Mybatis逆向工程

Mybaits需要程序员自己编写SQL语句，为了更方便开发Mybaits，官方提供逆向工程，可以针对单表自动生成Mybaits执行所需要的代码。实际开发中，常用的逆向工程方式，由数据库的表生成Java代码。

pom文件

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.1</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.22</version>
</dependency>

<dependency>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-core</artifactId>
    <version>1.3.7</version>
</dependency>

配置文件

<?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="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/test" userId="root"
            password="123456">
        </jdbcConnection>

        <!--默认false，把JDBC的DECIMAL和NUMERIC类型解析为 Integer-->
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false" />
        </javaTypeResolver>

        <!--targetProject:生成PO类的位置 -->
        <javaModelGenerator targetPackage="com.feige.mapper" targetProject=".srcmainjava">
            <!--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xml文件生成的位置-->
        <sqlMapGenerator targetPackage="com.feige.mapper" targetProject=".srcmainjava">
            <!--enableSubPackages:是否让schema作为包的后缀-->
            <property name="enableSubPackages" value="false" />
        </sqlMapGenerator>

        <!--targetPackage：Mapper接口文件生成的位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.feige.mapper" targetProject=".srcmainjava">
            <!-- 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="user"></table>       
    </context>
</generatorConfiguration>

Java代码

import java.io.File;
import java.util.*;
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 GeneratorSqlmap { 
    public void generator() throws Exception {
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        // 指定配置文件,相对路径不好用
        File configFile = new File("E://generatorConfig.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);
    }
    // 执行main方法以生成代码
    public static void main(String[] args) {
        try {
            GeneratorSqlmap generatorSqlmap = new GeneratorSqlmap();
            generatorSqlmap.generator();
            System.out.println("执行完毕了，一个log也没有给老子打印出来！艹！");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

生成文件User.java

public class User {
    private Integer id;

    private String name;

    private String hobby;

    private Integer age;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }
.......

生成文件UserExample.java

package com.feige.mapper;

import java.util.ArrayList;
import java.util.List;

public class UserExample {
    protected String orderByClause;

    protected boolean distinct;

    protected List<Criteria> oredCriteria;

    public UserExample() {
        oredCriteria = new ArrayList<Criteria>();
    }

    public void setOrderByClause(String orderByClause) {
        this.orderByClause = orderByClause;
    }

    public String getOrderByClause() {
        return orderByClause;
    }

    public void setDistinct(boolean distinct) {
        this.distinct = distinct;
    }

    public boolean isDistinct() {
        return distinct;
    }

    public List<Criteria> getOredCriteria() {
        return oredCriteria;
    }

    public void or(Criteria criteria) {
        oredCriteria.add(criteria);
    }

    public Criteria or() {
        Criteria criteria = createCriteriaInternal();
        oredCriteria.add(criteria);
        return criteria;
    }

    public Criteria createCriteria() {
        Criteria criteria = createCriteriaInternal();
        if (oredCriteria.size() == 0) {
            oredCriteria.add(criteria);
        }
        return criteria;
    }

    protected Criteria createCriteriaInternal() {
        Criteria criteria = new Criteria();
        return criteria;
    }

    public void clear() {
        oredCriteria.clear();
        orderByClause = null;
        distinct = false;
    }

    protected abstract static class GeneratedCriteria {
        protected List<Criterion> criteria;

        protected GeneratedCriteria() {
            super();
            criteria = new ArrayList<Criterion>();
        }

        public boolean isValid() {
            return criteria.size() > 0;
        }

        public List<Criterion> getAllCriteria() {
            return criteria;
        }

        public List<Criterion> getCriteria() {
            return criteria;
        }

        protected void addCriterion(String condition) {
            if (condition == null) {
                throw new RuntimeException("Value for condition cannot be null");
            }
            criteria.add(new Criterion(condition));
        }

        protected void addCriterion(String condition, Object value, String property) {
            if (value == null) {
                throw new RuntimeException("Value for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value));
        }

        protected void addCriterion(String condition, Object value1, Object value2, String property) {
            if (value1 == null || value2 == null) {
                throw new RuntimeException("Between values for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value1, value2));
        }

        public Criteria andIdIsNull() {
            addCriterion("id is null");
            return (Criteria) this;
        }

