Mybatis注解开发（超详细）_mybatis注解开发 实验

}

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"?>

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 users = userDao.findByName(“%Keafmd%”);

List 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：**

| @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;

}

@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 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 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 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 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 accounts;

public List getAccounts() {

return accounts;

}

public void setAccounts(List 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 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 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 findAll();

/**

• 根据用户id查询账户信息

• @param userId

• @return

*/

@Select(“select * from account where uid = #{userId}”)

List 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 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 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

---

自我介绍一下，小编13年上海交大毕业，曾经在小公司待过，也去过华为、OPPO等大厂，18年进入阿里一直到现在。

深知大多数前端工程师，想要提升技能，往往是自己摸索成长或者是报班学习，但对于培训机构动则几千的学费，着实压力不小。自己不成体系的自学效果低效又漫长，而且极易碰到天花板技术停滞不前！

因此收集整理了一份《2024年Web前端开发全套学习资料》，初衷也很简单，就是希望能够帮助到想自学提升又不知道该从何学起的朋友，同时减轻大家的负担。

既有适合小白学习的零基础资料，也有适合3年以上经验的小伙伴深入学习提升的进阶课程，基本涵盖了95%以上前端开发知识点，真正体系化！

由于文件比较大，这里只是将部分目录截图出来，每个节点里面都包含大厂面经、学习笔记、源码讲义、实战项目、讲解视频，并且会持续更新！

如果你觉得这些内容对你有帮助，可以扫码获取！！（资料价值较高，非无偿）

前端面试题汇总

---

前端面试题是我面试过程中遇到的面试题，每一次面试后我都会复盘总结。我做了一个整理，并且在技术博客找到了专业的解答，大家可以参考下：

由于篇幅有限，只能分享部分面试题，完整版面试题及答案可以【点击我】阅读下载哦~

感悟

on.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

---

自我介绍一下，小编13年上海交大毕业，曾经在小公司待过，也去过华为、OPPO等大厂，18年进入阿里一直到现在。

深知大多数前端工程师，想要提升技能，往往是自己摸索成长或者是报班学习，但对于培训机构动则几千的学费，着实压力不小。自己不成体系的自学效果低效又漫长，而且极易碰到天花板技术停滞不前！

因此收集整理了一份《2024年Web前端开发全套学习资料》，初衷也很简单，就是希望能够帮助到想自学提升又不知道该从何学起的朋友，同时减轻大家的负担。

[外链图片转存中…(img-CgRqL08K-1711687830353)]

[外链图片转存中…(img-VvJOIPCE-1711687830353)]

既有适合小白学习的零基础资料，也有适合3年以上经验的小伙伴深入学习提升的进阶课程，基本涵盖了95%以上前端开发知识点，真正体系化！

[外链图片转存中…(img-t0FtX1aH-1711687830354)]

由于文件比较大，这里只是将部分目录截图出来，每个节点里面都包含大厂面经、学习笔记、源码讲义、实战项目、讲解视频，并且会持续更新！

如果你觉得这些内容对你有帮助，可以扫码获取！！（资料价值较高，非无偿）

前端面试题汇总

---

前端面试题是我面试过程中遇到的面试题，每一次面试后我都会复盘总结。我做了一个整理，并且在技术博客找到了专业的解答，大家可以参考下：

由于篇幅有限，只能分享部分面试题，完整版面试题及答案可以【点击我】阅读下载哦~

感悟

春招面试的后期，运气和实力都很重要，自己也是运气比较好，为了回馈粉丝朋友们（毕竟自己也玩了这么久哈哈哈），整理个人感悟和总结以上。最后祝愿大家能够收获理想offer！！