在上一篇博客中说到，Mybatis是灵活的SQL语句应用，不想Hibernate一样有其封装好的方法，那么，当我们用Mybatis的时候（Hibernate），我们都需要编写其实体类，和配置文件。本篇博客，就介绍一下Mybatis的逆向生成工具。

一、思路

回想一下，在最早运用EF的时候，我们首先通过可视化界面，连接数据库，然后选择要使用的表单，然后，我们就可以自动生成实体类。在运用Hibernate的时候，我们可以先编写Hibernate的配置文件，连接数据库，然后编写实体类文件，然后通过读取HIbernate的配置文件，正向生成数据库表单。然后我们也可以运用工具，从数据库表，生成HIbernate的实体。那么，到了Mybatis这儿，可以怎么做呢？思路如下：

1，连接数据库，指定表单生成

2，指定代码生成后的存放路径，以及要生成哪些代码

2，读取配置文件，生成代码

二、实现

首先是建立了一个Java project，然后引入了5个jar包，分别是：

log4j-1.2.16.jar；Mybatis-3.2.3.jar；Mybatis-generator-core-1.3.2.jar；mysal-connector-java-5.1.28-bin.jar；ojdbc14.jar

版本可以自行确定！

然后，编写mybatis.xml配置文件，代码内容如下：

  1. <span style="font-family:KaiTi_GB2312;font-size:18px;"><?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE generatorConfiguration
  3.   PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
  4.   "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
  5.  
  6. <generatorConfiguration>
  7. 	<context id="testTables" targetRuntime="MyBatis3">
  8. 		<commentGenerator>
  9. 			<!-- 是否去除自动生成的注释 true：是 ： false:否 -->
  10. 			<property name="suppressAllComments" value="true" />
  11. 		</commentGenerator>
  12. 		<!--数据库连接的信息：驱动类、连接地址、用户名、密码 -->
  13. 		<jdbcConnection driverClass="com.mysql.jdbc.Driver"
  14. 			connectionURL="jdbc:mysql://localhost:3306/Test" userId="root"
  15. 			password="Angel0626">
  16. 		</jdbcConnection>
  17. 		<!-- 默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer，为 true时把JDBC DECIMAL 和
  18. 			NUMERIC 类型解析为java.math.BigDecimal -->
  19. 		<javaTypeResolver>
  20. 			<property name="forceBigDecimals" value="false" />
  21. 		</javaTypeResolver>
  22.  
  23. 		<!-- targetProject:生成PO类的位置 -->
  24. 		<javaModelGenerator targetPackage="pojo"
  25. 			targetProject=".\src">
  26. 			<!-- enableSubPackages:是否让schema作为包的后缀 -->
  27. 			<property name="enableSubPackages" value="false" />
  28. 			<!-- 从数据库返回的值被清理前后的空格 -->
  29. 			<property name="trimStrings" value="true" />
  30. 		</javaModelGenerator>
  31.         <!-- targetProject:mapper映射文件生成的位置 -->
  32. 		<sqlMapGenerator targetPackage="mapper"
  33. 			targetProject=".\src">
  34. 			<!-- enableSubPackages:是否让schema作为包的后缀 -->
  35. 			<property name="enableSubPackages" value="false" />
  36. 		</sqlMapGenerator>
  37. 		<!-- targetPackage：mapper接口生成的位置 -->
  38. 		<javaClientGenerator type="XMLMAPPER"
  39. 			targetPackage="mapper"
  40. 			targetProject=".\src">
  41. 			<!-- enableSubPackages:是否让schema作为包的后缀 -->
  42. 			<property name="enableSubPackages" value="false" />
  43. 		</javaClientGenerator>
  44. 		<!-- 指定数据库表 -->
  45. 		<table schema="" tableName="tb_content"></table>
  46. 		<table schema="" tableName="tb_content_category"></table>
  47. 		<table schema="" tableName="tb_item"></table>
  48. 		<table schema="" tableName="tb_item_cat"></table>
  49. 		<table schema="" tableName="tb_item_desc"></table>
  50. 		<table schema="" tableName="tb_item_param"></table>
  51. 		<table schema="" tableName="tb_item_param_item"></table>
  52. 		<table schema="" tableName="tb_order"></table>
  53. 		<table schema="" tableName="tb_order_item"></table>
  54. 		<table schema="" tableName="tb_order_shipping"></table>
  55. 		<table schema="" tableName="tb_user"></table>
  56.  
  57. 	</context>
  58. </generatorConfiguration>
  59. </span>

