MyBatis（2）CRUD操作
1.使用MyBatis对表执行CRUD操作——基于XML的实现
增删改查
Mapper接口本质就是原来的Dao接口，只是为了方便我们的书写。一个mapper接口对应一个mapper映射文件。
将UserMapper更名为UserDao，说明本质
修改对应的mapper映射文件的namespace属性，对应上接口。
创建数据库
CREATE DATABASE /*!32312 IF NOT EXISTS*/`mybatis` /*!40100 DEFAULT CHARACTER SET utf8 */;
USE `mybatis`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` INT(20) NOT NULL,
`name` VARCHAR(30) DEFAULT NULL,
`pwd` VARCHAR(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;
INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (1,'小二','123456'),(2,'张三','abcdef'),(3,'李四','987654');
创建的数据库表
创建Maven项目
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>com.kscnggroupId>
<artifactId>ssm-mybatis-studyartifactId>
<packaging>pompackaging>
<version>1.0-SNAPSHOTversion>
<modules>
<module>mybatis01module>
<module>mybatis02module>//本文所创建的Macen项目
<module>mybatis03module>
<module>mybatis04module>
<module>mybatis05module>
modules>
<dependencies>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.11version>
dependency>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.5.1version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.47version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
dependencies>
<build>
<resources>
<resource>
<directory>src/main/javadirectory>
<includes>
<include>**/*.propertiesinclude>
<include>**/*.xmlinclude>
includes>
<filtering>falsefiltering>
resource>
<resource>
<directory>src/main/resourcesdirectory>
<includes>
<include>**/*.propertiesinclude>
<include>**/*.xmlinclude>
includes>
<filtering>falsefiltering>
resource>
resources>
build>
project>
编写实体类User
package com.kscng.pojo;
public class User {
private int id;
private String name;
private String pwd;
public User() {
}
public User(int id, String name, String pwd) {
this.id = id;
this.name = name;
this.pwd = pwd;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", pwd='" + pwd + '\'' +
'}';
}
}
编写mybatis配置文件mybatis-config.xml
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/kscng/dao/userMapper.xml"/>
mappers>
configuration>
工具类MyBatisUtils
package com.kscng.utils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
//mybatis的工具类，重复的代码的提纯
public class MyBatisUtils {
//类变量不需要设置默认值；
private static SqlSessionFactory sqlSessionFactory;
static {
//在maven中，所有的资源文件一般都放在resourc目录下，我们可以直接拿到。
try{
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
//设置SqlSessionFactroy公共的方法
public static SqlSessionFactory getSqlSessionFactory(){
return sqlSessionFactory;
}
}
编写接口UserDao
package com.kscng.dao;
import com.kscng.pojo.User;
import java.util.List;
public interface UserDao {
//获取全部的用户
List<User> selectUser();
//根据id查找用户
User selectUserByID(int id);
//添加一个用户
int addUser(User user);
//删除用户
int deletUserById(int id);
//修改用户
int updateUser(User user);
}
对应的userMapper.xml
<mapper namespace="com.kscng.dao.UserDao">
<select id="selectUser" resultType="com.kscng.pojo.User">
select * from user
select>
<select id="selectUserById" resultType="com.kscng.pojo.User">
select *from user where id = #{id}
select>
<insert id="addUser" parameterType="com.kscng.pojo.User">
insert into user(id,name.pwd) values
(#{id},#{name},#{pwd})
insert>
<delete id="deleteUserBYID" parameterType="int">
delete from user where id = #{id}
delete>
<update id="updateUser" parameterType="com.kscng.pojo.User">
update user set name =#{name},pwd = #{pwd} where id = #{id}
update>
mapper>
测试
package com.kscng.dao;
import com.kscng.pojo.User;
import com.kscng.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
//(1)获取全部的用户
@Test
public void selectUser(){
//1.拿到sqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
//2.通过sqlSessionFactory对象openSession()创建一个sqlSession。
SqlSession sqlSession = sqlSessionFactory.openSession();
//3.通过sqlSession获得mapper对象，参数为映射文件对应的接口类的class对象
UserDao mapper = sqlSession.getMapper(UserDao.class);
//4.通过mapper对象来执行操作；
List<User> users = mapper.selectUser();
//获得结果集
for (User user : users){
System.out.println(user);
}
sqlSession.close();//关闭sqlSession
}
//(2)根据id查找用户
@Test
public void selectUserById(){
SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
//接口 对象名 = new 接口实现类
User user = mapper.selectUserByID(2);
System.out.println(user);
sqlSession.close(); //关闭sqlSession
}
//(3)添加一个用户
@Test
public void addUser(){
User user = new User(4,"卡卡","kaka");
SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
int i = mapper.addUser(user);
//没有插入成功的原因：没有提交事务；
sqlSession.commit(); //提交事务
sqlSession.close(); //关闭sqlSession
if (i>0){
System.out.println("插入成功！");
}
}
//(4)修改用户信息
@Test
public void updateUser(){
SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
User user = new User(1,"阿狗","dog");
mapper.updateUser(user);
System.out.println(i);
sqlSession.commit();//提交事务
sqlSession.close();//关闭sqlSession
if (i>0){
System.out.println("修改成功！");
}
}
}
//(5)删除用户
@Test
public void deleteUserById(){
SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
int i = mapper.deletUserById(2);
System.out.println(i);
//记得提交事务，否则删除不成功！
sqlSession.commit();//提交事务
sqlSession.close();//关闭sqlSession
if (i>0){
System.out.println("删除成功！");
}
}
}
结果展示
(1)获取全部的用户
(2)根据id查找用户
(3)添加一个用户
在获取一次全部用户查看成果
(4)修改用户信息
(5)删除用户
在获取一次全部用户查看成果
项目结构
2.CRUD注意点
1、事务
增，改，删需要提交事务！
增，改，删需要提交事务！
增，改，删需要提交事务！
重要的事说三遍！
2、乱码
如果出现乱码，先在sql中进行测试，sql没问题，就检查配置文件
jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8"
3、参数问题
如果是基本数据类型，可以省略，但建议写上
引用类型必须写指定的 包名+类名。