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How to implement new dishes and paging query in Java

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    1. Add new dishes

    1.1 Demand analysis

    The background system can manage classification information, classify dish classifications and set meal classifications. When we add dishes in the backend system, we need to select a dish category.

    When we add a set meal in the backend system, we need to select a set meal category. The corresponding dishes and set meals will also be displayed on the mobile terminal according to the dish classification and set meal category.

    How to implement new dishes and paging query in Java

    At the same time, add the dish category and package category on the category management page of the backend system:

    Add dish category

    How to implement new dishes and paging query in Java

    Add package category

    How to implement new dishes and paging query in Java

    ##Data model:

    Involves one table Category table:

    How to implement new dishes and paging query in Java

    The data JavaBean corresponding to the table is Category.java

    Category.java

    package com.itheima.reggie.entity;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.IdType;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.annotation.TableId;
    import lombok.Data;
    import lombok.Getter;
    import lombok.Setter;
    import java.io.Serializable;
    import java.time.LocalDateTime;
    /**
     * 分类
     */
    @Data
    public class Category implements Serializable {
        private static final long serialVersionUID = 1L;
        private Long id;
        //类型 1 菜品分类 2 套餐分类
        private Integer type;
        //分类名称
        private String name;
        //顺序
        private Integer sort;
        //创建时间
        @TableField(fill = FieldFill.INSERT)
        private LocalDateTime createTime;
        //更新时间
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private LocalDateTime updateTime;
        //创建人
        @TableField(fill = FieldFill.INSERT)
        private Long createUser;
        //修改人
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private Long updateUser;
        //是否删除
        private Integer isDeleted;
    }

    For the specific frame, please refer to the previous Employee entity construction.

    1.2 Code Development

    The service address requested for adding new dish categories and set meal categories is the same as the submitted JSON data structure. The server only needs to provide one method:

    API
    DescriptionValueRequest URL/categoryRequest data{
    "name": "Sichuan cuisine",
    "type": "1",
    "sort": "1"
    }
    Code
    Write new code in CategoryController.java:

    package com.itheima.reggie.controller;
    import com.itheima.reggie.common.R;
    import com.itheima.reggie.entity.Category;
    import com.itheima.reggie.service.CategoryService;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    import javax.annotation.Resource;
    /**
     * @author jektong
     * @date 2022年05月06日 21:47
     */
    @RestController
    @Slf4j
    @RequestMapping("/category")
    public class CategoryController {
        @Resource
        private CategoryService categoryService;
        /**
         * 新增分类
         * @param category
         * @return
         */
        @PostMapping
        public R<String> save(@RequestBody Category category){
            log.info("category:{}",category);
            categoryService.save(category);
            return R.success("新增分类成功");
        }
    }

    2. Category information paging query

    Paging query is the same as the previous employee information query. Go directly to the code:

    @GetMapping("/page")
        public R<Page> page(int page, int pageSize){
            // 分页构造
            Page<Category> pageInfo = new Page<Category>(page,pageSize);
            // 查询并排序
            LambdaQueryWrapper<Category> queryWrapper = new LambdaQueryWrapper();
            queryWrapper.orderByAsc(Category::getSort);
            // 分页查询
            categoryService.page(pageInfo,queryWrapper);
            return R.success(pageInfo);
        }

    3. Delete category

    3.1 Requirements analysis

    In the category management list Page, you can delete a category. It should be noted that when a category is associated with a dish or set meal, this category cannot be deleted.

    How to implement new dishes and paging query in Java

    API

    DescriptionValueRequest URL/category?id=
    You need to introduce two entities: dish and set meal:

    Dish.java: dish Entity

    package com.itheima.reggie.entity;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.IdType;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.annotation.TableId;
    import lombok.Data;
    import java.io.Serializable;
    import java.math.BigDecimal;
    import java.time.LocalDateTime;
    /**
     菜品
     */
    @Data
    public class Dish implements Serializable {
        private static final long serialVersionUID = 1L;
        private Long id;
        //菜品名称
        private String name;
        //菜品分类id
        private Long categoryId;
        //菜品价格
        private BigDecimal price;
        //商品码
        private String code;
        //图片
        private String image;
        //描述信息
        private String description;
        //0 停售 1 起售
        private Integer status;
        //顺序
        private Integer sort;
        @TableField(fill = FieldFill.INSERT)
        private LocalDateTime createTime;
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private LocalDateTime updateTime;
        @TableField(fill = FieldFill.INSERT)
        private Long createUser;
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private Long updateUser;
        //是否删除
        private Integer isDeleted;
    }

