Do not use SQL statements to add multiple tables in Springboot Mybatis-plus

The preparation work for the problems I encountered is broken down by simulating thinking in the test environment: Create a BrandDTO object simulation with parameters Passing parameters in the background

Problems I encountered

We all know that it is extremely difficult to perform multi-table operations in Mybatis-plus. If you do not use Mybatis-plus- For tools like join, you can only configure the corresponding Mapper. Flexibility allows us to more flexibly modify the functions required by Party A.
But if I am going to do a very ordinary small project, which does not require any flexible changes, and I do not want to write SQL statements, I want to use Mybatis directly -plus function to add multi-table (one master and multiple copies) data, then what should I do?

Looking at the database, we can know that we have a product table, but productfor Product image, Product parameter and Product type are all one-to-many or many-to-one relationships, but I want our front-end to directly submit a form You can complete the addition of data in multiple tables. Multi-table operations are inevitable

Preparation work

Because I have used mybatis before this operation -plus-join multi-table query operation, so I have generated a DTO entity class

@Data
public class BrandDTO {

    private Integer id;
    //類型表
    private String type;

    //商品表
    private String brandName;
    private String companyName;
    private String description;
    //圖片鏈接表
    private List<Img> imgUrlList;
    //參數(shù)表
    private List<Parameter> parameterList;

}

In this class you will wonder: Why don’t I directly encapsulate a Brand entity object?
Because I have used this class to perform join table queries before, and put the parameters of each entity class separately (there is no duplicate name hhhh), and this class needs to be displayed, so I added the attributes of the Brand class as they are, and The tpye corresponding to Brand should be many (type) to one (Brand), so I only encapsulated one here, but since Brand has a one-to-many relationship with Img and Parameter, I encapsulated them into a list< object >, In this way we got something similar to an intermediate class

Simulated in the test environment

We might as well think about it, with such a class, we only need to separate the parameters To add to each table, we need to imagine that we get a BrandDTO object encapsulating data, and then disassemble it and use the methods of the respective mapper interfaces to insert the table behavior
(First the interface must inherit the corresponding BaseMapper<> ;, you can perform quick operations. Of course, if you have a corresponding adding method in the interface, you can also do it, but since we use mybatis-plus, why do we have to go back and write the adding method ourselves?)

So, after After several repeated experiments, I got the following test method:

 @Test
    public void addBrand(){
        Brand brand = new Brand();
        Type type = new Type();
        Img img = new Img();
        Parameter parameter = new Parameter();

        BrandDTO brandDTO = new BrandDTO();
        brandDTO.setBrandName("測試商品3");
        brandDTO.setCompanyName("廠家3");
        brandDTO.setDescription("這是第二個(gè)個(gè)測試");

        brandDTO.setType("第Ⅱ型");

        List<Img> imgs =new ArrayList<>();
        imgs.add(new Img("w/daw/daw/daww"));
        imgs.add(new Img("xxwdAWd/dawd/wx"));
        brandDTO.setImgUrlList(imgs);


        List<Parameter> parameters = new ArrayList<>();
        parameters.add(new Parameter("110","270*860*270",30,450));
        parameters.add(new Parameter("120","170*4350*720",990,5530));
        brandDTO.setParameterList(parameters);


        List<Img> imgUrlList = brandDTO.getImgUrlList();
        List<Parameter> parameterList = brandDTO.getParameterList();


        brand.setBrandName(brandDTO.getBrandName());
        brand.setCompanyName(brandDTO.getCompanyName());
        brand.setDescription(brandDTO.getDescription());
        brandMapper.insert(brand);

        Integer id = brand.getId();

        type.setBType(brandDTO.getType());
        type.setBId(id);
        typeMapper.insert(type);

        for (Parameter parameterl : parameterList) {
            parameter.setBModel(parameterl.getBModel());
            parameter.setBOutput(parameterl.getBOutput());
            parameter.setBSize(parameterl.getBSize());
            parameter.setBId(id);
            parameterMapper.insert(parameter);
        }

        for (Img imgl : imgUrlList) {
            img.setImgUrl(imgl.getImgUrl());
            img.setBrandId(id);
            imgMapper.insert(img);
        }

