Mybatis

輸入映射 支持的類
    八大基礎數據類型
    list map pojo
    包裝類型
    可以通過對象導航的方式不斷向下獲取
    例如:#{user.username}
輸出映射
    八大基礎數據類型
    list map pojo
    輸出包裝類型時 需要自動映射字段

根據ID查找對象

User.java

package com.lanou.bean;

public class User {
    private int id;
    private String name;
    private String password;
    private String sex;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", password=" + password + ", sex=" + sex + "]";
    }

}

根據ID查找對象

public interface UserDao {
    // 根據ID查找對象
    public User findUserById(int id);

}

UserDao.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.lanou.dao.UserDao">
    <select id="findUserById" parameterType="Integer" resultType="User" >
        select * from User where id = #{param}
    </select>
</mapper>

MybatisTest.java

public class MybatisTest {
    @Test
    public void test() throws IOException {
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = builder.build(inputStream);
        SqlSession session = factory.openSession();
        UserDao dao = session.getMapper(UserDao.class);
        User user = dao.findUserById(6);
        System.out.println(user);
    }
}

使用包裝類

UserDataObj.java

package com.lanou.bean;

public class UserDataObj {

    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    @Override
    public String toString() {
        return "UserDataObj [user=" + user + "]";
    }
}

UserDao.java

public interface UserDao {
    // 根據ID查找對象
    public User findUserById(int id);
    // 使用包裝類添加對象
    public int insertUserByUserDataObj(UserDataObj obj);
}

UserDao.xml

<mapper  namespace="com.lanou.dao.UserDao">
    <select id="findUserById" parameterType="Integer" resultType="User" >
        select * from User where id = #{param}
    </select>

    <insert id="insertUserByUserDataObj" parameterType="UserDataObj">
        insert into user values (
        null,
        #{user.name},
        #{user.password},
        #{user.sex}
        )
    </insert>
</mapper>

MybatisTest.java

public void test1() throws IOException {
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
    User user = new User();
    user.setName("劉邦");
    user.setPassword("12345");
    user.setSex("男");
    UserDataObj obj = new UserDataObj();
    obj.setUser(user);
    UserDao dao = session.getMapper(UserDao.class);
    int i = dao.insertUserByUserDataObj(obj);
    System.out.println(i);
    session.commit();
}

標籤根據多個id查詢一堆user

根據一堆id查詢user, id in (1,2,3) foreach標籤用來遍歷參數
collection 指定被遍歷的集合
item 每一次遍歷得到的變量seperator
open 開始標記
close 結束標記

UserDao.java

public interface UserDao {
    // 根據ID查找對象
    public User findUserById(int id);
    // 使用包裝類添加對象
    public int insertUserByUserDataObj(UserDataObj obj);

    public List<User> selectUserByIds(Integer[] ids);
}

UserDao.xml

當我們傳的參數是一個數組時
java中沒有對應的包裝類型
可以寫object 也可以不寫
parameterType 作用是規範書寫 怕你轉錯類型

遍歷數組時 參數的名字是固定的 array
遍歷ArrayList時 參數的名字是固定的 list
Mybatis參數映射的原理
其實就是把你傳過來的參數轉成map 以鍵值對的方式傳遞
所以基礎數據類型的獲取方式是${value} value也是固定的


<select id="selectUserByIds" parameterType="java.lang.Object" resultType="User">
    select * from user where id in
    <foreach collection="array" item="item" separator="," open="(" close=")">
        #{item}
    </foreach>
</select>

MybatisTest.java

public void test2() throws IOException {
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
    Integer[] ids = new Integer[] {6,10,11}; 
    UserDao dao = session.getMapper(UserDao.class);
    List<User> list = dao.selectUserByIds(ids);
    for (User user : list) {
        System.out.println(user);
    }
}

