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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