zero 、 Preface

For ease of description , Let's abstract and simplify the project .
This is a front end for Angular、 For the back end Spring Project , project E-R One paragraph of the figure is as follows ：

It's not hard to see. , Towns and communities are 1 Relationship to many .

When managing lower level areas , You need foreign keys associated with higher-level areas （ for example ： The community must have a township ）

Because the queries in these areas are very frequent , In order to reduce SQL frequency , Cache is set in the background .
In order to avoid the error of the whole system caused by deleting data , Soft deletion is enabled globally .

One 、 Problem recurrence

In the management page of any entity （ Such as township management ） Delete an object from （ Township ）, The deleted data is no longer displayed in the list , You can also see in the database , Deleted objects deleted=1：

But in other entity Association queries （ When setting up towns in the community ）, You can find the deleted objects , And it can be saved ...

（ If you save the deleted data , It will cause the system to report an error ）

Just to summarize ：

Due to some problems with the project code , Soft deletion is normal in list paging query , But when foreign key association is needed , Soft deletion is invalid .

Two 、 Troubleshoot problems

Eliminate cache reasons

First of all, from the issue Look up , It may be caused by the back-end cache （ There have been similar problems before ）. The backend is set to clear the cache when logging in again , So the test is simple .
Tried browser refresh 、 Sign out and log back in 、 Change browser and other operations , It didn't solve the problem , Now basically eliminate the cache reason .

Further investigation ,Spring Use in debug The internal code of the mode step-by-step query function , It is found that the deleted information appears in the return value

So far, it can be concluded that it is not The cache problem It's about the query method .

Check the calling relationship

Since there is a problem with the query , Why can deleted data be normally distinguished in the township list ？

With questions , I found the calling relationship between the front end and the back end ：

Paging query initiated by township list , Finally call to findAll Method

And in the community -> Query the township in the township selector , It will eventually call findAll Method , But the parameters are different

// findAll No parameters 
@Override
public List<Town> findAll() {
  return (List<Town>) this.townRepository.findAll();
}

// page With parameters 
@Override
public Page<Town> page(String name, Pageable pageable) {
  return this.townRepository.findAll(TownSpecs.containingName(name)), pageable);
}

So the preliminary judgment , It's the warehouse floor TownRepository Of getAll() Method omits the function related to soft deletion , But in the code we have seen so far , There is no question about how soft deletion is implemented , So keep looking .

Explore the implementation of soft deletion

Now that we know what the problem is , Next, go to , In this project , How to realize soft deletion , And where are the key codes that affect the query of the warehouse layer , I start from the historical Pull Request Found soft deleted PR.

It is found that , All entities inherit the base entity , To enable soft deletion, you need to set deleted and deleteAt Field , And related Setter、Getter Method , Used to indicate deleted and deleted time ：

Then add @SQLDelete annotation , Replace the delete function with ” Set up deleted=1“
The second line @where(clause = "deleted = false") The function is to query only the data that has not been soft deleted .

At this time, I came up with a stupid method ： All on the warehouse floor findAll To add deleted = 0 Conditions , But the problem is , So many entities , A lot of duplicate code will be generated , And it didn't solve the problem fundamentally , So give up .

thus , After looking around, I still can't find the answer ： Logically speaking, this can already take effect , What is it for? findAll() It will be abnormal ？

Compare the latest version of local code , It is found that the inherited entity has been deleted @where(clause = "deleted = false")

Just when I wonder , I found a think no link in the code comment , Open a look at the soft delete blog written by teacher pan , So I read it again .
spring boot Realize soft deletion

Only then did I realize ：
@Where(clause = "deleted = false") Will cause us to carry on all or page When inquiring , Get one 500 EntiyNotFound error .

The blog also gives solutions ： Create a SoftDeleteCrudRepository Interface , Inherit and override JPA Inside CrudRepository Methods , Manually add deleted = false Conditions （ See blog for specific code ）, This can realize soft deletion and avoid 500 error .

3、 ... and 、 Untie BUG The veil of mystery

So you can guess , The problem must be that we wrote it ourselves SoftDeleteCrudRepository On , Probably because some methods do not override.

Come to the soft deletion warehouse of this project , About findAll Overloaded methods of have these ：

  @Override
  public Page<T> findAll(Pageable pageable) {
    return this.findAll(this.andDeleteFalseSpecification(null), pageable);
  }

  @Override
  public Page<T> findAll(@Nullable Specification<T> specification, Pageable pageable) {
    return super.findAll(this.andDeleteFalseSpecification(specification), pageable);
  }

  @Override
  public List<T> findAll(@Nullable Specification<T> specification, Sort sort) {
    return super.findAll(this.andDeleteFalseSpecification(specification), sort);
  }

So let's go back a little bit , How to call the two cases just now ：

// findAll No parameters 
@Override
public List<Town> findAll() {
  return (List<Town>) this.townRepository.findAll();
}

// page With parameters 
@Override
public Page<Town> page(String name, Pageable pageable) {
  return this.townRepository.findAll(TownSpecs.containingName(name)), pageable);
}

good , Solved the case , Our soft delete class does not override Empty parameter findAll Method , So for empty parameters , It doesn't automatically add deleted=1 Query criteria for .

So just add ：

  @Override
  public List<T> findAll(@Nullable Specification<T> specification) {
    return super.findAll(this.andDeleteFalseSpecification(specification));
  }

You can make the bug In all warehouses findAll() Methods disappear , In the future, there will be new calling methods , Just modify the soft delete class .
At this point, the problem is finally solved .

Reference material

spring boot Realize soft deletion ：https://segmentfault.com/a/11...

Postscript

In fact, this project is really The writing method is more complicated than that in the references ：

SoftDeleteCrudRepository No longer an interface , Instead, the implementation class
Other warehouses do not inherit directly SoftDeleteCrudRepository, Instead, use factory mode injection
I don't understand the code of factory mode in the project , In fact, I didn't understand it in the end , Are there any other warehouses extends either implements Under the circumstances , How to call SoftDeleteCrudRepository Of .

Copyright notice

The author of this article ： Dream cloud intelligence development team of Hebei University of technology - Liu Yuxuan
New people are inexperienced , If you have suggestions, welcome to exchange , If there are mistakes, please spray lightly