IDEA下Maven项目中使用Mybatis及Mybatis Generator

写在前面：

前面在《前后端分离的思考》的一文中提到又有一门课要开始写大作业了，在初步理解了需求了之后，项目准备采用Maven+Mybatis+Mysql+SpringMVC+Vue.js的架构。采用Maven解决依赖管理问题十分方便（貌似gradle后来者居上，更方便了）。后台用的SpringMVC框架，毕竟也是javaWeb方面很常用的了。前端框架采用的是Vue.js，本身没怎么系统的使用过前端框架，这次也是第一次使用Vue，如果学到了什么有价值的东西也会开一篇帖子专门来叙述一下。今天好好念叨一下Mybatis和MybatisGenerator吧。

1.什么是MyBatis？

官网的解释我直接copy过来：MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。

真正用一遍MyBatis在回来看这段话，确实写的很简洁明了。

2.怎么用Mybatis？

按照我前面说的架构，使用Mybatis还是很简单的，只需要把各项配置文件配置好就可以了。但是如果各种最一般的数据查询接口，实体类等等还要我们一个个去手写的话，那不但浪费时间还会磨掉你对开发的激情。所以最最重要的是使用Mybatis-generator去帮我们自动生成关于某些表的实体类，dao（data access object）层接口，mapper接口，xxxmapper.xml等等。

首先我这里直接把各种牵扯的配置文件给进来，看注释的应该都不难。在这之前先看一下项目的目录结构，这样便于后面理解

pom.xml

<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/maven-v4_0_0.xsd">  <modelVersion>4.0.0</modelVersion>  <groupId>com.zxx.web</groupId>  <artifactId>web-ssm</artifactId>  <packaging>war</packaging>  <version>1.0-SNAPSHOT</version>  <name>web-ssm Maven Webapp</name>  <url>http://maven.apache.org</url>  <properties>    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>    <!-- spring版本号 -->    <spring.version>4.2.5.RELEASE</spring.version>    <!-- mybatis版本号 -->    <mybatis.version>3.2.8</mybatis.version>    <!-- mysql驱动版本号 -->    <mysql-driver.version>5.1.29</mysql-driver.version>    <!-- log4j日志包版本号 -->    <slf4j.version>1.7.18</slf4j.version>    <log4j.version>1.2.17</log4j.version>    <velocity.version>1.7</velocity.version>    <velocity-tools.version>2.0</velocity-tools.version>  </properties>  <dependencies>    <!-- 添加jstl依赖 -->    <dependency>      <groupId>jstl</groupId>      <artifactId>jstl</artifactId>      <version>1.2</version>    </dependency>    <dependency>      <groupId>javax</groupId>      <artifactId>javaee-api</artifactId>      <version>7.0</version>    </dependency>    <!-- 添加junit4依赖 -->    <dependency>      <groupId>junit</groupId>      <artifactId>junit</artifactId>      <version>4.11</version>      <!-- 指定范围，在测试时才会加载 -->      <scope>test</scope>    </dependency>    <!-- 添加spring核心依赖 -->    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-core</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-web</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-oxm</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-tx</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-jdbc</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-webmvc</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-context</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-context-support</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-aop</artifactId>      <version>${spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-test</artifactId>      <version>${spring.version}</version>    </dependency>    <!-- 添加mybatis依赖 -->    <dependency>      <groupId>org.mybatis</groupId>      <artifactId>mybatis</artifactId>      <version>${mybatis.version}</version>    </dependency>    <!-- 添加mybatis/spring整合包依赖 -->    <dependency>      <groupId>org.mybatis</groupId>      <artifactId>mybatis-spring</artifactId>      <version>1.2.2</version>    </dependency>    <!-- 添加mysql驱动依赖 -->    <dependency>      <groupId>mysql</groupId>      <artifactId>mysql-connector-java</artifactId>      <version>${mysql-driver.version}</version>    </dependency>    <!-- 添加数据库连接池依赖 -->    <dependency>      <groupId>commons-dbcp</groupId>      <artifactId>commons-dbcp</artifactId>      <version>1.2.2</version>    </dependency>    <!-- 添加fastjson -->    <dependency>      <groupId>com.alibaba</groupId>      <artifactId>fastjson</artifactId>      <version>1.1.41</version>    </dependency>    <!-- 添加日志相关jar包 -->    <dependency>      <groupId>log4j</groupId>      <artifactId>log4j</artifactId>      <version>${log4j.version}</version>    </dependency>    <dependency>      <groupId>org.slf4j</groupId>      <artifactId>slf4j-api</artifactId>      <version>${slf4j.version}</version>    </dependency>    <dependency>      <groupId>org.slf4j</groupId>      <artifactId>slf4j-log4j12</artifactId>      <version>${slf4j.version}</version>    </dependency>    <!-- log end -->    <!-- 映入JSON -->    <dependency>      <groupId>org.codehaus.jackson</groupId>      <artifactId>jackson-mapper-asl</artifactId>      <version>1.9.13</version>    </dependency>    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-core</artifactId>      <version>2.8.0</version>    </dependency>    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-databind</artifactId>      <version>2.8.0</version>    </dependency>    <dependency>      <groupId>commons-fileupload</groupId>      <artifactId>commons-fileupload</artifactId>      <version>1.3.1</version>    </dependency>    <dependency>      <groupId>commons-io</groupId>      <artifactId>commons-io</artifactId>      <version>2.4</version>    </dependency>    <dependency>      <groupId>commons-codec</groupId>      <artifactId>commons-codec</artifactId>      <version>1.9</version>    </dependency>    <!--velocity-->    <dependency>      <groupId>org.apache.velocity</groupId>      <artifactId>velocity</artifactId>      <version>${velocity.version}</version>    </dependency>    <dependency>      <groupId>org.apache.velocity</groupId>      <artifactId>velocity-tools</artifactId>      <version>${velocity-tools.version}</version>      <exclusions>        <exclusion>          <groupId>commons-logging</groupId>          <artifactId>commons-logging</artifactId>        </exclusion>      </exclusions>    </dependency>    <dependency>      <groupId>org.freemarker</groupId>      <artifactId>freemarker</artifactId>      <version>2.3.22</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-context-support</artifactId>      <version>4.1.6.RELEASE</version>    </dependency>  </dependencies>  <build>    <finalName>web-ssm</finalName>    <plugins>      <plugin>        <groupId>org.mybatis.generator</groupId>        <artifactId>mybatis-generator-maven-plugin</artifactId>        <version>1.3.2</version>        <configuration>          <!--配置文件的位置-->      <configurationFile>src/main/resources/generatorConfig.xml</configurationFile>          <verbose>true</verbose>          <overwrite>true</overwrite>        </configuration>        <executions>          <execution>            <id>Generate MyBatis Artifacts</id>            <goals>              <goal>generate</goal>            </goals>          </execution>        </executions>        <dependencies>          <dependency>            <groupId>org.mybatis.generator</groupId>            <artifactId>mybatis-generator-core</artifactId>            <version>1.3.2</version>          </dependency>        </dependencies>      </plugin>    </plugins>  </build></project>

