Mybatis-Generator 自动生成代码

1.Mybatis-Generator官网介绍

链接：http://www.mybatis.org/generator/index.html

 2.我的项目结构：

3.首先是先创建好表格，后面的代码都是通过这个表格来创建的，我的表格如下：

4.添加依赖，我用的是数据库Mysql 8

<!--Mybatis-Generator-->
<dependency>
  <groupId>org.mybatis.generator</groupId>
  <artifactId>mybatis-generator-core</artifactId>
  <version>1.3.5</version>
</dependency>

5.添加插件，注意要改成自己的配置文件地址。

<plugins>
<plugin>
    <!--Mybatis-generator插件,用于自动生成Mapper和POJO-->
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-maven-plugin</artifactId>
    <version>1.3.2</version>
    <configuration>
        <!--这里面改成你自己的配置文件的位置-->
        <configurationFile>src/main/resources/mybatis-generator.xml</configurationFile>
        <verbose>true</verbose>
        <overwrite>true</overwrite>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.5</version>
        </dependency>
    </dependencies>
    <executions>
        <execution>
            <id>Generate MyBatis Artifacts</id>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>
</plugins>

添加好之后就会出现如下插件，下面配置好之后就是双击该插件进行自动生成代码：

6.在resources下创建xml文件mybatis-generator.xml，里面的配置一项一项地看下去就大致明白是什么意思了。Model，Mapper，和Dao这三个生成的顺序好像不可以调换。

<?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">
        <!--配置注释，如下是不生成注释-->
        <commentGenerator>
            <property name="suppressDate" value="true"/>
            <property name="suppressAllComments" value="true" />
        </commentGenerator>
        <!--配置数据库-->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://127.0.0.1:3306/db?characterEncoding=utf-8&amp;serverTimezone=GMT%2B8&amp;useSSL=false&amp;allowPublicKeyRetrieval=true"
                        userId="root"
                        password="123456">
        </jdbcConnection>

        <javaTypeResolver >
            <property name="forceBigDecimals" value="false" />
        </javaTypeResolver>

        <!--1.生成Model类存放位置-->
        <javaModelGenerator targetPackage="model" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!--2.生成映射文件存放位置-->
        <sqlMapGenerator targetPackage="resources" targetProject="src/main">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!--3.生成Dao类存放位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="dao" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <!--生成对应表及类名-->
        <table tableName="message" domainObjectName="Message" enableCountByExample="false" enableUpdateByExample="false"
               enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"/>

    </context>
</generatorConfiguration>

7.到此基本配置完成，双击插件即可生成代码

8.生成三个文分别是Model，Mapper，和Dao

Model-Message

package model;

public class Message {
    private Long id;

    private String userName;

    private String userSex;

    private String school;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName == null ? null : userName.trim();
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex == null ? null : userSex.trim();
    }

    public String getSchool() {
        return school;
    }

    public void setSchool(String school) {
        this.school = school == null ? null : school.trim();
    }
}

