Mybatis实现数据的增删改查实例（CRUD）

什么是 mybatis？

mybatis 是支持普通 sql 查询，存储过程和高级映射的优秀持久层框架。 mybatis 消除了几乎所有的 jdbc 代码和参数的手工设置以及对结果集的检索。mybatis 可以使用简单的xml 或注解用于配置和原始映射，将接口和 java 的 pojo（plain old java objects，普通的java对象）映射成数据库中的记录。

mybatis下载：

mybatis实例

对一个user表的crud操作：

user表：

-- ----------------------------
-- table structure for `user`
-- ----------------------------
drop table if exists `user`;
create table `user` (
 `id` int(11) not null auto_increment,
 `username` varchar(50) default null,
 `userage` int(11) default null,
 `useraddress` varchar(200) default null,
 primary key (`id`)
) engine=innodb auto_increment=6 default charset=utf8;

-- ----------------------------
-- records of user
-- ----------------------------
insert into `user` values ('1', 'summer', '30', 'shanghai');
insert into `user` values ('2', 'test2', '22', 'suzhou');
insert into `user` values ('3', 'test1', '29', 'some place');
insert into `user` values ('4', 'lu', '28', 'some place');
insert into `user` values ('5', 'xiaoxun', '27', 'nanjing');

在src目录下建一个mybatis的xml配置文件configuration.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>
  <!-- mybatis别名定义 -->
  <typealiases> 
    <typealias alias="user" type="com.mybatis.test.user"/> 
  </typealiases> 

  <environments default="development">
    <environment id="development">
    <transactionmanager type="jdbc"/>
      <datasource type="pooled">
      <property name="driver" value="com.mysql.jdbc.driver"/>
      <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis" />
      <property name="username" value="root"/>
      <property name="password" value="admin"/>
      </datasource>
    </environment>
  </environments>
  
  <!-- mybatis的mapper文件，每个xml配置文件对应一个接口 -->
  <mappers>
    <mapper resource="com/mybatis/test/user.xml"/>
  </mappers>
</configuration>

定义user mappers的user.xml配置文件

<?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.test.iuseroperation">

  <!-- select语句 -->
  <select id="selectuserbyid" parametertype="int" resulttype="user">
    select * from `user` where user.id = #{id}
  </select>
  
  <!-- 定义的resultmap，可以解决类的属性名和数据库列名不一致的问题-->
  <!-- <resultmap type="user" id="userresultmap">
    <id property="id" column="user_id" />
    <result property="username" column="user_username" />
    <result property="userage" column="user_userage" />
    <result property="useraddress" column="user_useraddress" />
  </resultmap> -->
  
  <!-- 返回list的select语句，注意 resultmap的值是指向前面定义好的 -->
  <!-- <select id="selectusersbyname" parametertype="string" resultmap="userresultmap">
    select * from user where user.username = #{username}
  </select> -->
  
  <select id="selectusersbyname" parametertype="string" resulttype="user">
    select * from user where user.username = #{username}
  </select>
  
  <!--执行增加操作的sql语句。id和parametertype分别与iuseroperation接口中的adduser方法的名字和参数类型一致。
  usegeneratedkeys设置为"true"表明要mybatis获取由数据库自动生成的主键；keyproperty="id"指定把获取到的主键值注入到user的id属性--> 
  <insert id="adduser" parametertype="user" 
    usegeneratedkeys="true" keyproperty="id"> 
    insert into user(username,userage,useraddress) 
       values(#{username},#{userage},#{useraddress}) 
  </insert>
  
  <update id="updateuser" parametertype="user" >
    update user set username=#{username},userage=#{userage},useraddress=#{useraddress} where id=#{id}
  </update>
  
  <delete id="deleteuser" parametertype="int">
    delete from user where id=#{id}
  </delete>
  
</mapper>

配置文件实现了接口和sql语句的映射关系。selectusersbyname采用了2种方式实现，注释掉的也是一种实现，采用resultmap可以把属性和数据库列名映射关系定义好，property为类的属性，column是表的列名，也可以是表列名的别名！

user类的定义：

package com.mybatis.test;

public class user {
  
  private int id;
  private string username;
  private int userage;
  private string useraddress;
  
