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MyBatis之动态sql，插件

悄然丝语 2022-04-18 阅读 102
sprint

动态SQL

  1. 基于OGNL表达式

  2. 完成多条件查询等逻辑实现

  3. 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

  1. 简化SQL语句中where条件判断

  2. 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

  1. 属性 prefix suffix prefixOverrides suffixOverrides

  2. 更灵活地去除多余关键字

  3. 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

  1. 迭代一个集合，通常用于in条件

  2. 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

  1. 相当于Java中switch语句

  2. 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

    @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());
    }

4.mybatis-generator

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

4.1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>

4.2.generatorConfig.xml配置

4.3.运行maven插件

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