MyBatis基於xml與註解配置入門實例與問題

基於xml配置的實例參考：https://blog.csdn.net/qq_39264561/article/details/102974261

基於註解配置的實例：

1、項目結構如圖：

注意：

若idea下Maven項目很卡，調整：Other Setting->default Setting->搜索maven->Runner中：VM Options設置爲：-DarchetypeCatalog=internal

2、pom.xml文件中導入如下座標

<packaging>war</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

3、創建log4j.properties配置文件

# 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

4、創建數據庫表並插入一條數據

CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `username` varchar(32) NOT NULL COMMENT '用戶名稱',
  `birthday` datetime default NULL COMMENT '生日',
  `sex` char(1) default NULL COMMENT '性別',
  `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','北京金燕龍'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龍'),(45,'傳智播客','2018-03-04 12:04:06','男','北京金燕龍'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小馬寶莉','2018-03-08 11:44:00','女','北京修正');

5、Mybatis的配置文件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>
    <!-- 配置環境 -->
    <environments default="mysql">
        <!-- 配置mysql的環境-->
        <environment id="mysql">
            <!-- 配置事務的類型-->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置數據源（連接池） -->
            <dataSource type="POOLED">
                <!-- 配置連接數據庫的4個基本信息 -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="orcl"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 指定映射配置文件的位置，映射配置文件指的是每個dao獨立的配置文件 -->
    <mappers>
        <mapper class="cn.itcast.dao.UserDao"/>
    </mappers>
</configuration>

6、創建實體類、持久層接口

實體類：

package cn.itcast.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
    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 "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

持久層接口：

package cn.itcast.dao;

import cn.itcast.domain.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

/**
 * 用戶持久層接口
 */
public interface UserDao {
    /**
     * 查詢所有操作
     * @return
     */

    @Select("select * from user")
    List<User> findAll();
}

7、測試類

package cn.itcast.test;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
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 java.io.InputStream;
import java.util.List;

/**
 * 入門案例
 */
public class MyBatisTest {
    public static void main(String[] args) throws Exception {
        //1、讀取配置文件
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");

        //2、創建SqlSessionFactory工廠
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);

        //3、使用SqlSessionFactory工廠創建SqlSession對象
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //4、使用SqlSession對象創建Dao接口的代理對象
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        //5、使用代理對象執行方法
        List<User> users = userDao.findAll();
        for (User user:users){
            System.out.println(user);
        }

        //6、釋放資源
        sqlSession.close();
        inputStream.close();
    }
}

8、輸出結果