Mybatis属于半自动ORM，在使用这个框架中，工作量最大的就是书写Mapping的映射文件，由于手动书写很容易出错，我们可以利用Mybatis-Generator来帮我们自动生成文件
关于Mybatis-Generator的下载可以到这个地址：https://github.com/mybatis/generator/releases
pom.xml添加jar依赖
<!-- https://mvnrepository.com/artifact/org.mybatis.generator/mybatis-generator-core -->
<dependency>
<groupId>org.mybatis.generator</groupId>
<artifactId>mybatis-generator-core</artifactId>
<version>1.3.5</version>
</dependency> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
</dependency>
创建表
create table `departments` (
`DEPARTMENT_ID` int ,
`DEPARTMENT_NAME` varchar ,
`MANAGER_ID` int ,
`LOCATION_ID` int
);CREATE TABLE `employees` (
`EMPLOYEE_ID` int(11) NOT NULL AUTO_INCREMENT,
`FIRST_NAME` varchar(20) DEFAULT NULL,
`LAST_NAME` varchar(20) DEFAULT NULL,
`EMAIL` varchar(20) DEFAULT NULL,
`PHONE_NUMBER` varchar(20) DEFAULT NULL,
`HIRE_DATE` date DEFAULT NULL,
`JOB_ID` int(11) DEFAULT NULL,
`SALARY` double DEFAULT NULL,
`COMMISSION_PCT` int(11) DEFAULT NULL,
`MANAGER_ID` int(11) DEFAULT NULL,
`DEPARTMENT_ID` int(11) DEFAULT NULL,
PRIMARY KEY (`EMPLOYEE_ID`)
) ENGINE=InnoDB AUTO_INCREMENT DEFAULT CHARSET=utf8;
编写generator.xml文件
<?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>
<context id="DB2Tables" targetRuntime="MyBatis3">
<!-- 不生成注释 -->
<commentGenerator>
<property name="suppressAllComments" value="true" />
</commentGenerator>
<!-- 配置数据库连接 -->
<jdbcConnection driverClass="com.mysql.jdbc.Driver"
connectionURL="jdbc:mysql://localhost:3306/crud" userId="root"
password="root">
</jdbcConnection>
<javaTypeResolver>
<property name="forceBigDecimals" value="false" />
</javaTypeResolver>
<!-- 指定javaBean生成的位置 -->
<javaModelGenerator targetPackage="com.me.bean"
targetProject=".\src\main\java">
<property name="enableSubPackages" value="true" />
<property name="trimStrings" value="true" />
</javaModelGenerator>
<!--指定sql映射文件生成的位置 -->
<sqlMapGenerator targetPackage="mapper" targetProject=".\src\main\resources">
<property name="enableSubPackages" value="true" />
</sqlMapGenerator>
<!-- 指定dao接口生成的位置，mapper接口 -->
<javaClientGenerator type="XMLMAPPER"
targetPackage="com.me.dao" targetProject=".\src\main\java">
<property name="enableSubPackages" value="true" />
</javaClientGenerator>
<!-- table指定每个表的生成策略 -->
<table tableName="tbl_emp" domainObjectName="Employee"></table>
<table tableName="tbl_dept" domainObjectName="Department"></table>
</context>
</generatorConfiguration>
main主方法
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import org.mybatis.generator.api.MyBatisGenerator;
import org.mybatis.generator.config.Configuration;
import org.mybatis.generator.config.xml.ConfigurationParser;
import org.mybatis.generator.internal.DefaultShellCallback;
public class Generator{
public static void main(String[] args) throws Exception {
List<String> warnings = new ArrayList<String>();
boolean overwrite = true;
File configFile = new File("generator.xml");
ConfigurationParser cp = new ConfigurationParser(warnings);
Configuration config = cp.parseConfiguration(configFile);
DefaultShellCallback callback = new DefaultShellCallback(overwrite);
MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config,
callback, warnings);
myBatisGenerator.generate(null);
}
}运行后会自动生成javaBean，Mapper Java和xml配置文件
注：多表查询语句还是要自己编写
连接多表查询语句的编写
EmployeeMapper接口添加方法，例如
List<Employee> selectByExampleWithDept(EmployeeExample example);
Employee selectByPrimaryKeyWithDept(Integer empId);
EmployeeMapper.xml编写对应sql查询
把自动selectByPrimaryKey和selectByExample 复制一份稍做修改
就可以了
