深入浅出Mybatis(九)逆向工程

一，前一篇博客中，介绍了一下Mybatis和hibernate的对比，在这一篇博客说说mybatis的逆向工程，展示一下，只要有一个数据库，你的持久层，你的D层从此不用你自己手写了。

二、什么是逆向工程？

mybaits需要程序员自己编写sql语句，mybatis官方提供逆向工程可以针对单表自动生成mybatis执行所需要的代码（mapper.java,mapper.xml、pojo），企业实际开发中，常用的逆向工程方式：由于数据库的表生成java代码。

三、Mybatis中逆向工程的使用

导入

导入已有的数据库，小编已经导入自己编写好的数据库，数据库结构如下：

把generatorSqlmapCustom JavaProject导入

修改配置文件的数据库连接以及数据库

指定数据库表

生成表对应的实体类

<javaModelGenerator targetPackage="com.dtt.mybatis.pojo"
			targetProject=".\src">
			<!-- 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>

mapper映射文件生成

<!-- targetProject:mapper映射文件生成的位置 -->
		<sqlMapGenerator targetPackage="com.dtt.mybatis.mapper"
			targetProject=".\src">
			<!-- enableSubPackages:是否让schema作为包的后缀 -->
			<property name="enableSubPackages" value="false" />
		</sqlMapGenerator>

mapper接口生成

<!-- targetPackage：mapper接口生成的位置 -->
		<javaClientGenerator type="XMLMAPPER"
			targetPackage="com.dtt.mybatis.mapper"
			targetProject=".\src">
			<!-- enableSubPackages:是否让schema作为包的后缀 -->
			<property name="enableSubPackages" value="false" />
		</javaClientGenerator>

     几个关键属性：

      javaModelGenerator ：实体类生成；

      sqlMapGenerator ：映射文件生成；

      javaClientGenerator ：接口生成；

      targetProject：生成文件的位置，本例中.\src，是指src下的目录；

      targetPackage：生成包的名称；

修改完成后，运行GeneratorSqlmap.java中的main方法，就可以生成。

以User表为例，展示生成的代码：

User.java

package com.dtt.mybatis.pojo;

import java.util.Date;

public class User {
    private Integer id;

    private String username;

    private Date birthday;

    private String sex;

    private String address;

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username == null ? null : username.trim();
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex == null ? null : sex.trim();
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address == null ? null : address.trim();
    }
}

UserMapper.java

这里生成了所有的增删改查的sql语句，调用的时候就直接使用对应的方法就可以了很方便吧。（重点学习一下自动生成的代码是如何封装的）

package com.dtt.mybatis.mapper;

import com.dtt.mybatis.pojo.User;
import com.dtt.mybatis.pojo.UserExample;
import java.util.List;
import org.apache.ibatis.annotations.Param;

public interface UserMapper {
    int countByExample(UserExample example);

    int deleteByExample(UserExample example);

    int deleteByPrimaryKey(Integer id);

    int insert(User record);

    int insertSelective(User record);

    List<User> selectByExample(UserExample example);

    User selectByPrimaryKey(Integer id);

    int updateByExampleSelective(@Param("record") User record, @Param("example") UserExample example);

    int updateByExample(@Param("record") User record, @Param("example") UserExample example);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);
}

