Mybatis注解开发（超详细）

末蓝、 2022-10-30 02:26 212阅读 0赞

### Mybatis注解开发 ###

*  mybatis的常用注解
 *  使用 Mybatis 注解实现基本 CRUD
 *   *  项目目录结构
     *  编写实体类
     *  使用注解方式开发持久层接口
     *  编写 SqlMapConfig.xml 配置文件
     *  编写测试代码
 *  使用注解实现复杂关系映射开发
 *   *  复杂关系映射的注解说明
     *  项目目录
     *  使用注解实现一对一复杂关系映射及立即加载
     *   *  添加 User 实体类及 Account 实体类
         *  添加账户的持久层接口并使用注解配置
         *  添加用户的持久层接口并使用注解配置
         *  测试一对一关联及立即加载
     *  使用注解实现一对多复杂关系映射及延迟加载
     *   *  User 实体类加入 List\`\`
         *  编写用户的持久层接口并使用注解配置
         *  编写账户的持久层接口并使用注解配置
         *  编写测试代码
 *  回顾下一级缓存
 *  mybatis 基于注解的二级缓存
 *   *  在 SqlMapConfig.xml 中开启二级缓存支持
     *  在持久层接口中使用注解配置二级缓存
     *  编写测试二级缓存的测试类

# mybatis的常用注解 #

<table> 
 <thead> 
  <tr> 
   <th>注解</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>@Insert</td> 
   <td>实现新增</td> 
  </tr> 
  <tr> 
   <td>@Delete</td> 
   <td>实现删除</td> 
  </tr> 
  <tr> 
   <td>@Update</td> 
   <td>实现更新</td> 
  </tr> 
  <tr> 
   <td>@Select</td> 
   <td>实现查询</td> 
  </tr> 
  <tr> 
   <td>@Result</td> 
   <td>实现结果集封装</td> 
  </tr> 
  <tr> 
   <td>@Results</td> 
   <td>可以与@Result 一起使用，封装多个结果集</td> 
  </tr> 
  <tr> 
   <td>@ResultMap</td> 
   <td>实现引用@Results 定义的封装</td> 
  </tr> 
  <tr> 
   <td>@One</td> 
   <td>实现一对一结果集封装</td> 
  </tr> 
  <tr> 
   <td>@Many</td> 
   <td>实现一对多结果集封装</td> 
  </tr> 
  <tr> 
   <td>@SelectProvider</td> 
   <td>实现动态 SQL 映射</td> 
  </tr> 
  <tr> 
   <td>@CacheNamespace</td> 
   <td>实现注解二级缓存的使用</td> 
  </tr> 
 </tbody> 
</table>

# 使用 Mybatis 注解实现基本 CRUD #

## 项目目录结构 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg4MzkxNw_size_16_color_FFFFFF_t_70]

## 编写实体类 ##

**User：**

package com.keafmd.domain;
    
    import java.io.Serializable;
    import java.util.Date;
    
    /** * Keafmd * * @ClassName: User * @Description: User实体类 * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:28 */
    public class User implements Serializable { 
        private Integer id;
        private String username;
        private String address;
        private String sex;
        private Date 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;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", address='" + address + '\'' +
                    ", sex='" + sex + '\'' +
                    ", birthday=" + birthday +
                    '}';
        }
    }

## 使用注解方式开发持久层接口 ##

**IUserDao：**

package com.keafmd.dao;
    
    import com.keafmd.domain.User;
    import org.apache.ibatis.annotations.Delete;
    import org.apache.ibatis.annotations.Insert;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.annotations.Update;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IUserDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:30 */
    
    /** * 在mybatis中针对CRUD一共有四个注解 * @Select @Insert @Update @Delete */
    public interface IUserDao { 
    
        /** * 查询所有用户 * @return */
        @Select("select * from user")
        List<User> findAll();
    
        /** * 保存用户 * @param user */
        @Insert("insert into user(username,address,sex,birthday)values(#{username},#{address},#{sex},#{birthday})")
        void saveUser(User user);
    
        /** * 更新用户 * @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);
    