        public Criteria andIdIsNotNull() {
            addCriterion("id is not null");
            return (Criteria) this;
        }

        public Criteria andIdEqualTo(Integer value) {
            addCriterion("id =", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdNotEqualTo(Integer value) {
            addCriterion("id <>", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdGreaterThan(Integer value) {
            addCriterion("id >", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdGreaterThanOrEqualTo(Integer value) {
            addCriterion("id >=", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdLessThan(Integer value) {
            addCriterion("id <", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdLessThanOrEqualTo(Integer value) {
            addCriterion("id <=", value, "id");
            return (Criteria) this;
        }

        public Criteria andIdIn(List<Integer> values) {
            addCriterion("id in", values, "id");
            return (Criteria) this;
        }

        public Criteria andIdNotIn(List<Integer> values) {
            addCriterion("id not in", values, "id");
            return (Criteria) this;
        }

        public Criteria andIdBetween(Integer value1, Integer value2) {
            addCriterion("id between", value1, value2, "id");
            return (Criteria) this;
        }

        public Criteria andIdNotBetween(Integer value1, Integer value2) {
            addCriterion("id not between", value1, value2, "id");
            return (Criteria) this;
        }

        public Criteria andNameIsNull() {
            addCriterion("name is null");
            return (Criteria) this;
        }

        public Criteria andNameIsNotNull() {
            addCriterion("name is not null");
            return (Criteria) this;
        }

        public Criteria andNameEqualTo(String value) {
            addCriterion("name =", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameNotEqualTo(String value) {
            addCriterion("name <>", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameGreaterThan(String value) {
            addCriterion("name >", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameGreaterThanOrEqualTo(String value) {
            addCriterion("name >=", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameLessThan(String value) {
            addCriterion("name <", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameLessThanOrEqualTo(String value) {
            addCriterion("name <=", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameLike(String value) {
            addCriterion("name like", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameNotLike(String value) {
            addCriterion("name not like", value, "name");
            return (Criteria) this;
        }

        public Criteria andNameIn(List<String> values) {
            addCriterion("name in", values, "name");
            return (Criteria) this;
        }

        public Criteria andNameNotIn(List<String> values) {
            addCriterion("name not in", values, "name");
            return (Criteria) this;
        }

        public Criteria andNameBetween(String value1, String value2) {
            addCriterion("name between", value1, value2, "name");
            return (Criteria) this;
        }

        public Criteria andNameNotBetween(String value1, String value2) {
            addCriterion("name not between", value1, value2, "name");
            return (Criteria) this;
        }

        public Criteria andHobbyIsNull() {
            addCriterion("hobby is null");
            return (Criteria) this;
        }

        public Criteria andHobbyIsNotNull() {
            addCriterion("hobby is not null");
            return (Criteria) this;
        }

        public Criteria andHobbyEqualTo(String value) {
            addCriterion("hobby =", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyNotEqualTo(String value) {
            addCriterion("hobby <>", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyGreaterThan(String value) {
            addCriterion("hobby >", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyGreaterThanOrEqualTo(String value) {
            addCriterion("hobby >=", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyLessThan(String value) {
            addCriterion("hobby <", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyLessThanOrEqualTo(String value) {
            addCriterion("hobby <=", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyLike(String value) {
            addCriterion("hobby like", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyNotLike(String value) {
            addCriterion("hobby not like", value, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyIn(List<String> values) {
            addCriterion("hobby in", values, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyNotIn(List<String> values) {
            addCriterion("hobby not in", values, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyBetween(String value1, String value2) {
            addCriterion("hobby between", value1, value2, "hobby");
            return (Criteria) this;
        }

        public Criteria andHobbyNotBetween(String value1, String value2) {
            addCriterion("hobby not between", value1, value2, "hobby");
            return (Criteria) this;
        }

        public Criteria andAgeIsNull() {
            addCriterion("age is null");
            return (Criteria) this;
        }

        public Criteria andAgeIsNotNull() {
            addCriterion("age is not null");
            return (Criteria) this;
        }

        public Criteria andAgeEqualTo(Integer value) {
            addCriterion("age =", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotEqualTo(Integer value) {
            addCriterion("age <>", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeGreaterThan(Integer value) {
            addCriterion("age >", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeGreaterThanOrEqualTo(Integer value) {
            addCriterion("age >=", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeLessThan(Integer value) {
            addCriterion("age <", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeLessThanOrEqualTo(Integer value) {
            addCriterion("age <=", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeIn(List<Integer> values) {
            addCriterion("age in", values, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotIn(List<Integer> values) {
            addCriterion("age not in", values, "age");
            return (Criteria) this;
        }