UserMapper.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="com.dtt.mybatis.mapper.UserMapper" >
  <resultMap id="BaseResultMap" type="com.dtt.mybatis.pojo.User" >
    <id column="id" property="id" jdbcType="INTEGER" />
    <result column="username" property="username" jdbcType="VARCHAR" />
    <result column="birthday" property="birthday" jdbcType="DATE" />
    <result column="sex" property="sex" jdbcType="CHAR" />
    <result column="address" property="address" jdbcType="VARCHAR" />
  </resultMap>
  <sql id="Example_Where_Clause" >
    <where >
      <foreach collection="oredCriteria" item="criteria" separator="or" >
        <if test="criteria.valid" >
          <trim prefix="(" suffix=")" prefixOverrides="and" >
            <foreach collection="criteria.criteria" item="criterion" >
              <choose >
                <when test="criterion.noValue" >
                  and ${criterion.condition}
                </when>
                <when test="criterion.singleValue" >
                  and ${criterion.condition} #{criterion.value}
                </when>
                <when test="criterion.betweenValue" >
                  and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
                </when>
                <when test="criterion.listValue" >
                  and ${criterion.condition}
                  <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Update_By_Example_Where_Clause" >
    <where >
      <foreach collection="example.oredCriteria" item="criteria" separator="or" >
        <if test="criteria.valid" >
          <trim prefix="(" suffix=")" prefixOverrides="and" >
            <foreach collection="criteria.criteria" item="criterion" >
              <choose >
                <when test="criterion.noValue" >
                  and ${criterion.condition}
                </when>
                <when test="criterion.singleValue" >
                  and ${criterion.condition} #{criterion.value}
                </when>
                <when test="criterion.betweenValue" >
                  and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
                </when>
                <when test="criterion.listValue" >
                  and ${criterion.condition}
                  <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Base_Column_List" >
    id, username, birthday, sex, address
  </sql>
  <select id="selectByExample" resultMap="BaseResultMap" parameterType="com.dtt.mybatis.pojo.UserExample" >
    select
    <if test="distinct" >
      distinct
    </if>
    <include refid="Base_Column_List" />
    from user
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null" >
      order by ${orderByClause}
    </if>
  </select>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from user
    where id = #{id,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from user
    where id = #{id,jdbcType=INTEGER}
  </delete>
  <delete id="deleteByExample" parameterType="com.dtt.mybatis.pojo.UserExample" >
    delete from user
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
  </delete>
  <insert id="insert" parameterType="com.dtt.mybatis.pojo.User" >
    insert into user (id, username, birthday, 
      sex, address)
    values (#{id,jdbcType=INTEGER}, #{username,jdbcType=VARCHAR}, #{birthday,jdbcType=DATE}, 
      #{sex,jdbcType=CHAR}, #{address,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="com.dtt.mybatis.pojo.User" >
    insert into user
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="username != null" >
        username,
      </if>
      <if test="birthday != null" >
        birthday,
      </if>
      <if test="sex != null" >
        sex,
      </if>
      <if test="address != null" >
        address,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=INTEGER},
      </if>
      <if test="username != null" >
        #{username,jdbcType=VARCHAR},
      </if>
      <if test="birthday != null" >
        #{birthday,jdbcType=DATE},
      </if>
      <if test="sex != null" >
        #{sex,jdbcType=CHAR},
      </if>
      <if test="address != null" >
        #{address,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <select id="countByExample" parameterType="com.dtt.mybatis.pojo.UserExample" resultType="java.lang.Integer" >
    select count(*) from user
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
  </select>
  <update id="updateByExampleSelective" parameterType="map" >
    update user
    <set >
      <if test="record.id != null" >
        id = #{record.id,jdbcType=INTEGER},
      </if>
      <if test="record.username != null" >
        username = #{record.username,jdbcType=VARCHAR},
      </if>
      <if test="record.birthday != null" >
        birthday = #{record.birthday,jdbcType=DATE},
      </if>
      <if test="record.sex != null" >
        sex = #{record.sex,jdbcType=CHAR},
      </if>
      <if test="record.address != null" >
        address = #{record.address,jdbcType=VARCHAR},
      </if>
    </set>
    <if test="_parameter != null" >
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByExample" parameterType="map" >
    update user
    set id = #{record.id,jdbcType=INTEGER},
      username = #{record.username,jdbcType=VARCHAR},
      birthday = #{record.birthday,jdbcType=DATE},
      sex = #{record.sex,jdbcType=CHAR},
      address = #{record.address,jdbcType=VARCHAR}
    <if test="_parameter != null" >
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByPrimaryKeySelective" parameterType="com.dtt.mybatis.pojo.User" >
    update user
    <set >
      <if test="username != null" >
        username = #{username,jdbcType=VARCHAR},
      </if>
      <if test="birthday != null" >
        birthday = #{birthday,jdbcType=DATE},
      </if>
      <if test="sex != null" >
        sex = #{sex,jdbcType=CHAR},
      </if>
      <if test="address != null" >
        address = #{address,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.dtt.mybatis.pojo.User" >
    update user
    set username = #{username,jdbcType=VARCHAR},
      birthday = #{birthday,jdbcType=DATE},
      sex = #{sex,jdbcType=CHAR},
      address = #{address,jdbcType=VARCHAR}
    where id = #{id,jdbcType=INTEGER}
  </update>
</mapper>

小结

逆向工程在很多软件里面都有，比如EA的逆向工程，PB的逆向工程。还有很多，总之，这个就是其中的一些很有价值的东西，在企业运用的时候很方便，而且这些生成好的类，尽量不要去修改，如果非要修改的话，可以用pv类来实现继承拓展。这是很好的选择。

posted @ 2018-11-01 18:40 palyer 阅读(312) 评论(0) 编辑收藏举报

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mtimeyu

深入浅出Mybatis(九)逆向工程

二、什么是逆向工程？

三、Mybatis中逆向工程的使用

导入

小结

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