MyBatis開發dao方法

一 SqlSession使用范圍
  • SqlSessionFactoryBuilder
    • 通過SqlSessionFactoryBuilder創建會話工廠SqlSessionFactory
    • 將SqlSessionFactoryBuilder當作一個工具類使用即可，不需要使用單例管理SqlSessionFactoryBuilder。
    • 在需要創建SqlSessionFactory時候，只需要new一次SqlSessionFactoryBuilder 即可
  • SqlSessionFactory
    • 通過SqlSessionFactory創建SqlSession使用單例模式管理SqlSessionFactory(工廠一旦創建，使用一個實例)
    • 將來mybatis和spring整合后使用單例模式管理sqlSessionFactory
  • SqlSession
    • SqlSession是一個面向用戶（程序員）的接口
    • SqlSession中提供了很多操作數據庫的方法，例如：selectOne/selectList
    • sqlSession是線程不安全的，在SqlSession實現類中除了有接口中的方法（操作數據庫的方法）還有ukulel域屬性
    • SqlSession最佳應用場合在方法體內，定義成局部變量使用
二 mybatis開發dao方法-原始dao開發方法-程序員需要寫dao接口和dao實現類
1 UserDao.java
package dao;

import entity.User;

public interface UserDao {
    //根據id查詢信息
    public User findUserById(int id) throws Exception;
    //添加用戶信息
    public void insertUser(User user) throws Exception;
    //刪除用戶信息
    public void deleteUser(int id) throws Exception;
}
2 UserDaoImpl.java
package dao.impl;

import dao.UserDao;
import entity.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.Date;

public class UserDaoImpl implements UserDao {
    //需要向dao實現類中注入SqlSessionFactory
        //這里通過構造方法注入
    private SqlSessionFactory sqlSessionFactory;
    public UserDaoImpl(SqlSessionFactory sqlSessionFactory){
        this.sqlSessionFactory = sqlSessionFactory;
    }


    public User findUserById(int id) throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        User user = sqlSession.selectOne("test.findUserById",id);
        sqlSession.close();
        return user;
    }
    public void insertUser(User user) throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.insert("test.insertUser",user);
        sqlSession.commit();
        sqlSession.close();
    }
    public void deleteUser(int id) throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.delete("test.deleteUser",id);
        sqlSession.commit();
        sqlSession.close();
    }
}
3 UserDaoImplTest.java
import dao.UserDao;
import dao.impl.UserDaoImpl;
import entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

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

public class UserDaoImplTest {
    private SqlSessionFactory sqlSessionFactory;
    //測試前執行    
@Before
    public void setUp() throws IOException {
        //配置文件
        String resource = "SqlMapConfig.xml";
        //的到配置文件流
        InputStream inputStream =  Resources.getResourceAsStream(resource);
        //創建會話工廠
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    @Test
    public void testFinUserById() throws Exception {
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        User user = userDao.findUserById(1);
        System.out.println(user);
    }
    @Test
    public void insertUser() throws Exception{
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        User user1 = new User();
        user1.setUsername("王麻子");
        user1.setBirthday(new Date());
        user1.setSex("女");
        user1.setAddress("日本東京");
        userDao.insertUser(user1);
    }
    @Test
    public void deleteUser() throws Exception{
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        userDao.deleteUser(13);
    }
}
查詢測試結果
三 mybatis開發dao方法-mapper代理開發方法-程序員只需要mapper接口（相當于dao接口）
  • 程序員不在需要編寫dao接口的實現
  • 程序員需要編寫mapper.xml映射文件，編寫時遵循一些開發規范，mybatis可以自動生成mapper接口類代理對象
1 開發規范
（1）在mapper.xml中namespace等于mapper接口地址
（2）mapper.java接口中的方法名和mapper.xml中statement的id一致
（3）mapper.java接口中的方法輸入類型和mapper.xml中statement的parameterType指定的類型一致
（4）mapper.java接口中方法返回值類型和mapper.xml中statement的resultType指定的類型一致
2 UserDaoMapper.java
package dao;

import entity.User;