        /** * 根据id查询用户 * @param userId * @return */
        @Select("select * from user where id=#{id}")
        User findById(Integer userId);
    
        /** * 根据用户名称模糊查询 * @param username * @return */
        //@Select("select * from user where username like #{username}") //占位符
        @Select("select * from user where username like '%${value}%'")  //字符串拼接
        List<User> findByName(String username);
    
        /** * 查询总数量 * @return */
        @Select("select count(*) from user")
        int findTotal();
    
    }

> **通过注解方式，就不需要再去编写 UserDao.xml 映射文件了。**

## 编写 SqlMapConfig.xml 配置文件 ##

**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>
        
        <properties resource="jdbcConfig.properties"></properties>
        
        <typeAliases>
            <package name="com.keafmd.domain"/>
        </typeAliases>
        
        <environments default="mysql">
            <environment id="mysql">
                <transactionManager type="JDBC"></transactionManager>
                <dataSource type="POOLED">
                    <property name="driver" value="${jdbc.driver}"></property>
                    <property name="url" value="${jdbc.url}"></property>
                    <property name="username" value="${jdbc.username}"></property>
                    <property name="password" value="${jdbc.password}"></property>
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            <package name="com.keafmd.dao"></package>
        </mappers>
    </configuration>

## 编写测试代码 ##

**AnnotationCRUDTest：**

package com.keafmd.test;
    
    import com.keafmd.dao.IUserDao;
    import com.keafmd.domain.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 org.junit.After;
    import org.junit.Before;
    import org.junit.Test;
    
    import java.io.InputStream;
    import java.util.Date;
    import java.util.List;
    
    /** * Keafmd * * @ClassName: AnnotationCRUDTest * @Description: 注解开发CRUD测试 * @author: 牛哄哄的柯南 * @date: 2021-02-16 21:05 */
    public class AnnotationCRUDTest { 
        private InputStream in;
        private SqlSessionFactory factory;
        private SqlSession session;
        private IUserDao userDao;
    
        @Before
        public void init() throws Exception{ 
            in = Resources.getResourceAsStream("SqlMapConfig.xml");
            factory = new SqlSessionFactoryBuilder().build(in);
            session = factory.openSession();
            userDao = session.getMapper(IUserDao.class);
        }
    
        @After
        public void destory() throws Exception{ 
            session.commit();
            session.close();
            in.close();
        }
    
        @Test
        public void testSave(){ 
            User user = new User();
            user.setUsername("mybatis annotation");
            user.setAddress("北京");
    
            userDao.saveUser(user);
        }
    
        @Test
        public void testUpdate(){ 
            User user = new User();
            user.setId(55);
            user.setUsername("mybatis annotation");
            user.setAddress("北京");
            user.setSex("男");
            user.setBirthday(new Date());
    
            userDao.updateUser(user);
        }
    
        @Test
        public void testDelete(){ 
            userDao.deleteUser(54);
        }
    
        @Test
        public void testFindOne(){ 
            User user = userDao.findById(55);
            System.out.println(user);
        }
    
        @Test
        public void testFindByName(){ 
            //List<User> users = userDao.findByName("%Keafmd%");
            List<User> users = userDao.findByName("Keafmd");
            for (User user : users) { 
                System.out.println(user);
            }
        }
    
        @Test
        public void testFindTotal(){ 
           int total = userDao.findTotal();
            System.out.println(total);
        }
    }

# 使用注解实现复杂关系映射开发 #

> **实现复杂关系映射之前我们可以在映射文件中通过配置`<resultMap>`来实现，在使用注解开发时我们需要借助@Results 注解，@Result 注解，@One 注解，@Many 注解。**

## 复杂关系映射的注解说明 ##

> **@Results 注解  
> 代替的是标签`<resultMap>`  
> 该注解中可以使用单个@Result 注解，也可以使用@Result 集合  
> @Results（\{@Result（），@Result（）\}）或@Results（@Result（））**

