Mybatis入门-基于注解实现单表、多表的增删改查

r囧r小猫 2021-09-25 06:40 323阅读 0赞

**Mybatis入门-基于注解实现单表、多表的增删改查**

Mybatis简介请看上篇博客

配置步骤

使用步骤

实体类

DAO接口+注解

主配置文件

测试类

总结mybatis注解

--------------------

# Mybatis简介请看上篇博客 #

**[Mybatis入门-基于xml配置实现单表的增删改查][Mybatis_-_xml]**

## 配置步骤 ##

> 1.引入Mybatis的jar包
> 
> 2.编写实体类与DAO接口
> 
> 3.添加主配置文件（配置mysql环境，事务类型，数据源，连接数据库的基本信息，映射文件的位置）
> 
> 4.使用mybatis中的注解
> 
> 5.使用mybatis框架

## 使用步骤 ##

> 1.读取配置文件，可使用mybatis封装的Resources类。
> 
> 2.创建SQLSessionFactory工厂
> 
> 3.使用工厂生产SQLsession对象
> 
> 4.使用SQLSession创建DAO接口的代理对象
> 
> 5.使用代理对象执行方法
> 
> 6.提交事务，释放资源

# 实体类 #

/**
     * @Author: Promsing
     * @Date: 2021/4/5 - 9:08
     * @Description: User类、Account类
     * @version： 1.0
     */
    public class User implements Serializable {
    
        private Integer id;
        private String username;
        private String address;
        private String sex;
        private Date birthday;
    
        //一对多关系映射 一个用户对应多个账户
        private List<Account> accounts;
    
        public List<Account> getAccounts() {
            return accounts;
        }
    
        public void setAccounts(List<Account> account) {
            this.accounts = account;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", address='" + address + '\'' +
                    ", sex='" + sex + '\'' +
                    ", birthday=" + birthday +
                    '}';
        }
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    
        public String getSex() {
            return sex;
        }
    
        public void setSex(String sex) {
            this.sex = sex;
        }
    
        public Date getBirthday() {
            return birthday;
        }
    
        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }
    }
    
    
    public class Account implements Serializable {
        private Integer id;
        private Integer uid;
        private Double money;
        //多对一 每个账户只能属于一个用户
        private User user;
    
        public User getUser() {
            return user;
        }
    
        public void setUser(User user) {
            this.user = user;
        }
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public Integer getUid() {
            return uid;
        }
    
        public void setUid(Integer uid) {
            this.uid = uid;
        }
    
        public Double getMoney() {
            return money;
        }
    
        public void setMoney(Double money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "Account{" +
                    "id=" + id +
                    ", uid=" + uid +
                    ", money=" + money +
                    '}';
        }
    }

# DAO接口+注解 #

/**
     * @Author: Promsing
     * @Date: 2021/4/5 - 9:10
     * @Description: mybatis：基于注解开发
     * @version： 1.0
     */
    public interface IUserDao {
    
        /**
         * 查询所有用户
         * @return
         */
        @Select("select * from User")
        //当实体类属性与MySQL列名不一致时
        //id属性可被其他方法引用---  @ResultMap("userMap")
        @Results(id="userMap", value = {
                //主键为true    库中列名     类中属性
                @Result(id=true,column = "id",property = "id"),
                @Result(column = "username",property = "username"),
                @Result(column = "birthday",property = "birthday"),
                @Result(column = "sex",property = "sex"),
                @Result(column = "address",property = "address"),
                //关系为一对多 延迟加载
                @Result(column = "id",property = "accounts",
                        many = @Many(
                                select = "com.dynamic_annotation_real.dao.IAccountDao.findAccountByUid",
                                fetchType = FetchType.LAZY))
        })
        List<User> findAll();
    
        /**
         * 查询一个
         * @param i
         * @return
         */
        @Select("select * from user where id=#{id}")
        User findById(Integer i);
    
        /**
         * 根据名称模糊查询
         * @param name
         * @return
         */
        @Select("select * from user where username like #{name}")
    
        List<User> findUserByName(String name);
    
        /**
         * 保存操作
         * @param user
         */
        @Insert("insert into user(username,address,sex,birthday) values(#{username},#{address},#{sex},#{birthday})")
        void saveUser(User user);
    
        /**
         * 更新操作
         * @param user
         */
        @Update("update user set username=#{username},sex=#{sex},birthday=#{birthday},address=#{address} where id=#{id}")
        void updateUser(User user);
    
        /**
         * 删除用户
         * @param userid
         */
        @Delete("delete from User where id=#{id}")
        void deleteUser(Integer userid);
    