    Setmeal.java: Package entity

    package com.itheima.reggie.entity;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.IdType;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.annotation.TableId;
    import lombok.Data;
    import java.io.Serializable;
    import java.math.BigDecimal;
    import java.time.LocalDateTime;
    /**
     * 套餐
     */
    @Data
    public class Setmeal implements Serializable {
        private static final long serialVersionUID = 1L;
        private Long id;
        //分类id
        private Long categoryId;
        //套餐名称
        private String name;
        //套餐价格
        private BigDecimal price;
        //状态 0:停用 1:启用
        private Integer status;
        //编码
        private String code;
        //描述信息
        private String description;
        //图片
        private String image;
        @TableField(fill = FieldFill.INSERT)
        private LocalDateTime createTime;
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private LocalDateTime updateTime;
        @TableField(fill = FieldFill.INSERT)
        private Long createUser;
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private Long updateUser;
        //是否删除
        private Integer isDeleted;
    }

    3.2 Core code

    CategoryServiceImpl.java

    package com.itheima.reggie.service.impl;
    import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
    import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
    import com.itheima.reggie.common.CustomException;
    import com.itheima.reggie.entity.Category;
    import com.itheima.reggie.entity.Dish;
    import com.itheima.reggie.entity.Setmeal;
    import com.itheima.reggie.mapper.CategoryMapper;
    import com.itheima.reggie.service.CategoryService;
    import com.itheima.reggie.service.DishService;
    import com.itheima.reggie.service.SetmealService;
    import org.springframework.stereotype.Service;
    import javax.annotation.Resource;
    /**
     * @author jektong
     * @date 2022年05月06日 21:44
     */
    @Service
    public class CategoryServiceImpl extends ServiceImpl<CategoryMapper, Category> implements CategoryService {
        @Resource
        private DishService dishService;
        @Resource
        private SetmealService setmealService;
        /**
         * 根据ID删除分类,分类之前需要判断
         * @param id
         */
        @Override
        public void remove(Long id) {
            LambdaQueryWrapper<Dish> dishLambdaQueryWrapper =  new LambdaQueryWrapper<>();
            // 查询当前分类是否关联了菜品,若关联菜品,抛出异常
            dishLambdaQueryWrapper.eq(Dish::getCategoryId,id);
            int count = dishService.count(dishLambdaQueryWrapper);
            if(count > 0){
                // 已经关联菜品,抛出异常
                throw new CustomException("当前分类已关联菜品,不可删除");
            }
            // 查询当前分类是否关联了套餐,若关联菜品,抛出异常
            LambdaQueryWrapper<Setmeal> setmealLambdaQueryWrapper =  new LambdaQueryWrapper<>();
            setmealLambdaQueryWrapper.eq(Setmeal::getCategoryId,id);
            int count1 = setmealService.count(setmealLambdaQueryWrapper);
            if(count>0){
                // 已经关联套餐,抛出异常
                throw new CustomException("当前分类已关联套餐,不可删除");
            }
            // 正常删除分类
            super.removeById(id);
        }
    }

    Add in the previous custom exception class:

    /**
         * 异常处理方法
         * @param customException
         * @return
         */
        @ExceptionHandler(CustomException.class)
        public R<String> exceptionHandler(CustomException customException){
            log.error(customException.getMessage());
            return R.error(customException.getMessage());
        }

    CustomException.java

    package com.itheima.reggie.common;
    /**
     * @author jektong
     * @date 2022年05月10日 22:26
     */
    public class CustomException extends RuntimeException{
        public CustomException(String msg){
            super(msg);
        }
    }

    4. Modify the classification

    Modifying the classification is very simple. Just modify it according to the classification ID. The code is as follows:

    @PutMapping
    public R<String> update(@RequestBody Category category){
      log.info("修改分类信息{}" + category);
      categoryService.updateById(category);
      return R.success("分类修改成功");
    }

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