將參數Integer[]改爲List

UserDao.java

public interface UserDao {
    // 根據ID查找對象
    public User findUserById(int id);
    // 使用包裝類添加對象
    public int insertUserByUserDataObj(UserDataObj obj);

    public List<User> selectUserByIds(List<Integer> ids);
}

UserDao.xml

<select id="selectUserByIds" parameterType="java.util.List" resultType="User">
    select * from user where id in
    <foreach collection="list" item="item" separator="," open="(" close=")">
        #{item}
    </foreach>
</select>

MybatisTest.java

public void test2() throws IOException {
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
    List<Integer> list = new ArrayList<>();
    list.add(6);
    list.add(10);
    UserDao dao = session.getMapper(UserDao.class);
    List<User> list2 = dao.selectUserByIds(list);
    for (User user : list2) {
        System.out.println(user);
    }
}

常用標籤

條件判斷

根據姓名和性別同時查詢

UserDao.java

public interface UserDao {
    // 根據ID查找對象
    public User findUserById(int id);
    // 使用包裝類添加對象
    public int insertUserByUserDataObj(UserDataObj obj);
    // 根據一組id進行查詢
    public List<User> selectUserByIds(List<Integer> ids);
    // 根據姓名和性別同時進行查詢
    public User getUser(User u);
}

UserDao.xml

之所以需要1=1 因爲如果name爲空 則不加1=1時 sql語句爲
select * from user where and sex = #{sex} 
或sex爲空 
select * from user where and name = #{sex} 
當加上1=1時
select * from user where 1=1 and sex = #{sex} 
select * from user where 1=1 and name = #{name} 
select * from user where 1=1 and name = #{name} and sex = #{sex} 


<select id="getUser" parameterType="User" resultType="User">
    select * from user where 1=1
    <if test="name != null and name != ''">
        and name = #{name}
    </if>
    <if test="sex != null and name !=''">
        and sex = #{sex}
    </if>
</select>

UserDao.xml

public void test3() throws IOException {
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
    User user = new User();
    user.setName("劉邦");
    user.setSex("男");
    UserDao dao = session.getMapper(UserDao.class);
    User user2 = dao.getUser(user);
    System.out.println(user2);
}

where標籤

where標籤的作用 執行內部的邏輯並拼接到外部的sql中 會自動刪除第一個and

<select id="getUser" parameterType="User" resultType="User">
    select * from user 
    <where>
        <if test="name != null and name != ''">
            and name = #{name}
        </if>
        <if test="sex != null and name !=''">
            and sex = #{sex}
        </if>
    </where>
</select>

sql標籤

如果有很多重複的sql語句 沒有必要每次寫 可以對它進行抽取
<sql id="selectUser">
    select * from User
</sql>

<select id="findUserById" parameterType="int" resultType="com.lanou.bean.User">
    <include refid="selectUser"></include> where id = #{param}
</select>

一對多查詢

在數據庫中建立兩張表 分別爲user和orders user爲主表 orders爲從表 orders中有一個鍵是外鍵
參照user主表中的id

AutoMapping 設爲true 可以自動將列名與屬性名稱對應數據映射
    一對一 javaType用來指定集合內元素的類型 必須寫 否則空指針異常

實現:
    在查詢user數據時自動查詢出對應的orders數據
    1.實體類中添加屬性
    2.接口中添加方法
    3.mapper實現sql
    4.手動映射關聯數據

user類

user與orders是一對多的關係 user中需要一個集合 用來保存orders中的信息
package com.lanou.bean;

import java.util.List;

public class User {
    private int id;
    private String name;
    private String password;
    private String sex;
    private List<Orders> orders;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public List<Orders> getOrders() {
        return orders;
    }
    public void setOrders(List<Orders> orders) {
        this.orders = orders;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", password=" + password + ", sex=" + sex + ", orders=" + orders
                + "]";
    }
}

Orders.java

package com.lanou.bean;

public class Orders {
    private int id;
    private String name;
    private double price;
    private int userid;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public int getUserid() {
        return userid;
    }
    public void setUserid(int userid) {
        this.userid = userid;
    }
    @Override
    public String toString() {
        return "Orders [id=" + id + ", name=" + name + ", price=" + price + ", userid=" + userid + "]";
    }
}

