【mybatis】学习笔记 2 动态代理 输入输出参数 关联查询

sqlMapConfig代码  没有改变

<?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"/>
      <!-- 小型配置文件的相对路径 以及 driver =url 的值!!!!!! -->
      <dataSource type="POOLED"><!-- 连接池连接数据库 -->
        <property name="driver" value="com.mysql.cj.jdbc.Driver"/><!-- 加载驱动类 -->
        <property name="url" value="jdbc:mysql://localhost:3306/ssm_mybatis?serverTimezone=UTC"/><!-- useSSL=false -->
        <property name="username" value="root"/>
        <property name="password" value="88888888"/>
    		</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="mapper/UserMapper.xml"/>
	</mappers>
</configuration>

UseMapper.xml     namespace为改为包名的路径

<?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="com.mapper.userMapper">
	<select id="userById" parameterType="Integer" resultType="com.user.user">
		select * from user where u_id= #{id}
	</select>
	<select id="userByusername" parameterType="String" resultType="com.user.user">
		select * from user where u_username like "%"#{username}"%"
	</select>
</mapper>

mybatisTest 的java代码    简化了SqlSession ss = ssf.openSession();    不用每条语句都 open 一次

userMapper mapper = ss.getMapper(userMapper.class); 增加了这条引入语句

package com.test;
 
import java.io.IOException;
import java.io.InputStream;
 
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.Test;
 
import com.mapper.userMapper;
import com.user.user;
 
public class mybatisTest {//ctrl + 1 可以显示错误提示
	@Test
	public void Test() throws IOException {
		String resource = "sqlMapConfig.xml";
		InputStream in = Resources.getResourceAsStream(resource);
		SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
		SqlSessionFactory ssf = ssfb.build(in);
		SqlSession ss = ssf.openSession();
		userMapper mapper = ss.getMapper(userMapper.class);
		user user = mapper.userById(1);
		System.out.println(user);
}
}

不用写具体的实现类 提供一个接口

package com.mapper;
 
import com.user.user;
 
public interface userMapper {
//动态代理开发四大原则
	//1、接口方法名需要和 mapper.xml的要调用的sql语句的id一致
	//2、接口的形参类型需要与mapper.xml parameterType一致
	//3、接口的返回值需要与mapper.xml resultType一致
	//4、namespace	找接口
	//5、注意mapper动态代理开发中，根据返回值类型来自动选择
	//通过id查询一个用户、
	public user userById(Integer id); //void -> user  ()里加形参
	
	public user userByusername(String name);
}

对mybatis 进行改造 简化 test 的代码

package com.test;
 
import java.io.IOException;
import java.io.InputStream;
 
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.Test;
 
import com.mapper.userMapper;
import com.user.user;
 
public class mybatisTest {//ctrl + 1 可以显示错误提示
	private static SqlSessionFactory ssf;
	static {
		try {
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
			ssf = ssfb.build(in);
			in.close();
 
		} catch (IOException e) {
			e.printStackTrace();
		}
		}
	private static SqlSession ss = ssf.openSession();
	private static userMapper mapper = ss.getMapper(userMapper.class);
	@Test
	public  void test() {
		user user = mapper.userById(1);
		System.out.println(user);
}
	@Test
	public  void test1() {
		List<user> l= mapper.userByusername("王");
		for(user s : l ) {
			System.out.println(s);
		}
}
}

sqlMapConfig-properties属性 进行配置设置！！！

properties 文件

key - value 有一个特定的名字  有些需要多个同名的key 所以需要区分出来

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm_mybatis?serverTimezone=UTC
jdbc.username=root
jdbc.password=88888888

sqlMapConfig文件

<?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">
  <!-- ctrl + shift + 方向键 -->
<configuration>
<properties resource="dp.properties" />
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <!-- 小型配置文件的相对路径 以及 driver =url 的值!!!!!! -->
      <dataSource type="POOLED"><!-- 连接池连接数据库 -->
        <property name="driver" value="${jdbc.driver}"/><!-- 加载驱动类 -->
        <property name="url" value="${jdbc.url}"/><!-- useSSL=false -->
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    		</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="mapper/UserMapper.xml"/>
	</mappers>
</configuration>

如果属性在不止一个地方进行了配置，那么mybatis将按照下面的顺序来加载
在properties 元素体内指定的属性首先被读取
然后根据properties元素中的resource属性读取类路径下属性文件或者根据url 属性指定的路径读取属性文件，并覆盖已读取的同名属性 
最后读取作为方法参数传递的属性，并覆盖已读取的同名属性
在userMapper 中的 用Integer 而不是用 java.util.Integer  因为mybatis 已经取了别名 Integer 所以直接用即可
现在的目标就是 com.user.user也设置一个别名 
下面设置完的话 就可以用user别名   如果类少的话可以用第一种         类多的话  用package 第二种

<typeAliases>
<typeAlias type="com.user.user" alias="user"/>
</typeAliases>

package 用包名进行命名 
推荐使用package 包的形式来配置别名 包的形式会扫描主包及子包下的所有文件 以对象类名为别名 大小写无限，推荐用小写

<typeAliases>
<package name="com.user"/>
</typeAliases>

通过下面的方法可以找到指定的路径~~~

mapper的配置   推荐使用package!!!!!

