mybatis

1最原始的mybatis使用方式

核心配置文件sqlMapConfig.xml文件

还要注意每个sqlMapConfig.xml文件中的标签的顺序,比如下面的就必须properties放在typeAliases前面

properties>settings>typeAliases>typeHandlers>objectFactory>objectWrapperFactory>plugins>environments>databaseIdProvider>mappers

<configuration>
<properties resource="jdbc.properties"/>   //使用properties文件避免硬编码问题
<typeAliases>
    <package name="com.wang.mybatis.pojo"/>   //设置别名,对应pojo的mapper类就不用指定类的全路径名,直接写类的名字就可以了,而且不区分大小写
</typeAliases>
<!-- 和spring整合后 environments配置将废除 -->
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理 -->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}" />
                <property name="url"
                    value="${url}" />
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <mapper resource="sqlmap/User.xml"/>
    </mappers>
</configuration>

usermapper.xml文件每个小的mapper.xml文件配置对应的一种pojo

在里面编写对应的pojo操作

<mapper namespace="user">
    <select id="finduerbyid" parameterType="Integer" resultType="User">
        select * from user where ID=#{v}
    </select>
    
    <select id="finduserbyname" parameterType="String" resultType="com.wang.mybatis.pojo.User">
        select * from user where name=#{v}
    </select>
    <select id="finduser" parameterType="String" resultType="com.wang.mybatis.pojo.User">
        SELECT * FROM user WHERE name LIKE "%"#{vaue}"%"
    </select>
    <!-- 插入数据并且返回其id -->
    <insert id="insertuser" parameterType="com.wang.mybatis.pojo.User">    
        insert into user(name,age,sex,birthday) values(#{name},#{age},#{sex},#{birthday})
        <selectKey keyProperty="ID" resultType="Integer" order="AFTER">
            select LAST_INSERT_ID()
        </selectKey>
    </insert>
    
    <update id="updateuser" parameterType="com.wang.mybatis.pojo.User">
        update user
        set name=#{name},sex=#{sex},age=#{age},birthday=#{birthday}
        where id=7{#ID}
    </update>
    
    
    <delete id="deleteuser" parameterType="Integer">
        delete from user where ID=#{v}
    </delete>
    
</mapper>

本例中的pojo示例,需要实现get和set方法,这样才能实现对数据库的操作

public class User implements Serializable{       //注意实现序列化接口
    String name;
    int age;
    String sex;
    Date birthday;
    int ID;
    
    public int getID() {
        return ID;
    }
    public void setID(int iD) {
        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;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + ", sex=" + sex + ", birthday=" + birthday + "]";
    }
}

最后Junit测试

@Test
    public void fun() throws IOException {
        
        //加载核心配置文件
        String resource="SqlMapConfig.xml" ;
        InputStream in=Resources.getResourceAsStream(resource);
        //获得工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //打开会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行mapper(写好的sql语句)
        User user = sqlSession.selectOne("user.finduerbyid", 1);   //找对应的mapper.xml文件,即user(namespace).finduserbyid(对应的sql语句)
        System.out.println(user);
        User user2 = sqlSession.selectOne("user.finduserbyname", "小王");
        System.out.println(user2);
        
        List<User> userlist = sqlSession.selectList("user.finduser", "小");
        for (User user3 : userlist) {
            System.out.println(user3);
        }

上面的test只是简单的测试，如果在dao开发中需要在每个dao实现类中声明sqlsessionfactory等一系列步骤，这样dao开发就会变得麻烦。所以下面的动态代理开发简化上面的步骤

---

mapper动态代理开发

四大原则:

1接口名称和mapper.xml文件中的namespace一致

2接口中方法名称和mapper文件中定义的操作语句的id一样

3接口中方法名称和mapper文件中定义的操作语句入参一致

4接口中方法名称和mapper文件中定义的操作语句返回值一致

sqlMapConfig.xml文件

<configuration>
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理 -->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url"
                    value="jdbc:mysql://localhost:3306/hello?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <!-- <mapper resource="SqlMap/User.xml"/> -->
        <package name="com.wang.pojo"/>    <!-- 如果含有多个mapper文件就指定扫描包 -->
    </mappers>

当含有多个mapper.xml文件时候（尽量放在一起）可以指定扫描包的形式

对应接口和

public interface UserMapper {
    public User FindUserByID(Integer i);
    public Integer count();
    public List<User> SelectAll();
}

mapper.xml文件

<mapper namespace="com.wang.pojo.UserMapper">
    <select id="FindUserByID" parameterType="Integer" resultType="com.wang.pojo.User">
        SELECT *FROM USER WHERE ID=#{v};
    </select>
    <select id="count" resultType="Integer">
        SELECT COUNT(1) FROM USER
    </select>
    <select id="SelectAll" resultType="com.wang.pojo.User">
        SELECT * FROM USER
    </select>
</mapper>

pojo和上面的一样，这里就不在写上

最后测试

    @Test
    public void testName() throws Exception {
        String Resource    ="SqlMapConfig.xml";
        //弄成输入流
        InputStream in = Resources.getResourceAsStream(Resource);
        //用builder创建sqlsession工厂
         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
         //打开会话
         SqlSession sqlSession = sqlSessionFactory.openSession();
         //获得接口
         UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
         //执行接口中的方法
         User user=userMapper.FindUserByID(3);
         System.out.println(user);
         System.out.println(userMapper.count());
         List<User> users=userMapper.SelectAll();
         for (User user2 : users) {
            System.out.println(user2);
        }    
    }

前者使用sqlSession直接操作，后者用sqlSession获得接口，使用接口操作