java使用插件pagehelper在mybatis中实现分页查询

摘要: com.github.pagehelper.PageHelper是一款好用的开源免费的Mybatis第三方物理分页插件

PageHelper是国内牛人的一个开源项目,有兴趣的可以去看源码,都有中文注释

开源项目地址: https://pagehelper.github.io/

 

请求URL:http://localhost:8080/listCity?page=1&limit=10

显示数据:

 

1、PageHelper的maven依赖及插件配置

<dependency>
  <groupId>com.github.pagehelper</groupId>
  <artifactId>pagehelper</artifactId>
  <version>5.1.6</version>
</dependency>

PageHelper除了本身的jar包外,它还依赖了一个叫jsqlparser的jar包,使用时,我们不需要单独指定jsqlparser的maven依赖,maven的间接依赖会帮我们引入。

2、配置拦截器插件

这个是配置在mybatis-config.xml文件中

文档中的示例

<!-- 
    plugins在配置文件中的位置必须符合要求,否则会报错,顺序如下:
    properties?, settings?, 
    typeAliases?, typeHandlers?, 
    objectFactory?,objectWrapperFactory?, 
    plugins?, 
    environments?, databaseIdProvider?, mappers?
-->
<plugins>
    <!-- com.github.pagehelper为PageHelper类所在包名 -->
    <plugin interceptor="com.github.pagehelper.PageInterceptor">
        <!-- 使用下面的方式配置参数,后面会有所有的参数介绍 -->
        <property name="param1" value="value1"/>
    </plugin>
</plugins>

3、我的配置mybatis-config.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    <typeAliases>
        <package name="edu.nf.entity"/>
    </typeAliases>
    <!-- 配置分页插件 -->
    <plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <!--helperDialect 方言:就表示此插件针对哪个数据库进行优化处理
            这个方言可以不配置,因为此插件可以依据你的 url 的信息来推断出
            你用的数据库是哪一个
            -->
            <property name="helperDialect" value="mysql"/>
            <!--分页合理化参数-->
            <property name="reasonable" value="true"/>
        </plugin>
    </plugins>
    <!--配置数据库-->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/citydb?useSSL=true&amp;useUnicode=true&amp;characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/city-mapper.xml"/>
    </mappers>
</configuration>

 

 

4、city-mapper.xml 数据库查询语句配置:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="edu.nf.dao.CityDao">
    <resultMap id="cityMap" type="city" >
        <id property="cityId" column="city_id"/>
        <result property="cityEn" column="city_en"/>
        <result property="cityCn" column="city_cn"/>
        <result property="countryCode" column="country_code"/>
        <result property="countryEn" column="country_en"/>
        <result property="countryCn" column="country_cn"/>
        <result property="provinceEn" column="province_en"/>
        <result property="provinceCn" column="province_cn"/>
    </resultMap>
    <!-- 这里写查询全部数据,配置好的分页插件他会自己加上limit 查询语句后面不能加; -->
    <select id="listCity" resultMap="cityMap">
      select * from city_test
    </select>
    <delete id="deleteCity" parameterType="java.util.List">
        delete from city_test where city_id in
        <foreach collection="list" item="city" open="(" separator="," close=")">
            #{city.cityId}
        </foreach>
    </delete>
</mapper>
View Code

5、后台分页查询 servlet:

 

/**
 * @author hh
 * @Date 2018/9/15
 */
@WebServlet("/listCity")
public class CityListServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("application/json;charset=utf-8");
        //取出前端请求参数
        String page=req.getParameter("page");
        String limit=req.getParameter("limit");

        //分页查询结果 page页数 limit显示行数
        List<City> listCity=new CityService().listCity(page,limit);

        // 包装Page对象 listCity:page结果 , navigatePages: 页码数量
        PageInfo<City> list=new PageInfo<>(listCity,1);

        //自己写的一个响应视图类,因为前端用的是layui框架需要自己,所以自己定义ResponseView
        ResponseView vo=new ResponseView();
        //设值 取出总数据行
        vo.setCount(list.getTotal());
        //设值 查询的结果
        vo.setData(list.getList());
        //响应前端
        resp.getWriter().print(new Gson().toJson(vo));
    }
}