其次，编写实现方法，代码如下：

  1. <span style="font-family:KaiTi_GB2312;font-size:18px;">package test;
  2.  
  3. import java.io.File;
  4. import java.util.ArrayList;
  5. import java.util.List;
  6.  
  7. import org.mybatis.generator.api.MyBatisGenerator;
  8. import org.mybatis.generator.config.Configuration;
  9. import org.mybatis.generator.config.xml.ConfigurationParser;
  10. import org.mybatis.generator.internal.DefaultShellCallback;
  11.  
  12. public class GeneratorSqlmap {
  13.  
  14. 	public void generator() throws Exception{
  15.  
  16. 		List<String> warnings=new ArrayList<String>();
  17. 		boolean overwrite=true;
  18.  
  19. 		File configFile=new File("mybatis.xml");
  20. 		ConfigurationParser cp=new ConfigurationParser(warnings);
  21. 		Configuration config=cp.parseConfiguration(configFile);
  22. 		DefaultShellCallback callback=new DefaultShellCallback(overwrite);
  23. 		MyBatisGenerator myBatisGenerator=new MyBatisGenerator(config,callback,warnings);
  24. 		myBatisGenerator.generate(null);
  25.  
  26. 	}
  27.  
  28. 	public static void main(String[] args) throws Exception{
  29. 		try{
  30. 			GeneratorSqlmap generatorSqlmap=new GeneratorSqlmap();
  31. 			generatorSqlmap.generator();
  32. 		}catch(Exception e){
  33. 			e.printStackTrace();
  34. 		}
  35. 	}
  36.  
  37. }
  38. </span>

运行其main方法，即可生成相应代码。

代码示例：以TbUser表为例：

实体类：

  1. <span style="font-family:KaiTi_GB2312;font-size:18px;">public class TbUser {
  2.     private Long id;
  3.  
  4.     private String username;
  5.  
  6.     private String password;
  7.  
  8.     private String phone;
  9.  
  10.     private String email;
  11.  
  12.     private Date created;
  13.  
  14.     private Date updated;
  15.  
  16.     public Long getId() {
  17.         return id;
  18.     }
  19.  
  20.     public void setId(Long id) {
  21.         this.id = id;
  22.     }</span>

mapper接口：

  1. <span style="font-family:KaiTi_GB2312;font-size:18px;">package mapper;
  2.  
  3. import java.util.List;
  4. import org.apache.ibatis.annotations.Param;
  5. import pojo.TbUser;
  6. import pojo.TbUserExample;
  7.  
  8. public interface TbUserMapper {
  9.     int countByExample(TbUserExample example);
  10.  
  11.     int deleteByExample(TbUserExample example);
  12.  
  13.     int deleteByPrimaryKey(Long id);
  14.  
  15.     int insert(TbUser record);
  16.  
  17.     int insertSelective(TbUser record);
  18.  
  19.     List<TbUser> selectByExample(TbUserExample example);
  20.  
  21.     TbUser selectByPrimaryKey(Long id);
  22.  
  23.     int updateByExampleSelective(@Param("record") TbUser record, @Param("example") TbUserExample example);
  24.  
  25.     int updateByExample(@Param("record") TbUser record, @Param("example") TbUserExample example);
  26.  
  27.     int updateByPrimaryKeySelective(TbUser record);
  28.  
  29.     int updateByPrimaryKey(TbUser record);
  30. }</span>

