Mybatis第二章

最新推荐文章于 2022-11-19 17:27:43 发布

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最新推荐文章于 2022-11-19 17:27:43 发布

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分类专栏： MyBatis

本文链接：https://blog.youkuaiyun.com/qq_41821006/article/details/103752584

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文章目录

- Mybatis第二章

Mybatis第二章

一、目标

1、mybatis实现CRUD

2、两种Dao开发

3、核心配置文件详解

4、输入参数和输出参数

二、mybatis实现CRUD

a、mybatis 的中文文档网址：http://www.mybatis.org/mybatis-3/zh/getting-started.html
b、 selectList 查询多个对象,返回一个list集合(也能查询一个)
    selectOne: 查询单个对象，返回一个对象
c、日志记录日常操作
	引入依赖: 
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
  引入日志的配置文件：log4j.properties
 d、增删改查
 	<!--UserMapper删除操作-->
    <delete id="del" parameterType="java.lang.Integer">
        delete from user where id = #{id}
    </delete>
 	<!--测试类-->   
    @Test
    public void testDel(){
        //获取输入流对象
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("SqlMapConfig.xml");
        //获取SqlSessionFactory对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //获取SqlSession对象
        //获取的sqlsession不能自动提交
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //执行sql语句
        sqlSession.delete("userMapper.del",3);
        //提交:只要修改了数据库必须提交
        sqlSession.commit();

        sqlSession.close();
    }
 e、模糊查询
 	参数： %a% 
 		配置文件： username like #{username}
 	参数: a
 		配置文件1： username like "%"#{username}"%"
 		配置文件2： username like "%${value}%"
 							如果传的是简单类型必须使用value
 							如果是pojo,属性名引用
 d、参数
 		简单类型： 基本数据类型,String
 				如果${} 必须用value引用
 				如果#{} 随便写
 		pojo类型：属性名引用	
 e、${} 与 #{}区别
 	${}:直接拼接,不会转换类型, 不能防注入
 	#{}:转换类型后拼接, 相当于占位符?,可以防注入

三、两种Dao开发

1、传统dao开发

1、pom.xml 依赖配置
	<dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>
 2、SqlMapConfig.xml配置
 	<?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>
    <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://127.0.0.1:3306/mybatisdb_sgw?characterEncoding=utf8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="cn/sgwks/dao/UserMapper.xml"></mapper>
    </mappers>
</configuration>
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">
<mapper namespace="userMapper">
    <!--查询全部-->
    <select id="findAll" resultType="cn.sgwks.domain.User">
        select * from user
    </select>
    <!--根据id查询-->
    <!--
    id="findById":唯一的标识
    resultType="com.itheima.domain.User" :返回值类型
    parameterType:参数类型
    在mybatis中：引入变量 #{}
    1.传递的是对象,里面的${}和#{}参数必须要和对象的属性名一致
    2.传递的参数是基本数据类型+String,
        #{}里面的参数随意，必须是标识符，不能有标点符号，不能为空
        ${}里面只能填写value: ${value}
    -->
    <select id="findById" resultType="cn.sgwks.domain.User" parameterType="java.lang.Integer">
        select * from user where id = #{id}
    </select>
    <!--添加
        :不用写返回值类型
        参数的名字必须和实体类的属性一致
    -->
    <insert id="insert" parameterType="cn.sgwks.domain.User">
        insert into user values(null ,#{username},#{password},#{sex},#{address},#{birthday});
    </insert>
    <!--修改-->
    <update id="update" parameterType="cn.sgwks.domain.User">
        update user set username=#{username},password=#{password},sex=#{sex},address=#{address},birthday=#{birthday}
        where id=#{id}
    </update>
    <!--删除操作-->
    <delete id="delete" parameterType="java.lang.Integer">
        delete from user where id=#{随意但不能为空}
    </delete>
    <!--根据姓名模糊查询-->
    <select id="findByUsername" resultType="cn.sgwks.domain.User" parameterType="java.lang.String">
       select * from user where username like "%"#{随便传递的是基本数据类型}"%"
    </select>
    <!--模糊查询方法二-->
<!--<select id="findByUsername" resultType="cn.sgwks.domain.User" parameterType="java.lang.String">
        select * from user where username like "%${value}%"
    </select>-->
    <!--查询总的记录数-->
    <select id="findTotalCount" resultType="java.lang.Integer">
        select count(*) from user
    </select>
</mapper>

