MyBatis使用總結和整合Spring

MyBatis 本是apache的一個開源項目iBatis, 2010年這個項目由apache software foundation 遷移到了google code，並且改名為MyBatis 。2013年11月遷移到Github。iBATIS一詞來源於“internet”和“abatis”的組合，是一個基於Java的持久層框架。

MyBatis是支持普通SQL查詢，存儲過程和高級映射的優秀持久層框架。MyBatis消除了幾乎所有的JDBC代碼和參數的手工設置以及對結果集的檢索封裝。MyBatis可以使用簡單的XML或注解用於配置和原始映射，將接口和Java的POJO（Plain Old Java Objects，普通的Java對象）映射成數據庫中的記錄。

1 第一個MyBatis程序

　　首先需要加入需要的jar包，構建Spring環境請參考：Spring學習之第一個hello world程序。見  http://www.linuxidc.com/Linux/2016-05/131391.htm    這裡我們需要加入mybatis包和MySQL驅動包，使用IDEA環境來開發程序，最後工程加入的包如下圖所示：

　　然後需要在test數據庫中新建測試表user，sql語句如下所示：

create table users (
    id int primary key auto_increment,
    name varchar(20),
    age int
);
insert into users (name, age) values('Tom', 12);
insert into users (name, age) values('Jack', 11);

1.1 定義表對應的實體類

public class User {

    private int id;
    private String name;
    private int age;

    public User() { }

    public User(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

1.2 定義MyBatista的mybatisConfig.xml配置文件和user表的sql映射文件userMapper.xml

mybatisConfig.xml文件，該文件是在src目錄下新建的。

<?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>
<environments default="development">
    <!-- development:開發環境 work:工作模式 -->
    <environment id="development">
        <transactionManager type="JDBC" />
        <!-- 數據庫連接方式 -->
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver" />
            <property name="url" value="jdbc:mysql://192.168.1.150/test" />
            <property name="username" value="root" />
            <property name="password" value="123456" />
        </dataSource>
    </environment>
</environments>

<!-- 注冊表映射文件 -->
<mappers>
    <mapper resource="com/mybatis/userMapper.xml"/>
</mappers>

</configuration>

 

userMapper.xml文件，該配置文件在com.mybatis包下，user表對應的實體類User也在com.mybatis包下。

<?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.mybatis.userMapper">
    <!-- 根據id查詢一個User對象 -->
    <select id="getUser" parameterType="int" resultType="com.mybatis.User">
        select * from users where id=#{id}
    </select>
    <select id="getUserAll" resultType="com.mybatis.User">
        select * from users
    </select>

    <!-- 插入一個User對象 -->
    <insert id="insertUser" parameterType="com.mybatis.User">
        insert into users (name, age) value(#{name}, #{age})
    </insert>

    <!-- 刪除一個User對象 -->
    <delete id="deleteUser" parameterType="int">
        delete from users where id=#{id}
    </delete>

    <!-- 更新一個User對象-->
    <update id="updateUser" parameterType="com.mybatis.User">
        update users set name=#{name}, age=#{age} where id=#{id}
    </update>
</mapper>

測試代碼如下：

public class mybaitstest {

    SqlSessionFactory sessionFactory = null;
    SqlSession sqlSession = null;

    {
        String resource = "mybatisConfig.xml";
        // 加載mybatis的配置文件（它也加載關聯的映射文件）
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 構建sqlSession的工廠
        sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 創建能執行映射文件中sql的sqlSession，默認是手動提交事務的，使用自動提交的話加上參數 true
        sqlSession = sessionFactory.openSession(true);
    }

    public void testSelectUser() {
        // 映射sql的標識字符串
        String statement = "com.mybatis.userMapper" + ".getUser";
        // 執行查詢返回一個唯一user對象的sql
        User user = sqlSession.selectOne(statement, 1);
        System.out.println(user);
    }

    public void testSelectAll() {
        List<User> users = sqlSession.selectList("com.mybatis.userMapper.getUserAll");
        System.out.println(users);
    }

    public void testInsertUser(User user) {
        int insert = sqlSession.insert("com.mybatis.userMapper.insertUser", user);
        // 如果不是自動提交的話，需要使用 sqlSession。commit()
        System.out.println(insert);
    }

    public void testDeleteUser(int id) {
        int delete = sqlSession.delete("com.mybatis.userMapper.deleteUser", id);
        System.out.println(delete);
    }

    public void testUpdateUser(User user) {
        int update = sqlSession.update("com.mybatis.userMapper.updateUser", user);
        System.out.println(update);
    }

    public static void main(String[] args) throws IOException {

        new mybaitstest().testSelectUser();
    }
}

最後輸出結果為：

Spring中如何配置Hibernate事務 http://www.linuxidc.com/Linux/2013-12/93681.htm

Struts2整合Spring方法及原理 http://www.linuxidc.com/Linux/2013-12/93692.htm

基於 Spring 設計並實現 RESTful Web Services http://www.linuxidc.com/Linux/2013-10/91974.htm

