MyBatis中解决实体类属性和数据库列名不对应的两种方式

数据库表

在IDEA中创建maven项目

整体架构

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.uek</groupId>
    <artifactId>mybatis02-study01-mabatisCRUD-property</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!--打包方式-->
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

</project>

MyBatis的主配置文件

在resource目录下------SqlMapConfig.xml

<?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>
    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!--配置映射文件的位置-->
    <mappers>
        <mapper resource="com/uek/dao/IUserDao.xml"></mapper>
    </mappers>
</configuration>

dao层接口

public interface IUserDao {

    //查询所有用户
    List<User> findAll();

    //插入
    void saveUser(User user);

    //更新
    void updateUser(User user);

    //根据id删除用户
    void deleteUser(Integer UserId);

    //根据id查询用户信息
    User findById(Integer userId);

    //根据名称模糊查询用户信息
    List<User>findByName(String username);

    //查询总的用户数
    int findTotal();

    //根据QueryVo中的条件查询用户
    List<User> findUserByVo(QueryVo Vo);

}

实体类

public class QueryVo {

    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

public class User implements Serializable {

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;


    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }
}

接口配置 IUserDao.xml

注意：在resource目录下新建包时一级一级的建立
必须和dao层的接口的包名一致。

<?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.uek.dao.IUserDao">
    <!--第一种方式-->
    <!--配置查询结果的列名和实体类的属性名的对应关系-->
    <resultMap id="userMap" type="com.uek.domian.User">
        <!--主键字段的对应-->
        <id property="userId" column="id"></id>
        <!--非主键字段的对应-->
        <result property="userName" column="username"></result>
        <result property="userAddress" column="address"></result>
        <result property="userSex" column="sex"></result>
        <result property="userBirthday" column="birthday"></result>
    </resultMap>

    <!--查询所有方法-->
    <select id="findAll" resultMap="userMap">
        <!--第二种方式-->
        <!--select id as userId,username as userName, address as userAddress,sex as userSex,birthday as userBirthday  from user-->
        select * from user
    </select>

    <!--插入-->
    <insert id="saveUser" parameterType="com.uek.domian.User">
        <!--配置插入操作后，获取插入数据的id-->
        <selectKey keyProperty="userId" keyColumn="id" resultType="int" order="AFTER">
            select last_insert_id();
        </selectKey>
        insert into user(username,address,sex,birthday)values(#{userName},#{userAddress},#{userSex},#{userBirthday});
    </insert>

    <!--更新-->
    <update id="updateUser" parameterType="com.uek.domian.User">
        update user set username=#{userName},address=#{userAddress},sex=#{userSex},birthday=#{userBirthday} where id=#{userId};
    </update>

    <!--删除用户-->
    <delete id="deleteUser" parameterType="java.lang.Integer">
        <!--#{uid}:可以随便写，因为只有一个-->
        delete from user where id = #{uid}
    </delete>

    <!--根据id查询用户信息-->
    <select id="findById" parameterType="int" resultMap="userMap">
        select * from user where id = #{uid}
    </select>

    <!--根据名称模糊查询-->
    <select id="findByName" parameterType="string" resultMap="userMap">
        select * from user where username like #{name}
        <!--select * from user where username like '%${value}%'   了解-->
    </select>

    <!--获取用户的总记录条数-->
    <select id="findTotal"  resultType="int">
        select count(id) from user;
    </select>

    <!--根据QueryVo的条件查询用户   OGNL表达式-->
    <select id="findUserByVo" parameterType="com.uek.domian.QueryVo" resultMap="userMap">
        select * from user where username like #{user.userName}
    </select>
</mapper>

测试类

public class MyBatisTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before   //用于在测试方法执行之前执行
    public void init() throws Exception {
        //1.读取配置文件，生成字节输入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.获取SqlSession对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.获取SqlSession对象
        sqlSession = factory.openSession();
        //4.获取dao的代理对象
        userDao = sqlSession.getMapper(IUserDao.class);
    }


    @After //用于在测试方法执行之后执行
    public void destroy() throws Exception {
        //提交事务
        sqlSession.commit();

        //6.释放资源
        sqlSession.close();
        in.close();
    }

    //测试：查询所有
    @Test
    public void testFindAll() throws Exception {
        //执行查询所有方法
        List<User>users = userDao.findAll();
        for (User user : users) {
            System.out.println(user);
        }
    }

    //测试：插入操作
    @Test
    public void testSave(){
        User user = new User();
        user.setUserName("modify User property");
        user.setUserAddress("太原市迎泽区");
        user.setUserSex("男");
        user.setUserBirthday(new Date());
        System.out.println("保存操作之前："+user);
        //5.执行插入方法
        userDao.saveUser(user);
        System.out.println("保存操作之后："+user);
    }

    //测试：更新操作
    @Test
    public void testUpdate(){
        User user = new User();
        user.setUserId(7);
        user.setUserName("mybatis update user");
        user.setUserAddress("太原市小店区");
        user.setUserSex("女");
        user.setUserBirthday(new Date());

        //5.执行插入方法
        userDao.updateUser(user);
    }

    //测试：删除操作
    @Test
    public void testDelete(){
        //执行删除方法
        userDao.deleteUser(9);
    }

    //测试：查询一个操作
    @Test
    public void testSelectOne(){
        //执行查询一个方法
        User byId = userDao.findById(8);
        System.out.println(byId);
    }

    //测试:模糊查询操作
    @Test
    public void testFindByName(){
        List<User>users = userDao.findByName("%王%");
//      List<User>users = userDao.findByName("王");
        for (User user : users) {
            System.out.println(user);
        }
    }

    //测试：总记录条数
    @Test
    public void testFindTotal(){
        int count = userDao.findTotal();
        System.out.println(count);
    }


    //测试:使用QueryVo作为查询条件
    @Test
    public void testQueryVo(){
        QueryVo vo = new QueryVo();
        User user = new User();
        user.setUserName("%王%");
        vo.setUser(user);
        List<User>users = userDao.findUserByVo(vo);
        for (User u : users) {
            System.out.println(u);
        }
    }
}