使用MybatisGenerator

1、向pom.xml添加依赖项

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.22</version>
</dependency>

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

Mybais-Generator依赖JDBC

2、编写config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>
    <!--JDBC库的绝对地址，默认maven下载到 C:\Users\xie\.m2\-->
    <classPathEntry location="C:\Users\xie\.m2\repository\mysql\mysql-connector-java\8.0.21/mysql-connector-java-8.0.21.jar" />

    <!--配置数据库连接-->
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://127.0.0.1:3306/school?serverTimezone=GMT%2B8&amp;characterEncoding=utf8"
                        userId="root"
                        password="123">
        </jdbcConnection>

        <!--配置模型产生的地址 targetPackage是目标包， targetProject是项目地址-->
        <javaModelGenerator targetPackage="com.william.mapper" targetProject="C:\Users\xie\IdeaProjects\dljdMybatis\src\main\java">
            <property name="enableSubPackages" value="false" />
            <property name="trimStrings" value="false" />
        </javaModelGenerator>

        <!--配置mapper文件产生的地址 targetPackage是目标包， targetProject是项目地址-->
        <sqlMapGenerator targetPackage="com.william.mapper"  targetProject="C:\Users\xie\IdeaProjects\dljdMybatis\src\main\java">
            <property name="enableSubPackages" value="false" />
        </sqlMapGenerator>

        <!--配置xml文件产生的地址 targetPackage是目标包， targetProject是项目地址-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.william.mapper"  targetProject="C:\Users\xie\IdeaProjects\dljdMybatis\src\main\java">
            <property name="enableSubPackages" value="false" />
        </javaClientGenerator>

        <!--配置表映射，这里不配置-->
        <table tableName="students" domainObjectName="Student" >
        </table>

    </context>
</generatorConfiguration>

3、运行命令行生成(也可以通过4、java程序生成)

java -jar PACKAGE_NAME -configfile CONFIG_FILE_NAME

其中，PACKAGE_NAME替换为maven仓库下载的mybatis-generator-core-1.4.0.jar的绝对路径，CONFIG_FILE_NAME替换为你写的配置文件的绝对路径
（如果有必要）

4、使用Java程序生成

public class Main {

    static public void main(String[] args) throws IOException, XMLParserException, InvalidConfigurationException, SQLException, InterruptedException {
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        File configFile = new File("src/main/java/com/william/mapper/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);


    }
}

将其中file路径替换即可，否则会报错

 

5、使用产生的Example

static public void main(String[] args) throws IOException, XMLParserException, InvalidConfigurationException, SQLException, InterruptedException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        System.out.println(inputStream.toString());
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        StudentMapper mapper = session.getMapper(StudentMapper.class);

        StudentExample studentExample = new StudentExample();
        studentExample.createCriteria().andAgeBetween(18,100);
        List<Student> students = mapper.selectByExample(studentExample);
        students.stream().forEach(student -> log.info(students.toString()));

    }

能够使用Example产生Criteria，能够用代码拼接sql语句。

优点：开发较快

缺点：效率低下，可能写出低效的sql