        public Criteria andAgeBetween(Integer value1, Integer value2) {
            addCriterion("age between", value1, value2, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotBetween(Integer value1, Integer value2) {
            addCriterion("age not between", value1, value2, "age");
            return (Criteria) this;
        }
    }

    public static class Criteria extends GeneratedCriteria {

        protected Criteria() {
            super();
        }
    }

    public static class Criterion {
        private String condition;

        private Object value;

        private Object secondValue;

        private boolean noValue;

        private boolean singleValue;

        private boolean betweenValue;

        private boolean listValue;

        private String typeHandler;

        public String getCondition() {
            return condition;
        }

        public Object getValue() {
            return value;
        }

        public Object getSecondValue() {
            return secondValue;
        }

        public boolean isNoValue() {
            return noValue;
        }

        public boolean isSingleValue() {
            return singleValue;
        }

        public boolean isBetweenValue() {
            return betweenValue;
        }

        public boolean isListValue() {
            return listValue;
        }

        public String getTypeHandler() {
            return typeHandler;
        }

        protected Criterion(String condition) {
            super();
            this.condition = condition;
            this.typeHandler = null;
            this.noValue = true;
        }

        protected Criterion(String condition, Object value, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.typeHandler = typeHandler;
            if (value instanceof List<?>) {
                this.listValue = true;
            } else {
                this.singleValue = true;
            }
        }

        protected Criterion(String condition, Object value) {
            this(condition, value, null);
        }

        protected Criterion(String condition, Object value, Object secondValue, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.secondValue = secondValue;
            this.typeHandler = typeHandler;
            this.betweenValue = true;
        }

        protected Criterion(String condition, Object value, Object secondValue) {
            this(condition, value, secondValue, null);
        }
    }
}