Mapper-MessageMapper.xml

<?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="dao.MessageMapper">
  <resultMap id="BaseResultMap" type="model.Message">
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="user_name" jdbcType="VARCHAR" property="userName" />
    <result column="user_sex" jdbcType="VARCHAR" property="userSex" />
    <result column="school" jdbcType="VARCHAR" property="school" />
  </resultMap>
  <sql id="Base_Column_List">
    id, user_name, user_sex, school
  </sql>
  <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from message
    where id = #{id,jdbcType=BIGINT}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
    delete from message
    where id = #{id,jdbcType=BIGINT}
  </delete>
  <insert id="insert" parameterType="model.Message">
    insert into message (id, user_name, user_sex, 
      school)
    values (#{id,jdbcType=BIGINT}, #{userName,jdbcType=VARCHAR}, #{userSex,jdbcType=VARCHAR}, 
      #{school,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="model.Message">
    insert into message
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="userName != null">
        user_name,
      </if>
      <if test="userSex != null">
        user_sex,
      </if>
      <if test="school != null">
        school,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=BIGINT},
      </if>
      <if test="userName != null">
        #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        #{school,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="model.Message">
    update message
    <set>
      <if test="userName != null">
        user_name = #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        user_sex = #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        school = #{school,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=BIGINT}
  </update>
  <update id="updateByPrimaryKey" parameterType="model.Message">
    update message
    set user_name = #{userName,jdbcType=VARCHAR},
      user_sex = #{userSex,jdbcType=VARCHAR},
      school = #{school,jdbcType=VARCHAR}
    where id = #{id,jdbcType=BIGINT}
  </update>
  <resultMap id="BaseResultMap" type="model.Message">
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="user_name" jdbcType="VARCHAR" property="userName" />
    <result column="user_sex" jdbcType="VARCHAR" property="userSex" />
    <result column="school" jdbcType="VARCHAR" property="school" />
  </resultMap>
  <sql id="Base_Column_List">
    id, user_name, user_sex, school
  </sql>
  <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from message
    where id = #{id,jdbcType=BIGINT}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
    delete from message
    where id = #{id,jdbcType=BIGINT}
  </delete>
  <insert id="insert" parameterType="model.Message">
    insert into message (id, user_name, user_sex, 
      school)
    values (#{id,jdbcType=BIGINT}, #{userName,jdbcType=VARCHAR}, #{userSex,jdbcType=VARCHAR}, 
      #{school,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="model.Message">
    insert into message
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="userName != null">
        user_name,
      </if>
      <if test="userSex != null">
        user_sex,
      </if>
      <if test="school != null">
        school,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=BIGINT},
      </if>
      <if test="userName != null">
        #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        #{school,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="model.Message">
    update message
    <set>
      <if test="userName != null">
        user_name = #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        user_sex = #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        school = #{school,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=BIGINT}
  </update>
  <update id="updateByPrimaryKey" parameterType="model.Message">
    update message
    set user_name = #{userName,jdbcType=VARCHAR},
      user_sex = #{userSex,jdbcType=VARCHAR},
      school = #{school,jdbcType=VARCHAR}
    where id = #{id,jdbcType=BIGINT}
  </update>
  <resultMap id="BaseResultMap" type="model.Message">
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="user_name" jdbcType="VARCHAR" property="userName" />
    <result column="user_sex" jdbcType="VARCHAR" property="userSex" />
    <result column="school" jdbcType="VARCHAR" property="school" />
  </resultMap>
  <sql id="Base_Column_List">
    id, user_name, user_sex, school
  </sql>
  <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from message
    where id = #{id,jdbcType=BIGINT}
  </select>

  <delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
    delete from message
    where id = #{id,jdbcType=BIGINT}
  </delete>

  <insert id="insert" parameterType="model.Message">
    insert into message (id, user_name, user_sex, 
      school)
    values (#{id,jdbcType=BIGINT}, #{userName,jdbcType=VARCHAR}, #{userSex,jdbcType=VARCHAR}, 
      #{school,jdbcType=VARCHAR})
  </insert>
    <!--判断是否为空进行插入-->
  <insert id="insertSelective" parameterType="model.Message">
    insert into message
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="userName != null">
        user_name,
      </if>
      <if test="userSex != null">
        user_sex,
      </if>
      <if test="school != null">
        school,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=BIGINT},
      </if>
      <if test="userName != null">
        #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        #{school,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
    <!--判断是否为空进行插入-->
  <update id="updateByPrimaryKeySelective" parameterType="model.Message">
    update message
    <set>
      <if test="userName != null">
        user_name = #{userName,jdbcType=VARCHAR},
      </if>
      <if test="userSex != null">
        user_sex = #{userSex,jdbcType=VARCHAR},
      </if>
      <if test="school != null">
        school = #{school,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=BIGINT}
  </update>

  <update id="updateByPrimaryKey" parameterType="model.Message">
    update message
    set user_name = #{userName,jdbcType=VARCHAR},
      user_sex = #{userSex,jdbcType=VARCHAR},
      school = #{school,jdbcType=VARCHAR}
    where id = #{id,jdbcType=BIGINT}
  </update>
</mapper>

Dao-MessageDao

package dao;

import model.User;

public interface UserDao {
    int saveUser(User user);
    int deleteUserById(Integer id);
    int updateUser(User user);
    User getUserById(Integer id);
    User getUserByName(String name);
}

至此mybatis-generator就大功告成了

PS：可能遇到的坑：

1.一定要记得要先创建表，一切都是通过表来自动生成代码的

2.MySQL 8的中一些问题都通过url来解决

connectionURL="jdbc:mysql://127.0.0.1:3306/db?characterEncoding=utf-8&serverTimezone=GMT%2B8&useSSL=false&allowPublicKeyRetrieval=true"

各含义如下：

characterEncoding=utf-8&------限定编码格式为utf8

serverTimezone=GMT%2B8&-------限定时区为本地

useSSL=false&------------禁用SSL

allowPublicKeyRetrieval=true------------允许使用主键进行查询