mybatis dynamic sql and pagination

1, mybatis dynamic sql

2, fuzzy query

3, the query returns a result set

4, paging query

5, special character handling

 

1.mybatis dynamic sql

If、trim、foreach

If the label is determined whether a field is empty

  <select id="list4" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book
    <where>
      <if test="null != bname and bname !=''">
        and bname like #{bname}
      </if>
    </where>
</select>

trim tab is generally used to remove excess sql statement and key, comma, or prior to splicing sql statement "where", "set" and "values ​​(" et prefix, or add ")" suffix, can be used to selectively insert, update, delete, query and other operations or condition.

    <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=DOUBLE},
      </if>
    </trim>

foreach tag through the collection, batch query, typically used in keyword

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

  </select>

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

test

 @Test
    public void selectByIn() {
        List list = new ArrayList();
        list.add(8);
        list.add(2);
        list.add(3);
        list.add(10);
        List<Book> books = this.bookService.selectByIn(list);
        for (Book b : books){
            System.out.println(b);
        }
    }

2. Fuzzy query (three ways)

2.1 %% directly into the argument

2.2 Use $ {...} instead of # {...} (do not recommend using this mode, there is the risk of SQL injection)

key: # {...} and $ {...} difference?
Parameters of type String # longitudinal single quotes will [ '], $ value directly inserted

Note:
. 1) MyBatis pass parameters used OGNL expression
2) {...} # precedence
present SQL 3) $ {...} risk injection mode

2.3 SQL string concatenation CONCAT

 <!--模糊查询-->
  <select id="selectByLike1" resultType="com.liuwenwu.model.Book" parameterType="java.lang.String">
    select * from t_mvc_book where bname like #{bname}
  </select>

  <select id="selectByLike2" resultType="com.liuwenwu.model.Book" parameterType="java.lang.String">
    select * from t_mvc_book where bname like '${bname}'
  </select>

  <select id="selectByLike3" resultType="com.liuwenwu.model.Book" parameterType="java.lang.String">
    select * from t_mvc_book where bname like concat(concat('%',#{bname}),'%')
  </select>

    List<Book> selectByLike1(@Param("bname")String bname);

    List<Book> selectByLike2(@Param("bname")String bname);

    List<Book> selectByLike3(@Param("bname")String bname);

test

    @Test
    public void selectByLike() {
//        List<Book> books = this.bookService.selectByLike1(StringUtil.toLikeStr("圣墟"));
//        List<Book> books = this.bookService.selectByLike2("%圣墟% or bid !=1");
        List<Book> books = this.bookService.selectByLike3("圣墟");
        for (Book b : books){
            System.out.println(b);
        }
    }

result:

3. Query processing returns result sets

resultMap: suitable return value is the case where the custom entity class

    resultType: suitable return value data type of non-custom, i.e. of the type provided jdk

 

    3.1 resultMap return custom type set

   

    3.2 resultType return List <T>

 

    3.3 resultType return a single object

 

    3.4 resultType return List <Map>, the result set returned applies to multi-table query

 

3.5 Use resultType return to Map <String, Object>, for multi-table queries return a single result set

 <!--3、查询返回结果集的处理-->
  <select id="list1" resultMap="BaseResultMap">
    select * from t_mvc_book
  </select>

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

  <select id="list3" resultType="com.liuwenwu.model.Book" parameterType="com.liuwenwu.model.BookVo">
    select * from t_mvc_book where bid in
    <foreach collection="bookIds" open="(" close=")" separator="," item="bid">
      #{bid}
    </foreach>
  </select>
  <select id="list4" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book
    <where>
      <if test="null != bname and bname !=''">
        and bname like #{bname}
      </if>
    </where>
</select>
  <select id="list5" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book
    <where>
      <if test="null != bid and bid !=''">
        and bid = #{bid}
      </if>
    </where>
  </select>

//    3.1 使用resultMap返回自定义类型集合
        List<Book> list1();
//    3.2 使用resultType返回List<T>
        List<Book> list2();
//    3.3 使用resultType返回单个对象
        Book list3(BookVo bookVo);
//    3.4 使用resultType返回List<Map>，适用于多表查询返回结果集
        List<Map> list4(Map map);
//    3.5 使用resultType返回Map<String,Object>，适用于多表查询返回单个结果集
        Map list5(Map map);

测试：

    @Test
    public void list() {
//        返回一个resultMap但是使用list<T>接收
//        List<Book> books = this.bookService.list1();
//        返回的是resulttype使用list<T>接收
//        List<Book> books = this.bookService.list2();
//        返回的是resulttype使用list<T>接收
//        for (Book b : books){
//            System.out.println(b);
//        }

//        返回的是resulttype使用T接收
//        BookVo bookVo =new BookVo();
//        List list = new ArrayList();
//        list.add(2);
//        bookVo.setBookIds(list);
//        Book book = this.bookService.list3(bookVo);
//        System.out.println(book);

//        返回的是resulttype使用list<Map>接收
        Map map =new HashMap();
//        map.put("bname",StringUtil.toLikeStr("圣墟"));
//        List<Map> list = this.bookService.list4(map);
//        for (Map m : list) {
//            System.out.println(m);
//        }
//        返回的是resulttype使用Map接收
        map.put("bid",2);
        Map m = this.bookService.list5(map);
        System.out.println(m);
    }

结果：

 

4.分页查询

为什么要重写mybatis的分页？

   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

2、Mybatis.cfg.xml配置拦截器

3、使用PageHelper进行分页

4、处理分页结果

Pom依赖

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

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>

  <select id="list4" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book
    <where>
      <if test="null != bname and bname !=''">
        and bname like #{bname}
      </if>
    </where>
</select>

 

  @Override
    public List<Map> listPager(Map map, PageBean pageBean) {

        if(pageBean!=null && pageBean.isPagination()){
            PageHelper.startPage(pageBean.getPage(),pageBean.getRows());
        }

        List<Map> list = this.bookMapper.list4(map);
        if(pageBean!=null && pageBean.isPagination()){
            PageInfo pageInfo =new PageInfo(list);
            System.out.println("当前的页码："+pageInfo.getPageNum());
            System.out.println("页数据量："+pageInfo.getPageSize());
            System.out.println("符合条件的记录数："+pageInfo.getTotal());
            pageBean.setTotal(pageInfo.getTotal()+"");

        }

        return list;
    }

测试：

   @Test
    public void listPager() {
        Map map =new HashMap();
        map.put("bname",StringUtil.toLikeStr("圣墟"));
        PageBean pageBean =new PageBean();
        pageBean.setPage(3);
//        pageBean.setPagination(false);
        List<Map> list = this.bookService.listPager(map, pageBean);
        for (Map m : list) {
            System.out.println(m);
        }
    }

结果：

 

5.特殊字符处理

>(&gt;)
<(&lt;)
&(&amp;)
空格(&nbsp;)

<![CDATA[ <= ]]>

 <select id="list6" resultType="java.util.Map" parameterType="com.liuwenwu.model.BookVo">
    select * from t_mvc_book
    <where>
      <if test="null != min and min !=''">
        and price &gt; #{min}
      </if>
      <if test="null != max and max !=''">
        and price &lt; #{max}
      </if>
    </where>
  </select>
  <select id="list7" resultType="java.util.Map" parameterType="com.liuwenwu.model.BookVo">
    select * from t_mvc_book
    <where>
      <if test="null != min and min !=''">
        <![CDATA[ and price > #{min} ]]>
      </if>
      <if test="null != max and max !=''">
        <![CDATA[ and price < #{max} ]]>
      </if>
    </where>
  </select>

//    特殊字符的处理方式
        List<Map> list6(BookVo bookVo);

        List<Map> list7(BookVo bookVo);

测试：

    @Test
    public void listSpecoal() {
        BookVo bookVo =new BookVo();
        bookVo.setMin(100.0);
        bookVo.setMax(500.0);
//        List<Map> list = this.bookService.list6(bookVo);
        List<Map> list = this.bookService.list7(bookVo);
        for (Map map : list) {
            System.out.println(map);
        }
    }

相关代码

PageBean 分页工具类

package com.liuwenwu.util;

import java.io.Serializable;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

public class PageBean implements Serializable {

    private static final long serialVersionUID = 2422581023658455731L;

    //页码
    private int page=1;
    //每页显示记录数
    private int rows=10;
    //总记录数
    private int total=0;
    //是否分页
    private boolean isPagination=true;
    //上一次的请求路径
    private String url;
    //获取所有的请求参数
    private Map<String,String[]> map;
    
    public PageBean() {
        super();
    }
    
    //设置请求参数
    public void setRequest(HttpServletRequest req) {
        String page=req.getParameter("page");
        String rows=req.getParameter("rows");
        String pagination=req.getParameter("pagination");
        this.setPage(page);
        this.setRows(rows);
        this.setPagination(pagination);
        this.url=req.getContextPath()+req.getServletPath();
        this.map=req.getParameterMap();
    }
    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public Map<String, String[]> getMap() {
        return map;
    }

    public void setMap(Map<String, String[]> map) {
        this.map = map;
    }

    public int getPage() {
        return page;
    }

    public void setPage(int page) {
        this.page = page;
    }
    
    public void setPage(String page) {
        if(null!=page&&!"".equals(page.trim()))
            this.page = Integer.parseInt(page);
    }

    public int getRows() {
        return rows;
    }

    public void setRows(int rows) {
        this.rows = rows;
    }
    
    public void setRows(String rows) {
        if(null!=rows&&!"".equals(rows.trim()))
            this.rows = Integer.parseInt(rows);
    }

    public int getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }
    
    public void setTotal(String total) {
        this.total = Integer.parseInt(total);
    }

    public boolean isPagination() {
        return isPagination;
    }
    
    public void setPagination(boolean isPagination) {
        this.isPagination = isPagination;
    }
    
    public void setPagination(String isPagination) {
        if(null!=isPagination&&!"".equals(isPagination.trim()))
            this.isPagination = Boolean.parseBoolean(isPagination);
    }
    
    /**
     * 获取分页起始标记位置
     * @return
     */
    public int getStartIndex() {
        //(当前页码-1)*显示记录数
        return (this.getPage()-1)*this.rows;
    }
    
    /**
     * 末页
     * @return
     */
    public int getMaxPage() {
        int totalpage=this.total/this.rows;
        if(this.total%this.rows!=0)
            totalpage++;
        return totalpage;
    }
    
    /**
     * 下一页
     * @return
     */
    public int getNextPage() {
        int nextPage=this.page+1;
        if(this.page>=this.getMaxPage())
            nextPage=this.getMaxPage();
        return nextPage;
    }
    
    /**
     * 上一页
     * @return
     */
    public int getPreivousPage() {
        int previousPage=this.page-1;
        if(previousPage<1)
            previousPage=1;
        return previousPage;
    }

    @Override
    public String toString() {
        return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", isPagination=" + isPagination
                + "]";
    }
}

Bookvo  

vo用来存放包括数据库表映射的字段以及多余的查询条件所需属性列，保证实体类纯粹，降低耦合度

package com.liuwenwu.model;

import java.util.List;

/**
 * @author LWW
 * @site www.lww.com
 * @company
 * @create 2019-09-20 19:05
 * vo用来存放包括数据库表映射的字段以及多余的查询条件所需属性列
 */
public class BookVo extends Book{
    private List<String> bookIds;
    private Double min;
    private Double max;

    public Double getMax() {
        return max;
    }

    public void setMax(Double max) {
        this.max = max;
    }

    public Double getMin() {
        return min;
    }

    public void setMin(Double min) {
        this.min = min;
    }

    public List<String> getBookIds() {
        return bookIds;
    }

    public void setBookIds(List<String> bookIds) {
        this.bookIds = bookIds;
    }
}

BookService

package com.liuwenwu.service;


import com.liuwenwu.model.Book;
import com.liuwenwu.model.BookVo;
import com.liuwenwu.util.PageBean;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

/**
 * @author LWW
 * @site www.lww.com
 * @company
 * @create 2019-09-19 22:23
 */
public interface BookService {
    int deleteByPrimaryKey(Integer bid);

    int insert(Book record);

    int insertSelective(Book record);

    Book selectByPrimaryKey(Integer bid);

    int updateByPrimaryKeySelective(Book record);

    int updateByPrimaryKey(Book record);

    List<Book> selectByIn(List bookIds);

    List<Book> selectByLike1(String bname);

    List<Book> selectByLike2(String bname);

    List<Book> selectByLike3(String bname);

    List<Book> list1();
    List<Book> list2();
    Book list3(BookVo bookVo);
    List<Map> list4(Map map);
    Map list5(Map map);

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

    List<Map> list6(BookVo bookVo);

    List<Map> list7(BookVo bookVo);
}

BookServiceImpl 

package com.liuwenwu.service.impl;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.liuwenwu.mapper.BookMapper;
import com.liuwenwu.model.Book;
import com.liuwenwu.model.BookVo;
import com.liuwenwu.service.BookService;
import com.liuwenwu.util.PageBean;

import java.util.List;
import java.util.Map;

/**
 * @author LWW
 * @site www.lww.com
 * @company
 * @create 2019-09-19 22:58
 */
public class BookServiceImpl implements BookService {
    private BookMapper bookMapper;

    public BookMapper getBookMapper() {
        return bookMapper;
    }

    public void setBookMapper(BookMapper bookMapper) {
        this.bookMapper = bookMapper;
    }

    @Override
    public int deleteByPrimaryKey(Integer bid) {
        return bookMapper.deleteByPrimaryKey(bid);
    }

    @Override
    public int insert(Book record) {
        return bookMapper.insert(record);
    }

    @Override
    public int insertSelective(Book record) {
        return bookMapper.insertSelective(record);
    }

    @Override
    public Book selectByPrimaryKey(Integer bid) {
        return bookMapper.selectByPrimaryKey(bid);
    }

    @Override
    public int updateByPrimaryKeySelective(Book record) {
        return bookMapper.updateByPrimaryKeySelective(record);
    }

    @Override
    public int updateByPrimaryKey(Book record) {
        return bookMapper.updateByPrimaryKey(record);
    }

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

    @Override
    public List<Book> selectByLike1(String bname) {
        return bookMapper.selectByLike1(bname);
    }

    @Override
    public List<Book> selectByLike2(String bname) {
        return bookMapper.selectByLike2(bname);
    }

    @Override
    public List<Book> selectByLike3(String bname) {
        return bookMapper.selectByLike3(bname);
    }

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

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

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

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

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

    @Override
    public List<Map> listPager(Map map, PageBean pageBean) {

        if(pageBean!=null && pageBean.isPagination()){
            PageHelper.startPage(pageBean.getPage(),pageBean.getRows());
        }

        List<Map> list = this.bookMapper.list4(map);
        if(pageBean!=null && pageBean.isPagination()){
            PageInfo pageInfo =new PageInfo(list);
            System.out.println("当前的页码："+pageInfo.getPageNum());
            System.out.println("页数据量："+pageInfo.getPageSize());
            System.out.println("符合条件的记录数："+pageInfo.getTotal());
            pageBean.setTotal(pageInfo.getTotal()+"");

        }

        return list;
    }

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

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