Spring-3.2.4 + Quartz-2.2.0集成實例 http://www.linuxidc.com/Linux/2013-10/91524.htm

使用 Spring 進行單元測試 http://www.linuxidc.com/Linux/2013-09/89913.htm

運用Spring注解實現Netty服務器端UDP應用程序 http://www.linuxidc.com/Linux/2013-09/89780.htm

Spring 3.x 企業應用開發實戰 PDF完整高清掃描版+源代碼 http://www.linuxidc.com/Linux/2013-10/91357.htm

2 基於注解的方式使用MyBatis

　　基於注解的方式使用MyBatis，首先定義對應表的sql映射接口。

public interface IUserMapper {

    @Insert("insert into users (name, age) value(#{name}, #{age})")
    public int add(User user);

    @Delete("delete from users where id=#{id}")
    public int deleteById(int id);

    @Update("update users set name=#{name}, age=#{age} where id=#{id}")
    public int update(User user);

    @Select("select * from users where id=#{id}")
    public User getById(int id);

    @Select("select * from users")
    public List<User> getAll();
}

　　然後在mybatisConfig.xml配置文件中注冊該接口：

<!-- 注冊表映射文件 -->
<mappers>
    <mapper class="com.mybatis.IUserMapper"/>
</mappers>

測試示例：

/**
 * 使用注解測試的方法
 */
public void test() {
    IUserMapper userMapper = sqlSession.getMapper(IUserMapper.class);

    User user = userMapper.getById(1);
    System.out.println(user);
} 

3 如何簡化配置操作

　　以上兩個程序示例都是直接在配置文件中寫連接數據庫的信息，其實還可以專門把數據庫連接信息寫到一個db.proteries文件中，然後由配置文件來讀取該db.properies文件信息。db.proteries文件內容如下：

user=root
password=123456
driverClass=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql://192.168.1.150/test

　　然後在mybatisConfig.xml配置文件中將數據庫環境信息更改為如下所示：

<properties resource="db.properties"/>

<environments default="development">
    <!-- development:開發環境 work:工作模式 -->
    <environment id="development">
        <transactionManager type="JDBC" />
        <!-- 數據庫連接方式 -->
        <dataSource type="POOLED">
            <property name="driver" value="${driverClass}" />
            <property name="url" value="${jdbcUrl}" />
            <property name="username" value="${user}" />
            <property name="password" value="${password}" />
        </dataSource>
    </environment>
</environments>

　　配置表對應的sql映射文件時，可以使用別名來簡化配置，在mybatisConfig.xml中添加如下配置，在userMapper中parameterType就可以配置為"_User"。

<typeAliases>
    <typeAlias type="com.mybatis.User" alias="_User"/>
</typeAliases>

 

4 字段名與實體類屬性名不匹配的沖突

　　新建表和數據，在test數據庫中執行以下SQL語句：

create table orders (
    order_id int primary key auto_increment,
    order_no varchar(20),
    order_price float
);
insert into orders (order_no, order_price) values('aaa', 12);
insert into orders (order_no, order_price) values('bbb', 13);
insert into orders (order_no, order_price) values('ccc', 14);

 

　　創建對應表的類：

public class Order {

    private int i;
    private String no;
    private float price;

    public Order() { }

    public Order(int i, String no, float price) {
        this.i = i;
        this.no = no;
        this.price = price;
    }

    public int getI() {
        return i;
    }

    public void setI(int i) {
        this.i = i;
    }

    public String getNo() {
        return no;
    }

    public void setNo(String no) {
        this.no = no;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }
}

　　mybaitsConfig.xml配置如下：

 

<?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>

    <properties resource="db.properties"/>

    <typeAliases>
        <typeAlias type="com.mybatis.Order" alias="Order"/>
    </typeAliases>

    <environments default="development">
        <!-- development:開發環境 work:工作模式 -->
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 數據庫連接方式 -->
            <dataSource type="POOLED">
                <property name="driver" value="${driverClass}" />
                <property name="url" value="${jdbcUrl}" />
                <property name="username" value="${user}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>

    <!-- 注冊表映射文件 -->
    <mappers>
        <mapper resource="com/mybatis/orderMapper.xml"/>
    </mappers>

