Mybatis基本使用

动态SQL

基于OGNL表达式

完成多条件查询等逻辑实现

用于实现动态SQL的元素主要有

if

trim

where

set

choose（when、otherwise）

foreach

if

改造查询用户信息列表的演示示例，增加查询条件用户角色（根据角色id查询）用户名称（模糊查询）

<!-- 当数据库中的字段信息与对象的属性不一致时需要通过resultMap来映射 --><resultMap type="User" id="userList"><result property="id" column="id"/><result property="userCode" column="userCode"/><result property="userName" column="userName"/><result property="phone" column="phone"/><result property="birthday" column="birthday"/><result property="gender" column="gender"/><result property="userRole" column="userRole"/><result property="userRoleName" column="roleName"/></resultMap><!-- 查询用户列表 --><select id="getUserList" resultMap="userList">select u.*,r.roleName from smbms_user u,smbms_role r where u.userRole = r.id<if test="userRole != null">and u.userRole = #{userRole}</if><if test="userName != null and userName != ''">and u.userName like CONCAT ('%',#{userName},'%') </if></select>

where

简化SQL语句中where条件判断
智能处理and和or

<select id="getUserList" resultType="User">select * from smbms_user <where><if test="userName != null and userName != ''">and userName like CONCAT ('%',#{userName},'%') </if><if test="userRole != null">and userRole = #{userRole}</if></where>
</select>

where:自动加where,自动去掉第一个and

set

若某个参数为null，则不需要更新，保持数据库原值

    <!-- 修改用户信息 --><update id="modify" parameterType="User">update smbms_user <set><if test="userCode != null">userCode=#{userCode},</if><if test="userName != null">userName=#{userName},</if><if test="userPassword != null">userPassword=#{userPassword},</if><if test="gender != null">gender=#{gender},</if><if test="birthday != null">birthday=#{birthday},</if><if test="phone != null">phone=#{phone},</if><if test="address != null">address=#{address},</if><if test="userRole != null">userRole=#{userRole},</if><if test="modifyBy != null">modifyBy=#{modifyBy},</if><if test="modifyDate != null">modifyDate=#{modifyDate}</if></set>where id = #{id}</update>

trim

属性 prefix suffix prefixOverrides suffixOverrides
更灵活地去除多余关键字
替代where和set

    <select id="getUserList" resultType="User">select * from smbms_user <trim prefix="where" prefixOverrides="and | or"><if test="userName != null and userName != ''">and userName like CONCAT ('%',#{userName},'%') </if><if test="userRole != null">and userRole = #{userRole}</if></trim></select>

使用if+trim替代if+set进行更新用户表数据

<update id ="modify" parameterType="User">
update smbms_user<trim prefix="set" suffixOverrides="," suffix="where id = #{id}">   <if test="userCode != null">userCode = #{userCode},</if><if test="userName!= null">userCode = #{userName },</if><if test="userPassword!= null">userPassword=#{userPassword },</if></trim></update>

foreach

迭代一个集合，通常用于in条件

属性

item

index

collection:必须指定

list

array

map-key

open

separator

close

    public List<User> getUserByRoleId_foreach_array(Integer[] roleIds);<!-- 根据用户角色列表，获取该角色列表下用户列表信息-foreach_array --><select id="getUserByRoleId_foreach_array" resultMap="userMapByRole">select * from smbms_user where userRole in <foreach collection="array" item="roleIds" open="(" separator="," close=")">#{roleIds}</foreach></select>

改造上一个演示示例，使用foreach实现，参数类型改为List

    public List<User> getUserByRoleId_foreach_list(List<Integer> roleList);<!-- 根据用户角色列表，获取该角色列表下用户列表信息-foreach_list --><select id="getUserByRoleId_foreach_list" resultMap="userMapByRole">select * from smbms_user where userRole in <foreach collection="list" item="roleList" open="(" separator="," close=")">#{roleList}</foreach></select>

在上一个演示示例中，增加一个参数：gender，要求查询出指定性别和用户角色列表下的用户列表

public List<User> getUserByRoleId_foreach_map(Map<String,Object> roleMap);
<!-- 根据用户角色列表(单参数)，获取该角色列表下用户列表信息-foreach_map --><select id="getUserByRoleId_foreach_map" resultMap="userMapByRole">select * from smbms_user where userRole in <foreach collection="rKey" item="roleMap" open="(" separator="," close=")">#{roleMap}</foreach></select>

choose

相当于Java中switch语句
当when有条件满足的时候，就跳出choose

    <!-- 查询用户列表(choose) --><select id="getUserList_choose" resultType="User">select * from smbms_user where 1=1<choose><when test="userName != null and userName != ''">and userName like CONCAT ('%',#{userName},'%')</when><when test="userCode != null and userCode != ''">and userCode like CONCAT ('%',#{userCode},'%')</when><when test="userRole != null">and userRole=#{userRole}</when><otherwise><!-- and YEAR(creationDate) = YEAR(NOW()) -->and YEAR(creationDate) = YEAR(#{creationDate})</otherwise></choose></select>

日志

pom.xml导入依赖

  <properties><log4j2.version>2.9.1</log4j2.version></properties>

<!--日志 -->
<dependency><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-api</artifactId><version>${log4j2.version}</version>
</dependency>
<dependency><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-core</artifactId><version>${log4j2.version}</version>
</dependency>

配置文件

log4j2.xml

分页

为用户管理之查询用户列表功能增加分页实现列表结果按照创建时间降序排列

添加分页jar

    <!--pageHelper分页--><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper</artifactId><version>5.1.4</version></dependency>

配置

在myatis配置文件中添加如下配置

<plugins><plugin interceptor="com.github.pagehelper.PageInterceptor"><!-- 设置数据库类型 Oracle,Mysql,MariaDB,SQLite,Hsqldb,PostgreSQL六种数据库--><property name="helperDialect" value="mysql"/></plugin>
</plugins>

使用测试

    @Testpublic void testGetUserList(){SqlSession sqlSession = MyBatisUtil.createSqlSession();//startPage(第几页,每页显示几条记录)PageHelper.startPage(2,5);UserMapper userMapper = sqlSession.getMapper(UserMapper.class);List<User> list = userMapper.getUserList();PageInfo<User> pageInfo = new PageInfo<>(list);sqlSession.close();for(User user : list){System.out.println(user.getId()+"\t"+user.getUserName());}System.out.println("总记录数="+pageInfo.getTotal());System.out.println("总页数="+pageInfo.getPages());}

mybatis-generator

MyBatis Generator（MBG）是MyBatis MyBatis 和iBATIS的代码生成器;根据数据库反向生成pojo、映射文件，映射接口

导入依赖

 <dependencies><dependency><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-maven-plugin</artifactId><version>1.4.0</version></dependency></dependencies><build><plugins><plugin><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-maven-plugin</artifactId><version>1.4.0</version><configuration><!-- 在控制台打印执行日志 --><verbose>true</verbose><!-- 重复生成时会覆盖之前的文件--><overwrite>true</overwrite><configurationFile>src/main/resources/generatorConfig.xml</configurationFile></configuration><dependencies><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency></dependencies></plugin></plugins></build>