Mybatis的动态sql以及分页

mybatis动态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);

再来看下工具类

Pagebean.java

    private static final long serialVersionUID = 2422581023658455731L;

    //页码

    private int page=;

    //每页显示记录数

    private int rows=;

    //总记录数

    private int total=;

    //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()-)*this.rows;

    }

    /**

     * 末页

     * @return

     */

    public int getMaxPage() {

        int totalpage=this.total/this.rows;

        if(this.total%this.rows!=)

            totalpage++;

        return totalpage;

    }

    /**

     * 下一页

     * @return

     */

    public int getNextPage() {

        int nextPage=this.page+;

        if(this.page>=this.getMaxPage())

            nextPage=this.getMaxPage();

        return nextPage;

    }

    /**

     * 上一页

     * @return

     */

    public int getPreivousPage() {

        int previousPage=this.page-;

        if(previousPage<)

            previousPage=;

        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、模糊查询

#{…}
${…}
Concat

注意：#{...}自带引号，${...}有sql注入的风险

<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);

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

3.2 使用resultType返回List<T>

3.3 使用resultType返回单个对象

3.4 使用resultType返回List<Map>，适用于多表查询返回结果集

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

<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();

        list.add();

        list.add();

//        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));

    }

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.</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>

使用分页插件

<select id="listPager" resultType="java.util.Map" parameterType="java.util.Map">

  select * from t_mvc_book where bname like concat(concat('%',#{bname}),'%')

</select>

Mapper层

List<Map> listPager(Map map);

Service层

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;

}

特殊字符处理

>(&gt;)

    <(&lt;)

    &(&amp;)

 空格(&nbsp;)

 <![CDATA[ <= ]]>