MyBatis是支持普通sql查询、存储过程和高级映射的持久层框架。
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封装。
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。
每一个Mybatis应用程序都以一个sqlSessionFactory对象的实例为核心。
sqlSessionFactory对象的实例可以通过sqlSessionFactoryBuilder对象来获得。sqlSessionFactoryBuilder对象可以通过xml配置文件，或从以往使用管理中准备好的Configuration类实例中来构建sqlSessionFactory对象。
【示例：使用配置类获取sqlSessionFactory】
DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();TransactionFactory transactionFactory = new JdbcTransactionFactory();//环境Environment environment = new Environment("development", transactionFactory, dataSource);Configuration configuration = new Configuration(environment);//映射器类configuration.addMapper(BlogMapper.class);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
注意这种情况下配置是添加映射器类。映射器类是Java类，这些类包含SQL映射语句的注解从而避免了xml文件的依赖，但是xml映射仍然在 大多数高级映射(比如：嵌套join映射)时需要。
出于这样的原因，如果存在xml配置文件的话，MyBatis将会自动查找和加载一个对等的XML文件(这种情况下，基于类路径下的BlogMapper.class类的类名，那么BlogMapper.xml将会被加载–即class 与 XML在同一个文件目录下。如果非，则需要手动配置加载xml)。
【1】基本增删改查xml配置
<?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.web.mapper.userMapper"> <!-- 可以解决model属性名与数据表中column列名不一致问题 jdbcType一定要大写 --> <resultMap type="User" id="UserMap"> <id property="id" column="id" javaType="int" jdbcType="INTEGER"/> <result property="name" column="username" javaType="string" jdbcType="VARCHAR"/> <result property="age" column="age" javaType="int" jdbcType="INTEGER"/> </resultMap> <!-- 注意这里的result，如果column == property 则可以直接返回Java object。 如果属性名与列名不一致，解决方法如下： 1. 使用resultMap; 2.返回hashmap ; 3.查询语句使用别名 --> <select id="getUser" parameterType="int" resultMap="UserMap"> select * from t_user where id=#{id} </select> <delete id="deleteUser" parameterType="int" > delete from t_user where id=#{id} </delete> <update id="updateUser" parameterType="User" > update t_user set username=#{name},age=#{age} where id=#{id} </update> <insert id="insertUser" parameterType="User" > insert into t_user(username,age) values(#{name},#{age}) </insert> <!-- model's attr(name) different from column(username), so the result use UserMap --> <select id="getUsers" resultMap="UserMap"> select * from t_user </select></mapper>
注册到mybatis.xml [当与spring结合时，将不需要这个配置文件]
mybatis的配置文件
<?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> <properties resource="jdbc.properties"/> <!-- 配置实体类的别名 --> <typeAliases> <!-- <typeAlias type="com.web.model.User" alias="User"/> --> <package name="com.web.model"/> </typeAliases><!-- development : 开发模式 work : 工作模式 --> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="${driver}" /> <property name="url" value="${url}" /> <property name="username" value="${username}" /> <property name="password" value="${password}" /> </dataSource> </environment> </environments> <mappers> <mapper resource="com/web/mapper/userMapper.xml"/> <mapper resource="com/web/mapper/orderMapper.xml"/> <mapper class="com.web.mapperClass.UserMapper"/> </mappers></configuration>
【2】通过SqlSessionFactory拿到session
这里使用xml文件获取sqlSessionFactory和sqlSession。
public static SqlSessionFactory getFactory(){ String resource = "mybatis.xml"; /*MybatisUtils.class.getResourceAsStream(resource)----- it's wrong !!!! * please distinguish the two up and down * */ InputStream inputStream = MybatisUtils.class.getClassLoader().getResourceAsStream(resource); SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream); return factory;}SqlSession session = factory.openSession(true);//默认手动提交；
【3】增删改查后台测试代码
