java——mybatis——Mybatis注解开发——@Select查询——查询所有条数

￡神魔★判官ぃ 2024-03-31 14:58 77阅读 0赞

DAO接口：

package com.sunxl.dao;
    
    import com.sunxl.pojo.User;
    import org.apache.ibatis.annotations.*;
    
    import java.util.List;
    
    public interface UserDao {
    
        @Select("select * from users")
        List<User> findAll();
    
        @Insert("insert into users (name,age) values(#{name},#{age})")
        @SelectKey(statement = "select last_insert_id()", keyProperty = "id", keyColumn = "id", resultType = int.class ,before = false)
        int saveUser(User user);
    
    
        @Update("update users set name = #{name},age = #{age} where id = #{id}")
        int updateUser(User user);
    
        @Delete("delete from users where id = #{id}")
        int deleteUser(Integer id);
    
        @Select("select count(*) from users")
        int findTotal();
    
        //
    //    User findById(Integer id);
    //
    //    List<User> findByName(String name);
    
    }

![064a0b985551d15be3c2afe42c0d3681.png][]

测试执行：

import com.sunxl.dao.UserDao;
    import com.sunxl.pojo.User;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.List;
    
    public class MybatisTest {
    
        public static void main(String[] args) throws IOException {
    
    //        InputStream config = Resources.getResourceAsStream("mybatis-config.xml");
    //
    //        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    //        SqlSessionFactory factory = builder.build(config);
    //        SqlSession ss = factory.openSession();
    //        UserDao userdao = ss.getMapper(UserDao.class);
    //
    //
    //        List<User> users = userdao.findAll();
    //
    //        for (User user: users){
    //            System.out.println(user);
    //        }
    //
    //
    //        ss.commit();
    //        ss.close();
    //        config.close();
    
    
    
            InputStream config = Resources.getResourceAsStream("mybatis-config.xml");
    
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
            SqlSessionFactory factory = builder.build(config);
            SqlSession ss = factory.openSession();
            UserDao userdao = ss.getMapper(UserDao.class);
    
    
    
            int a = userdao.findTotal();
            System.out.println(a);
    
    
    
            ss.commit();
            ss.close();
            config.close();
    
    
        }
    }

![283b1c8d9691c8bccbc310ca0fbf086e.png][]

![46e75c0db66ee468a25803df2f6bf487.png][]

![12025f700150f18a66b5b5980b041eb7.png][]

PS：因为之前删除了第一条记录。故总数只有1004条

![47b1f23d08342432fa31f8c273441cfd.png][]

[064a0b985551d15be3c2afe42c0d3681.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/c621173a9354440bbec02628ed816067.png
[283b1c8d9691c8bccbc310ca0fbf086e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/1f2c19f49d4b471aa5de058d428e4404.png
[46e75c0db66ee468a25803df2f6bf487.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/70a28ce0501b425b9d3d18ef0d9cb485.png
[12025f700150f18a66b5b5980b041eb7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/9d7d766924b54a2ea8235bb526269921.png
[47b1f23d08342432fa31f8c273441cfd.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/a874cbee8cc74c9985020e3851f84510.png