> **@Resutl 注解  
> 代替了`<id>` 标签和`<result>`标签  
> @Result 中的属性介绍：**

<table> 
 <thead> 
  <tr> 
   <th>@Result 中的属性</th> 
   <th>介绍</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>id</td> 
   <td>是否是主键字段</td> 
  </tr> 
  <tr> 
   <td>column</td> 
   <td>数据库的列名</td> 
  </tr> 
  <tr> 
   <td>property</td> 
   <td>需要装配的属性名</td> 
  </tr> 
  <tr> 
   <td>one</td> 
   <td>需要使用的@One 注解（@Result（one=@One）（）））</td> 
  </tr> 
  <tr> 
   <td>many</td> 
   <td>需要使用的@Many 注解（@Result（many=@many）（）））</td> 
  </tr> 
 </tbody> 
</table>

> **@One 注解（一对一）  
> 代替了`<assocation>`标签，是多表查询的关键，在注解中用来指定子查询返回单一对象。  
> @One 注解属性介绍：  
> select 指定用来多表查询的 sqlmapper  
> fetchType 会覆盖全局的配置参数 lazyLoadingEnabled。  
> 使用格式：@Result(column=" “,property=”",one=@One(select=""))**

> **@Many 注解（多对一）  
> 代替了`<collection>`标签,是是多表查询的关键，在注解中用来指定子查询返回对象集合。  
> 注意：聚集元素用来处理“一对多”的关系。需要指定映射的 Java 实体类的属性，属性的 javaType（一般为 ArrayList）但是注解中可以不定义。  
> 使用格式：@Result(property="",column="",many=@Many(select=""))**

## 项目目录 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg4MzkxNw_size_16_color_FFFFFF_t_70 1]

## 使用注解实现一对一复杂关系映射及立即加载 ##

> **需求：加载账户信息时并且加载该账户的用户信息，根据情况可实现立即加载。（注解方式实现）**

### 添加 User 实体类及 Account 实体类 ###

**User：**

package com.keafmd.domain;
    
    import java.io.Serializable;
    import java.util.Date;
    import java.util.List;
    
    /** * Keafmd * * @ClassName: User * @Description: User实体类 * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:28 */
    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 +
                    '}';
        }
    }

**Account：**

package com.keafmd.domain;
    
    import java.io.Serializable;
    
    /** * Keafmd * * @ClassName: Account * @Description: 账户实体类 * @author: 牛哄哄的柯南 * @date: 2021-02-16 22:51 */
    public class Account implements Serializable { 
    
        private Integer id;
        private Integer uid;
        private Double money;
    
        //多对一（mybatis中称之为一对一）的映射，一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 +
                    '}';
        }
    }

### 添加账户的持久层接口并使用注解配置 ###

**IAccountDao：**

package com.keafmd.dao;
    
    import com.keafmd.domain.Account;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IAccountDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 22:54 */
    
    public interface IAccountDao { 
    
        /** * 查询所有账户，并且获取每个账户下的用户信息,一对一 * @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"),
                @Result(property = "user",column = "uid",one=@One(select="com.keafmd.dao.IUserDao.findById",fetchType= FetchType.EAGER))
        })
        List<Account> findAll();
    
    }

### 添加用户的持久层接口并使用注解配置 ###

package com.keafmd.dao;
    
    import com.keafmd.domain.User;
    import org.apache.ibatis.annotations.*;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IUserDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:30 */
    
    /** * 在mybatis中针对CRUD一共有四个注解 * @Select @Insert @Update @Delete */
    public interface IUserDao { 
    
        /** * 查询所有用户 * @return */
        @Select("select * from user")
        @Results(id="userMap",value={ 
                @Result(id = true,column = "id",property = "userId"),
                @Result(column = "id",property = "userId"),
                @Result(column = "username",property = "userName"),
                @Result(column = "sex",property = "userSex"),
                @Result(column = "birthday",property = "userBirthday")
    
        })
        List<User> findAll();
    
    
        /** * 根据id查询用户 * @param userId * @return */
        @Select("select * from user where id=#{id}")
        //@ResultMap(value={"userMap"})
        @ResultMap("userMap")
        User findById(Integer userId);
    
        /** * 根据用户名称模糊查询 * @param username * @return */
        @Select("select * from user where username like #{username}") //占位符
        @ResultMap("userMap")
        List<User> findByName(String username);
    