spring-mybatis.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"       xsi:schemaLocation="http://www.springframework.org/schema/beans                        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd                        http://www.springframework.org/schema/context                        http://www.springframework.org/schema/context/spring-context-3.1.xsd                        http://www.springframework.org/schema/tx                        http://www.springframework.org/schema/tx/spring-tx.xsd">    <!-- 自动扫描 -->    <!--<context:component-scan base-package="com.zxx.ssm"/>-->    <!-- 第一种方式：加载一个properties文件 -->    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">        <property name="location" value="classpath:jdbc.properties"/>    </bean>    <!-- 第二种方式：加载多个properties文件    <bean id="configProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">        <property name="locations">            <list>                <value>classpath:jdbc.properties</value>                <value>classpath:common.properties</value>            </list>        </property>        <property name="fileEncoding" value="UTF-8"/>    </bean>    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PreferencesPlaceholderConfigurer">        <property name="properties" ref="configProperties"/>    </bean>    -->    <!-- 配置数据源 -->    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"          destroy-method="close">        <property name="driverClassName" value="${driverClasss}"/>        <property name="url" value="${jdbcUrl}"/>        <property name="username" value="${username}"/>        <property name="password" value="${password}"/>        <!-- 初始化连接大小 -->        <property name="initialSize" value="${initialSize}"></property>        <!-- 连接池最大数量 -->        <property name="maxActive" value="${maxActive}"></property>        <!-- 连接池最大空闲 -->        <property name="maxIdle" value="${maxIdle}"></property>        <!-- 连接池最小空闲 -->        <property name="minIdle" value="${minIdle}"></property>        <!-- 获取连接最大等待时间 -->        <property name="maxWait" value="${maxWait}"></property>    </bean>    <!-- mybatis和spring完美整合，不需要mybatis的配置映射文件 -->    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">        <property name="dataSource" ref="dataSource"/>        <!-- 自动扫描mapping.xml文件 -->        <property name="mapperLocations" value="classpath:mapping/*.xml"></property>    </bean>    <!-- DAO接口所在包名，Spring会自动查找其下的类 -->    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">        <property name="basePackage" value="com.zxx.ssm.mapper"/>        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>    </bean>    <!-- (事务管理)transaction manager, use JtaTransactionManager for global tx -->    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">        <property name="dataSource" ref="dataSource"/>    </bean>    <!-- (事务管理)transaction manager, use JtaTransactionManager for global tx -->    <tx:annotation-driven transaction-manager="transactionManager"/></beans>

