从零到企业级SSM电商项目实战教程（三十二）加入购物车功能开发

购物车模块功能

1、加入商品

2、更新商品数

3、查询商品数

4、移除商品

5、单选/取消

6、全选/取消

7、购物车列表

学习目标

1、购物车模块的设计思想

2、如何封装一个高复用的购物车核心方法

3、解决浮点型商业运算中丢失精度的问题

CartController.java

controller.portal 包下新建一个 CartController.java

package com.mmall.controller.portal;

import com.mmall.common.Const;
import com.mmall.common.ResponseCode;
import com.mmall.common.ServerResponse;
import com.mmall.pojo.User;
import com.mmall.service.ICartService;
import com.mmall.vo.CartVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpSession;

/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 8:46
 * @Description:
 */
@Controller
@RequestMapping("/cart")
public class CartController {

    @Autowired
    private ICartService iCartService;

    @RequestMapping("add.do")
    public ServerResponse<CartVo> add(HttpSession session, Integer count, Integer productId) {
        User user = (User) session.getAttribute(Const.CURRENT_USER);
        if (user == null) {
            return ServerResponse.createByErrorCodeMessage(ResponseCode.NEED_LOGIN.getCode(), ResponseCode.NEED_LOGIN.getDesc());
        }
        return iCartService.add(user.getId(), productId, count);
    }
}

ICartService.java

service 包下新建 ICartService.java 及其实现类 CartServiceImpl.java

package com.mmall.service;

import com.mmall.common.ServerResponse;
import com.mmall.vo.CartVo;

/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 8:48
 * @Description:
 */
public interface ICartService {

    ServerResponse<CartVo> add(Integer userId, Integer productId, Integer count);
}

CartServiceImpl.java

编写实现类

package com.mmall.service.impl;

import com.google.common.collect.Lists;
import com.mmall.common.Const;
import com.mmall.common.ResponseCode;
import com.mmall.common.ServerResponse;
import com.mmall.dao.CartMapper;
import com.mmall.dao.ProductMapper;
import com.mmall.pojo.Cart;
import com.mmall.pojo.Product;
import com.mmall.service.ICartService;
import com.mmall.util.BigDecimalUtil;
import com.mmall.util.PropertiesUtil;
import com.mmall.vo.CartProductVo;
import com.mmall.vo.CartVo;
import org.apache.commons.collections.CollectionUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.math.BigDecimal;
import java.util.List;


/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 8:49
 * @Description:
 */

@Service("iCartService")
public class CartServiceImpl implements ICartService {

    @Autowired
    private CartMapper cartMapper;
    @Autowired
    private ProductMapper productMapper;

    public ServerResponse<CartVo> add(Integer userId,Integer productId,Integer count){
        if(productId == null || count == null){
            return ServerResponse.createByErrorCodeMessage(ResponseCode.ILLEGAL_ARGUMENT.getCode(),ResponseCode.ILLEGAL_ARGUMENT.getDesc());
        }

        Cart cart = cartMapper.selectCartByUserIdProductId(userId,productId);
        if(cart == null){
            //这个产品不在这个购物车里,需要新增一个这个产品的记录
            Cart cartItem = new Cart();
            cartItem.setQuantity(count);
            cartItem.setChecked(Const.Cart.CHECKED);
            cartItem.setProductId(productId);
            cartItem.setUserId(userId);
            cartMapper.insert(cartItem);
        }else{
            //这个产品已经在购物车里了.
            //如果产品已存在,数量相加
            count = cart.getQuantity() + count;
            cart.setQuantity(count);
            cartMapper.updateByPrimaryKeySelective(cart);
        }
        CartVo cartVo = this.getCartVoLimit(userId);
        return ServerResponse.createBySuccess(cartVo);
    }


    private CartVo getCartVoLimit(Integer userId){
        CartVo cartVo = new CartVo();
        List<Cart> cartList = cartMapper.selectCartByUserId(userId);
        List<CartProductVo> cartProductVoList = Lists.newArrayList();

        BigDecimal cartTotalPrice = new BigDecimal("0");

        if(CollectionUtils.isNotEmpty(cartList)){
            for(Cart cartItem : cartList){
                CartProductVo cartProductVo = new CartProductVo();
                cartProductVo.setId(cartItem.getId());
                cartProductVo.setUserId(userId);
                cartProductVo.setProductId(cartItem.getProductId());

