mybatis简单项目

た入场券 2021-12-12 06:23 189阅读 0赞

1,mybatis

MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以使用简单的 XML 或注解来配置和映射原生类型、接口和 Java 的 POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

2,mybatis的简单实例

mysql 建表

CREATE TABLE `user` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `username` varchar(45) DEFAULT NULL,
      `sex` varchar(45) DEFAULT NULL,
      `birthday` date DEFAULT NULL,
      `address` varchar(45) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
    SELECT * FROM testdb.user;

maven 依赖

<dependencies>
      
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.4.4</version>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.16</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.8.2</version>
                <scope>test</scope>
            </dependency>
     </dependencies>

User 表对应的类：

import java.util.Date;
    import lombok.Getter;
    import lombok.Setter;
    @Setter
    @Getter
    public class User {
        private int id;
        private String username;
        private String sex;
        private Date birthday;
        private String address_city;
    }

mybatis的配置文件mybatis-xml，目标位置src/main/resources 下

<?xml version="1.0" encoding="UTF-8" ?>  
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"  
    "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        
        <typeAliases>
            <typeAlias  type="com.ys.entity.User" alias="User" />
        </typeAliases>
        
        
        <environments default="development">
            <environment id="development">
                
                <transactionManager type="JDBC" />
                
                <dataSource type="POOLED">
                    
                    <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                    
                    <property name="url" value="jdbc:mysql://127.0.0.1:3306/testdb" />
                    
                    <property name="username" value="root" />
                    
                    <property name="password" value="123456" />
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            <mapper resource="com/ys/mappersxml/UserMapper.xml"></mapper>
        </mappers>
    </configuration>

mybatis.xml 的标签的作用：

<typeAliases>
            <typeAlias  type="com.ys.entity.User" alias="User" />
        </typeAliases>

将每个mapper.xml 注册到mybatis 中

接下来就是UserMapper.xml:

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
      PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
      "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.ys.mappers.UserMapper">
    
        
        <select id="selectUserById" resultType="User" parameterType="int">
            
            select * from user where id = #{id}
        </select>
    
        <insert id="insertUser" parameterType="com.ys.entity.User">
            insert into
            user(id,username,sex,birthday,address)
            value(#{id},#{username},#{sex},#{birthday},#{address})
        </insert>
    
        <select id="selectAllUser" resultType="com.ys.entity.User">
            select * from user
        </select>
    
        <select id="selectUserNameLike" parameterType="java.lang.String"
            resultType="com.ys.entity.User">
            select * from user where username like '%${value}%'
        </select>
    
        <select id="selectByName" parameterType="java.lang.String"
            resultType="com.ys.entity.User">
            select * from user where username = #{username}
        </select>
    
        <delete id="deleteUserById" parameterType="int">
            delete from user where
            id=#{id}
        </delete>
    
        <update id="updateUserById" parameterType="java.util.Map">
            update user set
            username=#{username} where id=#{id}
        </update>
    
        
    
        <resultMap id="userResultMap" type="User">
            <id property="id" column="id" />
            <result property="username" column="username" />
            <result property="address_city" column="address" />
        </resultMap>
       
           <select id="selectUserByIdMap" resultMap="userResultMap" parameterType="int">
               
            select id,username,address from user where id =#{id}
        </select>
    
    
    </mapper>

UserMapper 接口，定义了需要的查询方法：UserMapper.xml 里面的方法名称要和 UserMapper.java 里面一样：

package com.ys.mappers;
    
    import java.util.List;
    import java.util.Map;
    
    import org.apache.ibatis.annotations.Param;
    import org.apache.ibatis.annotations.Select;
    
    import com.ys.entity.User;
    
    public interface UserMapper {
    
        void insertUser(User user);
    
        User selectUserById(int id);
    
        List<User> selectAllUser();
    
        //模糊查询的
        List<User> selectUserNameLike(String username);
    
        List<User> selectByName(String username);
    
        void deleteUserById(int id);
    
        // 多参数 传递方式1
        // public void updateUserById(@Param("id")int id,@Param("username")String
        // username);
    
        // 多参数 传递方式2
        void updateUserById(Map<String, Object> map);
    
        // 使用注解 字符串替换 不用写根据id查 根据username查 根据address 查
        @Select("select * from user where ${column} = #{value}")
        List<User> findByColumn(@Param("column") String column, @Param("value") String value);
    
        // resultMap 结果映射   只想输出部分的属性
        User selectUserByIdMap(int id);
    
    }

测试：

ublic class App {
        public static void main(String[] args) {
            String resource = "mybatis.xml";
            // 加载 mybatis 全局配置文件
            InputStream inputStream = CRUDTest.class.getClassLoader().getResourceAsStream(resource);
            // 构建sqlSession的工厂
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            // 根据 sqlSessionFactory 产生 session
            SqlSession session = sessionFactory.openSession();
            UserMapper mapper = session.getMapper(UserMapper.class);
            User user = mapper.selectUserById(1);
            System.out.println(user.getUsername());
    
            // 插入
    //         User u = new User();
    //         u.setUsername("Jimmy");
    //         u.setSex("female");
    //         u.setAddress_city("Pekin");
    //         mapper.insertUser(u);
    
            // 查询所有
            List<User> users = mapper.selectAllUser();
            for (User user2 : users) {
                System.out.println("selectAll:  " + user2.getUsername());
            }
    
            // 模糊查询
            List<User> userLikes = mapper.selectUserNameLike("L");
            for (User user2 : userLikes) {
                System.out.println("selectUserNameLike: " + user2.getUsername());
            }
    
            // 根据姓名查询
            List<User> selectByName = mapper.selectByName("Jim");
            for (User user2 : selectByName) {
                System.out.println("selectByName:  " + user2.getUsername());
            }
            
            //根据id 删除
            //mapper.deleteUserById(3);
            
            //更新   多个不同类型的传参 map
            HashMap<String, Object> map = new HashMap<String, Object>();
            map.put("id", 1);
            map.put("username", "Linda");
            mapper.updateUserById(map);
            
            
            //字符串替换
            List<User> findByColumn = mapper.findByColumn("username","Linda");
            for (User user2 : findByColumn) {
                System.out.println("findByColumn: " + user2.getUsername());
                //数据库的字段是address   javaBean是属性是address 所以直接查询不能映射，需要resultMap
                System.out.println("findByColumn: "+user2.getAddress_city());
            }
            
            //resultMap 结果映射 
            User selectUserByIdMap = mapper.selectUserByIdMap(1);
            System.out.println("resultMapSelect "+selectUserByIdMap.getAddress_city());
            
            
            session.close();
        }
    
    }

转载于:https://www.cnblogs.com/pickKnow/p/11158845.html