1、创建数据库和表(针对MySQL)
SQL脚本如下:
Create DATABASE spring4_mybatis3;
USE spring4_mybatis3;
DROP TABLE IF EXISTS t_user;
CREATE TABLE t_user (
user_id char(32) NOT NULL,
user_name varchar(30) DEFAULT NULL,
user_birthday date DEFAULT NULL,
user_salary double DEFAULT NULL,
PRIMARY KEY (user_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
创建好的数据库和表如下:
2、使用generator工具生成代码
在网上找到了一个generator工具可以根据创建好的数据库表生成MyBatis的表对应的实体类,SQL映射文件和dao,找到generator工具根目录下的generator.xml文件,这个文件是用来配置代码生成规则的,如下图所示:
编辑generator.xml文件,内容如下:
<?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>
<!-- 数据库驱动包位置 -->
<classPathEntry location="D:\javaLib\hiblib\mysql-connector-java-5.1.7-bin.jar" />
<!-- <classPathEntry location="C:\oracle\product\10.2.0\db_1\jdbc\lib\ojdbc14.jar" />-->
<context id="DB2Tables" targetRuntime="MyBatis3">
<commentGenerator>
<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://localhost:3306/spring4_mybatis3" userId="root" password="root">
<!--<jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver" connectionURL="jdbc:oracle:thin:@localhost:1521:orcl" userId="msa" password="msa">-->
</jdbcConnection>
<javaTypeResolver>
<property name="forceBigDecimals" value="false" />
</javaTypeResolver>
<!-- 生成实体类的包名和位置,这里配置将生成的实体类放在com.demo.domain这个包下 -->
<javaModelGenerator targetPackage="com.demo.bean" targetProject="D:\workspace2\spring_mybatis\src">
<property name="enableSubPackages" value="true" />
<property name="trimStrings" value="true" />
</javaModelGenerator>
<!-- 生成的SQL映射文件包名和位置,这里配置将生成的SQL映射文件放在com.demo.mapping这个包下 -->
<sqlMapGenerator targetPackage="com.demo.mapper" targetProject="D:\workspace2\spring_mybatis\src">
<property name="enableSubPackages" value="true" />
</sqlMapGenerator>
<!-- 生成DAO的包名和位置,这里配置将生成的dao类放在com.demo.dao这个包下 -->
<javaClientGenerator type="XMLMAPPER" targetPackage="com.demo.dao" targetProject="D:\workspace2\spring_mybatis\src">
<property name="enableSubPackages" value="true" />
</javaClientGenerator>
<!-- 要生成那些表(更改tableName和domainObjectName就可以) -->
<table tableName="t_user" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" />
</context>
</generatorConfiguration>
打开命令行窗口,切换到生成工具的根目录下,执行如下命令:
E:\EclipseEE\eclipse\WorkPlace\MyBatisShopping> java -jar E:\EclipseEE\eclipse\WorkPlace\MyBatisShopping\mybatis-generator-core-1.3.2.jar -configfile generator.xml -overwrite
如下图所示:
刚才我们在generator.xml文件中配置将生成的代码和SQL映射文件放到" D:\workspace2\spring_mybatis\src "这个目录下,这个目录就是我们的spring-mybatis项目所在目录,我们刷新一下src目录,就可以看到生成的代码和映射文件了,如下图所示:
生成的代码和映射文件一行都不用改,可以直接应用到项目当中。下面我们看一眼由generator工具生成的代码和映射文件:
1.生成的dao类:
public interface UserMapper {
int deleteByPrimaryKey(String userId);
int insert(User record);
int insertSelective(User record);
User selectByPrimaryKey(String userId);
int updateByPrimaryKeySelective(User record);
int updateByPrimaryKey(User record);
}
生成的UserMapper是一个接口,里面定义了一些操作t_user表的增删改查方法。
2、生成的实体类
public class User {
private String userId;
private String userName;
private Date userBirthday;
private Double userSalary;
//setter和getter省略
}
User类是t_user表的对应的实体类,User类中定义的属性和t_user表中的字段一一对应。
3、生成的SQL映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.demo.dao.UserMapper" >
<resultMap id="BaseResultMap" type="com.demo.bean.User" >
<id column="user_id" property="userId" jdbcType="CHAR" />
<result column="user_name" property="userName" jdbcType="VARCHAR" />
<result column="user_birthday" property="userBirthday" jdbcType="DATE" />
<result column="user_salary" property="userSalary" jdbcType="DOUBLE" />
</resultMap>
<sql id="Base_Column_List" >
user_id, user_name, user_birthday, user_salary
</sql>
<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.String" >
select
<include refid="Base_Column_List" />
from t_user
where user_id = #{userId,jdbcType=CHAR}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.String" >
delete from t_user
where user_id = #{userId,jdbcType=CHAR}
</delete>
<insert id="insert" parameterType="com.demo.bean.User" >
insert into t_user (user_id, user_name, user_birthday,
user_salary)
values (#{userId,jdbcType=CHAR}, #{userName,jdbcType=VARCHAR}, #{userBirthday,jdbcType=DATE},
#{userSalary,jdbcType=DOUBLE})
</insert>
<insert id="insertSelective" parameterType="com.demo.bean.User" >
insert into t_user
<trim prefix="(" suffix=")" suffixOverrides="," >
<if test="userId != null" >
user_id,
</if>
<if test="userName != null" >
user_name,
</if>
<if test="userBirthday != null" >
user_birthday,
</if>
<if test="userSalary != null" >
user_salary,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides="," >
<if test="userId != null" >
#{userId,jdbcType=CHAR},
</if>
<if test="userName != null" >
#{userName,jdbcType=VARCHAR},
</if>
<if test="userBirthday != null" >
#{userBirthday,jdbcType=DATE},
</if>
<if test="userSalary != null" >
#{userSalary,jdbcType=DOUBLE},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.demo.bean.User" >
update t_user
<set >
<if test="userName != null" >
user_name = #{userName,jdbcType=VARCHAR},
</if>
<if test="userBirthday != null" >
user_birthday = #{userBirthday,jdbcType=DATE},
</if>
<if test="userSalary != null" >
user_salary = #{userSalary,jdbcType=DOUBLE},
</if>
</set>
where user_id = #{userId,jdbcType=CHAR}
</update>
<update id="updateByPrimaryKey" parameterType="com.demo.bean.User" >
update t_user
set user_name = #{userName,jdbcType=VARCHAR},
user_birthday = #{userBirthday,jdbcType=DATE},
user_salary = #{userSalary,jdbcType=DOUBLE}
where user_id = #{userId,jdbcType=CHAR}
</update>
</mapper>
UserMapper.xml这个文件的内容是编写操作t_user表的SQL语句,重点说一下UserMapper.xml配置中需要注意的几个小细节问题:
1、UserMapper.xml的<mapper>标签的namespace必须是UserMapper接口的全类名,既<mapper namespace="com.demo.dao.UserMapper" >
2、UserMapper.xml的定义操作数据库的<select><delete><update><insert>这些标签的id属性的值必须和UserMapper接口定义的方法名一致,如下图所示:
之所以有上述说的这两点要求,就是为了能够让MyBatis能够根据UserMapper接口和UserMapper.xml文件去自动实现UserMapper接口中定义的相关方法,这样我们就不再需要针对UserMapper接口去编写具体的实现代码了。