                Product product = productMapper.selectByPrimaryKey(cartItem.getProductId());
                if(product != null){
                    cartProductVo.setProductMainImage(product.getMainImage());
                    cartProductVo.setProductName(product.getName());
                    cartProductVo.setProductSubtitle(product.getSubtitle());
                    cartProductVo.setProductStatus(product.getStatus());
                    cartProductVo.setProductPrice(product.getPrice());
                    cartProductVo.setProductStock(product.getStock());
                    //判断库存
                    int buyLimitCount = 0;
                    if(product.getStock() >= cartItem.getQuantity()){
                        //库存充足的时候
                        buyLimitCount = cartItem.getQuantity();
                        cartProductVo.setLimitQuantity(Const.Cart.LIMIT_NUM_SUCCESS);
                    }else{
                        buyLimitCount = product.getStock();
                        cartProductVo.setLimitQuantity(Const.Cart.LIMIT_NUM_FAIL);
                        //购物车中更新有效库存
                        Cart cartForQuantity = new Cart();
                        cartForQuantity.setId(cartItem.getId());
                        cartForQuantity.setQuantity(buyLimitCount);
                        cartMapper.updateByPrimaryKeySelective(cartForQuantity);
                    }
                    cartProductVo.setQuantity(buyLimitCount);
                    //计算总价
                    cartProductVo.setProductTotalPrice(BigDecimalUtil.mul(product.getPrice().doubleValue(),cartProductVo.getQuantity()));
                    cartProductVo.setProductChecked(cartItem.getChecked());

                    //如果不判断是否有商品就进行添加购物车操作，会报空指针异常。
                    if(cartItem.getChecked() == Const.Cart.CHECKED){
                        //如果已经勾选,增加到整个的购物车总价中
                        cartTotalPrice = BigDecimalUtil.add(cartTotalPrice.doubleValue(),cartProductVo.getProductTotalPrice().doubleValue());
                    }
                    cartProductVoList.add(cartProductVo);
                }

            }
        }
        cartVo.setCartTotalPrice(cartTotalPrice);
        cartVo.setCartProductVoList(cartProductVoList);
        cartVo.setAllChecked(this.getAllCheckedStatus(userId));
        cartVo.setImageHost(PropertiesUtil.getProperty("ftp.server.http.prefix"));

        return cartVo;
    }

    private boolean getAllCheckedStatus(Integer userId){
        if(userId == null){
            return false;
        }
        return cartMapper.selectCartProductCheckedStatusByUserId(userId) == 0;

    }
}

CartMapper.java

Cart selectCartByUserIdProductId(@Param("userId") Integer userId, @Param("productId")Integer productId);

List<Cart> selectCartByUserId(Integer userId);

int selectCartProductCheckedStatusByUserId(Integer userId);

CartMapper.xml

<select id="selectCartByUserIdProductId" resultMap="BaseResultMap" parameterType="map">
  SELECT
  <include refid="Base_Column_List"/>
  from mmall_cart
  where user_id = #{userId}
  and product_id = #{productId}
</select>

<select id="selectCartByUserId" resultMap="BaseResultMap" parameterType="int">
  SELECT
  <include refid="Base_Column_List"/>
  from mmall_cart
  where user_id = #{userId}
</select>

<select id="selectCartProductCheckedStatusByUserId" resultType="int" parameterType="int">
  SELECT  count(1) from mmall_cart where checked = 0 and user_id = #{userId}
</select>

Const.java

public interface Cart{
    int CHECKED = 1;//即购物车选中状态
    int UN_CHECKED = 0;//购物车中未选中状态

    String LIMIT_NUM_FAIL = "LIMIT_NUM_FAIL";
    String LIMIT_NUM_SUCCESS = "LIMIT_NUM_SUCCESS";
}

CartProductVo.java

package com.mmall.vo;

import java.math.BigDecimal;

/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 8:56
 * @Description:
 */
public class CartProductVo {