UserDao.java

public interface UserDao {
    // 選擇用戶及其對應的訂單
    public List<User> selectUsersAndOrders();
}

UserDao.xml

<mapper  namespace="com.lanou.dao.UserDao">

    <resultMap type="User" id="UserMap" autoMapping="true">
        <result property="id" column="u_id"/>
        <result property="name" column="u_name"/>
        <collection property="orders" autoMapping="true" ofType="Orders">
            <result property="name" column="o_name"/>
            <result property="id" column="o_id"/>
        </collection>
    </resultMap>


    <select id="selectUsersAndOrders" resultMap="UserMap">
        SELECT *,
        User.id as u_id,
        User.name as u_name,
        Orders.name as o_name,
        Orders.id as o_id
        FROM User left join Orders 
        ON User.id = Orders.userid
    </select>
</mapper>

MybatisTest.java

public class MybatisTest {
    @Test
    public void test3() throws IOException {
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = builder.build(inputStream);
        SqlSession session = factory.openSession();
        UserDao dao = session.getMapper(UserDao.class);
        List<User> list = dao.selectUsersAndOrders();
        for (User user : list) {
            System.out.println(user);
        }
    }
}

一對一查詢

一個員工可以有多張訂單 一張訂單對應一個員工 從員工角度看 員工與訂單是一對多關係
從訂單角度看 訂單與員工是一對一關係 即一張訂單對應一個員工 

實現:獲取訂單時 自動獲取user
創建映射文件 添加方法用來獲取所有訂單數據

Orders.java

public class Orders {
    private int id;
    private String name;
    private double price;
    private int userid;
    private User user;


    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public int getUserid() {
        return userid;
    }
    public void setUserid(int userid) {
        this.userid = userid;
    }
    @Override
    public String toString() {
        return "Orders [id=" + id + ", name=" + name + ", price=" + price + ", userid=" + userid + ", user=" + user
                + "]";
    }
}

OrderDao.java

public interface OrderDao {
    public List<Orders> selectAllOrdersAndUser();
}

OrderDao.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.lanou.dao.OrderDao">
    <resultMap type="Orders" id="OrdersMap" autoMapping="true">
        <result property="id" column="o_id"/>
        <result property="name" column="o_name"/>
        <association property="user" autoMapping="true" javaType="User">
            <result property="id" column="u_id"/>
            <result property="name" column="u_name"/>
        </association>
    </resultMap>

    <select id="selectAllOrdersAndUser" resultMap="OrdersMap">
        select *,
        Orders.id as o_id,
        Orders.name as o_name,
        User.id as u_id,
        User.name as u_name
        from Orders left join
        User on Orders.userid = User.id
    </select>
</mapper>

MybatisTest2.java

public class MybatisTest2 {
    @Test
    public void test3() throws IOException {
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = builder.build(inputStream);
        SqlSession session = factory.openSession();
        OrderDao dao = session.getMapper(OrderDao.class);
        List<Orders> list = dao.selectAllOrdersAndUser();
        for (Orders orders : list) {
            System.out.println(orders);
        }
    }
}

多對多

現有group和user
  需求 查詢user同時查詢相關的groups
  需求 查詢groups 同時查詢相關的user

建立user表 建立groups表 兩表之間的聯繫是一張中間表

Groups.java

package com.lanou.bean;

import java.util.List;

public class Groups {
    private int g_id;
    private String g_name;
    private String g_msg;
    private String g_manager;

    private List<User> users;

    public int getG_id() {
        return g_id;
    }

    public void setG_id(int g_id) {
        this.g_id = g_id;
    }

    public String getG_name() {
        return g_name;
    }

    public void setG_name(String g_name) {
        this.g_name = g_name;
    }

    public String getG_msg() {
        return g_msg;
    }

    public void setG_msg(String g_msg) {
        this.g_msg = g_msg;
    }

    public String getG_manager() {
        return g_manager;
    }

    public void setG_manager(String g_manager) {
        this.g_manager = g_manager;
    }

    public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }

    @Override
    public String toString() {
        return "groups [g_id=" + g_id + ", g_name=" + g_name + ", g_msg=" + g_msg + ", g_manager=" + g_manager
                + ", users=" + users + "]";
    }
}