生成文件UserMapper.java

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);
}

生成文件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.feige.mapper.UserMapper">
  <resultMap id="BaseResultMap" type="com.feige.mapper.User">
    <id column="id" jdbcType="INTEGER" property="id" />
    <result column="name" jdbcType="VARCHAR" property="name" />
    <result column="hobby" jdbcType="VARCHAR" property="hobby" />
    <result column="age" jdbcType="INTEGER" property="age" />
  </resultMap>
  <sql id="Example_Where_Clause">
    <where>
      <foreach collection="oredCriteria" item="criteria" separator="or">
        <if test="criteria.valid">
          <trim prefix="(" prefixOverrides="and" suffix=")">
            <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 close=")" collection="criterion.value" item="listItem" open="(" 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="(" prefixOverrides="and" suffix=")">
            <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 close=")" collection="criterion.value" item="listItem" open="(" separator=",">
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Base_Column_List">
    id, name, hobby, age
  </sql>
  <select id="selectByExample" parameterType="com.feige.mapper.UserExample" resultMap="BaseResultMap">
    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" parameterType="java.lang.Integer" resultMap="BaseResultMap">
    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.feige.mapper.UserExample">
    delete from user
    <if test="_parameter != null">
      <include refid="Example_Where_Clause" />
    </if>
  </delete>
  <insert id="insert" parameterType="com.feige.mapper.User">
    insert into user (id, name, hobby, 
      age)
    values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{hobby,jdbcType=VARCHAR}, 
      #{age,jdbcType=INTEGER})
  </insert>
  <insert id="insertSelective" parameterType="com.feige.mapper.User">
    insert into user
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="name != null">
        name,
      </if>
      <if test="hobby != null">
        hobby,
      </if>
      <if test="age != null">
        age,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=INTEGER},
      </if>
      <if test="name != null">
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="hobby != null">
        #{hobby,jdbcType=VARCHAR},
      </if>
      <if test="age != null">
        #{age,jdbcType=INTEGER},
      </if>
    </trim>
  </insert>
  <select id="countByExample" parameterType="com.feige.mapper.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.name != null">
        name = #{record.name,jdbcType=VARCHAR},
      </if>
      <if test="record.hobby != null">
        hobby = #{record.hobby,jdbcType=VARCHAR},
      </if>
      <if test="record.age != null">
        age = #{record.age,jdbcType=INTEGER},
      </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},
      name = #{record.name,jdbcType=VARCHAR},
      hobby = #{record.hobby,jdbcType=VARCHAR},
      age = #{record.age,jdbcType=INTEGER}
    <if test="_parameter != null">
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByPrimaryKeySelective" parameterType="com.feige.mapper.User">
    update user
    <set>
      <if test="name != null">
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="hobby != null">
        hobby = #{hobby,jdbcType=VARCHAR},
      </if>
      <if test="age != null">
        age = #{age,jdbcType=INTEGER},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.feige.mapper.User">
    update user
    set name = #{name,jdbcType=VARCHAR},
      hobby = #{hobby,jdbcType=VARCHAR},
      age = #{age,jdbcType=INTEGER}
    where id = #{id,jdbcType=INTEGER}
  </update>
  <resultMap id="BaseResultMap" type="com.feige.mapper.User">
    <id column="id" jdbcType="INTEGER" property="id" />
    <result column="name" jdbcType="VARCHAR" property="name" />
    <result column="hobby" jdbcType="VARCHAR" property="hobby" />
    <result column="age" jdbcType="INTEGER" property="age" />
  </resultMap>
  <sql id="Example_Where_Clause">
    <where>
      <foreach collection="oredCriteria" item="criteria" separator="or">
        <if test="criteria.valid">
          <trim prefix="(" prefixOverrides="and" suffix=")">
            <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 close=")" collection="criterion.value" item="listItem" open="(" 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="(" prefixOverrides="and" suffix=")">
            <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 close=")" collection="criterion.value" item="listItem" open="(" separator=",">
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Base_Column_List">
    id, name, hobby, age
  </sql>
  <select id="selectByExample" parameterType="com.feige.mapper.UserExample" resultMap="BaseResultMap">
    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" parameterType="java.lang.Integer" resultMap="BaseResultMap">
    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.feige.mapper.UserExample">
    delete from user
    <if test="_parameter != null">
      <include refid="Example_Where_Clause" />
    </if>
  </delete>
  <insert id="insert" parameterType="com.feige.mapper.User">
    insert into user (id, name, hobby, 
      age)
    values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{hobby,jdbcType=VARCHAR}, 
      #{age,jdbcType=INTEGER})
  </insert>
  <insert id="insertSelective" parameterType="com.feige.mapper.User">
    insert into user
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="name != null">
        name,
      </if>
      <if test="hobby != null">
        hobby,
      </if>
      <if test="age != null">
        age,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=INTEGER},
      </if>
      <if test="name != null">
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="hobby != null">
        #{hobby,jdbcType=VARCHAR},
      </if>
      <if test="age != null">
        #{age,jdbcType=INTEGER},
      </if>
    </trim>
  </insert>
  <select id="countByExample" parameterType="com.feige.mapper.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.name != null">
        name = #{record.name,jdbcType=VARCHAR},
      </if>
      <if test="record.hobby != null">
        hobby = #{record.hobby,jdbcType=VARCHAR},
      </if>
      <if test="record.age != null">
        age = #{record.age,jdbcType=INTEGER},
      </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},
      name = #{record.name,jdbcType=VARCHAR},
      hobby = #{record.hobby,jdbcType=VARCHAR},
      age = #{record.age,jdbcType=INTEGER}
    <if test="_parameter != null">
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByPrimaryKeySelective" parameterType="com.feige.mapper.User">
    update user
    <set>
      <if test="name != null">
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="hobby != null">
        hobby = #{hobby,jdbcType=VARCHAR},
      </if>
      <if test="age != null">
        age = #{age,jdbcType=INTEGER},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.feige.mapper.User">
    update user
    set name = #{name,jdbcType=VARCHAR},
      hobby = #{hobby,jdbcType=VARCHAR},
      age = #{age,jdbcType=INTEGER}
    where id = #{id,jdbcType=INTEGER}
  </update>
</mapper>

总结

在平常的开发中，有时会使用Mybatis的逆向工程，来快速的创建类，其中在创建实例的过程中有一个以Example结尾的类，这个类是用来专门对这个单表操作的类，就相当于，对该单表的增、删、改、查是脱离SQL的，直接在Service层就可以完成。