    }

### 测试一对一关联及立即加载 ###

package com.keafmd.test;
    
    import com.keafmd.dao.IAccountDao;
    import com.keafmd.dao.IUserDao;
    import com.keafmd.domain.Account;
    import com.keafmd.domain.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 org.junit.After;
    import org.junit.Before;
    import org.junit.Test;
    
    import java.io.InputStream;
    import java.util.List;
    
    /** * Keafmd * * @ClassName: AnnotationCRUDTest * @Description: 注解开发CRUD测试 * @author: 牛哄哄的柯南 * @date: 2021-02-16 21:05 */
    public class AccountTest { 
        private InputStream in;
        private SqlSessionFactory factory;
        private SqlSession session;
        private IAccountDao accountDao;
    
        @Before
        public void init() throws Exception{ 
            in = Resources.getResourceAsStream("SqlMapConfig.xml");
            factory = new SqlSessionFactoryBuilder().build(in);
            session = factory.openSession();
            accountDao = session.getMapper(IAccountDao.class);
        }
    
        @After
        public void destory() throws Exception{ 
            session.commit();
            session.close();
            in.close();
        }
    
        @Test
        public void testFindAll(){ 
            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());
            }
        }
    
    }

**运行结果：**

2021-02-17 03:04:39,939 163    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:04:40,190 414    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 1176735295.
    2021-02-17 03:04:40,190 414    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:04:40,195 419    [           main] DEBUG keafmd.dao.IAccountDao.findAll  - ==>  Preparing: select * from account
    2021-02-17 03:04:40,226 450    [           main] DEBUG keafmd.dao.IAccountDao.findAll  - ==> Parameters: 
    2021-02-17 03:04:40,267 491    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ====>  Preparing: select * from user where id=?
    2021-02-17 03:04:40,268 492    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ====> Parameters: 41(Integer)
    2021-02-17 03:04:40,270 494    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <====      Total: 1
    2021-02-17 03:04:40,271 495    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ====>  Preparing: select * from user where id=?
    2021-02-17 03:04:40,271 495    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ====> Parameters: 45(Integer)
    2021-02-17 03:04:40,272 496    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <====      Total: 1
    2021-02-17 03:04:40,273 497    [           main] DEBUG keafmd.dao.IAccountDao.findAll  - <==      Total: 3
    -----每个账户信息-----
    Account{ id=1, uid=41, money=1000.0}
    User{ userId=41, userName='update user clear cache', userAddress='null', userSex='男', userBirthday=Tue Feb 27 17:47:08 CST 2018}
    -----每个账户信息-----
    Account{ id=2, uid=45, money=1000.0}
    User{ userId=45, userName='新一', userAddress='null', userSex='男', userBirthday=Sun Mar 04 12:04:06 CST 2018}
    -----每个账户信息-----
    Account{ id=3, uid=41, money=2000.0}
    User{ userId=41, userName='update user clear cache', userAddress='null', userSex='男', userBirthday=Tue Feb 27 17:47:08 CST 2018}
    2021-02-17 03:04:40,274 498    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:04:40,274 498    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:04:40,274 498    [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 1176735295 to pool.
    
    Process finished with exit code 0

## 使用注解实现一对多复杂关系映射及延迟加载 ##

> **需求：查询用户信息时，也要查询他的账户列表。使用注解方式实现。  
> 分析：一个用户具有多个账户信息，所以形成了用户(User)与账户(Account)之间的一对多关系。**

### User 实体类加入 List`<Account>` ###

**User：**

package com.keafmd.domain;
    
    import java.io.Serializable;
    import java.util.Date;
    import java.util.List;
    
    /** * Keafmd * * @ClassName: User * @Description: User实体类 * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:28 */
    public class User implements Serializable { 
        private Integer userId;
        private String userName;
        private String userAddress;
        private String userSex;
        private Date userBirthday;
    
        //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> accounts) { 
            this.accounts = accounts;
        }
    
        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 +
                    '}';
        }
    }

### 编写用户的持久层接口并使用注解配置 ###

package com.keafmd.dao;
    
    import com.keafmd.domain.User;
    import org.apache.ibatis.annotations.*;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IUserDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:30 */
    