//结合了产品和购物车的一个抽象对象

    private Integer id;
    private Integer userId;
    private Integer productId;
    private Integer quantity;//购物车中此商品的数量
    private String productName;
    private String productSubtitle;
    private String productMainImage;
    private BigDecimal productPrice;
    private Integer productStatus;
    private BigDecimal productTotalPrice;
    private Integer productStock;
    private Integer productChecked;//此商品是否勾选

    private String limitQuantity;//限制数量的一个返回结果

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public Integer getProductId() {
        return productId;
    }

    public void setProductId(Integer productId) {
        this.productId = productId;
    }

    public Integer getQuantity() {
        return quantity;
    }

    public void setQuantity(Integer quantity) {
        this.quantity = quantity;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public String getProductSubtitle() {
        return productSubtitle;
    }

    public void setProductSubtitle(String productSubtitle) {
        this.productSubtitle = productSubtitle;
    }

    public String getProductMainImage() {
        return productMainImage;
    }

    public void setProductMainImage(String productMainImage) {
        this.productMainImage = productMainImage;
    }

    public BigDecimal getProductPrice() {
        return productPrice;
    }

    public void setProductPrice(BigDecimal productPrice) {
        this.productPrice = productPrice;
    }

    public Integer getProductStatus() {
        return productStatus;
    }

    public void setProductStatus(Integer productStatus) {
        this.productStatus = productStatus;
    }

    public BigDecimal getProductTotalPrice() {
        return productTotalPrice;
    }

    public void setProductTotalPrice(BigDecimal productTotalPrice) {
        this.productTotalPrice = productTotalPrice;
    }

    public Integer getProductStock() {
        return productStock;
    }

    public void setProductStock(Integer productStock) {
        this.productStock = productStock;
    }

    public Integer getProductChecked() {
        return productChecked;
    }

    public void setProductChecked(Integer productChecked) {
        this.productChecked = productChecked;
    }

    public String getLimitQuantity() {
        return limitQuantity;
    }

    public void setLimitQuantity(String limitQuantity) {
        this.limitQuantity = limitQuantity;
    }
}

CartVo.java

package com.mmall.vo;

import java.math.BigDecimal;
import java.util.List;

/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 8:57
 * @Description:
 */
public class CartVo {

    private List<CartProductVo> cartProductVoList;
    private BigDecimal cartTotalPrice;
    private Boolean allChecked;//是否已经都勾选
    private String imageHost;

    public List<CartProductVo> getCartProductVoList() {
        return cartProductVoList;
    }

    public void setCartProductVoList(List<CartProductVo> cartProductVoList) {
        this.cartProductVoList = cartProductVoList;
    }

    public BigDecimal getCartTotalPrice() {
        return cartTotalPrice;
    }

    public void setCartTotalPrice(BigDecimal cartTotalPrice) {
        this.cartTotalPrice = cartTotalPrice;
    }

    public Boolean getAllChecked() {
        return allChecked;
    }

    public void setAllChecked(Boolean allChecked) {
        this.allChecked = allChecked;
    }

    public String getImageHost() {
        return imageHost;
    }

    public void setImageHost(String imageHost) {
        this.imageHost = imageHost;
    }
}

BigDecimalUtil.java

util 包下新建 BigDecimalUtil 工具类

package com.mmall.util;

import java.math.BigDecimal;

/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 9:09
 * @Description:
 */
public class BigDecimalUtil {

    private BigDecimalUtil(){

    }

    public static BigDecimal add(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.add(b2);
    }

    public static BigDecimal sub(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.subtract(b2);
    }


    public static BigDecimal mul(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.multiply(b2);
    }

    public static BigDecimal div(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.divide(b2,2,BigDecimal.ROUND_HALF_UP);//四舍五入,保留 2 位小数

        //除不尽的情况
    }
}

测试

编写测试文件 BigDecimalTest.java

package com.mmall.test;

import java.math.BigDecimal;
import org.junit.Test;
/**
 * @Author: Geekerstar(jikewenku.com)
 * @Date: 2018/6/24 9:02
 * @Description:
 */
public class BigDecimalTest {

    @Test
    public void test1(){
        System.out.println(0.05+0.01);
        System.out.println(1.0-0.42);
        System.out.println(4.015*100);
        System.out.println(123.3/100);
    }

    @Test
    public void test2(){
        BigDecimal b1 = new BigDecimal(0.05);
        BigDecimal b2 = new BigDecimal(0.01);
        System.out.println(b1.add(b2));
    }

    @Test
    public void test3(){
        BigDecimal b1 = new BigDecimal("0.05");
        BigDecimal b2 = new BigDecimal("0.01");
        System.out.println(b1.add(b2));

    }

}

test1

test2

test3

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