</configuration>

 

　　接下來配置orderMapper.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.mybatis.orderMapper">

    <!-- 根據id查詢一個Order對象 -->
    <select id="getOrder" parameterType="int" resultType="Order">
      SELECT order_id id, order_no no, order_price price FROM orders WHERE order_id=#{id}
    </select>

    <!-- 這種解決字段與屬性沖突方式較常用 -->
    <select id="getOrder2" parameterType="int" resultType="Order" resultMap="getOrder2Map">
        SELECT * FROM orders WHERE order_id=#{id}
    </select>
    <!--
        resultMap 封裝映射關系
            id    專門針對主鍵
            result 針對一般字段
    -->
    <resultMap id="getOrder2Map" type="Order">
        <id property="id" column="order_id"/>
        <result property="no" column="order_price"/>
        <result property="price" column="order_price"/>
    </resultMap>

</mapper>

View Code

測試用例：

public class MyBaitsMain {
    SqlSessionFactory sessionFactory = null;
    SqlSession sqlSession = null;

    {
        String resource = "mybatisConfig.xml";
        // 加載mybatis的配置文件（它也加載關聯的映射文件）
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 構建sqlSession的工廠
        sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 創建能執行映射文件中sql的sqlSession，默認是手動提交事務的，使用自動提交的話加上參數 true
        sqlSession = sessionFactory.openSession(true);
    }

    public static void main(String[] args) {
        String statement = "com.mybatis.orderMapper.getOrder";
        String statement2 = "com.mybatis.orderMapper.getOrder2";

        Order order = new MyBaitsMain().sqlSession.selectOne(statement, 2);
        System.out.println(order);
        order = new MyBaitsMain().sqlSession.selectOne(statement2, 2);
        System.out.println(order);
    }
}

輸出結果為：

5 實現關聯表查詢

5.1 一對一關聯

　　這裡實現班級id查詢班級信息，班級信息中包括老師信息。首先創建表結構：

 

CREATE TABLE teacher(
    t_id INT PRIMARY KEY AUTO_INCREMENT, 
    t_name VARCHAR(20)
);
CREATE TABLE class(
    c_id INT PRIMARY KEY AUTO_INCREMENT, 
    c_name VARCHAR(20), 
    teacher_id INT
);
ALTER TABLE class ADD CONSTRAINT fk_teacher_id FOREIGN KEY (teacher_id) REFERENCES teacher(t_id);    

INSERT INTO teacher(t_name) VALUES('LS1');
INSERT INTO teacher(t_name) VALUES('LS2');

INSERT INTO class(c_name, teacher_id) VALUES('bj_a', 1);
INSERT INTO class(c_name, teacher_id) VALUES('bj_b', 2);

View Code

　　定義表對應的實體類：

public class Teacher {

    private int id;
    private String name;

    public Teacher() {
    }

    public Teacher(int id, String name) {
        this.id = id;
        this.name = name;
    }

    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;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

Teacher類

public class Classes {

    private int id;
    private String name;
    private Teacher teacher;

    public Classes() {
    }

    public Classes(int id, String name, Teacher teacher) {
        this.id = id;
        this.name = name;
        this.teacher = teacher;
    }

    public int getId() {
        return id;
    }

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

    public Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Classes{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", teacher=" + teacher +
                '}';
    }
}

Classes類

　　定義sql映射文件，需要在mybatisConfig.xml中注冊該表映射文件。

<?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.mybatis.classesMapper">

    <!-- 根據班級id查詢班級信息（包括老師信息） -->
    <select id="getClasses" parameterType="int" resultMap="ClassesMap">
        SELECT * FROM class c, teacher t WHERE c.teacher_id = t.t_id and c.c_id = #{id}
    </select>
    <!-- 聯表查詢 -->
    <resultMap id="ClassesMap" type="com.mybatis.Classes">
        <id property="id" column="c_id"/>
        <result property="name" column="c_name"/>
        <association property="teacher" column="teacher_id" javaType="com.mybatis.Teacher">
            <id property="id" column="t_id"/>
            <result property="name" column="t_name"/>
        </association>
    </resultMap>

    <!-- 嵌套查詢 -->
    <select id="getClasses2" parameterType="int" resultMap="ClassesMap2">
        SELECT * FROM class WHERE c_id=#{id}
    </select>
    <select id="getTeacher" parameterType="int" resultType="com.mybatis.Teacher">
        SELECT t_id id, t_name  FROM teacher WHERE t_id=#{id}
    </select>
    <resultMap id="ClassesMap2" type="com.mybatis.Classes">
        <id property="id" column="c_id"/>
        <result property="name" column="c_name"/>
        <association property="teacher" column="teacher_id" select="getTeacher">
        </association>
    </resultMap>

