Mybatis的环境配置与简单使用

环境配置

参考官网：入门_MyBatis中文网

创建一个空的maven项目

在pom.xml文件添加mybatis,mysql,junit等依赖

		
        
            org.mybatis
            mybatis
            3.5.5
        

        
            mysql
            mysql-connector-java
            5.1.32
        

        
            junit
            junit
            4.13
            test

在IDEA中安装MybatisX插件

创建mybatis配置文件：mybatis-config.xml，并且放入resource目录

创建pojo包，创建User类并且放入

使用mapper进行代理开发

1.在resource文件夹内创建和pojo包前缀相同的目录，如(com.xzh.pojo包)，目录为comxzh
2.在resource文件夹创建comxzhmapper目录，创建UserMapper.xml,存放sql语句

    
    
        select * from tb_user;
    


3.在java文件夹创建com.xzh.mapper包，创建同名的UserMapper接口
public interface UserMapper {

    List selectAll();

}
        
4.配置好后，对应接口和sql语句位置会出现蓝红鸟对应(mybatisx插件功能)，这样就配置好了

在测试类里面创建com.xzh.test包，创建对应测试类。

    @Test
    public void testSelectAll() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        List brands = brandMapper.selectAll();
        System.out.println(brands);
        
        sqlSession.close();
    }

如果数据库字段和pojo里面定义类的字段不一致，需要用resultMap进行封装


    
    
        
        
    
    
    
        select * from tb_brand;

执行方法，测试

查询-根据id查询

sql映射文件：

    
        select * from tb_brand
        
            
                and status = #{status}
            
            
                and brand_name like #{brandName}
            
            
                and company_name like #{companyName}

多参数设置的方法

散装参数：需要用@Param(“SQL中的参数名称”) *使用麻烦

List selectByCondition(@Param("status") int status, @Param("companyName") String companyName, @Param("brandName") String brandName);

实体类封装参数 *只需要保证SQL中的参数名和实体类属性名对应上就行

List selectByCondition(Brand brand);

    @Test
    public void testSelectByCondition() throws IOException {
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";
        //模糊查询需要用%
        companyName = "%" + companyName + "%";
        brandName = "%" + brandName + "%";
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);

        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        List brands = brandMapper.selectByCondition(brand);
        System.out.println(brands);

        sqlSession.close();
    }

map集合 *只需要保证SQL中的参数名和map集合的键对的上即可

List selectByCondition(Map map);

    @Test
    public void testSelectByCondition() throws IOException {
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";
        companyName = "%" + companyName + "%";
        brandName = "%" + brandName + "%";

        Map map = new HashMap<>();
        map.put("status", status + "");
        map.put("companyName", companyName);
        map.put("brandName", brandName);
 
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        List brands = brandMapper.selectByCondition(map);
        System.out.println(brands);

        sqlSession.close();
    }

动态sql where关键字

以下语句如果用户只给了brandName的值那么语句就会出错（where and brand_name like #{brandName}）

    
        select * from tb_brand
        
            
                and status = #{status}
            
            
                and brand_name like #{brandName}
            
            
                and company_name like #{companyName}

choose关键字