1、分頁結果的封裝類：

響應結果：

• total：總條數

• items：當前頁資料

• totalPage：有些還需要總頁數

 <!-- 分頁助手啟動器 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>${pageHelper.starter.version}</version>
        </dependency>
 

這裡我們封裝一個類，來表示分頁結果：

package com.leyou.common.pojo;

import java.util.List;

/**
 * @author: Lucifer
 * @create: 2018-11-03 14:56
 * @description:
 **/
public class PageResult<T> {
    private Long total;// 總條數
    private Long totalPage;// 總頁數
    private List<T> items;// 當前頁資料

    public PageResult() {
    }

    public PageResult(Long total, List<T> items) {
        this.total = total;
        this.items = items;
    }

    public PageResult(Long total, Long totalPage, List<T> items) {
        this.total = total;
        this.totalPage = totalPage;
        this.items = items;
    }

    public Long getTotal() {
        return total;
    }

    public void setTotal(Long total) {
        this.total = total;
    }

    public List<T> getItems() {
        return items;
    }

    public void setItems(List<T> items) {
        this.items = items;
    }

    public Long getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(Long totalPage) {
        this.totalPage = totalPage;
    }
}
 

2、pojo:品牌的實體類。

注：@Table(name="資料庫中對應的表名") 

@Getter，@Setter，@ToString這三個註解是lombok,需要引入這個jar包，可以不需要再去寫get/set/tostring等方法了，具體可以查百度。

dependencies>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
</dependencies>
 

package com.leyou.item.pojo;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

/**
 * @author: Lucifer
 * @create: 2018-11-03 15:00
 * @description:
 **/
@Getter
@Setter
@ToString
@Table(name = "tb_brand")
public class Brand {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;// 品牌名稱
    private String image;// 品牌圖片
    private Character letter;
}

3、品牌的controller方法：

package com.leyou.item.controller;

import com.leyou.common.pojo.PageResult;
import com.leyou.item.pojo.Brand;
import com.leyou.item.service.BrandService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author: Lucifer
 * @create: 2018-11-03 15:04
 * @description:
 **/
@RestController
@RequestMapping("brand")
public class BrandController {

    @Autowired
    private BrandService brandService;

    @GetMapping("page")
    public ResponseEntity<PageResult<Brand>> queryBrandByPage(
            @RequestParam(value = "page", defaultValue = "1") Integer page,
            @RequestParam(value = "rows", defaultValue = "5") Integer rows,
            @RequestParam(value = "sortBy", required = false) String sortBy,
            @RequestParam(value = "desc", defaultValue = "false") Boolean desc,
            @RequestParam(value = "key", required = false) String key) {
        PageResult<Brand> result = this.brandService.queryBrandByPageAndSort(page, rows, sortBy, desc, key);
        if (result == null || result.getItems().size() == 0) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
        return ResponseEntity.ok(result);
    }
}

@RequestParam：

HttpStatus.NOT_FOUND 對應的是404，通過原始碼可以看到：

4、使用通用mapper可以簡化開發。

package com.leyou.item.mapper;

import com.leyou.item.pojo.Brand;
import tk.mybatis.mapper.common.Mapper;

public interface BrandMapper extends Mapper<Brand> {
}

使用通用mapper的話，簡單的增刪改查就不需要去寫sql語句，底層都已經封裝好了。

5、品牌的實現類：

     這裡為了方便直接寫類 BrandService ，並沒有service介面；當然在公司不能這麼做。

package com.leyou.item.service;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.leyou.common.pojo.PageResult;
import com.leyou.item.mapper.BrandMapper;
import com.leyou.item.pojo.Brand;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import tk.mybatis.mapper.entity.Example;

/**
 * @author: Lucifer
 * @create: 2018-11-03 15:05
 * @description:
 **/
@Service
public class BrandService {

    @Autowired
    private BrandMapper brandMapper;

    public PageResult<Brand> queryBrandByPageAndSort(
            Integer page, Integer rows, String sortBy, Boolean desc, String key) {
        // 開始分頁
        PageHelper.startPage(page, rows);
        // 過濾
        Example example = new Example(Brand.class);
        if (StringUtils.isNotBlank(key)) {
            example.createCriteria().andLike("name", "%" + key + "%")
                    .orEqualTo("letter", key);
        }
        if (StringUtils.isNotBlank(sortBy)) {
            // 排序
            String orderByClause = sortBy + (desc ? " DESC" : " ASC");
            example.setOrderByClause(orderByClause);
        }
        // 查詢
        Page<Brand> pageInfo = (Page<Brand>) brandMapper.selectByExample(example);
        // 返回結果
        return new PageResult<>(pageInfo.getTotal(), pageInfo);
    }
}

 6、測試

檢視控制檯的sql語句的列印，應該就可以知道service執行了什麼了： 

可以看下圖：

通過debug可以看到是通過@Table(name="")去找到對應的表的。

至於怎麼去增刪改查，這裡就不把截圖發出來了，可以自己去debug看看。