mapper.xml实现：

  1. <span style="font-family:KaiTi_GB2312;font-size:18px;"><?xml version="1.0" encoding="UTF-8" ?>
  2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
  3. <mapper namespace="mapper.TbUserMapper" >
  4.   <resultMap id="BaseResultMap" type="pojo.TbUser" >
  5.     <id column="id" property="id" jdbcType="BIGINT" />
  6.     <result column="username" property="username" jdbcType="VARCHAR" />
  7.     <result column="password" property="password" jdbcType="VARCHAR" />
  8.     <result column="phone" property="phone" jdbcType="VARCHAR" />
  9.     <result column="email" property="email" jdbcType="VARCHAR" />
  10.     <result column="created" property="created" jdbcType="TIMESTAMP" />
  11.     <result column="updated" property="updated" jdbcType="TIMESTAMP" />
  12.   </resultMap>
  13.   <sql id="Example_Where_Clause" >
  14.     <where >
  15.       <foreach collection="oredCriteria" item="criteria" separator="or" >
  16.         <if test="criteria.valid" >
  17.           <trim prefix="(" suffix=")" prefixOverrides="and" >
  18.             <foreach collection="criteria.criteria" item="criterion" >
  19.               <choose >
  20.                 <when test="criterion.noValue" >
  21.                   and ${criterion.condition}
  22.                 </when>
  23.                 <when test="criterion.singleValue" >
  24.                   and ${criterion.condition} #{criterion.value}
  25.                 </when>
  26.                 <when test="criterion.betweenValue" >
  27.                   and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
  28.                 </when>
  29.                 <when test="criterion.listValue" >
  30.                   and ${criterion.condition}
  31.                   <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
  32.                     #{listItem}
  33.                   </foreach>
  34.                 </when>
  35.               </choose>
  36.             </foreach>
  37.           </trim>
  38.         </if>
  39.       </foreach>
  40.     </where>
  41.   </sql>
  42.   <sql id="Update_By_Example_Where_Clause" >
  43.     <where >
  44.       <foreach collection="example.oredCriteria" item="criteria" separator="or" >
  45.         <if test="criteria.valid" >
  46.           <trim prefix="(" suffix=")" prefixOverrides="and" >
  47.             <foreach collection="criteria.criteria" item="criterion" >
  48.               <choose >
  49.                 <when test="criterion.noValue" >
  50.                   and ${criterion.condition}
  51.                 </when>
  52.                 <when test="criterion.singleValue" >
  53.                   and ${criterion.condition} #{criterion.value}
  54.                 </when>
  55.                 <when test="criterion.betweenValue" >
  56.                   and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
  57.                 </when>
  58.                 <when test="criterion.listValue" >
  59.                   and ${criterion.condition}
  60.                   <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
  61.                     #{listItem}
  62.                   </foreach>
  63.                 </when>
  64.               </choose>
  65.             </foreach>
  66.           </trim>
  67.         </if>
  68.       </foreach>
  69.     </where>
  70.   </sql>
  71.   <sql id="Base_Column_List" >
  72.     id, username, password, phone, email, created, updated
  73.   </sql>
  74.   <select id="selectByExample" resultMap="BaseResultMap" parameterType="pojo.TbUserExample" >
  75.     select
  76.     <if test="distinct" >
  77.       distinct
  78.     </if>
  79.     <include refid="Base_Column_List" />
  80.     from tb_user
  81.     <if test="_parameter != null" >
  82.       <include refid="Example_Where_Clause" />
  83.     </if>
  84.     <if test="orderByClause != null" >
  85.       order by ${orderByClause}
  86.     </if>
  87.   </select>
  88.   <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long" >
  89.     select
  90.     <include refid="Base_Column_List" />
  91.     from tb_user
  92.     where id = #{id,jdbcType=BIGINT}
  93.   </select>
  94.   <delete id="deleteByPrimaryKey" parameterType="java.lang.Long" >
  95.     delete from tb_user
  96.     where id = #{id,jdbcType=BIGINT}
  97.   </delete>
  98.   <delete id="deleteByExample" parameterType="pojo.TbUserExample" >
  99.     delete from tb_user
  100.     <if test="_parameter != null" >
  101.       <include refid="Example_Where_Clause" />
  102.     </if>
  103.   </delete>
  104.   <insert id="insert" parameterType="pojo.TbUser" >
  105.     insert into tb_user (id, username, password,
  106.       phone, email, created,
  107.       updated)
  108.     values (#{id,jdbcType=BIGINT}, #{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR},
  109.       #{phone,jdbcType=VARCHAR}, #{email,jdbcType=VARCHAR}, #{created,jdbcType=TIMESTAMP},
  110.       #{updated,jdbcType=TIMESTAMP})
  111.   </insert>
  112.   <insert id="insertSelective" parameterType="pojo.TbUser" >
  113.     insert into tb_user
