Demand:

1. Query a user

2. Query multiple users (List)

Step 1: Make a global configuration file under config/SqlMapConfig.xml (note header information)

<?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>
	
	<!-- Configuring data sources -->
	<!-- and spring After integration environments Configuration will be abolished-->
	<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?characterEncoding=utf-8" />
				<property name="username" value="root" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	
	<!-- To configure mapper Mapping file -->
	<mappers>
		<mapper resource="sqlmap/User.xml"/>
	</mappers>
	
</configuration>

Adding config/log4j.properties can print sql statements on the console

Step 2: Create Entity Classes User.java

Step 3: Configure the User.xml mapping file under config/sqlmap/User.xml (note header information)

<?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 namespace: As a token, but if you use the mapper dynamic proxy method, you need to configure the mapper interface address here - >.
<mapper namespace="test">
	
	<!-- 
	
		Query a record based on the user's ID (return a single record) 
		
		
		The select tag represents the sql query, and the content is encapsulated in Mapped Statement.
		You can call this select tag a Statement.
		id attribute: the unique identity of the Statement
		
		# {}: Represents a placeholder that avoids sql injection
		${}: Represents a splicer
		
		parameterType: Represents the type of input, that is, what type of placeholder to enter
		ResultType: The type representing the output result set, and the field name of the select query is the same as the resultType attribute name to map successfully.
		# {id}:id represents the variable for the parameter input parameter
		
	-->
	<select id="findUserById" parameterType="int" resultType="com.mo.pojo.User">
		SELECT * FROM USER  WHERE id = #{id}
	</select>
	
	<!-- 
		Query the list of users by name (return to the List collection) 
		
		Regardless of how many results are returned, resultType specifies the type of a single record mapping java object
		
		${}: Represents sql splicing, which is equivalent to splicing sql strings, and sql injection is unavoidable.
		${value}:value represents the variable for the parameter input parameter. With ${}, the variable name must use value.
				Splice value directly into sql without any modification
				
			'%${value}%': Modification can be used in this way
				Client input sheet 
				sql splices to% sheet%
			
	-->
	<select id="findUserListByName" parameterType="String" resultType="com.mo.pojo.User">
		SELECT * FROM USER WHERE username LIKE '%${value}%'
	</select>
	
</mapper>

Step 4: Test Unit

package com.mo;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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.mo.pojo.User;

public class MybatisTest {

	@Test
	public void test() throws IOException{
		//1. Loading configuration files
		String resource = "SqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		
		//2. Create SqlSessionFactory based on configuration file
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		
		//3. Create SqlSession according to SqlSession Factory
		SqlSession sqlSession = sqlSessionFactory.openSession();
		
		
		//4. Query returns multiple entries
		/**
		 *  Operating the database through the API of sqlSession
		 *	The first parameter is statement: specify the id of the state in the mapper mapping file
		 *		When specified, add the space name to which the state belongs
		 * 	The second is to assign parameters.	
		 * 
		 * 	selectOne Returns a single record, and if select returns multiple records (list collection), selectOne will report an error.
		 * 	
		 * 	Returning a worthwhile type is the resultType in the mapping file
		 */
		User user = sqlSession.selectOne("test.findUserById", 1);
		
		
		List<User> list = sqlSession.selectList("test.findUserListByName","Zhang");
		
		System.out.println(list.size());
		
		System.out.println(user);
		
		//5. Close sqlSession
		sqlSession.close();
	}
}