qū)動(dòng)類、鏈接地址、用戶名、密碼-->
<jdbcConnection
driverClass="${jdbc.driverClass}"
connectionURL="${jdbc.connectionURL}"
userId="${jdbc.userId}"
password="${jdbc.password}">
</jdbcConnection>

<!-- 非必需，類型處理器，在數(shù)據(jù)庫(kù)類型和java類型之間的轉(zhuǎn)換控制-->
<javaTypeResolver>
<property name="forceBigDecimals" value="false"/>
</javaTypeResolver>

<!-- Model模型生成器,用來(lái)生成含有主鍵key的類，記錄類 以及查詢Example類
targetPackage 指定生成的model生成所在的包名
targetProject 指定在該項(xiàng)目下所在的路徑
-->
<javaModelGenerator targetPackage="com.technologies.bear.entity"
targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
<property name="trimStrings" value="true"/>
</javaModelGenerator>


<!--Mapper映射文件生成所在的目錄 為每一個(gè)數(shù)據(jù)庫(kù)的表生成對(duì)應(yīng)的SqlMap文件 -->
<sqlMapGenerator targetPackage="mappers"
targetProject="src/main/resources">
<property name="enableSubPackages" value="false"/>
</sqlMapGenerator>

<!-- 客戶端代碼，生成易于使用的針對(duì)Model對(duì)象和XML配置文件 的代碼
type="ANNOTATEDMAPPER",生成Java Model 和基于注解的Mapper對(duì)象
type="MIXEDMAPPER",生成基于注解的Java Model 和相應(yīng)的Mapper對(duì)象
type="XMLMAPPER",生成SQLMap XML文件和獨(dú)立的Mapper接口
-->
<javaClientGenerator type="XMLMAPPER" targetPackage="com.technologies.bear.dao"
targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
</javaClientGenerator>

<!-- 數(shù)據(jù)表進(jìn)行生成操作 tableName:表名; domainObjectName:對(duì)應(yīng)的DO -->
<table tableName="bear_user" domainObjectName="User"
enableCountByExample="false" enableUpdateByExample="false"
enableDeleteByExample="false" enableSelectByExample="false"
selectByExampleQueryId="false">
</table>
<table tableName="bear_role" domainObjectName="Role"
enableCountByExample="false" enableUpdateByExample="false"
enableDeleteByExample="false" enableSelectByExample="false"
selectByExampleQueryId="false">
</table>
</context>
</generatorConfiguration>

配置文件中有一個(gè) properties 標(biāo)簽標(biāo)注配置文件 generator.properties 在 generatorConfig.xml同級(jí)目錄下創(chuàng)建

jdbc.driverLocation=D:\\Downloads\\mysql-connector-java-8.0.11\\mysql-connector-java-8.0.11\\mysql-connector-java-8.0.11.jar
jdbc.driverClass=com.mysql.cj.jdbc.Driver
jdbc.connectionURL=jdbc:mysql://****：3306/db?useUnicode=true&characterEncoding=utf-8
jdbc.userId=***
jdbc.password=***

在 generator.properties 配置文件中有段 jdbc.driverLocation=url.jar 的配置，這個(gè)jar包自行下載，把電腦里的路徑拷貝過(guò)來(lái)就可以

雙擊運(yùn)行插件：

運(yùn)行日志：

[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------------< com.technologies:bear >------------------------
[INFO] Building bear 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- mybatis-generator-maven-plugin:1.3.2:generate (default-cli) @ bear ---
[INFO] Connecting to the Database
Wed Apr 08 10:46:38 CST 2020 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
[INFO] Introspecting table bear_user
log4j:WARN No appenders could be found for logger (org.mybatis.generator.internal.db.DatabaseIntrospector).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
[INFO] Introspecting table bear_role
[INFO] Introspecting table bear_permission
[INFO] Introspecting table bear_user_role
[INFO] Introspecting table bear_role_permission
[INFO] Generating Record class for table bear_user
[INFO] Generating Mapper Interface for table bear_user
[INFO] Generating SQL Map for table bear_user
[INFO] Generating Record class for table bear_role
[INFO] Generating Mapper Interface for table bear_role
[INFO] Generating SQL Map for table bear_role
[INFO] Generating Record class for table bear_permission
[INFO] Generating Mapper Interface for table bear_permission
[INFO] Generating SQL Map for table bear_permission
[INFO] Generating Record class for table bear_user_role
[INFO] Generating Mapper Interface for table bear_user_role
[INFO] Generating SQL Map for table bear_user_role
[INFO] Generating Record class for table bear_role_permission
[INFO] Generating Mapper Interface for table bear_role_permission
[INFO] Generating SQL Map for table bear_role_permission
[INFO] Saving file UserMapper.xml
[INFO] Saving file RoleMapper.xml
[INFO] Saving file PermissionMapper.xml
[INFO] Saving file UserRoleMapper.xml
[INFO] Saving file RolePermissionMapper.xml
[INFO] Saving file User.java
[INFO] Saving file UserMapper.java
[INFO] Saving file Role.java
[INFO] Saving file RoleMapper.java
[INFO] Saving file Permission.java
[INFO] Saving file PermissionMapper.java
[INFO] Saving file UserRole.java
[INFO] Saving file UserRoleMapper.java
[INFO] Saving file RolePermission.java
[INFO] Saving file RolePermissionMapper.java
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
[WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.995 s
[INFO] Finished at: 2020-04-08T10:46:39+08:00
[INFO] ------------------------------------------------------------------------

Process finished with exit code 0

我生成的持久層的 mapper路徑： com.technologies.bear.dao 在xml的配置文件中配了

在resource目錄下會(huì)多一個(gè)mapper文件夾，存放的是mapper.xml映射文件

恭喜 SUCCESS!

posted @ 2020-04-08 13:16 siwei_Wu 閱讀(1795) 評(píng)論(0) 收藏舉報(bào)

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