Mybatis中的注解开发 -＞（个人学习记录笔记）

Mybatis中的注解开发

1. 环境搭建

<dependencies>
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.4.5version>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.23version>
        dependency>
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
            <version>1.2.12version>
        dependency>
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
            <scope>testscope>
        dependency>

    dependencies>

• SqlMapConfig.xml 改为

    <mappers>
        <mapper class="xyz.slienceme.dao.IUserDao"/>
    mappers>

2. 单表CRUD操作（代理Dao方式）

2.1 IUserDao接口代码

package xyz.slienceme.dao;
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 xyz.slienceme.domain.User;
import java.util.List;

/**
 * @Author slience_me
 * @Time : 2021/6/26  11:24
 * @File : IUserDao.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 * 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} ")
    @Select("select * from user where username like '%${value}%' ")
    List<User> findUserByName(String username);

    /**
     * 查询总用户数量
     * @return
     */
    @Select("select count(*) from user ")
    int findTotalUser();
}

2.2 测试方法

package xyz.slienceme.test;

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 xyz.slienceme.dao.IUserDao;
import xyz.slienceme.domain.User;

import java.io.IOException;
import java.io.InputStream;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.Date;
import java.util.List;

/**
 * @Author slience_me
 * @Time : 2021/6/26  15:44
 * @File : AnnotationCRUDTest.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 */
public class AnnotationCRUDTest {

    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
        sqlSession = factory.openSession();
        userDao = sqlSession.getMapper(IUserDao.class);
    }

    @After
    public void destroy() throws IOException {

        sqlSession.commit();
        sqlSession.close();
        in.close();
    }

    @Test
    public void testSaveUser(){
        User user = new User();
        user.setUsername("宋保贤");
        user.setAddress("牛驼镇");
        userDao.saveUser(user);

    }

    @Test
    public void testUpdateUser(){
        User user = new User();
        user.setId(54);
        user.setUsername("宋保贤");
        user.setAddress("牛驼镇");
        user.setSex("男");
        userDao.updateUser(user);

    }

    @Test
    public void testDeleteUser(){
        userDao.deleteUser(52);
    }

    @Test
    public void testFindOne(){
        User user = userDao.findById(54);
        System.out.println(user);
    }

    @Test
    public void testFindByName(){
//        List users = userDao.findUserByName("%mybatis%");
        List<User> users = userDao.findUserByName("mybatis");
        for(User user : users){
            System.out.println(user);
        }
    }

    @Test
    public void testFindTotal(){
        int total = userDao.findTotalUser();
        System.out.println(total);
    }
}

3. 多表查询操作

3.1 内容重点解析

3.1.1 @Results和@Result注解的使用

• @Results(id="accountMap" ,value = {})
• 有主键的@Result(id = true,column = "",property = "") id为true
• 无主键的@Result(column = "",property = "") id为默认false省略

@Results(id="accountMap" ,value = {
     @Result(id = true,column = "id",property = "id"),
     @Result(column = "uid",property = "uid"),
     @Result(column = "money",property = "money"),
     @Result(column = "uid",property = "user",
     one = @One(select="xyz.slienceme.dao.IUserDao.findById",
     fetchType= FetchType.EAGER)),
    })

3.1.2 多对一关系

• 一个账户只对应一个用户，多对一关系

注解@One，fetchType应设置立即查询

• 在注解@Result内部写one = @One(select="",fetchType=))

@Result(column = "uid",property = "user",
one = @One(select="xyz.slienceme.dao.IUserDao.findById",
fetchType= FetchType.EAGER))

3.1.3 一对多关系

• 一个用户可以有多个帐户，一对多关系

注解@Many，fetchType应设置延迟加载

• 在注解@Result内部写many = @Many(select="",fetchType=))

@Result(property = "accounts",column = "id",
many = @Many(select = "xyz.slienceme.dao.IAccountDao.findAccountByUid",
fetchType = FetchType.LAZY))