1、Dao层
    package cn.sgwks.dao.impl;

import cn.sgwks.dao.UserDao;
import cn.sgwks.domain.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;

public class UserDaoImpl implements UserDao {
    //所有的方法共用的factory对象,应该是属于应用级别
    private SqlSessionFactory sqlSessionFactory;

    public UserDaoImpl(SqlSessionFactory sqlSessionFactory) {
        this.sqlSessionFactory = sqlSessionFactory;
    }

    /**
     * 查询所有user表数据
     * @return 返回集合类型，遍历
     */
    @Override
    public List<User> findAll() {
        //每一个方法应该获取一个SqlSession对象,用完应该立即关闭,因为线程不安全
        SqlSession sqlSession = sqlSessionFactory.openSession();
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        //释放资源
        sqlSession.close();
        return userList;
    }

    /**
     * 添加数据
     * @param user 传递user对象
     */
    @Override
    public void insert(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.insert("userMapper.insert",user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }

    /**
     * 修改数据
     * @param user
     */
    @Override
    public void update(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.update("userMapper.update",user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }

    /**
     * 删除数据
     * @param id
     */
    @Override
    public void delete(Integer id) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.delete("userMapper.delete",id);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }
}
2、Domain层
    public class User {
    private Integer id;
    private String username;
    private String password;
    private String sex;
    private String address;
    private String birthday;
    ...}
3、测试类
     //提升作用域
    SqlSessionFactory sqlSessionFactory = null;
    /**
     * 执行命令前提前初始化
     */
    @Before
    public void init(){
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("SqlMapConfig.xml");
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    /**
     * 查询所有数据
     */
    @Test
    public void testFindAll(){
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        List<User> userList = userDao.findAll();
        for (User user : userList) {
            System.out.println(user);
        }
    }
    /**
     * 添加数据
     */
    @Test
    public void testInsert(){
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        User user = new User();
        user.setUsername("索隆");
        user.setPassword("suolong");
        user.setSex("男");
        user.setAddress("大剑客");
        user.setBirthday("1995-06-10");
        userDao.insert(user);
    }
    /**
     * 添加数据
     */
    @Test
    public void testUpdate(){
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        User user = new User();
        user.setId(3);
        user.setUsername("娜美");
        user.setPassword("namei");
        user.setSex("女");
        user.setAddress("航海士");
        user.setBirthday("1998-02-11");
        userDao.update(user);
    }
    /**
     * 添加数据
     */
    @Test
    public void testDelete(){
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        userDao.delete(15);
    }

2、动态代理模式开发

1、pom.xml
	<dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>
2、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>
    <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://127.0.0.1:3306/mybatisdb_sgw?characterEncoding=utf8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="cn/sgwks/dao/UserMapper.xml"></mapper>
    </mappers>
</configuration>
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">
<!--
    动态代理模式：规范必须遵守
        namespace:必须是对应接口的全限类名
        select|update|insert|delete: 四个标签 id必须对应dao接口的方法名
-->
<mapper namespace="cn.sgwks.dao.UserDao">
    <select id="findAll" resultType="cn.sgwks.domain.User">
        select * from user
    </select>
    <insert id="insert" parameterType="cn.sgwks.domain.User">
        insert into user values(null ,"${username}",#{password},#{sex},#{address},#{birthday})
    </insert>
    <update id="update" parameterType="cn.sgwks.domain.User">
         update user set username=#{username},password=#{password},sex=#{sex},address=#{address},birthday=#{birthday}
         where id = #{id}
    </update>
    <delete id="delete" parameterType="java.lang.Integer">
        delete from user where id = #{随意}
    </delete>
</mapper>

1、Dao层
	package cn.sgwks.dao.impl;

import cn.sgwks.dao.UserDao;
import cn.sgwks.domain.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;

public class UserDaoImpl implements UserDao {
    //所有的方法共用的factory对象,应该是属于应用级别
    private SqlSessionFactory sqlSessionFactory;

    public UserDaoImpl(SqlSessionFactory sqlSessionFactory) {
        this.sqlSessionFactory = sqlSessionFactory;
    }

    /**
     * 查询所有user表数据
     * @return 返回集合类型，遍历
     */
    @Override
    public List<User> findAll() {
        //每一个方法应该获取一个SqlSession对象,用完应该立即关闭,因为线程不安全
        SqlSession sqlSession = sqlSessionFactory.openSession();
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        //释放资源
        sqlSession.close();
        return userList;
    }

    /**
     * 添加数据
     * @param user 传递user对象
     */
    @Override
    public void insert(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.insert("userMapper.insert",user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }

    /**
     * 修改数据
     * @param user
     */
    @Override
    public void update(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.update("userMapper.update",user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }

    /**
     * 删除数据
     * @param id
     */
    @Override
    public void delete(Integer id) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.delete("userMapper.delete",id);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }
}
2、domain层
    public class User {
    private Integer id;
    private String username;
    private String password;
    private String sex;
    private String address;
    private String birthday;
    ...}
3、测试类
    package cn.sgwks;

import cn.sgwks.dao.UserDao;
import cn.sgwks.domain.User;
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.util.List;

public class TestMybatisProxy {
    //提升作用域
    SqlSessionFactory sqlSessionFactory = null;
    /**
     * 执行命令前提前初始化
     */
    @Before
    public void init(){
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(this.getClass().getClassLoader().getResourceAsStream("SqlMapConfig.xml"));
    }
    @Test
    public void testFindAll(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取Dao接口的动态代理对象
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.findAll();
        for (User user : userList) {
            System.out.println(user);
        }
        //释放资源
        sqlSession.close();
    }

    /**
     * 添加数据
     */
    @Test
    public void testInsert(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取Dao接口的动态代理对象
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        User user = new User();
        user.setUsername("罗宾");
        user.setPassword("luobin");
        user.setSex("女");
        user.setAddress("魔族");
        user.setBirthday("1996-09-10");
        userDao.insert(user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }
    /**
     * 修改数据
     */
    @Test
    public void testUpdate(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取Dao接口的动态代理对象
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        User user = new User();
        user.setId(4);
        user.setUsername("乔巴");
        user.setPassword("qiaoba");
        user.setSex("鹿");
        user.setAddress("雪上");
        user.setBirthday("2018-01-01");
        userDao.update(user);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }
    /**
     * 删除数据
     */
    @Test
    public void testDelete(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取Dao接口的动态代理对象
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.delete(13);
        //必须自动提交
        sqlSession.commit();
        //释放资源
        sqlSession.close();
    }
}

四、核心配置文件详解

1. 配置文件中的标签和顺序
properties?, 						配置属性(学习)
settings?, 							全局配置：缓存，延迟加载
typeAliases?, 					类型别名(学习)
typeHandlers?, 					类型转换(操作)(了解)
objectFactory?, 	 objectWrapperFactory?,  reflectorFactory?, 
plugins?, 							插件:分页插件
environments?, 					环境配置（数据源）
databaseIdProvider?, 		
mappers?								引入映射配置文件(学习)

? : 一个或者零个
| : 任选其一
+ : 最少一个
* : 零个或多个
, : 必须按照此顺序编写

五、输入参数类型和输出参数类型

1. 输入参数
	简单类型: 基本数据类型+ String类型
				#{} :名称随便
				${} :${value}
	pojo 类型
		#{} :${} : 属性名引用
	包装对象类型
		引用  #{属性.属性名}
	Map集合
		引用： #{key}
	多个参数
		引用时：#{param1},#{param2}.....#{paramN}
2. 返回值类型
	如果列与属性名不一致，对应的属性为null, 必须写映射配置