    /** * 在mybatis中针对CRUD一共有四个注解 * @Select @Insert @Update @Delete */
    public interface IUserDao { 
    
        /** * 查询所有用户 * @return */
        @Select("select * from user")
        @Results(id="userMap",value={ 
                @Result(id = true,column = "id",property = "userId"),
                @Result(column = "id",property = "userId"),
                @Result(column = "username",property = "userName"),
                @Result(column = "sex",property = "userSex"),
                @Result(column = "birthday",property = "userBirthday"),
                @Result(property = "accounts" ,column = "id",
                        many = @Many(select = "com.keafmd.dao.IAccountDao.findAccountByUid",
                                fetchType = FetchType.LAZY))
    
        })
        List<User> findAll();
    
    
        /** * 根据id查询用户 * @param userId * @return */
        @Select("select * from user where id=#{id}")
        //@ResultMap(value={"userMap"})
        @ResultMap("userMap")
        User findById(Integer userId);
    
        /** * 根据用户名称模糊查询 * @param username * @return */
        @Select("select * from user where username like #{username}") //占位符
        @ResultMap("userMap")
        List<User> findByName(String username);
    
    
    }

### 编写账户的持久层接口并使用注解配置 ###

package com.keafmd.dao;
    
    import com.keafmd.domain.Account;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IAccountDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 22:54 */
    
    public interface IAccountDao { 
    
        /** * 查询所有账户，并且获取每个账户下的用户信息,一对一 ，* 这里用不到这个findAll() * @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"),
                @Result(property = "user",column = "uid",one=@One(select="com.keafmd.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);
    
    }

### 编写测试代码 ###

**运行testFindAll()的结果：**

2021-02-17 03:14:19,655 378    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:14:20,124 847    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 1176735295.
    2021-02-17 03:14:20,124 847    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:14:20,135 858    [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - ==>  Preparing: select * from user
    2021-02-17 03:14:20,183 906    [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - ==> Parameters: 
    2021-02-17 03:14:20,471 1194   [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - <==      Total: 9
    -----每个用户的信息
    2021-02-17 03:14:20,473 1196   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,474 1197   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 41(Integer)
    2021-02-17 03:14:20,475 1198   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 2
    User{ userId=41, userName='update user clear cache', userAddress='null', userSex='男', userBirthday=Tue Feb 27 17:47:08 CST 2018}
    [Account{ id=1, uid=41, money=1000.0}, Account{ id=3, uid=41, money=2000.0}]
    -----每个用户的信息
    2021-02-17 03:14:20,476 1199   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,476 1199   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 42(Integer)
    2021-02-17 03:14:20,477 1200   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=42, userName='update', userAddress='null', userSex='男', userBirthday=Mon Feb 08 19:37:31 CST 2021}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,479 1202   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,480 1203   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 43(Integer)
    2021-02-17 03:14:20,481 1204   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=43, userName='小二王', userAddress='null', userSex='女', userBirthday=Sun Mar 04 11:34:34 CST 2018}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,481 1204   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,482 1205   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 45(Integer)
    2021-02-17 03:14:20,483 1206   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 1
    User{ userId=45, userName='新一', userAddress='null', userSex='男', userBirthday=Sun Mar 04 12:04:06 CST 2018}
    [Account{ id=2, uid=45, money=1000.0}]
    -----每个用户的信息
    2021-02-17 03:14:20,484 1207   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,484 1207   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 50(Integer)
    2021-02-17 03:14:20,484 1207   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=50, userName='Keafmd', userAddress='null', userSex='男', userBirthday=Mon Feb 08 15:44:01 CST 2021}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,485 1208   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,485 1208   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 51(Integer)
    2021-02-17 03:14:20,486 1209   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=51, userName='update DAO', userAddress='null', userSex='男', userBirthday=Tue Feb 09 11:31:38 CST 2021}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,488 1211   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,489 1212   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 52(Integer)
    2021-02-17 03:14:20,491 1214   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=52, userName='Keafmd DAO', userAddress='null', userSex='男', userBirthday=Tue Feb 09 11:29:41 CST 2021}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,491 1214   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,492 1215   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 53(Integer)
    2021-02-17 03:14:20,493 1216   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=53, userName='Keafmd laset insertid 1', userAddress='null', userSex='男', userBirthday=Fri Feb 12 20:53:46 CST 2021}
    []
    -----每个用户的信息
    2021-02-17 03:14:20,493 1216   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:14:20,493 1216   [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 55(Integer)
    2021-02-17 03:14:20,494 1217   [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    []
    2021-02-17 03:14:20,495 1218   [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:14:20,495 1218   [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:14:20,495 1218   [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 1176735295 to pool.
    