</mapper>

classesMapper.xml文件

測試類：

public class MyBaitsMain {
    SqlSessionFactory sessionFactory = null;
    SqlSession sqlSession = null;

    {
        String resource = "mybatisConfig.xml";
        // 加載mybatis的配置文件（它也加載關聯的映射文件）
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 構建sqlSession的工廠
        sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 創建能執行映射文件中sql的sqlSession，默認是手動提交事務的，使用自動提交的話加上參數 true
        sqlSession = sessionFactory.openSession(true);
    }

    public static void main(String[] args) {

        String statement = "com.mybatis.classesMapper.getClasses";
        String statement2 = "com.mybatis.classesMapper.getClasses2";

        Classes classes = new MyBaitsMain().sqlSession.selectOne(statement, 1);
        System.out.println(classes);
        classes = new MyBaitsMain().sqlSession.selectOne(statement2, 1);
        System.out.println(classes);
    }
}

MyBatisMain測試類

輸出結果：

5.2 一對多關聯

　　這裡實現班級id查詢班級信息，班級信息中包括老師信息和學生信息。首先創建表結構：

CREATE TABLE student(
    s_id INT PRIMARY KEY AUTO_INCREMENT, 
    s_name VARCHAR(20), 
    class_id INT
);
INSERT INTO student(s_name, class_id) VALUES('xs_A', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_B', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_C', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_D', 2);
INSERT INTO student(s_name, class_id) VALUES('xs_E', 2);
INSERT INTO student(s_name, class_id) VALUES('xs_F', 2);

　　定義表對應的實體類：

public class Student {

    private int id;
    private String name;

    public Student(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public Student() {
    }

    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;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}Student類

　　定義sql映射文件，需要在mybatisConfig.xml中注冊該表映射文件。

 

<?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.mybatis.classesMapper2">

    <select id="getClasses" parameterType="int" resultMap="ClassesMap">
        SELECT * FROM class c, student s, teacher t WHERE c.c_id=s.class_id AND c.c_id=#{id}
    </select>
    <resultMap id="ClassesMap" type="com.mybatis.Classes">
        <id property="id" column="c_id"/>
        <result property="name" column="c_name"/>
        <association property="teacher" javaType="com.mybatis.Teacher">
            <id property="id" column="t_id"/>
            <result property="name" column="t_name"/>
        </association>
        <!--
            collection: 做一對多關聯查詢的
                ofType: 指定集合中元素對象的類型
        -->
        <collection property="students" ofType="com.mybatis.Student">
            <id property="id" column="s_id"/>
            <result property="name" column="s_name"/>
        </collection>
    </resultMap>

    <!-- 第二種方式 -->
    <select id="getClasses2" resultMap="ClassesMap2">
        SELECT * FROM class WHERE c_id=#{id}
    </select>
    <select id="getTeacher" resultType="com.mybatis.Teacher">
        SELECT t_id id, t_name name FROM teacher WHERE  t_id=#{id}
    </select>
    <select id="getStudent" resultType="com.mybatis.Student">
        SELECT s_id id, s_name name FROM student WHERE  class_id=#{id}
    </select>
    <resultMap id="ClassesMap2" type="com.mybatis.Classes">
        <id property="id" column="c_id"/>
        <result property="name" column="c_name"/>
        <association property="teacher" column="teacher_id" select="getTeacher">
        </association>
        <collection property="students" column="c_id" select="getStudent">
        </collection>
    </resultMap>

</mapper>

classesMapper2.xml文件

　　測試類：

 

public class MyBaitsMain {
    SqlSessionFactory sessionFactory = null;
    SqlSession sqlSession = null;

    {
        String resource = "mybatisConfig.xml";
        // 加載mybatis的配置文件（它也加載關聯的映射文件）
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 構建sqlSession的工廠
        sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 創建能執行映射文件中sql的sqlSession，默認是手動提交事務的，使用自動提交的話加上參數 true
        sqlSession = sessionFactory.openSession(true);
    }

    public static void main(String[] args) {

        String statement = "com.mybatis.classesMapper2.getClasses";
        String statement2 = "com.mybatis.classesMapper2.getClasses2";

        Classes classes = new MyBaitsMain().sqlSession.selectOne(statement, 1);
        System.out.println(classes);
        classes = new MyBaitsMain().sqlSession.selectOne(statement2, 1);
        System.out.println(classes);
    }
}

MyBaitsMain測試類

輸出結果：

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