<!-- List<Employee> selectByExampleWithDept(EmployeeExample example); Employee
selectByPrimaryKeyWithDept(Integer empId); -->
<resultMap id="WithDeptResultMap" type="com.me.bean.Employee">
<id column="emp_id" jdbcType="INTEGER" property="empId" />
<result column="emp_name" jdbcType="VARCHAR" property="empName" />
<result column="gender" jdbcType="CHAR" property="gender" />
<result column="email" jdbcType="VARCHAR" property="email" />
<result column="d_id" jdbcType="INTEGER" property="dId" />
<!-- 指定联合查询出部门字段的封装 -->
<association property="department" javaType="com.me.bean.Department">
<id column="dept_id" jdbcType="INTEGER" property="deptId" />
<result column="dept_name" jdbcType="VARCHAR" property="deptName" />
</association>
</resultMap>
<sql id="WithDept_Column_List">
e.emp_id, e.emp_name, e.gender, e.email, e.d_id, d.dept_id, d.dept_name
</sql>
<select id="selectByExampleWithDept" parameterType="com.me.bean.EmployeeExample"
resultMap="WithDeptResultMap">
select
<if test="distinct">
distinct
</if>
<include refid="WithDept_Column_List" />
FROM tbl_emp e LEFT JOIN tbl_dept d ON e.`d_id`= d.`dept_id`
<if test="_parameter != null">
<include refid="Example_Where_Clause" />
</if>
<if test="orderByClause != null">
order by ${orderByClause}
</if>
</select>
<select id="selectByPrimaryKeyWithDept" parameterType="java.lang.Integer"
resultMap="WithDeptResultMap">
select
<include refid="WithDept_Column_List" />
FROM tbl_emp e LEFT JOIN tbl_dept d ON e.`d_id`= d.`dept_id`
where emp_id = #{empId,jdbcType=INTEGER}
</select>idea mybatis.generator使用
-
<build> <plugins> <!-- mybatis generator 自动生成代码插件 --> <plugin> <groupId>org.mybatis.generator</groupId> <artifactId>mybatis-generator-maven-plugin</artifactId> <version>1.3.2</version> <configuration> <configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile> <overwrite>true</overwrite> <verbose>true</verbose> </configuration> </plugin> </plugins> </build>在目录下<configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile>新建generatorConfig.xml
<?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>
<!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包-->
<classPathEntry location="D:\java\apache-maven-3.3.9\repo\mysql\mysql-connector-java\5.1.47\mysql-connector-java-5.1.47.jar"/>
<context id="DB2Tables" targetRuntime="MyBatis3">
<commentGenerator>
<property name="suppressDate" value="true"/>
<!-- 是否去除自动生成的注释 true：是 ： false:否 -->
<property name="suppressAllComments" value="true"/>
</commentGenerator>
<!--数据库链接URL，用户名、密码 -->
<jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://127.0.0.1/mytest?characterEncoding=utf8" userId="root" password="123456">
</jdbcConnection>
<javaTypeResolver>
<property name="forceBigDecimals" value="false"/>
</javaTypeResolver>
<!-- 生成模型的包名和位置-->
<javaModelGenerator targetPackage="com.caffz.model" targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
<property name="trimStrings" value="true"/>
</javaModelGenerator>
<!-- 生成映射文件的包名和位置-->
<sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources">
<property name="enableSubPackages" value="true"/>
</sqlMapGenerator>
<!-- 生成DAO的包名和位置-->
<javaClientGenerator type="XMLMAPPER" targetPackage="com.caffz.mapper" targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
</javaClientGenerator>
<!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
<table tableName="t_user" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
</context>
</generatorConfiguration>
点击右侧栏maven Projects，再打开Plugins插件点击mybatis-generator即可