    Process finished with exit code 0

> **可以看出来延迟加载，在每次加载每个用户时都会查询一次。**

**修改测试代码：**

@Test
    public void testFindAll(){ 
        List<User> users = userDao.findAll();
        /*for (User user : users) { System.out.println("-----每个用户的信息"); System.out.println(user); System.out.println(user.getAccounts()); }*/
    }

**运行结果：**

2021-02-17 03:17:26,203 166    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:17:26,500 463    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 1176735295.
    2021-02-17 03:17:26,500 463    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:17:26,505 468    [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - ==>  Preparing: select * from user
    2021-02-17 03:17:26,540 503    [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - ==> Parameters: 
    2021-02-17 03:17:26,613 576    [           main] DEBUG om.keafmd.dao.IUserDao.findAll  - <==      Total: 9
    2021-02-17 03:17:26,614 577    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:17:26,614 577    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@46238e3f]
    2021-02-17 03:17:26,614 577    [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 1176735295 to pool.
    
    Process finished with exit code 0

> **这样通过对比就可以很明显的看出来延迟加载的效果。**

# 回顾下一级缓存 #

**运行代码：**

@Test
    public void testFindOne(){ 
        User user = userDao.findById(55);
        System.out.println(user);
    
        User user2 = userDao.findById(55);
        System.out.println(user2);
    
        System.out.println(user==user2);
    }

运行结果：

2021-02-17 03:26:22,736 164    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:26:22,970 398    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 85445963.
    2021-02-17 03:26:22,971 399    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:26:22,975 403    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==>  Preparing: select * from user where id=?
    2021-02-17 03:26:23,001 429    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==> Parameters: 55(Integer)
    2021-02-17 03:26:23,054 482    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <==      Total: 1
    2021-02-17 03:26:23,055 483    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:26:23,055 483    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 55(Integer)
    2021-02-17 03:26:23,056 484    [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    true
    2021-02-17 03:26:23,056 484    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:26:23,056 484    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:26:23,057 485    [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 85445963 to pool.
    
    Process finished with exit code 0

# mybatis 基于注解的二级缓存 #

## 在 SqlMapConfig.xml 中开启二级缓存支持 ##

<settings>
        <setting name="cacheEnabled" value="true"/>
    </settings>

## 在持久层接口中使用注解配置二级缓存 ##

package com.keafmd.dao;
    
    import com.keafmd.domain.User;
    import org.apache.ibatis.annotations.*;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    /** * Keafmd * * @ClassName: IUserDao * @Description: * @author: 牛哄哄的柯南 * @date: 2021-02-16 20:30 */
    
    /** * 在mybatis中针对CRUD一共有四个注解 * @Select @Insert @Update @Delete */
    @CacheNamespace(blocking = true) //mybatis 基于注解方式实现配置二级缓存 *这里*
    public interface IUserDao { 
    
        /** * 查询所有用户 * @return */
        @Select("select * from user")
        @Results(id="userMap",value={ 
                @Result(id = true,column = "id",property = "userId"),
                @Result(column = "id",property = "userId"),
                @Result(column = "username",property = "userName"),
                @Result(column = "sex",property = "userSex"),
                @Result(column = "birthday",property = "userBirthday"),
                @Result(property = "accounts" ,column = "id",
                        many = @Many(select = "com.keafmd.dao.IAccountDao.findAccountByUid",
                                fetchType = FetchType.LAZY))
    
        })
        List<User> findAll();
    