 

 

 

6、响应视图类 ResponseView (因为前端用的是layui框架需要自己,所以自己定义ResponseView):

package edu.nf.vo;

/**
 * @author hh
 * @Date 2018/9/15
 */
public class ResponseView {
    private int code =0;
    private Long count=0L;
    private Object data;

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public Long getCount() {
        return count;
    }

    public void setCount(Long count) {
        this.count = count;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }
}
View Code

7、实体类 City:

package edu.nf.entity;

/**
 * @author hh
 * @Date 2018/9/14
 */
public class City {
    private String cityId;
    private String cityEn;
    private String cityCn;
    private String countryCode;
    private String countryEn;
    private String countryCn;
    private String provinceEn;
    private String provinceCn;

    public String getCityId() {
        return cityId;
    }

    public void setCityId(String cityId) {
        this.cityId = cityId;
    }

    public String getCityEn() {
        return cityEn;
    }

    public void setCityEn(String cityEn) {
        this.cityEn = cityEn;
    }

    public String getCityCn() {
        return cityCn;
    }

    public void setCityCn(String cityCn) {
        this.cityCn = cityCn;
    }

    public String getCountryCode() {
        return countryCode;
    }

    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }

    public String getCountryEn() {
        return countryEn;
    }

    public void setCountryEn(String countryEn) {
        this.countryEn = countryEn;
    }

    public String getCountryCn() {
        return countryCn;
    }

    public void setCountryCn(String countryCn) {
        this.countryCn = countryCn;
    }

    public String getProvinceEn() {
        return provinceEn;
    }

    public void setProvinceEn(String provinceEn) {
        this.provinceEn = provinceEn;
    }

    public String getProvinceCn() {
        return provinceCn;
    }

    public void setProvinceCn(String provinceCn) {
        this.provinceCn = provinceCn;
    }
}
View Code

8、service 逻辑业务层(CityService):

/**
 * @author hh
 * @Date 2018/9/15
 */
public class CityService {
    /**
     * 分页查询 城市信息集合
     * @return
     */
    public List<City> listCity(String offest,String pageSize){
        //类型转换
        Integer pnum=Integer.valueOf(offest);
        Integer psize=Integer.valueOf(pageSize);
        //调用PageHelper获取第1页,10条内容,默认查询总数count
        PageHelper.startPage(pnum,psize);
        //调用CityDaoImpl 分页查询
        return new CityDaoImpl().listCity();
    }

    /**
     * 批量删除
     * @param cityData
     * @return
     */
    public int deleteCity(String cityData){
        List<City> list=new Gson().fromJson(cityData,new TypeToken<List<City>>(){}.getType());
        try {
            new CityDaoImpl().deleteCity(list);
            return 200;
        } catch (Exception e) {
            e.printStackTrace();
            return 403;
        }
    }
}

 

9、Dao 接口类:

/**
 * @author hh
 * @Date 2018/9/14
 */
public interface CityDao {
    /**
     * 城市信息列表
     * @return
     */
    List<City> listCity();

    /**
     * 批量删除
     * @param listCity
     */
    void deleteCity(List<City> listCity);
}

 

10、Dao实现类:

/**
 * @author hh
 * @Date 2018/9/14
 */
public class CityDaoImpl implements CityDao {
    @Override
    public List<City> listCity() {
        List<City> list=null;
        try(SqlSession sqlSession = MybatisUtil.getSqlSession()){
            CityDao cityDao=sqlSession.getMapper(CityDao.class);
            list=cityDao.listCity();
        }
        return list;
    }

    @Override
    public void deleteCity(List<City> listCity) {
        try(SqlSession sqlSession = MybatisUtil.getSqlSession()){
            CityDao cityDao=sqlSession.getMapper(CityDao.class);
            cityDao.deleteCity(listCity);
        }
    }
}

 

 我的项目案例(包括了上一篇博客的分页查询):点我下载

项目结构:

 

posted @ 2018-09-19 16:48  黄浩#  阅读(24257)  评论(0编辑  收藏  举报