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：https://github.com/mybatis/mybatis-3/releases

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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