逆向工程(generator)----->由表帮我们来生成dao、bean、xml

1)引入mybatis-generator的jar包

2)在工程目录下新建generator.xml文件（复制官网内容）

<?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jar包所在的位置 -->
  <classPathEntry location="D:\mybatis\generator830\lib\mysql-connector-java-5.1.47.jar" />
  <context id="DB2Tables" targetRuntime="MyBatis3">
 <!--  去除注释 -->
      <commentGenerator>
      <property name="suppressAllComments" value="true" />
        </commentGenerator>
   <!--  数据源信息 -->
    <jdbcConnection driverClass="com.mysql.jdbc.Driver"
        connectionURL="jdbc:mysql://localhost:3306/mybatis"
        userId="root"
        password="root">
    </jdbcConnection>
    <javaTypeResolver >
      <property name="forceBigDecimals" value="false" />
    </javaTypeResolver>
    <!-- 生成的实体类所在的位置 -->
    <javaModelGenerator targetPackage="com.zhiyou.clg.bean" targetProject="./src">
      <property name="enableSubPackages" value="true" />
      <property name="trimStrings" value="true" />
    </javaModelGenerator>
    <!-- 生成的映射文件所在的位置 -->
    <sqlMapGenerator targetPackage="com.zhiyou.clg.mapper"  targetProject="./resource">
      <property name="enableSubPackages" value="true" />
    </sqlMapGenerator>
    <!-- 生成的dao所在的位置 -->
    <javaClientGenerator type="XMLMAPPER" targetPackage="com.zhiyou.clg.dao"  targetProject="./src">
      <property name="enableSubPackages" value="true" />
    </javaClientGenerator>
    <!-- 表和实体类的对象关系
        schema：该表所在的数据库
        tableName：表名
        domainObjectName：实体类名
     -->
    <table schema="DB2ADMIN" tableName="user" domainObjectName="User"  
     enableCountByExample="false" enableDeleteByExample="false" enableSelectByExample="false" enableUpdateByExample="false" >
      <property name="useActualColumnNames" value="true"/>
      <generatedKey column="ID" sqlStatement="DB2" identity="true" />
      <columnOverride column="DATE_FIELD" property="startDate" />
      <ignoreColumn column="FRED" />
      <columnOverride column="LONG_VARCHAR_FIELD" jdbcType="VARCHAR" />
    </table>

  </context>
</generatorConfiguration>

3)在src目录下新建test包，再新建Test类，在main下复制官网内容，导包后运行

package com.zhiyou.clg.test;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.mybatis.generator.api.MyBatisGenerator;
import org.mybatis.generator.config.Configuration;
import org.mybatis.generator.config.xml.ConfigurationParser;
import org.mybatis.generator.exception.XMLParserException;
import org.mybatis.generator.internal.DefaultShellCallback;

public class TestGenerator {
    public static void main(String[] args) throws Exception{
        List<String> warnings = new ArrayList<String>();
           boolean overwrite = true;
           File configFile = new File("generator.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);
    }
}