        /**
         * 查询总行数
         * @return
         */
        @Select("select count(id) from user")
        int findTotalUser();
    }
    
    
    public interface IAccountDao {
    
        /**
         * 查询所有
         * @return
         */
        @Select("select * from Account")
        @Results(id="accountMap",value = {
                @Result(id=true,column = "id",property = "id"),
                @Result(column = "uid",property = "uid"),
                @Result(column = "money",property = "money"),
                //配置立即加载
                @Result(property ="user", column = "uid",
                        one = @One(
                                select = "com.dynamic_annotation_real.dao.IUserDao.findById",
                                fetchType = FetchType.EAGER)),
        })
        List<Account> findAll();
    
        /**
         * 根据用户id查询账户信息
         * @param userId
         * @return
         */
        @Select("select * from Account where uid=#{userId}")
        List<Account> findAccountByUid(Integer userId);
    }

# 主配置文件 #

<?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>
            <package name="com.dynamic_annotation_real.domain"/>
        </typeAliases>
    
        
        <environments default="mysql">
            
            <environment id="mysql">
                
                <transactionManager type="JDBC"></transactionManager>
                
                <dataSource type="POOLED">
                    
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/eesy"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
           <package name="com.dynamic_annotation_real.dao"></package>
        </mappers>
        
        
       
    </configuration>

# 测试类 #

public class AnnotationTest {
    
        private SqlSession sqlSession;
        private InputStream in;
    
        private IUserDao userDao;
        private IAccountDao accountDao;
    
        @Before
        public void init() throws Exception{
            //1.读取配置文件
            in= Resources.getResourceAsStream("SqlMapConfig_realanno.xml");
            //2.创建SqlSessionFactory工程
            SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(in);
            //3.通过工厂创建SqlSession
             sqlSession = factory.openSession();
             //4.代理模式增强方法
            userDao = sqlSession.getMapper(IUserDao.class);
            accountDao = sqlSession.getMapper(IAccountDao.class);
    
        }
        @After
        public void destroy()  throws Exception{
            sqlSession.commit();
            sqlSession.close();
            in.close();
        }
    
        @Test
        public void testFindAll(){
            List<User> users = userDao.findAll();
            for (User user : users) {
                System.out.println("---每个用户的账户信息---");
                System.out.println(user);
                System.out.println(user.getAccounts());
            }
        }
        @Test
        public void testSaveUser(){
           User user=new User();
           user.setUsername("alibaba");
           user.setAddress("壹号院");
           user.setSex("女");
           user.setBirthday(new Date());
           userDao.saveUser(user);
        }
        @Test
        public void testUpdateUser(){
            User user=new User();
            user.setUsername("CSDN");
            user.setAddress("北京");
            user.setSex("男");
            user.setBirthday(new Date());
            user.setId(45);
            userDao.updateUser(user);
        }
    
        @Test
        public void testDelete(){
    
            userDao.deleteUser(53);
        }
    
        @Test
        public void testFindOne(){
            User user = userDao.findById(52);
            System.out.println(user);
            //默认开启一级缓存
            User user2 = userDao.findById(52);
            System.out.println(user2);
            System.out.println(user==user2);
        }
    
        @Test
        public void testFindByName(){
            List<User> users = userDao.findUserByName("%s%");
            for (User user : users) {
                System.out.println(user);
            }
        }
    
        @Test
        public void testFindTotal(){
            int totalUser = userDao.findTotalUser();
            System.out.println(totalUser);
        }
    
        /*注解一对一，一对多*/
        @Test
        public void testAccountFindAll(){
            List<Account> accounts = accountDao.findAll();
            for (Account account : accounts) {
                System.out.println("---每个账户信息---");
                System.out.println(account);
                System.out.println(account.getUser());
            }
        }
    
    
    }

# **总结mybatis注解** #

> @Insert：实现新增
> 
> @Update：实现更新
> 
> @Delete：实现删除
> 
> @Select：实现查询
> 
> @Result：实现结果集封装
> 
> @Results：可以与@Result一起使用，封装多个结果集
> 
> @ResultMap：实现引用@Results定义的封装
> 
> @One：实现一对一结果集封装
> 
> @Many：实现一对多结果集封装

**总体来说：基于注解的的增删改查总体来说比基于xml配置的增删改查进行开发，效率高一些，也比较简单。所以现在公司使用的项目都是基于注解开发。能记住这些注解，我们就是最棒的，多记注解，多练习。哈哈哈！**

[Mybatis_-_xml]: https://blog.csdn.net/promsing/article/details/115380863