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

注解 说明
@Insert 实现新增
@Delete 实现删除
@Update 实现更新
@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
@SelectProvider 实现动态 SQL 映射
@CacheNamespace 实现注解二级缓存的使用

使用 Mybatis 注解实现基本 CRUD

项目目录结构

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;}@Overridepublic 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 configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!--引入外部配置文件--><properties resource="jdbcConfig.properties"></properties><!--配置别名--><typeAliases><package name="com.keafmd.domain"/></typeAliases><!--配置环境--><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><!--指定带有注解的dao接口所在位置--><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;@Beforepublic void init() throws Exception{in = Resources.getResourceAsStream("SqlMapConfig.xml");factory = new SqlSessionFactoryBuilder().build(in);session = factory.openSession();userDao = session.getMapper(IUserDao.class);}@Afterpublic void destory() throws Exception{session.commit();session.close();in.close();}@Testpublic void testSave(){User user = new User();user.setUsername("mybatis annotation");user.setAddress("北京");userDao.saveUser(user);}@Testpublic 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);}@Testpublic void testDelete(){userDao.deleteUser(54);}@Testpublic void testFindOne(){User user = userDao.findById(55);System.out.println(user);}@Testpublic void testFindByName(){//List<User> users = userDao.findByName("%Keafmd%");List<User> users = userDao.findByName("Keafmd");for (User user : users) {System.out.println(user);}}@Testpublic 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：

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

@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

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;}@Overridepublic 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;}@Overridepublic 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;@Beforepublic void init() throws Exception{in = Resources.getResourceAsStream("SqlMapConfig.xml");factory = new SqlSessionFactoryBuilder().build(in);session = factory.openSession();accountDao = session.getMapper(IAccountDao.class);}@Afterpublic void destory() throws Exception{session.commit();session.close();in.close();}@Testpublic 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;}@Overridepublic 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

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 UserTest {private InputStream in;private SqlSessionFactory factory;private SqlSession session;private IUserDao userDao;@Beforepublic void init() throws Exception{in = Resources.getResourceAsStream("SqlMapConfig.xml");factory = new SqlSessionFactoryBuilder().build(in);session = factory.openSession();userDao = session.getMapper(IUserDao.class);}@Afterpublic void destory() throws Exception{session.commit();session.close();in.close();}@Testpublic 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

<!--配置开启二级缓存-->
<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

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.List;/*** Keafmd** @ClassName: SecondLevelCatchTest* @Description: 二级缓存测试* @author: 牛哄哄的柯南* @date: 2021-02-16 23:37*/
public class SecondLevelCatchTest {private InputStream in;private SqlSessionFactory factory;@Beforepublic void init() throws Exception{in = Resources.getResourceAsStream("SqlMapConfig.xml");factory = new SqlSessionFactoryBuilder().build(in);}@Afterpublic void destory() throws Exception{in.close();}@Testpublic void testFindOne(){SqlSession session = factory.openSession();IUserDao userDao = session.getMapper(IUserDao.class);User user = userDao.findById(55);System.out.println(user);session.close();//释放一级缓存SqlSession session1 = factory.openSession();//再次打开sessionIUserDao userDao1 = session1.getMapper(IUserDao.class);User user2 = userDao1.findById(55);System.out.println(user2);System.out.println(user==user2);}}

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}
falseProcess 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}
falseProcess 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]

加油！

共同努力！

Keafmd

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