Mybatis 學習筆記——原生DAO實現資料增刪改查
阿新 • • 發佈:2018-12-15
一、開發環境
- JDK java version “1.8.0_171” Java™ SE Runtime Environment (build 1.8.0_171-b11) Java HotSpot™ 64-Bit Server VM (build 25.171-b11, mixed mode)
- Eclipse Eclipse Java EE IDE for Web Developers. Version: Oxygen.3a Release (4.7.3a)
- MySQL 其中的資料庫檔案在地址:點選下載
- Mybatis mybatis-3.4.6
二、專案結構
三、編寫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> <!-- 載入屬性檔案 --> <properties resource="config/db.properties"></properties> <!-- 定義別名 --> <typeAliases> <!-- 針對批量別名定義,別名就是類名(首字母大小寫都可以) --> <package name="com.po"/> </typeAliases> <!-- 和Spring整合後environments配置將廢除 --> <environments default="development"> <environment id="development"> <!-- 使用JDBC事務管理,事務控制由mybatis管理 --> <transactionManager type="JDBC" /> <!-- 資料庫連線池,由mybatis管理 --> <dataSource type="POOLED"> <property name="driver" value="${jdbc.driver}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </dataSource> </environment> </environments> <!-- 載入對映檔案 --> <mappers> <!-- 通過resource載入 --> <mapper resource="config/sqlmap/User.xml" /> </mappers> </configuration>
db.properties檔案內容為:
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=123456
四、編寫User.xml
檔案中包含有簡單查詢、模糊查詢、插入、更新、刪除操作。
<?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:名稱空間,作用是對sql進行分類化管理, 注意:在mapper代理方法開發, namespace有特殊作用 --> <mapper namespace="test"> <select id="findUserById" parameterType="int" resultType="user"> SELECT * FROM USER WHERE ID = #{id} </select> <select id="findUserByName" parameterType="java.lang.String" resultType="user"> SELECT * FROM USER WHERE USERNAME LIKE '%${value}%' </select> <insert id="insertUser" parameterType="user"> <!-- 將插入的主鍵返回到user物件中 SELECT LAST_INSERT_ID():得到將insert進去的記錄的主鍵值,只適用與自增主鍵 keyProperty:將查詢到的主鍵設定到parameterType指定的物件的哪個屬性 order:SQL語句執行的順序,BEFORE或AFTER --> <selectKey keyProperty="id" order="AFTER" resultType="int"> SELECT LAST_INSERT_ID() </selectKey> INSERT INTO USER(USERNAME,SEX,BIRTHDAY,ADDRESS) VALUES(#{username},#{sex},#{birthday},#{address}) </insert> <delete id="deleteUser" parameterType="int"> DELETE FROM USER WHERE ID = #{id} </delete> <update id="updateUser" parameterType="user"> UPDATE USER SET USERNAME = #{username}, SEX = #{sex}, BIRTHDAY = #{birthday}, ADDRESS = #{address} WHERE ID = #{id} </update> </mapper>
五、編寫介面UserDao.java
package com.dao;
import java.util.List;
import com.po.User;
/**
* 描述:原生dao介面,管理使用者
* @author 歐陽
* @since 2018年10月9日
*/
public interface UserDao {
//根據id查詢使用者資訊
public User findUserById(int id) throws Exception;
//根據username查詢使用者資訊
public List<User> findUserByName(String name) throws Exception;
//插入使用者資訊
public void insertUser(User user) throws Exception;
//更新使用者資訊
public void updateUser(User user) throws Exception;
//根據id刪除使用者資訊
public void deleteUserById(int id) throws Exception;
}
六、實現介面UserDao.java
package com.dao;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import com.po.User;
/**
* 描述:原生dao開發實現類
* @author 歐陽
* @since 2018年10月9日
*/
public class UserDaoImpl implements UserDao {
//通過建構函式注入SqlSessionFactory
private SqlSessionFactory sqlSessionFactory;
public UserDaoImpl(SqlSessionFactory sqlSessionFactory) {
super();
this.sqlSessionFactory = sqlSessionFactory;
}
@Override
public User findUserById(int id) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
User user = sqlSession.selectOne("test.findUserById", id);
sqlSession.close();
return user;
}
@Override
public List<User> findUserByName(String name) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> user = sqlSession.selectList("test.findUserById", name);
sqlSession.close();
return user;
}
@Override
public void insertUser(User user) throws Exception{
SqlSession sqlSession = sqlSessionFactory.openSession();
sqlSession.insert("test.insertUser", user);
sqlSession.commit();
sqlSession.close();
}
@Override
public void deleteUserById(int id) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
sqlSession.delete("test.deleteUser", id);
sqlSession.commit();
sqlSession.close();
}
@Override
public void updateUser(User user) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
sqlSession.insert("test.updateUser", user);
sqlSession.commit();
sqlSession.close();
}
}
七、測試
package com.dao;
import java.io.InputStream;
import java.util.List;
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 com.po.User;
public class UserDaoImplTest {
private SqlSessionFactory sqlSessionFactory;
//此方法是在執行testFindUserById之前執行
@Before
public void setUp() throws Exception {
String resource = "config/SqlMapConfig.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
// 建立會話工廠
this.sqlSessionFactory = new SqlSessionFactoryBuilder()
.build(inputStream);
}
@Test
public void testFindUserById() {
UserDao userDao = new UserDaoImpl(this.sqlSessionFactory);
try {
User user = userDao.findUserById(2);
System.out.println(user);
} catch (Exception e) {
e.printStackTrace();
}
}
@Test
public void testFindUserByName() {
UserDao userDao = new UserDaoImpl(this.sqlSessionFactory);
try {
List<User> users = userDao.findUserByName("小");
System.out.println(users.size());
} catch (Exception e) {
e.printStackTrace();
}
}
@Test
public void testInsertUser() {
UserDao userDao = new UserDaoImpl(this.sqlSessionFactory);
try {
//插入使用者物件
User user = new User();
user.setUsername("王小姐");
user.setAddress("中國");
userDao.insertUser(user);
} catch (Exception e) {
e.printStackTrace();
}
}
@Test
public void testDeleteUserById() {
UserDao userDao = new UserDaoImpl(this.sqlSessionFactory);
try {
userDao.deleteUserById(17);
} catch (Exception e) {
e.printStackTrace();
}
}
@Test
public void testUpdateUser() {
UserDao userDao = new UserDaoImpl(this.sqlSessionFactory);
try {
//插入使用者物件
User user = new User();
user.setId(3);
user.setUsername("王小姐");
user.setAddress("中國");
userDao.updateUser(user);
} catch (Exception e) {
e.printStackTrace();
}
}
}
八、問題總結
1、在 UserDao 介面的實現類 UserDaoImpl 中,各實現方法存在大量模板方法,存在程式碼冗餘,不利於程式設計師開發和維護;
2、呼叫 sqlSession 方法時將 statement 的id硬編碼了;
3、在UserDaoImpl 類中每個實現方法中呼叫sqlSession 方法時傳入的變數,由於sqlsession方法使用泛型,即使變數型別傳入錯誤,在編譯階段也不報錯,不利於程式設計師開發。
基於以上問題,在Mybatis 開發時使用Mapper 代理開發。