Mybatis基礎

1.配置項目所需要的jar包

<dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

2.創建JavaBean，成員變量名和數據庫中字段一致

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 + '\'' +
                '}';
    }
}

3.創建用戶持久層接口

public interface IUserDao {
    /**
     * 查找所有用戶
     * @return
     */
    List<User> findAll();
}

4.在resources下創建兩個配置文件

配置文件1-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">
<configuration>
    <!--配置環境-->
    <environments default="mysql">
        <!--配置mysql環境-->
        <environment id="mysql">
            <!--配置事務類型-->
            <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>
                <property name="url" value="jdbc:mysql://localhost:3306/eesy"></property>
                <property name="username" value="root"></property>
                <property name="password" value="123456"></property>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/sx/dao/IUserDao.xml"></mapper>
    </mappers>
</configuration>

配置文件2-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">
 <mapper namespace="com.sx.dao.IUserDao">
    <!--配置查詢所有User的方法和返回類型-->
    <select id="findAll" resultType="com.sx.domain.User">
        select * from user
    </select>
</mapper>

5.查詢數據庫

		//1.讀取配置文件
        InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.創建SqlSessionFactory工廠
        SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
        SqlSessionFactory ssf = ssfb.build(is);
        //3.使用工廠生產SqlSession對象
        SqlSession ss = ssf.openSession();
        //4.使用SqlSession創建Dao接口的代理對象
        IUserDao iud = ss.getMapper(IUserDao.class);
        //5.使用代理對象執行方法
        List<User> users = iud.findAll();
        for (User user : users) {
            System.out.println(user);
        }
        //6.釋放資源
        ss.close();
        is.close();

6.不書寫IUserDao.xml使用註解

刪除IUserDao.xml後,在用戶持久層接口的方法中加上註解
	@Select("select * from user")
    List<User> findAll();

在SqlMapConfig.xml中修改mappers
	<mappers>
        <mapper class="com.sx.dao.IUserDao"></mapper>
    </mappers>