16.MyBatis配置文件2

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使用代理

1.删除Dao的impl包及其实现类

2.Mapper.xml与Dao接口

(1)<mapper namespace="[Dao接口的全限定名]">

(2)<insert id="[Dao接口中的对应方法名]">

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package com.course.dao;

import java.util.List;

import com.course.vo.User;

public interface UserDao {

	public void addUser(User user);
	
	public void updateUser(User user);
	
	public void deleteUser(Integer id);
	
	public User getUserById(Integer id);
	
	public List<User> getAllUser();	
}
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<?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.course.dao.UserDao">
	<insert id="addUser" parameterType="com.course.vo.User">
		insert into user(name, age, address, birthday) 
			values(#{name}, #{age}, #{address}, #{birthday})
	</insert>
	
	<update id="updateUser" parameterType="com.course.vo.User">
		update user set name=#{name}, age=#{age}, address=#{address}, birthday=#{birthday}
			where id=#{id}
	</update>
	
	<delete id="deleteUser" parameterType="int">
		delete from user 
			where id=#{val}
	</delete>
	
	<select id="getUserById" parameterType="int" resultType="com.course.vo.User">
		select * from user where id=#{val}
	</select>
	
	<select id="getAllUser" resultType="com.course.vo.User">
		select * from user
	</select>
</mapper>

3.测试类

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package com.course.test;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import com.course.dao.UserDao;
import com.course.util.MyBatisUtil;
import com.course.vo.User;

public class MainTest {

	public static void main(String[] args) {
		SqlSession sqlSession = MyBatisUtil.openSqlSession();
        // 得到UserDao的代理对象
		UserDao userDao = sqlSession.getMapper(UserDao.class);

        System.out.println(userDao);
        // org.apache.ibatis.binding.MapperProxy@313ac989
		System.out.println(userDao.getClass().getSimpleName());
		// $Proxy3
        
		List<User> userList = userDao.getAllUser();
		for (User user : userList) {
			System.out.println(user.toString());
		}
		
		MyBatisUtil.closeSqlSession(sqlSession);
	}
	
}
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DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.ibatis.reflection.Reflector (file:/G:/eclipse/eclipse-2020-12/project/mybatis/03_mybatis_proxy/WebContent/WEB-INF/lib/mybatis-3.3.0.jar) to method java.lang.Object.finalize()
WARNING: Please consider reporting this to the maintainers of org.apache.ibatis.reflection.Reflector
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
DEBUG [main] - Created connection 1262408432.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@4b3ed2f0]
DEBUG [main] - ==>  Preparing: select * from user 
DEBUG [main] - ==> Parameters: 
DEBUG [main] - <==      Total: 10
User [id=1, name=user1, age=10, address=address1, birthday=Fri Aug 13 12:35:22 CST 2021]
User [id=2, name=user2, age=10, address=address2, birthday=Fri Aug 13 16:51:11 CST 2021]
User [id=4, name=user1, age=10, address=address1, birthday=Fri Aug 13 16:55:22 CST 2021]
User [id=5, name=user2, age=10, address=address2, birthday=Fri Aug 13 16:55:22 CST 2021]
User [id=7, name=user1, age=10, address=address1, birthday=Fri Aug 13 16:57:01 CST 2021]
User [id=8, name=user2, age=10, address=address2, birthday=Fri Aug 13 16:57:01 CST 2021]
User [id=9, name=user3, age=10, address=address3, birthday=Fri Aug 13 16:57:01 CST 2021]
User [id=11, name=user11, age=10, address=address11, birthday=Fri Aug 13 16:58:27 CST 2021]
User [id=12, name=user12, age=10, address=address2, birthday=Mon Aug 16 15:54:29 CST 2021]
User [id=14, name=user3, age=10, address=address3, birthday=Mon Aug 16 15:53:30 CST 2021]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@4b3ed2f0]
DEBUG [main] - Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@4b3ed2f0]
DEBUG [main] - Returned connection 1262408432 to pool.

