使用mybatis开发原始Dao层

　　本文将介绍使用框架mybatis开发原始dao层来对一个对数据库进行增删改查的案例。

　　本次使用的mybatis版本为mybatis-3.2.7，开发工具为eclipse，数据库为mysql，jdk版本jdk1.8.0_151。

　　1、首先，使用eclipse新建一个java工程，在lib目录下加入mybatis核心包、依赖包、数据驱动包，然后buildpath一下。。

　　

　　2、添加日志文件，在classpath下创建log4j.properties如下：

# global logging configuration
log4j.rootlogger=debug, stdout
# console output...
log4j.appender.stdout=org.apache.log4j.consoleappender
log4j.appender.stdout.layout=org.apache.log4j.patternlayout
log4j.appender.stdout.layout.conversionpattern=%5p [%t] - %m%n

　　3、在classpath下创建config资源文件夹，并在config文件夹下创建sqlmapconfig.xml，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>
    <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/mybatis?characterencoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </datasource>
        </environment>
    </environments>
</configuration>

　　sqlmapconfig.xml是mybatis核心配置文件，上边文件的配置内容为数据源、事务管理。

　　4、创建数据封装使用的user类

package com.xyfer.po;

import java.util.date;
/**
 * 
 * @author xyfer
 * 数据封装使用的user类
 *
 */
public class user {
    
    private int       id;          //id
    private string    username;    //姓名
    private string    sex;         //性别
    private date      birthday;    // 生日
    private string    address;     // 地址
    public int getid() {
        return id;
    }
    public void setid(int id) {
        this.id = id;
    }
    public string getusername() {
        return username;
    }
    public void setusername(string username) {
        this.username = username;
    }
    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;
    }
    public string getaddress() {
        return address;
    }
    public void setaddress(string address) {
        this.address = address;
    }

}

　　5、在classpath下的资源文件夹sqlmapper目录下创建sql映射文件user.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="test">
    <!-- 根据id查询用户 -->
    <select id="finduserbyid" parametertype="int" resulttype="com.xyfer.po.user">
        select * from user where id = #{id}
    </select>
    <!-- 添加用户 -->
    <insert id="insertuser" parametertype="com.xyfer.po.user">
    <selectkey keyproperty="id" order="after" resulttype="java.lang.integer">
        select last_insert_id() 
    </selectkey>
      insert into user(username,birthday,sex,address) 
      values(#{username},#{birthday},#{sex},#{address})
    </insert>
    <!-- 修改用户 -->
    <update id="updateuser" parametertype="com.xyfer.po.user">
        update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
        where id=#{id}
    </update>
    <!-- 删除用户 -->
    <delete id="deleteuserbyid" parametertype="int">
        delete from user where id=#{id}
    </delete>
    
</mapper>

 

　　6、mybatis框架需要加载映射文件，将users.xml添加在sqlmapconfig.xml，如下：

<mappers>
        <mapper resource="user.xml"/>
</mappers>

　　7、dao层接口

package com.xyfer.dao;

import com.xyfer.po.user;

public interface userdao {

    public user getuserbyid(int id);   //根据id值查询一个用户
    public void insertuser(user user); //新增一个用户
    public void updateuser(user user); //修改一个用户
    public void deleteuser(int id);    //删除一个用户
    
}

　　dao层接口实现类

package com.xyfer.dao.impl;

import org.apache.ibatis.session.sqlsession;
import org.apache.ibatis.session.sqlsessionfactory;

import com.xyfer.dao.userdao;
import com.xyfer.po.user;

public class userdaoimpl implements userdao {
    //注入sqlsessionfactory
    public userdaoimpl(sqlsessionfactory sqlsessionfactory){
            this.setsqlsessionfactory(sqlsessionfactory);
        }
            
    private sqlsessionfactory sqlsessionfactory;
        
    public sqlsessionfactory getsqlsessionfactory() {
        return sqlsessionfactory;
    }

    public void setsqlsessionfactory(sqlsessionfactory sqlsessionfactory) {
        this.sqlsessionfactory = sqlsessionfactory;
    }

    @override
    public user getuserbyid(int id) {
        sqlsession session = sqlsessionfactory.opensession();
        user user = null;
        try {
            //通过sqlsession调用selectone方法获取一条结果集
            //参数1：指定定义的statement的id,参数2：指定向statement中传递的参数
            user = session.selectone("test.finduserbyid", 1);
            system.out.println(user);
                        
        } finally{
            session.close();
        }
        return user;
    }

    @override
    public void insertuser(user user) {
        sqlsession sqlsession = sqlsessionfactory.opensession();
        try {
            sqlsession.insert("test.insertuser", user);
            sqlsession.commit();
        } finally{
            sqlsession.close();
        }
    }

    @override
    public void updateuser(user user) {
        sqlsession sqlsession = sqlsessionfactory.opensession();
        try {
            sqlsession.update("test.updateuser", user);
            sqlsession.commit();
        } finally{
            sqlsession.close();
        }
    }

    @override
    public void deleteuser(int id) {
        sqlsession sqlsession = sqlsessionfactory.opensession();
        try {
            sqlsession.update("test.deleteuserbyid", id);
            sqlsession.commit();
        } finally{
            sqlsession.close();
        }
    }

}

　　8、创建一个junit的测试类，对userdao进行测试。

package com.xyfer.dao.impl;

import static org.junit.assert.*;

import java.io.inputstream;
import java.util.date;

import org.apache.ibatis.io.resources;
import org.apache.ibatis.session.sqlsessionfactory;
import org.apache.ibatis.session.sqlsessionfactorybuilder;
import org.junit.before;
import org.junit.test;

import com.xyfer.dao.userdao;
import com.xyfer.po.user;

public class userdaoimpltest {

    private sqlsessionfactory sqlsessionfactory;
    
    @before
    public void init() throws exception {
        sqlsessionfactorybuilder sessionfactorybuilder = new sqlsessionfactorybuilder();
        inputstream inputstream = resources.getresourceasstream("sqlmapconfig.xml");
        sqlsessionfactory = sessionfactorybuilder.build(inputstream);
    }

    @test
    public void testgetuserbyid() {
        userdao userdao = new userdaoimpl(sqlsessionfactory);
        user user = userdao.getuserbyid(22);
        system.out.println(user);
    }

    @test
    public void testinsertuser() {
        user user = new user();
        user.setusername("小李");
        user.setsex("男");
        user.setbirthday(new date());
        user.setaddress("杭州市");
        userdao userdao = new userdaoimpl(sqlsessionfactory);
        userdao.insertuser(user);
    }

    @test
    public void testupdateuser() {
        user user = new user();
        user.setid(10);
        user.setusername("小威");
        user.setsex("男");
        user.setbirthday(new date());
        user.setaddress("杭州市");
        userdao userdao = new userdaoimpl(sqlsessionfactory);
        userdao.updateuser(user);
    }

    @test
    public void testdeleteuser() {
        userdao userdao = new userdaoimpl(sqlsessionfactory);
        userdao.deleteuser(10);
    }

}

　　以上步骤，完成使用mybatis框架开发原始dao层，并对数据库进行增删改查操作。

　　需要注意的是，上文提到的config文件夹和sqlmapper文件夹均为资源文件夹（source folder），默认会加载该路径下的文件。