Mybatis dynamic sql and pagination

mybatis dynamic sql

If、trim、foreach

<select id="selectBooksIn" resultType="com.jt.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> selectBooksIn(@Param("bookIds") List bookIds);

Then look at the tools

Pagebean.java

    Private  static Final Long serialVersionUID = 2422581023658455731L ; 

    // p 
    Private  int Page = . 1 ;
     // Number per page recording 
    Private  int rows = 10 ;
     // total number of records 
    Private  int Total = 0 ;
     // if the tab 
    Private Boolean = isPagination to true ;
     // a path request 
    Private String URL;
     // get all request parameters 
    Private the 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() {
        returnisPagination; 
    } 
    
    public  void setPagination (Boolean isPagination) {
         the this .isPagination = isPagination; 
    } 
    
    public  void setPagination (String isPagination) {
         IF ( null !! = isPagination && "" .equals (isPagination.trim ()))
             the this .isPagination = Boolean .parseBoolean (isPagination); 
    } 
    
    / * * 
     * start mark position acquiring tab 
     * @return 
     * / 
    public  int getStartIndex () {
         // (current page -1) * number of records 
        return ( the 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
                + "]";
    }

StringUtils

public class StringUtils {

    public static String toLikeStr(String str) {
        return "%"+str+"%";
    }

}

2, fuzzy query

#{…}
${…}
Concat

Note: # {...} comes with quotation marks, $ {...} There sql risk injected

<select id="selectBooksLike1" resultType="com.jt.model.Book" parameterType="java.lang.String">
  select * from t_mvc_book where bname like #{bname}
</select>
<select id="selectBooksLike2" resultType="com.jt.model.Book" parameterType="java.lang.String">
  select * from t_mvc_book where bname like '${bname}'
</select>
<select id="selectBooksLike3" resultType="com.jt.model.Book" parameterType="java.lang.String">
  select * from t_mvc_book where bname like concat(concat('%',#{bname}),'%')
</select>

List<Book> selectBooksLike1(@Param("bname")String bname);
    List<Book> selectBooksLike2(@Param("bname")String bname);
    List<Book> selectBooksLike3(@Param("bname")String bname);

Return result sets query processing

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

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

3.1 Use resultMap return custom type set

3.2 Use resultType return List <T>

3.3 Use resultType return a single object

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

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

<select id="list1" resultMap="BaseResultMap">
    select * from t_mvc_book
  </select>
  <select id="list2" resultType="com.jt.model.Book">
    select * from t_mvc_book
  </select>
  <select id="list3" resultType="com.jt.model.Book"ParameterType ="com.jt.model.vo.BookVo">
    select * from t_mvc_book where bid in
    <foreach collection="bookIds" item="bid" open="(" close=")" separator=",">
      #{bid}
    </foreach>
  </select>
  <select id="list4" resultType="java.util.Map" parameterType="java.util.Map">
    select * from t_mvc_book where bid in
    <foreach collection="bookIds" item="bid" open="(" close=")" separator=",">
      #{bid}
    </foreach>
  </select>
  <select id="list5" resultType="java.util.Map">
    select * from t_mvc_book where bid = #{bid}
  </select>

public void list() {
//        List<Book> books = this.bookService.list1();
//        List<Book> books = this.bookService.list2();
        List list=new ArrayList();
        list.add(1);
        list.add(12);
        list.add(16);
//        BookVo bookVo=new BookVo();
//        bookVo.setBookIds(list);
//        List<Book> books = this.bookService.list3(bookVo);
//
//
//        for (Book b : books) {
//            System.out.println(b);
//        }

//        Map map=new HashMap();
//        map.put("bookIds",list);
//        List<Map> mapList = this.bookService.list4(map);
//        for (Map m : mapList) {
//            System.out.println(m);
//
//        }
//        map.put("bid",1);
//        System.out.println(this.bookService.list5(map));


    }

Paging query

Why rewrite mybatis paging?

Mybatis paging function is weak, it is the memory-based page ( isolated then all records offsets offset and boundary limit take result ) , this tab is substantially not used in the case of a large amount of data

Use pagination plug-in step-outs

1, introduced pom dependent

2, Mybatis.cfg.xml arranged interceptors

3, using PageHelper paging

4, the processing result tab

pom-dependent

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

Mybatis.cfg.xml configured interceptor

<plugins> 
    <-! widget configuring paging PageHelper, 4.0 future automatic identification .0 version supports the use of a database -> 
    <= plugin Interceptor " com.github.pagehelper.PageInterceptor " > 
    </ plugin> 
</ plugins>

Use pagination plug-in

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

Mapper layer

List<Map> listPager(Map map);

Service Layer

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

@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("页码："+pageInfo.getPageNum());
        System.out.println("页大小："+pageInfo.getPageSize());
        System.out.println("总记录："+pageInfo.getTotal());
        pageBean.setTotal(pageInfo.getTotal()+"");
    }
    return list;
}

Special Character Handling

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

The relevant code configuration

<select id="list6" resultType="com.jt.model.Book" parameterType="com.jt.model.vo.BookVo">
    select * from t_mvc_book where <![CDATA[ price >#{min} and price <#{max} ]]>
  </select>
  <select id="list7" resultType="com.jt.model.Book" parameterType="com.jt.model.vo.BookVo">
    select * from t_mvc_book where &gt;#{min} and price &lt;#{max}
  </select>