若<mapper namespace="">与接口的全限定名不对应: 

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Exception in thread "main" org.apache.ibatis.binding.BindingException: Type interface com.course.dao.UserDao is not known to the MapperRegistry.
	at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
	at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:675)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:250)
	at com.course.test.MainTest.main(MainTest.java:15)

若Mapper.xml的节点id与接口中的方法名不对应: 

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Exception in thread "main" org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.course.dao.UserDao.getUserById
	at org.apache.ibatis.binding.MapperMethod$SqlCommand.<init>(MapperMethod.java:196)
	at org.apache.ibatis.binding.MapperMethod.<init>(MapperMethod.java:44)
	at org.apache.ibatis.binding.MapperProxy.cachedMapperMethod(MapperProxy.java:59)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
	at com.sun.proxy.$Proxy3.getUserById(Unknown Source)
	at com.course.test.MainTest.main(MainTest.java:23)

Mapper.xml详解

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<?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.course.dao.UserDao">
	<!-- 
		1. id: 节点的唯一标识，对应接口中的方法名，不能重复
		2. parameterType: 参数类型
		3. parameterMap: 参数map类型
		4. useGeneratedKeys="true": 是否使用自动增长，默认为true
		说明: parameterType和parameterMap只能存在一个
	 -->
	 
	<!-- 
	<insert id="addUser" parameterType="com.course.vo.User" >
		insert into user(name, age, address, birthday) 
			values(#{name}, #{age}, #{address}, #{birthday})
	</insert>
	 -->
	<parameterMap type="com.course.vo.User" id="userVO">
		<parameter property="name" javaType="java.lang.String"/>
		<parameter property="address" javaType="java.lang.String"/>
	</parameterMap>
	<insert id="addUser" parameterMap="userVO">
		insert into user(name, age, address, birthday) 
			values(#{name}, #{age}, #{address}, #{birthday})
	</insert>
	
	<!-- 
		1. id: 节点的唯一标识，对应接口中的方法名，不能重复
		2. parameterType: 参数类型
	 -->
	<update id="updateUser" parameterType="com.course.vo.User">
		update user set name=#{name}, age=#{age}, address=#{address}, birthday=#{birthday}
			where id=#{id}
	</update>
	
	<!-- 
		1. id: 节点的唯一标识，对应接口中的方法名，不能重复
		2. parameterType: 参数类型，如果是基本数据类型或者String，可以不配置parameterType
	 -->
	<delete id="deleteUser" parameterType="int">
		delete from user 
			where id=#{val}
	</delete>
	
	<!-- 
		1. id: 节点的唯一标识，对应接口中的方法名，不能重复
		2. parameterType: 参数类型
		3. resultType: 返回值的类型
	 -->
	<select id="getUserById" parameterType="int" resultType="com.course.vo.User">
		select * from user where id=#{val}
	</select>
	
	<!-- 
		1. id: 节点的唯一标识，对应接口中的方法名，不能重复
		2. resultMap: 如果查询的结果集字段名与实体类属性名不同，可以使用resultMap
		3. resultType: 返回值的类型，查询的结果集字段名与实体类属性名相同
		说明: resultType和resultMap只能存在一个
	 -->
	<!-- 
	<select id="getAllUser" resultType="com.course.vo.User">
		select 
			id as userId,
			name as userName,
			age as userAge,
			address as addr,
			birthday as birth
		from user
	</select>
	 -->
	<resultMap type="com.course.vo.User" id="userVO">
		<id property="id" column="userId"/>
		<result property="name" column="userName"/>
		<result property="age" column="userAge"/>
		<result property="address" column="addr"/>
		<result property="birthday" column="birth"/>
	</resultMap>
	<select id="getAllUser" resultMap="userVO">
		select 
			id as userId,
			name as userName,
			age as userAge,
			address as addr,
			birthday as birth
		from user
	</select>
</mapper>

parameterMap和resultMap的id可以相同

配置别名

mybatis.cfg.xml

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<?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>
	<!-- 
	The content of element type "configuration" must match 
 		"(properties?,settings?,typeAliases?,typeHandlers?,
 		objectFactory?,objectWrapperFactory?,reflectorFactory?,
 		plugins?,environments?,databaseIdProvider?,mappers?)".
 		