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://java.sun.com/xml/ns/javaee"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"         version="3.0">  <display-name>Archetype Created Web Application</display-name>  <context-param>    <param-name>contextConfigLocation</param-name>    <param-value>classpath:spring-mybatis.xml</param-value>  </context-param>  <context-param>    <param-name>log4jConfigLocation</param-name>    <param-value>classpath:log4j.properties</param-value>  </context-param>  <!-- 编码过滤器 -->  <filter>    <filter-name>encodingFilter</filter-name>    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>    <init-param>      <param-name>encoding</param-name>      <param-value>UTF-8</param-value>    </init-param>  </filter>  <filter-mapping>    <filter-name>encodingFilter</filter-name>    <url-pattern>/*</url-pattern>  </filter-mapping>  <!-- spring监听器 -->  <listener>    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  </listener>  <!-- 防止spring内存溢出监听器，比如quartz -->  <listener>    <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class>  </listener>  <!-- spring mvc servlet-->  <servlet>    <servlet-name>dispatcher</servlet-name>    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>    <init-param>      <param-name>contextConfigLocation</param-name>      <param-value>/WEB-INF/dispatcher-servlet.xml</param-value>    </init-param>    <load-on-startup>1</load-on-startup>    <async-supported>true</async-supported>  </servlet>  <servlet-mapping>    <servlet-name>dispatcher</servlet-name>    <!-- 此处也可以配置成 *.do 形式 -->    <url-pattern>/</url-pattern>  </servlet-mapping>  <welcome-file-list>    <welcome-file>/index.html</welcome-file>  </welcome-file-list>  <!-- session配置 -->  <session-config>    <session-timeout>15</session-timeout>  </session-config></web-app>

dispatcher-servlet.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"       xmlns:context="http://www.springframework.org/schema/context"       xmlns:mvc="http://www.springframework.org/schema/mvc"       xsi:schemaLocation="http://www.springframework.org/schema/beans                        http://www.springframework.org/schema/beans/spring-beans-4.0.xsd                        http://www.springframework.org/schema/context                        http://www.springframework.org/schema/context/spring-context-4.0.xsd                        http://www.springframework.org/schema/mvc                        http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">    <!-- 自动扫描  @Controller-->    <context:component-scan base-package="com.zxx.ssm"/>    <mvc:annotation-driven></mvc:annotation-driven>    <mvc:resources mapping="/assets/**" location="/WEB-INF/assets/"/>    <!--避免IE执行AJAX时，返回JSON出现下载文件 -->    <bean id="mappingJacksonHttpMessageConverter"          class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">        <property name="supportedMediaTypes">            <list>                <value>text/html;charset=UTF-8</value>            </list>        </property>    </bean>    <!-- 启动SpringMVC的注解功能，完成请求和注解POJO的映射 -->    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">        <property name="messageConverters">            <list>                <ref bean="mappingJacksonHttpMessageConverter"/> <!-- JSON转换器 -->            </list>        </property>    </bean>    <!-- 设置freeMarker的配置文件路径 -->    <bean id="freemarkerConfiguration"          class="org.springframework.beans.factory.config.PropertiesFactoryBean">        <!--注释掉的下方代码是指引freemarker的基本信息的配置位置，因为我已经将配置信息移到了applicationContext文件下，所以这里就没必要存在了，不注释也不会有问题的 -->        <property name="location" value="/WEB-INF/config/freemarker.properties" />    </bean>    <bean id="freemarkerConfig"          class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">        <property name="freemarkerSettings" ref="freemarkerConfiguration" />        <property name="templateLoaderPath" value="/WEB-INF/views/" />    </bean>    <bean id="viewResolver" class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">        <property name="cache" value="true" />        <property name="suffix" value=".html" />        <!--只是这里后缀改成.html -->        <property name="viewClass"                  value="org.springframework.web.servlet.view.freemarker.FreeMarkerView" />        <property name="exposeSpringMacroHelpers" value="true" />        <property name="exposeRequestAttributes" value="true" />        <property name="exposeSessionAttributes" value="true" />        <property name="requestContextAttribute" value="rc" />        <property name="contentType" value="text/html;charset=UTF-8" />    </bean>   <!-- <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">        <property name="prefix" value="/WEB-INF/page/"/>        <property name="suffix" value=".jsp"/>    </bean>-->    <!-- 文件上传配置 -->    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">        <!-- 默认编码 -->        <property name="defaultEncoding" value="UTF-8"/>        <!-- 上传文件大小限制为31M，31*1024*1024 -->        <property name="maxUploadSize" value="32505856"/>        <!-- 内存中的最大值 -->        <property name="maxInMemorySize" value="4096"/>    </bean></beans>