public interface UserDaoMapper {
    //根據id查詢
    public User findUserById(int id) throws Exception;
    //插入用戶
    public void insertUser(User user) throws Exception;
    //刪除用戶
    public void deleteUser(int id) throws Exception;
    //修改用戶信息
    public void updateUser(User user) throws Exception;
}
3 userMapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
        <!--namespace命名空間，作用就是對sql進行分類化管理，區分不同的sql空間
        注意：使用mapper代理方法開發，namespace有特殊重要作用-->
<mapper namespace="dao.UserDaoMapper">
    <!--在映射文件中配置很多sql語句-->
   <!-- 需求：通過id查詢用戶表的記錄-->
 <!--   通過select執行數據庫查詢
    id：標識映射文件中sql，將sql語句封裝到mappedStatement對象中，所以將id稱為statement的id
    parameterType：指定輸入參數的類型，這里指定int型
    resultType:指定sql輸出結果所映射的java對象類型
    #{ }表示一個占位符
    #{id}：其中的id表示接收輸入的參數，參數名稱就是id-->
    <select id="findUserById" parameterType="int" resultType="entity.User">
    SELECT * FROM user WHERE id = #{id}
</select>
    <!--根據用戶名稱模糊查詢信息-->
    <!--可能返回多條信息
    ${}：表示拼接sql串，將接收到的參數的內容不加任何修飾拼接在sql中
    使用${}拼接sql，引起sql注入
    ${value}：接收輸入參數的內容，如果出入類型是簡單類型，${}只能使用value-->
    <select id="findUserByName" parameterType="String" resultType="entity.User">
        SELECT * FROM  user WHERE username LIKE "${value}%"
    </select>
    <!--添加用戶-->
    <insert id="insertUser" parameterType="entity.User">
        <!--將插入數據的主鍵返回
        SELECT Last_insert_ID 得到剛插入的主鍵值 只適用與自增主鍵

        keyProperty :將查詢到主鍵值設置到parameterType指定的對象的那個屬性
        order:SELECT Last_insert_ID執行順序，相對于insert語句來說它的執行順序
        resultType:指定SELECT LAST_INSERT_ID()的結果類型
        -->
        <selectKey keyProperty="id" order="AFTER" resultType="int">
            SELECT LAST_INSERT_ID()
        </selectKey>
        INSERT INTO user (username,birthday,sex,address) VALUES(#{username},#{birthday},#{sex},#{address})
    </insert>
    <!--刪除用戶 通過id-->
    <delete id="deleteUser" parameterType="int">
        DELETE from user where id = #{id}
    </delete>
    <!--修改用戶信息 根據id-->
    <update id="updateUser" parameterType="entity.User">
        UPDATE user SET username = #{username},birthday = #{birthday},sex = #{sex},address = #{address} WHERE  id = #{id}
    </update>
</mapper>
4 UserDaoMapperTest
import dao.UserDaoMapper;
        import entity.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.Before;
        import org.junit.Test;


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

public class UserDaoMapperTest {
    private SqlSessionFactory sqlSessionFactory;
    @Before
    public void setUp() throws IOException{
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    @Test
    public void findUserById() throws Exception{
        SqlSession sqlSession= sqlSessionFactory.openSession();
        //創建UserMapper對象，mybatis自動生成mapper代理對象
        UserDaoMapper userDaoMapper = sqlSession.getMapper(UserDaoMapper.class);
        //調用usermapper對象
        User user = userDaoMapper.findUserById(10);
        System.out.println(user);
    }
    @Test
    public void insertUserd() throws Exception{
        SqlSession sqlSession= sqlSessionFactory.openSession();
        //創建UserMapper對象，mybatis自動生成mapper代理對象
        UserDaoMapper userDaoMapper = sqlSession.getMapper(UserDaoMapper.class);
        //調用usermapper對象
        User user = new User();
        user.setUsername("短毛");
        user.setBirthday(new Date());
        user.setSex("女");
        user.setAddress("德國柏林");
        userDaoMapper.insertUser(user);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserDaoMapper userDaoMapper = sqlSession.getMapper(UserDaoMapper.class);
        userDaoMapper.deleteUser(13);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser() throws Exception{
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserDaoMapper userDaoMapper = sqlSession.getMapper(UserDaoMapper.class);
        User user = new User();
        user.setId(12);
        user.setUsername("短毛");
        user.setBirthday(new Date());
        user.setSex("女");
        user.setAddress("德國柏林");
    userDaoMapper.updateUser(user);
    sqlSession.commit();
    sqlSession.close();
    }

}
查詢執行結果
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