WeChat Ordering System Chapter 4 - Buyer Category

1. Add dependencies

1. Added Mysql driver (Mysql dependency)

 <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
 </dependency>

2. Tools for operating the database (spring-boot-starter-data-jpa)

 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
 </dependency>

3. Tools to automatically write getter and setter methods

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

Need to be used with the lombok plugin

Second, configure the database information

1. Find the application.properties file under the resources file and modify its suffix to .yml
Note: Why use the .yml format instead of the .properties format?
Because the .yml format can make the configuration more concise

2. Configure database information

spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: 123456
    url: jdbc:mysql://192.168.5.38:3306/sell?characterEncoding=utf-8&useSSL=false
  jpa:
    show-sql: true

3. Objects mapped from the new data table

package com.bdu.dataobject;


import lombok.Data;
import org.hibernate.annotations.DynamicUpdate;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import java.util.Date;


@Entity
@DynamicUpdate
@Data
public class ProductCategory {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer categoryId;
  private String categoryName;
  private Integer categoryType;

  public ProductCategory() {
  }

  public ProductCategory(String categoryName, Integer categoryType) {
    this.categoryName = categoryName;
    this.categoryType = categoryType;
  }
}

4. Dao layer

1. Create a new package named com.bdu.repository

2. Create a new ProductCategoryRepository interface under the repository package to inherit JpaRepository
3. Write code

package com.bdu.repository;

import com.bdu.dataobject.ProductCategory;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.List;

/**
 * @author wanqing
 * @date 2022/1/17 17:26
 */
public interface ProductCategoryRepository extends JpaRepository<ProductCategory,Integer> {
//            查看类目列表
    List<ProductCategory> findByCategoryTypeIn(List<Integer> categoryType);
}

Five, service layer

1. Create a new package named com.bdu.service

2. Create a new CategoryService interface in the service package

package com.bdu.service;

import com.bdu.dataobject.ProductCategory;

import java.util.List;

public interface CategoryService {

    //查询一条记录
    ProductCategory findOne(Integer categoryId);

    //查看类目列表
    List<ProductCategory> findAll();

    //买家端
    List<ProductCategory> findByCategoryTypeIn(List<Integer> categoryTypeList);

    //卖家端-新增、更新
    ProductCategory save(ProductCategory productCategory);

}

3. Create a new com.bdu.service.impl package to store the interface implementation class

4. Create a new implementation class CategoryServiceImpl of the CategoryService interface in the com.bdu.service.impl package

package com.bdu.service.impl;

import com.bdu.dataobject.ProductCategory;
import com.bdu.repository.ProductCategoryRepository;
import com.bdu.service.CategoryService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class CategoryServiceImpl implements CategoryService {

    @Autowired
    private ProductCategoryRepository repository;

    @Override
    public ProductCategory findOne(Integer categoryId) {
//        return repository.findById(categoryId).get();

        return repository.findById(categoryId).get();
    }

    @Override
    public List<ProductCategory> findAll() {
        return repository.findAll();
    }

    @Override
    public List<ProductCategory> findByCategoryTypeIn(List<Integer> categoryTypeList) {
        return repository.findByCategoryTypeIn(categoryTypeList);
    }

    @Override
    public ProductCategory save(ProductCategory productCategory) {
        return repository.save(productCategory);
    }
}

6. Errors encountered

1) java: The method findOne in the interface org.springframework.data.repository.query.QueryByExampleExecutor cannot be applied to the given type;

2) Reason: ProductCategoryRepositoryTest class is not a public class

1. The class com.bdu.repository.ProductCategoryRepositoryTest is not public.
2. Test class should have exactly one public constructor
   after modification
   

3) Table 'sell.hibernate_sequence' doesn't exist

Before modification:

After modification: