mybatis之动态sql及分页

1、mybatis动态sql

foreach

BookMapper.xml

 <!--foreach标签-->
  <select id="selectBookIn" resultType="com.javachz.model.Book" parameterType="java.util.List">
    select * from t_mvc_book where bid in
    <foreach collection="bookIds" item="bid" open="(" close=")" separator=",">
      #{bid}
    </foreach>
  </select>

BookMapper.java

BookService.java

 List<Book> selectBookIn(@Param("bookIds") List bookIds);

BookServiceImpl.java

测试结果
BookServiceImplTest

If，trim

BookMapper.xml

 <!--if标签-->
  <insert id="insertSelective" parameterType="com.javachz.model.Book" >
    insert into t_mvc_book
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="bid != null" >
        bid,
      </if>
      <if test="bname != null" >
        bname,
      </if>
      <if test="price != null" >
        price,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="bid != null" >
        #{bid,jdbcType=INTEGER},
      </if>
      <if test="bname != null" >
        #{bname,jdbcType=VARCHAR},
      </if>
      <if test="price != null" >
        #{price,jdbcType=REAL},
      </if>
    </trim>
  </insert>

BookMapper.java

BookService.java

int insertSelective(Book record);

BookServiceImpl.java

测试结果
BookServiceImplTest

2、模糊查询

#{…}
KaTeX parse error: Expected 'EOF', got '#' at position 17: …...} Concat 注意：#̲{...}自带引号，{…}有sql注入的风险
BookMapper.xml

<!--模糊查询-->
<select id="selectBooksLike1" resultType="com.javachz.model.Book" parameterType="java.lang.String">
  select * from t_mvc_book
  <where>
    bname like #{bname}
  </where>
</select>

  <!--模糊查询-->
  <select id="selectBooksLike2" resultType="com.javachz.model.Book" parameterType="java.lang.String">
    select * from t_mvc_book
    <where>
      bname like '${bname}'
    </where>
  </select>

  <!--模糊查询-->
  <select id="selectBooksLike3" resultType="com.javachz.model.Book" parameterType="java.lang.String">
    select * from t_mvc_book
    <where>
      bname like concat('%',#{bname},'%')
    </where>
  </select>

BookMapper.java

BookService.java

 List<Book> selectBooksLike1(@Param("bname")String bname);

    List<Book> selectBooksLike2(@Param("bname")String bname);

    List<Book> selectBooksLike3(@Param("bname")String bname);

BookServiceImpl.java

测试结果
BookServiceImplTest

3、查询返回结果集的处理

resultMap：适合使用返回值是自定义实体类的情况
resultType：适合使用返回值的数据类型是非自定义的，即jdk的提供的类型

3.1 使用resultMap返回自定义类型集合

BookMapper.xml

<select id="list1" resultMap="BaseResultMap">
    select *from t_mvc_book
  </select>

BookMapper.java

 List<Book> list1();

BookService.java

List<Book> list1();

BookServiceImpl.java

  @Override
    public List<Book> list1() {
        return bookMapper.list1();
    }

测试结果
BookServiceImplTest

3.2 使用resultType返回List

BookMapper.xml

<select id="list2" resultType="com.javachz.model.Book">
  select * from t_mvc_book
</select>

BookMapper.java

 List<Book> list2();

BookService.java

 List<Book> list2();

BookServiceImpl.java

 @Override
    public List<Book> list2() {
        return bookMapper.list2();
    }

测试结果
BookServiceImplTest

3.3 使用resultType返回单个对象

BookMapper.xml

<select id="list3" resultType="com.javachz.model.BookVo" parameterType="com.javachz.model.BookVo">
  select * from t_mvc_book where bid in
  <foreach collection="bookIds" item="bid" open="(" close=")" separator=",">
    #{bid}
  </foreach>
</select>

BookMapper.java

List<Book> list3(BookVo bookVo);

BookService.java

 List<Book> list3(BookVo bookVo);

BookServiceImpl.java

 @Override
    public List<Book> list3(BookVo bookVo) {
        return bookMapper.list3(bookVo);
    }

测试结果
BookServiceImplTest

3.4 使用resultType返回List

适用于多表查询返回结果集
BookMapper.xml

 <select id="list4" resultType="java.util.Map">
    select * from t_mvc_book
  </select>

BookMapper.java

List<Map> list4();

BookService.java

List<Map> list4();

BookServiceImpl.java

 @Override
    public List<Map> list4() {
        return bookMapper.list4();
    }

测试结果
BookServiceImplTest

3.5 使用resultType返回Map<String,Object>，适用于多表查询返回单个结果集

BookMapper.xml

<select id="list5" resultType="java.util.Map" parameterType="java.util.Map">
    select *from t_mvc_book where bid=#{bid}
  </select>

BookMapper.java

 Map list5(Map map);

BookService.java

Map list5(Map map);

BookServiceImpl.java

  @Override
    public Map list5(Map map) {
        return bookMapper.list5(map);
    }

测试结果
BookServiceImplTest

4、分页查询

为什么要重写mybatis的分页？

因为Mybatis的分页功能很弱，它是基于内存的分页(查出所有记录再按偏移量offset和边界limit取结果)，在大数据量的情况下这样的分页基本上是没有用的
使用分页插件步奏

1、导入pom依赖

  <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>5.1.2</version>
    </dependency>

2、Mybatis.cfg.xml配置拦截器

<plugins>
    <!-- 配置分页插件PageHelper, 4.0.0以后的版本支持自动识别使用的数据库 -->
    <plugin interceptor="com.github.pagehelper.PageInterceptor">
    </plugin>
</plugins>

按照dtd的设置放在对应配置的地方
举例

使用分页插件

BookMapper.xml

<select id="listPager" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book where bname like concat(concat('%',#{bname}),'%')
  </select>

BookMapper.java

 List<Map> listPager(Map map);

BookService.java

List<Map> listPager(Map map, PageBean pageBean);

BookServiceImpl.java

使用PageHelper进行分页

 @Override
    public List<Map> listPager(Map map, PageBean pageBean) {
      if(pageBean!=null && pageBean.isPagination()){
          PageHelper.startPage(pageBean.getPage(),pageBean.getRows());
      }
      List<Map> list=bookMapper.listPager(map);
        if(pageBean!=null && pageBean.isPagination()){
            PageInfo pageInfo=new PageInfo(list);
            System.out.println("当前页:" + pageInfo.getPageNum());
            System.out.println("显示当前内容数量：" + pageInfo.getPageSize());
            System.out.println("符合条件的总记录数据：" + pageBean.getTotal());
        }
        return list;
    }

测试结果
BookServiceImplTest
4、处理分页结果

5、 特殊字符处理

>(>)   
    <(&lt;)  
    &(&amp;) 
 空格(&nbsp;)
  <![CDATA[ <= ]]> 

相关代码配置

BookMapper.xml

<select id="list6" resultType="com.javachz.model.Book" parameterType="com.javachz.model.BookVo">
    select * from t_mvc_book
    <where>
      <if test="null != min and min != ''">
        <![CDATA[  and #{min} < price ]]>
      </if>
      <if test="null != max and max != ''">
        <![CDATA[ and #{max} > price ]]>
      </if>
    </where>
  </select>

  <select id="list7" resultType="com.javachz.model.Book" parameterType="com.javachz.model.BookVo">
    select * from t_mvc_book
    <where>
      <if test="null != min and min != ''">
        and #{min} &lt; price
      </if>
      <if test="null != max and max != ''">
        and #{max} &gt; price
      </if>
    </where>
  </select>

BookMapper.java

  List<Book> list6(BookVo bookVo);

  List<Book> list7(BookVo bookVo);

BookService.java

List<Book> list6(BookVo bookVo);

List<Book> list7(BookVo bookVo);

BookServiceImpl.java

 @Override
    public List<Book> list6(BookVo bookVo) {
        return bookMapper.list6(bookVo);
    }

    @Override
    public List<Book> list7(BookVo bookVo) {
        return bookMapper.list7(bookVo);
    }

测试结果
BookServiceImplTest