Mybatis simple add delete change check

Mybatis simple add delete change check

This is the 25th day of my participation in the November Gwen Challenge. Check out the event details: The last Gwen Challenge 2021

Mybatis is an excellent persistence layer framework that supports customized SQL, stored procedures, and advanced mapping. MyBatis avoids almost all of the JDBC code and manual parameter setting and result set extraction. MyBatis uses simple XML or annotations to configure and map the base body, mapping interfaces and Java’s POJOs(Plain Old Java Objects) to records in the database.

Tools: Navicat Premium, IntelliJ IDEA

Simple directory structure

1. Create the mysql database

Create a firenD_MQ database, create a table named Users, and insert some data

2. Create a Maven project and import the dependencies

 <dependencies>
        <! -- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <! Add myBatis dependency -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <! - a JDBC driver - >
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <! -- Junit Test class -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
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3. Create mybatis-config. XML under resources folder and write the core configuration file of Mybaits

      
<! DOCTYPEconfiguration
        PUBLIC "- / / mybatis.org//DTD Config / 3.0 / EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<! -- Configuration Core configuration file -->
<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://localhost:3306/firend_mq? useSSL=false&amp;useUnicode=&amp;characterEncodeing=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
<! - registered mapper -- -- >
    <mappers>
        <mapper resource="dao/UserMapper.xml"/>
    </mappers>
</configuration>
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IntelliJ IDEA: “/” mysql > connect to mysql. mysql > connect to mysql. mapper: “/”

4. Write myBatis utility class

//SqlSessionFactory
public class Mybatisutil {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {// Use mybaatis to get the SqlSessionFactory object
            String resource="mybatis-config.xml";
            InputStream inputStream= Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch(IOException e) { e.printStackTrace(); }}// With SqlSessionFactory, as the name implies, we can get an instance of SqlSession from it. SqlSession
    // Provides all the methods needed to execute SQL commands in the database. You can use the SqlSession instance to execute the mapped SQL statement directly

    public static SqlSession getSqlSession(a){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        returnsqlSession; }}Copy the code

5. Write myBatis entity class

package pojo;

public class User {
    private int id;
    private String username;
    private String password;

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public User(a) {}public int getId(a) {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername(a) {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword(a) {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString(a) {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\' ' +
                ", password='" + password + '\' ' +
                '} '; }}Copy the code

The preparatory work has been completed and the code has begun

6. Write the Dao layer interface

public interface UserDao {
    // Query all users
    List<User> getUserList(a);

    // Query the user with the specified ID
    User getUserById(int id);

    // Add a user
    int addUser(User user);

    // Modify the user
    int updateUser(User user);

    // Delete a user
    int deleteUser(int id);
}
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The interface implementation class is changed from UserDaoImpl to Mapper configuration folder

<! -- Namespace = bind a corresponding Dao/Mapper interface -->
<mapper namespace="dao.UserDao">
<! Select * from 'select';
    <select id="getUserList" resultType="pojo.User">
        select * from firend_mq.users
    </select>
<! -- query by id -->
    <select id="getUserById" parameterType="int" resultType="pojo.User">
        select * from firend_mq.users where id = #{id}
    </select>

<! Add an attribute to the user object.
    <insert id="addUser" parameterType="pojo.User">
        insert into firend_mq.users (id,username,password) value (#{id},#{username},#{password})
    </insert>

    <update id="updateUser" parameterType="pojo.User">
        update firend_mq.users set username=#{username},password=#{password}  where id=#{id};
    </update>

<! -- Delete a user -->
    <delete id="deleteUser" parameterType="int">
        delete from firend_mq.users where id=#{id}
    </delete>
</mapper>
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Note:

• Mapper configuration files must be registered in mybatis-config.xml
• Tags are the type of add, delete, change, and check. In the tag, write the original SQL statement, using #{} to pass the value
• Namespace = Bind a corresponding Dao/Mapper interface. Do not bind an incorrect interface
• Id is the name of the method in the interface
• ParameterType is the parameterType of a method. ResultType is the return value type of a method.

8. Write test classes

public class UserDaoText {
    // Query all users
    @Test
    public void getUserList(a){
        // Step 1: Get the sqlSession object
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        // Method 1: getMapper
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
// Query the user with the specified ID
    @Test
    public void getUserById(a){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
       User user = mapper.getUserById(2);
        System.out.println(user);
        sqlSession.close();
    }
    // All additions, deletions and changes must be committed to the transaction
    // Add a user
    @Test
    public void addUser(a){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.addUser(new User(4."Zhang"."10086"));
        // Commit the transaction
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(a){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.updateUser(new User(4."Ha ha"."123"));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(a){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.deleteUser(4); sqlSession.commit(); sqlSession.close(); }}Copy the code

Such a simple Mybatis to add, delete, change, check is finished, details are annotated in the code.