  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 int getuserage() {
    return userage;
  }
  
  public void setuserage(int userage) {
    this.userage = userage;
  }
  
  public string getuseraddress() {
    return useraddress;
  }
  
  public void setuseraddress(string useraddress) {
    this.useraddress = useraddress;
  }
  
  @override
  public string tostring(){
    return this.username+" "+this.userage+" "+this.useraddress;
  }

}

iuseroperaton定义：

package com.mybatis.test;

import java.util.list;

public interface iuseroperation {
  
  public user selectuserbyid(int id);
  
  public list<user> selectusersbyname(string username);
  
  public void adduser(user user);
  
  public void updateuser(user user);
  
  public void deleteuser(int id);
  
}

iuseroperation为操作接口，函数名和mybatis的xml配置文件中的操作id名对应。

测试类test：

package com.mybatis.test;

import java.io.reader;
import java.util.list;

import org.apache.ibatis.io.resources;
import org.apache.ibatis.session.sqlsession;
import org.apache.ibatis.session.sqlsessionfactory;
import org.apache.ibatis.session.sqlsessionfactorybuilder;

public class test {

  private static sqlsessionfactory sqlsessionfactory;
  private static reader reader;

  static {
    try {
      reader = resources.getresourceasreader("configuration.xml");
      sqlsessionfactory = new sqlsessionfactorybuilder().build(reader);
    } catch (exception e) {
      e.printstacktrace();
    }
  }

  public static sqlsessionfactory getsession() {
    return sqlsessionfactory;
  }

  public void getuserbyid(int userid) {
    sqlsession session = sqlsessionfactory.opensession();
    try {
      iuseroperation useroperation = session
          .getmapper(iuseroperation.class);
      user user = useroperation.selectuserbyid(userid);
      if (user != null) {
        system.out.println(user.getid() + ":" + user.getusername()
            + ":" + user.getuseraddress());
      }

    } finally {
      session.close();
    }
  }

  public void getuserlist(string username) {
    sqlsession session = sqlsessionfactory.opensession();
    try {
      iuseroperation useroperation = session
          .getmapper(iuseroperation.class);
      list<user> users = useroperation.selectusersbyname(username);
      for (user user : users) {
        system.out.println(user.getid() + ":" + user.getusername()
            + ":" + user.getuseraddress());
      }

    } finally {
      session.close();
    }
  }

  /**
   * 增加后要commit
   */
  public void adduser() {
    user user = new user();
    user.setuseraddress("place");
    user.setusername("test_add");
    user.setuserage(30);
    sqlsession session = sqlsessionfactory.opensession();
    try {
      iuseroperation useroperation = session
          .getmapper(iuseroperation.class);
      useroperation.adduser(user);
      session.commit();
      system.out.println("新增用户id：" + user.getid());
    } finally {
      session.close();
    }
  }

  /**
   * 修改后要commit
   */
  public void updateuser() {
    sqlsession session = sqlsessionfactory.opensession();
    try {
      iuseroperation useroperation = session
          .getmapper(iuseroperation.class);
      user user = useroperation.selectuserbyid(1);
      if (user != null) {
        user.setuseraddress("a new place");
        useroperation.updateuser(user);
        session.commit();
      }
    } finally {
      session.close();
    }
  }

  /**
   * 删除后要commit.
   * 
   * @param id
   */
  public void deleteuser(int id) {
    sqlsession session = sqlsessionfactory.opensession();
    try {
      iuseroperation useroperation = session
          .getmapper(iuseroperation.class);
      useroperation.deleteuser(id);
      session.commit();
    } finally {
      session.close();
    }
  }

  public static void main(string[] args) {
    try {
      test test = new test();
      // test.getuserbyid(1);
      // test.getuserlist("test1");
      // test.adduser();
      // test.updateuser();
      // test.deleteuser(6);

    } catch (exception e) {
      system.out.println(e.getmessage());
    }
  }

}

代码下载：mybaitssimpledemo_jb51.rar

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