		<properties></properties>
		<typeAliases></typeAliases>
		<plugins></plugins>
		<environments></environments>
		<mappers></mappers>
	 -->
	
	<!-- 配置类的别名 -->
	<!-- 
		<typeAliases>
			一个一个配置
			<typeAlias type="com.course.vo.User" alias="User"/>
		</typeAliases>
	 -->
	<typeAliases>
		<!-- 批量配置包下所有的实体类 -->
		<package name="com.course.vo"/>
	</typeAliases>
</configuration>

mapper.xml

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<?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.course.dao.UserDao">

	<select id="getAllUser" resultType="User">
		select 
			id,
			name,
			age,
			address,
			birthday
		from user
	</select>

</mapper>

mybatis占位符的处理

1，占位符一：#{xxx}

PreparedStatement预编译sql语句

xxx表达式的写法

  • 参数类型为javabean类，xxx表达式必须和javabean中属性对应的get方法名字一样
  • 参数类型为简单类型，xxx表达式随表写，保持和参数的名字一致
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<mapper namespace="com.course.dao.UserDao">
	<insert id="addUser" parameterType="com.course.vo.User" >
		insert into user(name, age, address, birthday) 
			values(#{name}, #{age}, #{address}, #{birthday})
	</insert>
</mapper>
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DEBUG [main] - ==>  Preparing: insert into user(name, age, address, birthday) values(?, ?, ?, ?) 
DEBUG [main] - ==> Parameters: user18(String), 10(Integer), address18(String), 2021-08-20 17:41:03.196(Timestamp)
DEBUG [main] - <==    Updates: 1

2，占位符二：${xxx}

Statement拼接sql语句

xxx表达式的写法

  • 参数类型为javabean类，xxx表达式必须和javabean中属性对应的get方法名字一样
  • 参数类型为简单类型，xxx表达式执行只能写${value}
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<mapper namespace="com.course.dao.UserDao">
	<insert id="addUser" parameterType="com.course.vo.User" >
		insert into user(name, age, address) 
			values('${name}', ${age}, '${address}')
	</insert>
</mapper>
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DEBUG [main] - ==>  Preparing: insert into user(name, age, address) values('user18', 10, 'address18') 
DEBUG [main] - ==> Parameters: 
DEBUG [main] - <==    Updates: 1
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<mapper namespace="com.course.dao.UserDao">
	<select id="getUserById" parameterType="int" resultType="com.course.vo.User">
		select * from user where id=${val}
	</select>
</mapper>
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Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'val' in 'class java.lang.Integer'
### Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'val' in 'class java.lang.Integer'
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:122)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:113)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:73)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:69)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
	at com.sun.proxy.$Proxy3.getUserById(Unknown Source)
	at com.course.test.MainTest.main(MainTest.java:32)
Caused by: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'val' in 'class java.lang.Integer'
	at org.apache.ibatis.reflection.Reflector.getGetInvoker(Reflector.java:381)
	at org.apache.ibatis.reflection.MetaClass.getGetInvoker(MetaClass.java:164)
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<mapper namespace="com.course.dao.UserDao">
	<select id="getUserById" parameterType="int" resultType="com.course.vo.User">
		select * from user where id=${value}
	</select>
</mapper>
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DEBUG [main] - ==>  Preparing: select * from user where id=12 
DEBUG [main] - ==> Parameters: 
DEBUG [main] - <==      Total: 1
User [id=12, name=user12, age=10, address=address2, birthday=Mon Aug 16 15:54:29 CST 2021]