Query users by id

sql used:

SELECT * FROM `user` WHERE id = 1

Add the select tag in user.xml and write sql:

<?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, for isolation sql，There is also a very important role, which will be discussed later. -->
<mapper namespace="test">

	<!-- id:statement Of id Or called sql Of id-->
	<!-- parameterType:Declare the type of input parameter -->
	<!-- resultType:Declare the type of output result, which should be filled in pojo Full path -->
	<!-- #{}: placeholder for input parameter, equivalent to jdbc's? >
	<select id="queryUserById" parameterType="int"
		resultType="cn.itcast.mybatis.pojo.User">
		SELECT * FROM `user` WHERE id  = #{id}
	</select>

</mapper>

Test procedure:

Test procedure steps:

1. Create SqlSessionFactoryBuilder object

2. Load SqlMapConfig.xml configuration file

3. Create SqlSessionFactory object

4. Create SqlSession object

5. Execute SqlSession object to execute query and get the result User

6. Print results

7. Release resources

public class MybatisTest {
	private SqlSessionFactory sqlSessionFactory = null;

	@Before
	public void init() throws Exception {
		// 1. Create SqlSessionFactoryBuilder object
		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();

		// 2. Load SqlMapConfig.xml configuration file
		InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");

		// 3. Create SqlSessionFactory object
		this.sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
	}

	@Test
	public void testQueryUserById() throws Exception {
		// 4. Create SqlSession object
		SqlSession sqlSession = sqlSessionFactory.openSession();

		// 5. Execute the SqlSession object to query and get the result User.
		// The first parameter is the id of the statement of User.xml, and the second parameter is required for executing sql.
		Object user = sqlSession.selectOne("queryUserById", 1);

		// 6. Print results
		System.out.println(user);

		// 7. Release resources
		sqlSession.close();
	}
}

Fuzzy query of users based on user name

Query sql:

SELECT * FROM `user` WHERE username LIKE '% Wang%'

Method 1: add the following content to the User.xml configuration file:

<!-- If multiple results are returned, mybatis Will automatically put the returned results in the list Container -->
	<!-- resultType The configuration of is the same as that of returning a result. -->
	<select id="queryUserByUsername1" parameterType="string"
		resultType="cn.itcast.mybatis.pojo.User">
		SELECT * FROM `user` WHERE username LIKE #{username}
	</select>

        @Test
	public void testQueryUserByUsername1() throws Exception {
		// 4. Create SqlSession object
		SqlSession sqlSession = sqlSessionFactory.openSession();

		// 5. Execute the SqlSession object to query and get the result User.
		// Query multiple data using the selectList method
		List<Object> list = sqlSession.selectList("queryUserByUsername1", "%king%");

		// 6. Print results
		for (Object user : list) {
			System.out.println(user);
		}

		// 7. Release resources
		sqlSession.close();
	}

Method two:

Add the following to the User.xml configuration file

        <!-- If the parameter passed in is a simple data type, ${}It has to be written value -->
	<select id="queryUserByUsername2" parameterType="string"
		resultType="cn.itcast.mybatis.pojo.User">
		SELECT * FROM `user` WHERE username LIKE '%${value}%'
	</select>

@Test
public void testQueryUserByUsername2() throws Exception {
	// 4. Create SqlSession object
	SqlSession sqlSession = sqlSessionFactory.openSession();

	// 5. Execute the SqlSession object to query and get the result User.
	// Query multiple data using the selectList method
	List<Object> list = sqlSession.selectList("queryUserByUsername2", "king");

	// 6. Print results
	for (Object user : list) {
		System.out.println(user);
	}

	// 7. Release resources
	sqlSession.close();
}