    
        /** * 根据id查询用户 * @param userId * @return */
        @Select("select * from user where id=#{id}")
        //@ResultMap(value={"userMap"})
        @ResultMap("userMap")
        User findById(Integer userId);
    
        /** * 根据用户名称模糊查询 * @param username * @return */
        @Select("select * from user where username like #{username}") //占位符
        @ResultMap("userMap")
        List<User> findByName(String username);
    
    
    }

## 编写测试二级缓存的测试类 ##

**不开启二级缓存配置的运行结果：**

2021-02-17 03:31:32,119 320    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:31:32,509 710    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 85445963.
    2021-02-17 03:31:32,510 711    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:31:32,514 715    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==>  Preparing: select * from user where id=?
    2021-02-17 03:31:32,551 752    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==> Parameters: 55(Integer)
    2021-02-17 03:31:32,633 834    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <==      Total: 1
    2021-02-17 03:31:32,634 835    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:31:32,634 835    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 55(Integer)
    2021-02-17 03:31:32,635 836    [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    2021-02-17 03:31:32,635 836    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:31:32,636 837    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:31:32,636 837    [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 85445963 to pool.
    2021-02-17 03:31:32,636 837    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:31:32,636 837    [           main] DEBUG source.pooled.PooledDataSource  - Checked out connection 85445963 from pool.
    2021-02-17 03:31:32,636 837    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@517cd4b]
    2021-02-17 03:31:32,636 837    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==>  Preparing: select * from user where id=?
    2021-02-17 03:31:32,637 838    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==> Parameters: 55(Integer)
    2021-02-17 03:31:32,639 840    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <==      Total: 1
    2021-02-17 03:31:32,641 842    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:31:32,641 842    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 55(Integer)
    2021-02-17 03:31:32,642 843    [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    false
    
    Process finished with exit code 0

**开启二级缓存配置的运行结果：**

2021-02-17 03:29:23,197 373    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
    2021-02-17 03:29:23,605 781    [           main] DEBUG source.pooled.PooledDataSource  - Created connection 500179317.
    2021-02-17 03:29:23,606 782    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1dd02175]
    2021-02-17 03:29:23,617 793    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==>  Preparing: select * from user where id=?
    2021-02-17 03:29:23,668 844    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - ==> Parameters: 55(Integer)
    2021-02-17 03:29:23,777 953    [           main] DEBUG m.keafmd.dao.IUserDao.findById  - <==      Total: 1
    2021-02-17 03:29:23,781 957    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==>  Preparing: select * from account where uid = ?
    2021-02-17 03:29:23,782 958    [           main] DEBUG o.IAccountDao.findAccountByUid  - ==> Parameters: 55(Integer)
    2021-02-17 03:29:23,782 958    [           main] DEBUG o.IAccountDao.findAccountByUid  - <==      Total: 0
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    2021-02-17 03:29:23,790 966    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1dd02175]
    2021-02-17 03:29:23,791 967    [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@1dd02175]
    2021-02-17 03:29:23,791 967    [           main] DEBUG source.pooled.PooledDataSource  - Returned connection 500179317 to pool.
    2021-02-17 03:29:23,800 976    [           main] DEBUG        com.keafmd.dao.IUserDao  - Cache Hit Ratio [com.keafmd.dao.IUserDao]: 0.5
    User{ userId=55, userName='mybatis annotation', userAddress='null', userSex='男', userBirthday=Tue Feb 16 22:15:36 CST 2021}
    false
    
    Process finished with exit code 0

> **效果很明显，开启使用二级缓存时第二次并没有发起查询，证明使用的就是二级缓存。**

> **以上就是Mybatis注解开发（超详细）的全部内容。**

**看完如果对你有帮助，感谢点赞支持！  
如果你是电脑端的话，看到右下角的 “一键三连” 了吗，没错点它\[哈哈\]**  
![在这里插入图片描述][20210115230629703.gif_pic_center]

**加油！**

**共同努力！**

**Keafmd**

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[20210115230629703.gif_pic_center]: /images/20221024/8f788c8d64c245b79c3eb2c49dfb02d7.png