3.2 两个实体类

package xyz.slienceme.domain;
import java.io.Serializable;

/**
 * @Author slience_me
 * @Time : 2021/6/26  16:30
 * @File : Account.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 */
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;
}

package xyz.slienceme.domain;
import java.io.Serializable;
import java.time.LocalDateTime;
import java.util.List;
/**
 * @Author slience_me
 * @Time : 2021/6/26  11:22
 * @File : User.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 */
public class User implements Serializable {
    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private LocalDateTime userBirthday;
    private List<Account> accounts;
}

3.3 两个接口

package xyz.slienceme.dao;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;
import xyz.slienceme.domain.Account;
import java.util.List;
/**
 * @Author slience_me
 * @Time : 2021/6/26  11:24
 * @File : IAccountDao.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 * 在mybatis中针对，CRUD一共有四个注解
 * @Select @Insert @Update @Delete
 */
public interface IAccountDao {
    /**
     * 查询所有账户，并且获取每个账户所属的用户信息
     * @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(column = "uid",property = "user",one = @One(select="xyz.slienceme.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);
}

package xyz.slienceme.dao;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;
import xyz.slienceme.domain.User;
import java.util.List;

/**
 * @Author slience_me
 * @Time : 2021/6/26  11:24
 * @File : IUserDao.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 * 在mybatis中针对，CRUD一共有四个注解
 * @Select @Insert @Update @Delete
 */
@CacheNamespace(blocking = true)
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 = "username",property = "userName"),
            @Result(column = "address",property = "userAddress"),
            @Result(column = "sex",property = "userSex"),
            @Result(column = "birthday",property = "userBirthday"),
            @Result(property = "accounts",column = "id",
                    many = @Many(select = "xyz.slienceme.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("userMap")
    User findById(Integer userId);

}

3.4 测试方法模板

package xyz.slienceme.test;

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 xyz.slienceme.dao.IAccountDao;
import xyz.slienceme.dao.IUserDao;
import xyz.slienceme.domain.Account;
import xyz.slienceme.domain.User;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @Author slience_me
 * @Time : 2021/6/26  15:44
 * @File : AnnotationCRUDTest.java
 * @Software : IntelliJ IDEA
 * @MyBlog : https://blog.csdn.net/slience_me
 */
public class AccountTest {

    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession sqlSession;
    private IAccountDao accountDao;

    @Before
    public void init() throws IOException {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
        sqlSession = factory.openSession();
        accountDao = sqlSession.getMapper(IAccountDao.class);
    }

    @After
    public void destroy() throws IOException {

        sqlSession.commit();
        sqlSession.close();
        in.close();
    }

    @Test
    public void testFindAll(){
        List<Account> accounts = accountDao.findAll();
        for (Account account : accounts) {
            System.out.println("--------每个账户的信息-----------");
            System.out.println(account);
            System.out.println(account.getUser());

        }
    }
    


}

4. 缓存的配置

4.1 在SqlMapConfig.xml配置

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

4.2 在Dao上添加注解

@CacheNamespace(blocking = true) 开启二级缓存

• blocking 默认是flase，关闭二级缓存

@CacheNamespace(blocking = true)
public interface IUserDao {

}

4.3 一级缓存测试

@Test
    public void testFindOne(){

        //一级缓存测试
        User user = userDao.findById(54);
        System.out.println(user);

        User user2 = userDao.findById(54);
        System.out.println(user2);

        System.out.println(user == user2);
    }

4.4 二级缓存测试

package xyz.slienceme.test;
import xyz.slienceme.dao.IUserDao;
import xyz.slienceme.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;

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 destroy()throws  Exception{
        in.close();
    }
    
    @Test
    public void testFindOne(){
        SqlSession session = factory.openSession();
        IUserDao userDao = session.getMapper(IUserDao.class);
        User user = userDao.findById(54);
        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 user1 = userDao1.findById(54);
        System.out.println(user1);
        session1.close();
    }
}