mybatis entry --day01: configured by xml

1 Introduction

• Presentation Layer: Display Data
• Business layer: processing business requirements
• Persistence: interact with the database

mybatis official address: http://www.mybatis.org/mybatis-3/zh/getting-started.html

• mybatis is a persistence framework, encapsulates the details jdbc, so that we can focus sql statement itself, without concern registration drive, create complicated process connections. It uses ORM thought
• ORM (object relational mapping): object-relational mapping. That is, the database and the entity class and an entity class attribute correspondence, so that we can work with entity classes to achieve operation of the database table

2. Configure a simple case of flow

Overall structure is as follows:

① create a maven project, pom configuration file

    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <!--mybatis和数据库交互，所以需要有mysql的依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            
            <!--勿用5.1.6-->
            <!--<version>8.0.16</version>-->
            <version>5.1.46</version>
        </dependency>

        <!--日志-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>

        <!--单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

② create entity classes (User)

public class User {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "com.itheima.domain.User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

③ user interfaces Persistence Layer (IUserDao)

public interface IUserDao {

    //查询所有操作
    List<User> findAll();
}

④ configuration mybatis main configuration file (the SqlMapConfig.xml)

<?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">

<!--mybatis的主配置文件-->
<configuration>
    <!--配置环境-->
    <environments default="mysql">
        <!--配置数据库环境-->
        <environment id="mysql">
            <!--配置事务类型JDBC-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <!--配置连接数据库的4个基本信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://172.20.10.13:3306/dl?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="11250825"/>
            </dataSource>
        </environment>
    </environments>

    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>
</configuration>

Mybatis position mapping profile (IUserDao.xml) and packet structure to be similar to the interface dao

⑤ Each configuration profile dao independent, i.e. mapping configuration file (IUserDao.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">

<!--namespace表示方法findAll在哪个dao实现接口-->
<mapper namespace="com.itheima.dao.IUserDao">
    <!--配置查询所有-->
    <!--resultType表示要封装到哪里去-->
    <select id="findAll" resultType="com.itheima.domain.User">
        select * from user
    </select>
</mapper>

namespace representation findAll implement the interface in which dao.
resultType said to go package.

mapper label mapping configuration file in the namespace attribute value must be a fully qualified class name dao interface
Operating configuration mapping configuration file (select, etc.), the value of the id attribute name must be a method dao interface
After complying with the above yellow bottom line of three points in development will need to write a dao implementation class.

---

In mapping configuration file (IUserDao.xml), the package needs to be informed mybatis which entity classes. Is arranged to specify the fully qualified class name of the entity class.

<select id="findAll" resultType="com.itheima.domain.User">

⑥ Import log4j.properties file resources in

# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE

# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

⑦ In the test - create a test class (MybatisTest) java in

/**
 * Mybatis 入门案例
 */
public class MybatisTest {
    public static void main(String[] args) throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");

        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);

        //3.使用工厂生产SqlSession对象
        SqlSession session = factory.openSession();

        //4.创建Dao接口的代理对象（动态代理）
        IUserDao userDao = session.getMapper(IUserDao.class);

        //5.使用代理对象执行方法
        List<User> users = userDao.findAll();

        for (User user : users) {
            System.out.println(user);
        }

        //6.释放资源
        session.close();
        in.close();
    }
}

The meaning of the above program:

⑧ configuration mysql

CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `username` varchar(32) NOT NULL COMMENT '用户名称',
  `birthday` datetime default NULL COMMENT '生日',
  `sex` char(1) default NULL COMMENT '性别',
  `address` varchar(256) default NULL COMMENT '地址',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');