        System.out.println(id);

    }

Thinking breakdown:

Next, I will decompose and express each part of the method body

Create A BrandDTO object with parameters

First we simulated a BrandDTO object encapsulating various parameters:

        Type type = new Type();
        Img img = new Img();
        Parameter parameter = new Parameter();

        BrandDTO brandDTO = new BrandDTO();
        brandDTO.setBrandName("測試商品3");
        brandDTO.setCompanyName("廠家3");
        brandDTO.setDescription("這是第二個(gè)個(gè)測試");

        brandDTO.setType("第Ⅱ型");

        List<Img> imgs =new ArrayList<>();
        //此操作能成功是因?yàn)槲以趯?yīng)的對象中生成了除了id屬性和外鍵屬性的有參構(gòu)造
        imgs.add(new Img("w/daw/daw/daww"));
        imgs.add(new Img("xxwdAWd/dawd/wx"));
        brandDTO.setImgUrlList(imgs);


        List<Parameter> parameters = new ArrayList<>();
        //此操作能成功是因?yàn)槲以趯?yīng)的對象中生成了除了id屬性和外鍵屬性的有參構(gòu)造
        parameters.add(new Parameter("110","270*860*270",30,450));
        parameters.add(new Parameter("120","170*4350*720",990,5530));
        brandDTO.setParameterList(parameters);

This part is mainly the encapsulation of parameters, which is the work of the front end. Let us do the background work The server receives a BrandDTO object with parameters

Simulates passing parameters to the background

Takes out the corresponding parameters in each table

		//取出ImgUrlList和ParameterList()
		List<Img> imgUrlList = brandDTO.getImgUrlList();
        List<Parameter> parameterList = brandDTO.getParameterList();

		//單獨(dú)封裝brand對象
        brand.setBrandName(brandDTO.getBrandName());
        brand.setCompanyName(brandDTO.getCompanyName());
        brand.setDescription(brandDTO.getDescription());
        //調(diào)用對應(yīng)Mapper接口的insert方法(或者你自己寫的添加方法)
        brandMapper.insert(brand);
        //使用主鍵返回(要確保mybatis中設(shè)置了主鍵自增并且在各個(gè)實(shí)體類中聲明了主鍵屬性)
        Integer id = brand.getId();

After the above operations, we report to Brand A row of information is added to the table, and the primary key is returned.

So our other tables know the ID of the corresponding product, and can use this ID to define the foreign key ID in the table:

(Please note that in this test class, I injected the Mapper interface of each entity class that I need to use, so I can call the insert method)

		//向Type表中添加數(shù)據(jù)并指定外鍵(BrandID)的id
		type.setBType(brandDTO.getType());
        type.setBId(id);
        typeMapper.insert(type);
        //向Paramater表中添加數(shù)據(jù)并指定外鍵(BrandID)的id
        for (Parameter parameterl : parameterList) {
            parameter.setBModel(parameterl.getBModel());
            parameter.setBOutput(parameterl.getBOutput());
            parameter.setBSize(parameterl.getBSize());
            parameter.setBId(id);
            parameterMapper.insert(parameter);
        }
        //向Img表中添加數(shù)據(jù)并指定外鍵(BrandID)的id
        for (Img imgl : imgUrlList) {
            img.setImgUrl(imgl.getImgUrl());
            img.setBrandId(id);
            imgMapper.insert(img);
        }

Use a loop Add, we can add the data in the object to each table one by one. Next, we need to use the console to get the primary key id corresponding to the product we added:

System.out.println(id);

After that we run, what I got here The data is 3, and then we call the method of querying products by ID:
I am using Apifox here:

It can be seen that our information has been inserted into the table The return value part is null because the multi-table query I wrote has some small bugs, but there is still data in the database. It can be seen that this test is successful. Next, just CV the code to the corresponding service. The controller layer can simulate passing in a Json object to check whether it is feasible!

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