<mappers>
		<!--  <mapper resource="mapper/UserMapper.xml"/>--><!-- 仅配置相对路径 -->
		<!-- <mapper url="file:\C:UsersDELLDesktop编程javaeemybatis1srcmapperUserMapper.xml"/> --><!-- 需要配置绝对路径 -->
		<!--  <mapper class="com.mapper.userMapper"/>--><!-- 需要xml文件 和 java文件同名 需要放在接口文件里面 并且两个同名-->
		<package name="com.mapper"/>
	</mappers>

输入输出参数 映射
对user进行封装

package com.user;
 
public class userVo {
	// 包装类 需要全部的user对象信息
	private user user;
 
	public user getUser() {
		return user;
	}
 
	public void setUser(user user) {
		this.user = user;
	}
 
}

userMapper.xml增加的语句为

<select id="selectUserByuserVoId" parameterType="userVo" resultType="user">
		select * from user where u_id= #{user.u_id}
	</select>

userMapper.java interface类中为添加

public user selectUserByuserVoId(userVo vo);
测试函数为

@Test
	public  void test1() {//ctrl shift o 导包
		userVo uservo = new userVo();
		user u = new user();
		u.setU_id(5);
		uservo.setUser(u);
		user m =mapper.selectUserByuserVoId(uservo);
		System.out.println(m);
}

输出映射resultType

测试方法为：

	@Test
		public  void test1() {//ctrl shift o 
			Integer m = mapper.selectUserCount();
			System.out.println(m);
		}

intereface类中加

public Integer selectUserCount();

xml文件中加

<select id="selectUserCount" resultType="Integer">
		select Count(*) from user
	</select>

resultType在 对象user类中 变量名需要跟数据库名一一对应 只要改名字就映射不上

resultMap在对象user类中 变量名不用跟数据库名一一对应 需要用resultMapper手动映射

代码如下： sqlMapConfig 自己修改 其他代码如下

interface  countryMapper：
package com.mapper;
 
import java.util.List;
 
import com.bean.Country;
 
public interface countryMapper {
		List<Country> selectAll();
}

countryMapper.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="com.mapper.countryMapper">
 
<resultMap type="Country" id="country">
<result property="id" column="c_id"/>
</resultMap>
	
	<select id="selectAll" resultMap="country">
	SELECT * FROM ssm_mybatis.country;
	</select>
</mapper>

只加上需要修改的测试代码

	private static countryMapper mapper = ss.getMapper(countryMapper.class);
 
	@Test
	public void test1() {// ctrl shift o
		List<Country> selectAll = mapper.selectAll();
		for (Country country : selectAll) {
			System.out.println(country);
		}
	}
}

对象类

private Integer id; //这里 id 跟数据库c_id 不一样
	private String c_countryname;
	private String c_capital;

关联查询
多表查询的时候 不能省略字段 即使java跟数据库名字相同

1对1
country类忽略

usermapper.xml

多表查询不能省略字段 全都要写

association!!!

<?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="com.mapper.UserMapper">
 
	<resultMap type="UserVo" id="userVolist">
		<id property="u_id" column="u_id" />
		<id property="u_username" column="u_username" />
		<association property="country" javaType="Country">
			<result property="id" column="c_id"/>
			<result property="c_countryname" column="c_countryname" />
		</association>
	</resultMap>
 
	<select id="selectAll" resultMap="userVolist">
		SELECT u.u_id,
		u.u_username,
		c.c_id,
		c.c_countryname,
		FROM user u
		left join country c on u.u_cid = c.c_id
	</select>
</mapper>

test方法

@Test
	public void test1() {// ctrl shift o
		List<userVo> selectAll = mapper.selectAll();
		for (userVo userVo : selectAll) {
			System.out.println(userVo);
		}
	}

封装类

package com.bean;
//SELECT u.u_id,u.u_username,c.c_countryname FROM user u  left join country c on  u.u_cid  = c.c_id
 
public class userVo extends User{
	private Country country ;
 
	public Country getCountry() {
		return country;
	}
 
	public void setCountry(Country country) {
		this.country = country;
	}
 
	@Override
	public String toString() {
		return "userVo [country=" + country + ", getU_id()=" + getU_id() + ", getU_username()=" + getU_username() + "]";
	}
	
}

1对多

userMapper.xml        注意property

userMapper.java

package com.mapper;
import java.util.List;
 
import com.bean.countryVo;
public interface UserMapper {
		List<countryVo> selectAll();
}
<?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="com.mapper.UserMapper">
 
	<resultMap type="countryVo" id="CountryVo">
		<id property="id" column="c_id" />
		<result property="c_countryname" column="c_countryname" />
		<result property="c_capital" column="c_capital" />
		<collection property="userlist" ofType="User">
			<id property="u_id" column="u_id" />
			<result property="u_username" column="u_username" />
			<result property="u_sex" column="u_sex" />
			<result property="u_cid" column="u_cid" />
		</collection>
	</resultMap>
 
	<select id="selectAll" resultMap="CountryVo">
		select * from
		country c
		left join
		user u on
		c.c_id = u.u_cid
	</select>
</mapper>

test方法

	@Test
	public void test1() {// ctrl shift o
		List<countryVo> selectAll = mapper.selectAll();
		for (countryVo countryVo : selectAll) {
			System.out.println(countryVo);
		}
	}

package com.bean;
 
import java.util.List;
import com.bean.User;
public class countryVo extends Country{
	List<User> userlist;
	public List<User> getUserlist() {
		return userlist;
	}
	public void setUserlist(List<User> userlist) {
		this.userlist = userlist;
	}
	@Override
	public String toString() {//处理输出
		return "countryVo [ toString()=" + super.toString() +"user=" + userlist + "]";
	}	
}