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

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>
    <!--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;

    @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：

@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;
    }

    @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

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;

    @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 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;

    @Before
    public void init() throws Exception{
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
    }

    @After
    public void destory() throws Exception{


        in.close();
    }


    @Test
    public 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session
        IUserDao 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}
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。

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