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This article mainly explains "what is the logic of findTreeByParentId". Interested friends may wish to take a look at it. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn "what is the logic of findTreeByParentId"?

Logic:

Recursive query logic, findTreeByParentId logic

Due to a code logic error, if the parentId is null, the following occurs:

Entity entity = new Entity ()

Entity.setPro (null) / / assume that Pro is an attribute of entity

Example example = Example.of (entity)

Repository.findAll (example)

Results:

Query all the results in the table (the problem is a bit serious, if the data in the table is too large, burst memory, stack and other resources in minutes)

= split =

Analogy:

String pro = null

Repository.findByPro (pro)

Results:

= = > query the result that the pro field in the query table is null, as expected, and there will be no unexpected oom or stack depletion

JPA version: spring-data-jpa-2.0.0.10RELEASE

Other versions are not tested.

Troubleshooting and corrective measures:

1. Key fields must be null-checked, such as key fields: pro

two。 Use FindAll (example) with caution and return full table data if a null value is passed in.

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