MyBatis是支持普通sql查詢、存儲(chǔ)過(guò)程和高級(jí)映射的持久層框架。
MyBatis消除了幾乎所有的JDBC代碼和參數(shù)的手工設(shè)置以及對(duì)結(jié)果集的檢索封裝。
MyBatis可以使用 簡(jiǎn)單的XML或注解用于配置和原始映射，將接口和Java的POJO(Plain Old Java Objects 普通的Java對(duì)象)映射成數(shù)據(jù)庫(kù)中的記錄。
每一個(gè)Mybatis應(yīng)用程序都以一個(gè)sqlSessionFactory對(duì)象的實(shí)例為核心。
sqlSessionFactory對(duì)象的實(shí)例可以通過(guò)sqlSessionFactoryBuilder對(duì)象來(lái)獲得。sqlSessionFactoryBuilder對(duì)象可以通過(guò)xml配置文件，或從以往使用管理中準(zhǔn)備好的Configuration類實(shí)例中來(lái)構(gòu)建sqlSessionFactory對(duì)象。
【示例：使用配置類獲取sqlSessionFactory】
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DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();TransactionFactory transactionFactory = new JdbcTransactionFactory();//環(huán)境Environment environment = new Environment("development", transactionFactory, dataSource);Configuration configuration = new Configuration(environment);//映射器類configuration.addMapper(BlogMapper.class);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration); |
注意這種情況下配置是添加映射器類。映射器類是Java類，這些類包含SQL映射語(yǔ)句的注解從而避免了xml文件的依賴，但是xml映射仍然在 大多數(shù)高級(jí)映射(比如：嵌套join映射)時(shí)需要。
出于這樣的原因，如果存在xml配置文件的話，MyBatis將會(huì)自動(dòng)查找和加載一個(gè)對(duì)等的XML文件(這種情況下，基于類路徑下的BlogMapper.class類的類名，那么BlogMapper.xml將會(huì)被加載–即class 與 XML在同一個(gè)文件目錄下。如果非，則需要手動(dòng)配置加載xml)。
【1】基本增刪改查xml配置
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<?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"> <!-- 可以解決model屬性名與數(shù)據(jù)表中column列名不一致問(wèn)題 jdbcType一定要大寫 --> <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> <!-- 注意這里的result，如果column == property 則可以直接返回Java object。 如果屬性名與列名不一致，解決方法如下： 1. 使用resultMap; 2.返回hashmap ; 3.查詢語(yǔ)句使用別名 --> <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> |
注冊(cè)到mybatis.xml [當(dāng)與spring結(jié)合時(shí)，將不需要這個(gè)配置文件]
mybatis的配置文件
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<?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"/> <!-- 配置實(shí)體類的別名 --> <typeAliases> <!-- <typeAlias type="com.web.model.User" alias="User"/> --> <package name="com.web.model"/> </typeAliases><!-- development : 開(kāi)發(fā)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】通過(guò)SqlSessionFactory拿到session
這里使用xml文件獲取sqlSessionFactory和sqlSession。
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public static SqlSessionFactory getFactory(){ /* flow the src dir*/ 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);//默認(rèn)手動(dòng)提交；/* 兩種解決方式： 1.factory.opensession(true); 2.session.commit(); */ |
【3】增刪改查后臺(tái)測(cè)試代碼
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/*use sql xml not annotation*/@Test public void testAdd(){ SqlSession session = MybatisUtils.getFactory().openSession(); String statement = "com.web.mapper.userMapper.insertUser"; /*return the effect rows*/ int insert= session.insert(statement, new User("tom5", 15)); /*default is not auto commit*/ session.commit(true); session.close(); System.out.println("effect rows.."+insert);}@Test public void testSelect(){ /*set auto commit ,which equals to the above*/ SqlSession session = MybatisUtils.getFactory().openSession(true); String statement = "com.web.mapper.userMapper.getUser"; /*return the effect rows*/ 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"; /*return the effect rows*/ 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"; /*return the effect rows*/ int delete= session.delete(statement, 6); /* commit by yourself*/ 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"; /*return the List<User>*/ List<User> users= session.selectList(statement); session.commit(); System.out.println("effect rows.."+users); session.close();} |
Tips ：
parameterType 和 resultType 為 hashmap ：
- mapper.xml :
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<select id="getUserForMap" parameterType="hashmap" resultType="hashmap"> select * from c_user where id=#{id}; </select> |
- test code :
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@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); /*return the effect rows*/ Object selectOne = session.selectOne(statement, map); /*default is not auto commit*/ session.commit(true); session.close(); System.out.println("effect rows.."+selectOne+" ,class :"+selectOne.getClass());} |
- result as follows :
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effect rows..{id=1, age=12, name=luli} ,class :class java.util.HashMap |
綜上可知：mybatis 會(huì)根據(jù)參數(shù)類型和結(jié)果類型，自動(dòng)進(jìn)行解析封裝。
【擴(kuò)展 基本方法】
【1】分頁(yè)列表
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<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 --使用動(dòng)態(tài)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> --添加分頁(yè) limit ${(page-1)*pagesize},${pagesize}</select> |
【2】刪除方法–根據(jù)對(duì)象或者Id
如果參數(shù)為pojo,mybatis會(huì)自動(dòng)從對(duì)象里面獲取id ;
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<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】根據(jù) id list 刪除數(shù)據(jù)
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<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
通常與getListPage聯(lián)合使用。
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<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> |
總結(jié)
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原文鏈接：http://blog.csdn.net/J080624/article/details/53374067