  114.     <trim prefix="(" suffix=")" suffixOverrides="," >
  115.       <if test="id != null" >
  116.         id,
  117.       </if>
  118.       <if test="username != null" >
  119.         username,
  120.       </if>
  121.       <if test="password != null" >
  122.         password,
  123.       </if>
  124.       <if test="phone != null" >
  125.         phone,
  126.       </if>
  127.       <if test="email != null" >
  128.         email,
  129.       </if>
  130.       <if test="created != null" >
  131.         created,
  132.       </if>
  133.       <if test="updated != null" >
  134.         updated,
  135.       </if>
  136.     </trim>
  137.     <trim prefix="values (" suffix=")" suffixOverrides="," >
  138.       <if test="id != null" >
  139.         #{id,jdbcType=BIGINT},
  140.       </if>
  141.       <if test="username != null" >
  142.         #{username,jdbcType=VARCHAR},
  143.       </if>
  144.       <if test="password != null" >
  145.         #{password,jdbcType=VARCHAR},
  146.       </if>
  147.       <if test="phone != null" >
  148.         #{phone,jdbcType=VARCHAR},
  149.       </if>
  150.       <if test="email != null" >
  151.         #{email,jdbcType=VARCHAR},
  152.       </if>
  153.       <if test="created != null" >
  154.         #{created,jdbcType=TIMESTAMP},
  155.       </if>
  156.       <if test="updated != null" >
  157.         #{updated,jdbcType=TIMESTAMP},
  158.       </if>
  159.     </trim>
  160.   </insert>
  161.   <select id="countByExample" parameterType="pojo.TbUserExample" resultType="java.lang.Integer" >
  162.     select count(*) from tb_user
  163.     <if test="_parameter != null" >
  164.       <include refid="Example_Where_Clause" />
  165.     </if>
  166.   </select>
  167.   <update id="updateByExampleSelective" parameterType="map" >
  168.     update tb_user
  169.     <set >
  170.       <if test="record.id != null" >
  171.         id = #{record.id,jdbcType=BIGINT},
  172.       </if>
  173.       <if test="record.username != null" >
  174.         username = #{record.username,jdbcType=VARCHAR},
  175.       </if>
  176.       <if test="record.password != null" >
  177.         password = #{record.password,jdbcType=VARCHAR},
  178.       </if>
  179.       <if test="record.phone != null" >
  180.         phone = #{record.phone,jdbcType=VARCHAR},
  181.       </if>
  182.       <if test="record.email != null" >
  183.         email = #{record.email,jdbcType=VARCHAR},
  184.       </if>
  185.       <if test="record.created != null" >
  186.         created = #{record.created,jdbcType=TIMESTAMP},
  187.       </if>
  188.       <if test="record.updated != null" >
  189.         updated = #{record.updated,jdbcType=TIMESTAMP},
  190.       </if>
  191.     </set>
  192.     <if test="_parameter != null" >
  193.       <include refid="Update_By_Example_Where_Clause" />
  194.     </if>
  195.   </update>
  196.   <update id="updateByExample" parameterType="map" >
  197.     update tb_user
  198.     set id = #{record.id,jdbcType=BIGINT},
  199.       username = #{record.username,jdbcType=VARCHAR},
  200.       password = #{record.password,jdbcType=VARCHAR},
  201.       phone = #{record.phone,jdbcType=VARCHAR},
  202.       email = #{record.email,jdbcType=VARCHAR},
  203.       created = #{record.created,jdbcType=TIMESTAMP},
  204.       updated = #{record.updated,jdbcType=TIMESTAMP}
  205.     <if test="_parameter != null" >
  206.       <include refid="Update_By_Example_Where_Clause" />
  207.     </if>
  208.   </update>
  209.   <update id="updateByPrimaryKeySelective" parameterType="pojo.TbUser" >
  210.     update tb_user
  211.     <set >
  212.       <if test="username != null" >
  213.         username = #{username,jdbcType=VARCHAR},
  214.       </if>
  215.       <if test="password != null" >
  216.         password = #{password,jdbcType=VARCHAR},
  217.       </if>
  218.       <if test="phone != null" >
  219.         phone = #{phone,jdbcType=VARCHAR},
  220.       </if>
  221.       <if test="email != null" >
  222.         email = #{email,jdbcType=VARCHAR},
  223.       </if>
  224.       <if test="created != null" >
  225.         created = #{created,jdbcType=TIMESTAMP},
  226.       </if>
  227.       <if test="updated != null" >
  228.         updated = #{updated,jdbcType=TIMESTAMP},
  229.       </if>
  230.     </set>
  231.     where id = #{id,jdbcType=BIGINT}
  232.   </update>
  233.   <update id="updateByPrimaryKey" parameterType="pojo.TbUser" >
  234.     update tb_user
  235.     set username = #{username,jdbcType=VARCHAR},
  236.       password = #{password,jdbcType=VARCHAR},
  237.       phone = #{phone,jdbcType=VARCHAR},
  238.       email = #{email,jdbcType=VARCHAR},
  239.       created = #{created,jdbcType=TIMESTAMP},
  240.       updated = #{updated,jdbcType=TIMESTAMP}
  241.     where id = #{id,jdbcType=BIGINT}
  242.   </update>
  243. </mapper></span>

三、总结

从生成的代码可以看出，生成的代码，基本上解决了对于一个实体操作的增删改查，但是，每个实体的代码都是这样的丰富，还能不能继续往上抽象一层呢？下一篇博客介绍Mybatis的底层封装思路！

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