Mybatis generator

逆向工程：先创建数据库表，由框架负责根据数据库表，反向生成如下资源：
Java实体类
Mapper接口
Mapper映射文件

有以下两种实现逆向工程的方式

依赖式使用

引入依赖

    <dependency>
      <groupId>mysqlgroupId>
      <artifactId>mysql-connector-javaartifactId>
      <version>5.1.18version>
    dependency>
    
    <dependency>
      <groupId>org.mybatis.generatorgroupId>
      <artifactId>mybatis-generator-coreartifactId>
      <version>1.3.7version>
    dependency>

    
    <dependency>
      <groupId>org.mybatis.spring.bootgroupId>
      <artifactId>mybatis-spring-boot-starterartifactId>
      <version>1.3.3version>
    dependency>

配置文件设置

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">
        
        <commentGenerator>
          
        commentGenerator>
        
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/zycf?characterEncoding=utf8"
                        userId="root"
                        password="123456">
        jdbcConnection>

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

        
        
        <javaModelGenerator targetPackage="com.lhh.entity"
                            targetProject=".\src\main\java">
            
            <property name="enableSubPackages" value="true" />
            
            <property name="trimStrings" value="true" />
        javaModelGenerator>

        
        <sqlMapGenerator targetPackage="resources.mapper"
                         targetProject=".\src\main">
            <property name="enableSubPackages" value="true" />
        sqlMapGenerator>

        
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.lhh.dao"
                             targetProject=".\src">
            <property name="enableSubPackages" value="true" />
        javaClientGenerator>

        
        
        <table tableName="zycf_mediaoperate_weixin_release" domainObjectName="MediaRelease"
               enableCountByExample="true" enableUpdateByExample="true"
               enableDeleteByExample="true" enableSelectByExample="true"
               selectByExampleQueryId="true">
            
           
            
            
            
            
        table>
        <table tableName="zycf_mediaoperate_weixin_article" domainObjectName="Article">table>
    context>
generatorConfiguration>

生成

启动方式：SpringBoot项目，此处直接用测试类来运行了

/**
 * @(#)generatorTest.java, 2019/11/24.
 * 

 * Copyright 2019 Netease, Inc. All rights reserved.
 * NETEASE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.lhh;

import org.junit.Test;
import org.mybatis.generator.api.MyBatisGenerator;
import org.mybatis.generator.config.Configuration;
import org.mybatis.generator.config.xml.ConfigurationParser;
import org.mybatis.generator.exception.InvalidConfigurationException;
import org.mybatis.generator.exception.XMLParserException;
import org.mybatis.generator.internal.DefaultShellCallback;
import org.springframework.boot.test.context.SpringBootTest;

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

/**
 * @author 吕厚厚(wb.lvhouhou @ mesg.corp.netease.com)
 */

@SpringBootTest
public class generatorTest {

    @Test
    public void generator(){
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        //指向逆向工程配置文件
        try {
            File configFile = new File("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);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (XMLParserException e) {
            e.printStackTrace();
        } catch (InvalidConfigurationException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

使用中出现的异常

Exception in thread “main” java.io.FileNotFoundException: generatorConfig.xml (系统找不到指定的文件。)
解决：

Mybatis中javaType和jdbcType对应关系

JDBCType	JavaType
CHAR	String
VARCHAR	String
LONGVARCHAR	String
NUMERIC	java.math.BigDecimal
DECIMAL	java.math.BigDecimal
BIT	boolean
BOOLEAN	boolean
TINYINT	byte
SMALLINT	short
INTEGER	int
BIGINT	long
REAL	float
FLOAT	double
DOUBLE	double
BINARY	byte[]
VARBINARY	byte[]
LONGVARBINARY	byte[]
DATE	java.sql.Date
TIME	java.sql.Time
TIMESTAMP	java.sql.Timestamp
CLOB	Clob
BLOB	Blob
ARRAY	Array
DISTINCT	mapping of underlying type
STRUCT	Struct
REF	Ref

如：数据库字段为smallint时，逆向工程生成的Short类型
数据库表：

自动生成的实体类属性：

int、bigint、smallint 和 tinyint是使用整数数据的精确数字数据类型。

主要类型、范围、存储体如下：

1）bigint：从 -2^63 (-9223372036854775808) 到 2^63-1 (9223372036854775807) 的整型数据（19位数字），存储 8 个字节。————有点儿像Java的long

2）int：从 -2^31 (-2,147,483,648) 到 2^31 - 1 (2,147,483,647)（10位数字，±21亿） 的整型数据。存储 4 个字节。 ————有点儿像int

3）smallint：从 -2^15 (-32,768) 到 2^15 - 1 (32,767) （5位数字，65535）的整型数据，存储2 个字节。 ————有点儿像short

4）tinyint：从 0 到 255（256） 的整型数据，存储 1 字节。 ————有点儿像byte 如果“tinyInt 长度为Bit” 值为0或1 MySQL中 使用布尔类型的字段，就用 tinyint(1)，true 为1 false 为0

插件式使用

添加依赖和插件

<dependencies>
	
	<dependency>
		<groupId>org.mybatisgroupId>
		<artifactId>mybatisartifactId>
		<version>3.5.9version>
	dependency>
	
	<dependency>
		<groupId>junitgroupId>
		<artifactId>junitartifactId>
		<version>4.13.2version>
		<scope>testscope>
	dependency>
	
	<dependency>
		<groupId>mysqlgroupId>
		<artifactId>mysql-connector-javaartifactId>
		<version>8.0.27version>
	dependency>
	
	<dependency>
		<groupId>log4jgroupId>
		<artifactId>log4jartifactId>
		<version>1.2.17version>
	dependency>
dependencies>

<build>
	
	<plugins>
		
		<plugin>
			<groupId>org.mybatis.generatorgroupId>
			<artifactId>mybatis-generator-maven-pluginartifactId>
			<version>1.3.0version>
			
			<dependencies>
				
				<dependency>
					<groupId>org.mybatis.generatorgroupId>
					<artifactId>mybatis-generator-coreartifactId>
					<version>1.3.2version>
				dependency>
				
				<dependency>
					<groupId>com.mchangegroupId>
					<artifactId>c3p0artifactId>
					<version>0.9.2version>
				dependency>
				
				<dependency>
					<groupId>mysqlgroupId>
					<artifactId>mysql-connector-javaartifactId>
					<version>8.0.27version>
				dependency>
			dependencies>
		plugin>
	plugins>
build>

创建逆向工程的配置文件

文件名必须是：generatorConfig.xml

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="MyBatis3Simple">
        
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mybatis"
                        userId="root"
                        password="123456">
        jdbcConnection>
        
        <javaModelGenerator targetPackage="com.atguigu.mybatis.pojo" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        javaModelGenerator>
        
        <sqlMapGenerator targetPackage="com.atguigu.mybatis.mapper"
                         targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        sqlMapGenerator>
        
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.atguigu.mybatis.mapper" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        javaClientGenerator>
        
        
        
        <table tableName="t_emp" domainObjectName="Emp"/>
        <table tableName="t_dept" domainObjectName="Dept"/>
    context>
generatorConfiguration>

执行MBG插件的generate目标

如果出现报错：Exception getting JDBC Driver，可能是pom.xml中，数据库驱动配置错误

下面两处的驱动版本要相同

1、dependency中的驱动

2、mybatis-generator-maven-plugin插件中的驱动

执行结果