Mybatis实现数据的增删改查实例（CRUD）

2019-11-26 12:18:52

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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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