@Test public void testAdd(){ SqlSession session = MybatisUtils.getFactory().openSession(); String statement = "com.web.mapper.userMapper.insertUser"; int insert= session.insert(statement, new User("tom5", 15)); session.commit(true); session.close(); System.out.println("effect rows.."+insert);}@Test public void testSelect(){ SqlSession session = MybatisUtils.getFactory().openSession(true); String statement = "com.web.mapper.userMapper.getUser"; User user = session.selectOne(statement, 3); System.out.println("effect rows.."+user);}@Test public void testUpdate(){ SqlSession session = MybatisUtils.getFactory().openSession(true); String statement = "com.web.mapper.userMapper.updateUser"; int update= session.update(statement, new User(3,"tom4", 13)); System.out.println("effect rows.."+update);}@Test public void testDelete(){ SqlSession session = MybatisUtils.getFactory().openSession(); String statement = "com.web.mapper.userMapper.deleteUser"; int delete= session.delete(statement, 6); session.commit(); System.out.println("effect rows.."+delete); session.close();}@Test public void testGetUsers(){ SqlSession session = MybatisUtils.getFactory().openSession(); String statement = "com.web.mapper.userMapper.getUsers"; List<User> users= session.selectList(statement); session.commit(); System.out.println("effect rows.."+users); session.close();}
Tips ：
parameterType 和 resultType 为 hashmap ：
<select id="getUserForMap" parameterType="hashmap" resultType="hashmap"> select * from c_user where id=#{id}; </select>
@Test public void getUserForMap(){ SqlSession session = MybatisUtils.getFactory().openSession(); String statement = "com.web.mapper.userMapper.getUserForMap"; HashMap<String, Object> map = new HashMap<String, Object>(); map.put("id", 1); Object selectOne = session.selectOne(statement, map); session.commit(true); session.close(); System.out.println("effect rows.."+selectOne+" ,class :"+selectOne.getClass());}
effect rows..{id=1, age=12, name=luli} ,class :class java.util.HashMap
综上可知：mybatis 会根据参数类型和结果类型，自动进行解析封装。
【扩展 基本方法】
【1】分页列表
<select id="getListPage" parameterType="hashmap" resultMap="siteExtendDaoMap"> select id,site_id,site_name,site_number,province,city,area,address,internal_number,longitude,latitude from tb_site --使用动态sql <trim prefix="where" prefixOverrides="AND |OR "> <if test="checkState!= null and checkState!=''"> and check_state = #{checkState,jdbcType=INTEGER} </if> <if test="siteId!= null and siteId!=''"> and site_id like concat('%',#{siteId},'%') </if> <if test="siteName!= null and siteName!=''"> and site_name like concat('%',#{siteName},'%') </if> <if test="siteNumber!= null and siteNumber!=''"> and site_number like concat('%', #{siteNumber},'%') </if> <if test="province!= null and province!=''"> and province = #{province} </if> <if test="city!= null and city!=''"> and city = #{city} </if> <if test="area!= null and area!=''"> and area = #{area} </if> </trim> --添加排序 <if test="sortname!= null and sortname!='' and sortorder!= null and sortorder!=''"> order by ${sortname} ${sortorder} </if> --添加分页 limit ${(page-1)*pagesize},${pagesize} </select>
【2】删除方法–根据对象或者Id
如果参数为pojo,mybatis会自动从对象里面获取id ;
<delete id="delete" parameterType="User"> delete from tb_user where id = #{id} </delete> <delete id="deleteById" parameterType="long"> delete from tb_user where id = #{id} </delete>
【3】根据 id list 删除数据
<delete id="deleteByIds"> delete from tb_user where id in --使用foreach <foreach collection="list" item="id" open="(" separator=","close=")"> #{id} </foreach> </delete>
【4】getRows
通常与getListPage联合使用。
<select id="getRows" parameterType="hashmap" resultType="long"> select count(*) from tb_sys_role <if test="keySysRole!= null"> <trim prefix="WHERE" prefixOverrides="AND |OR "> <if test="keySysRole.id!= null"> and id = #{keySysRole.id} </if> <if test="keySysRole.name!= null and keySysRole.name!=''"> and name = #{keySysRole.name} </if> <if test="keySysRole.available!= null and keySysRole.available!=''"> and available = #{keySysRole.available} </if> </trim> </if> </select>
总结
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