其实后面的dispatcher-servlet.xml和mybatis就没多大关系了，就是怕有人按照我的配置文件在搭项目。。。少了它就搭不全了

假设按照上面的几个配置文件，大家都配置好了，项目的目录结构也按照我说的创建好了，现在开始使用Mybatis-generator

step1:

在相应的目录位置创建generatorConfig.xml文件

step2:

配置相应的内容，注意mysq连接数据库的jar的location去你的C盘相应的路径找吧，可能会变得就是你的用户名变了，还有可能那个版本号不一样了

<?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>    <!--<properties resource="jdbc.properties"></properties>-->    <!--mysql 连接数据库jar 这里选择自己本地位置-->    <classPathEntry location="C:\Users\bwju\.m2\repository\mysql\mysql-connector-java\5.1.29\mysql-connector-java-5.1.29.jar" />    <context id="testTables" targetRuntime="MyBatis3">        <commentGenerator>            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->            <property name="suppressAllComments" value="true" />        </commentGenerator>        <!--数据库连接的信息：驱动类、连接地址、用户名、密码 -->        <jdbcConnection driverClass="com.mysql.jdbc.Driver"                        connectionURL="jdbc:mysql://localhost:3306/attendance" userId="root"                        password="root">        </jdbcConnection>        <!-- 默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer，为 true时把JDBC DECIMAL 和           NUMERIC 类型解析为java.math.BigDecimal -->        <javaTypeResolver>            <property name="forceBigDecimals" value="false" />        </javaTypeResolver>        <!-- targetProject:生成PO类的位置 -->        <javaModelGenerator targetPackage="com.zxx.ssm.dao"                            targetProject="src/main/java">            <!-- enableSubPackages:是否让schema作为包的后缀 -->            <property name="enableSubPackages" value="false" />            <!-- 从数据库返回的值被清理前后的空格 -->            <property name="trimStrings" value="true" />        </javaModelGenerator>        <!-- targetProject:mapper映射文件生成的位置           如果maven工程只是单独的一个工程，targetProject="src/main/java"           若果maven工程是分模块的工程，targetProject="所属模块的名称"，例如：           targetProject="ecps-manager-mapper"，下同-->        <sqlMapGenerator targetPackage="resources.mapping"                         targetProject="src/main">            <!-- enableSubPackages:是否让schema作为包的后缀 -->            <property name="enableSubPackages" value="false" />        </sqlMapGenerator>        <!-- targetPackage：mapper接口生成的位置 -->        <javaClientGenerator type="XMLMAPPER"                             targetPackage="com.zxx.ssm.mapper"                             targetProject="src/main/java">            <!-- enableSubPackages:是否让schema作为包的后缀 -->            <property name="enableSubPackages" value="false" />        </javaClientGenerator>        <!-- 指定数据库表 -->        <table schema="" tableName="employee"></table>    </context></generatorConfiguration>

step3:运行这个mybatis-generator

首先先要在你的IDEA里安装mybatis-plugin

File->Settings->Plugins 搜索mybatis然后install就可以了，不过估计大部分朋友没有activtion license,可以下个破解版的用，网上搜mybatis plugin破解版，一大堆

装好插件以后，点击右上角的那个运行按钮旁边的下拉菜单，找到Edit Configurations,点击+号配置一个和下图一样的东西

主要就是那个命令要写对，Name叫什么不重要，工作路径按默认的来就好

最后，选择自己创建的generateMapper，点击运行按钮，Boom！你会发现你的项目里多了好多东西，快去看看吧，我在上述的配置文件中指定了它为我数据库中的Employee表去自动生成相关文件，生成完之后成了这样，可以看到它们都被自动生成啦

在系统设计到的表数目较多时，用mybatis-generator可以省下大把的时间，让开发者更关注在后台的逻辑中，而且mybatis自动生成的代码能够满足绝大多数情况下的使用了。非常方便，然而，非常特别的方法还是要自己去写方法的嗯嗯，祝大家都能使用这一工具。

如果有收获的话可以扫码侧面的二维码打赏一下哟，感谢您的鼓励~