目录
动态SQL
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>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
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
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
@Test
public 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
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>generatorConfig.xml配置
运行maven插件
总结