User.java

package com.lanou.bean;

import java.util.List;

public class User {
    private int id;
    private String name;
    private String password;
    private String sex;
    private List<Groups> groups;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public List<Groups> getGroups() {
        return groups;
    }
    public void setGroups(List<Groups> groups) {
        this.groups = groups;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", password=" + password + ", sex=" + sex + ", groups=" + groups
                + "]";
    }

}

UserDao.java

public interface UserDao {
    // 選擇用戶及其對應的羣組
    public List<User> selectUsersAndGroups();
}

UserDao.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.lanou.dao.UserDao">

    <resultMap type="User" id="UserMap" autoMapping="true">
        <result property="id" column="id"/>
        <collection property="groups" autoMapping="true" ofType="Groups">
        </collection>
    </resultMap>
    <select id="selectUsersAndGroups" resultMap="UserMap">
        select *
        from user 
        left join u_r_g on user.id = u_r_g.uid
        left join groups on u_r_g.gid = groups.g_id
    </select>
</mapper>

MybatisTest3.java

public void test3() throws IOException {
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
     UserDao dao = session.getMapper(UserDao.class);
     List<User> user = dao.selectUsersAndGroups();
     for (User user2 : user) {
        System.out.println(user2);
    }
}

Groups對User

groupsDao.java

public interface groupsDao {
    // 獲取所有羣組和對應的用戶
    public List<Groups> selectAllGroups();
}

groupsDao.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.lanou.dao.groupsDao">
    <resultMap type="Groups" id="GroupsMap" autoMapping="true">
        <result property="id" column="id"/>
        <collection property="users" ofType="User" autoMapping="true">  
        </collection>
    </resultMap>

    <select id="selectAllGroups" resultMap="GroupsMap">
        select * FROM
        groups left join u_r_g on groups.g_id = u_r_g.gid
        left join user on u_r_g.uid = user.id
    </select>
</mapper>

MybatisTestnVnTest3.java

public class MybatisTestnVnTest3 {
    @Test
    public void testFun1() throws IOException{
        // 構建器
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        // 讀取配置文件
        InputStream input = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 1.獲取會話工廠
        SqlSessionFactory factory = builder.build(input);
        // 2.獲取會話
        SqlSession session = factory.openSession();
        // 3.crud
        groupsDao mapper = session.getMapper(groupsDao.class);
        List<Groups> groups = mapper.selectAllGroups();
        for (Groups groups2 : groups) {
            System.out.println(groups2);
        }

    }
}

Mybatis進階之表之間的關係

Mybatis

根據ID查找對象

User.java

根據ID查找對象

UserDao.xml

MybatisTest.java

使用包裝類

UserDataObj.java

UserDao.java

UserDao.xml

MybatisTest.java

標籤根據多個id查詢一堆user

UserDao.java

UserDao.xml

MybatisTest.java

將參數Integer[]改爲List

UserDao.java

UserDao.xml

MybatisTest.java

常用標籤

條件判斷

UserDao.java

UserDao.xml

UserDao.xml

where標籤

sql標籤

一對多查詢

user類

Orders.java

UserDao.java

UserDao.xml

MybatisTest.java

一對一查詢

Orders.java

OrderDao.java

OrderDao.xml

MybatisTest2.java

多對多

Groups.java

User.java

UserDao.java

UserDao.xml

MybatisTest3.java

Groups對User

groupsDao.java

groupsDao.xml

MybatisTestnVnTest3.java