48 lines
1.5 KiB
Plaintext
48 lines
1.5 KiB
Plaintext
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`FetchType` is an enumeration in the Java Persistence API (JPA) that is used to define the fetching strategy for associations (relationships) between entities in a relational database.
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There are two main values for FetchType:
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- `FetchType.EAGER`: the association is loaded immediately when the owning entity is loaded.
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- `FetchType.LAZY`: the association is not loaded unless it is explicitly accessed.
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This rule raises an issue when the `fetch` argument is explicitly set to `FetchType.EAGER`.
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== Why is this an issue?
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Using `FetchType.EAGER` can lead to inefficient data loading and potential performance issues.
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Eager Loading initializes associated data on the spot, potentially fetching more data than needed.
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== How to fix it
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Remove or replace `FetchType.EAGER` with `FetchType.LAZY` in JPA annotations.
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=== Code examples
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==== Noncompliant code example
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[source,java,diff-id=1,diff-type=noncompliant]
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----
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@OneToMany(mappedBy = "parent", fetch = FetchType.EAGER) // Noncompliant
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private List<ChildEntity> children;
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@OneToMany(mappedBy = "child", fetch = FetchType.EAGER) // Noncompliant
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private List<ParentEntity> parents;
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----
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==== Compliant solution
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[source,java,diff-id=1,diff-type=compliant]
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----
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@OneToMany(mappedBy = "parent", fetch = FetchType.LAZY) // Compliant
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private List<ChildEntity> children;
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@OneToMany(mappedBy = "child") // Compliant
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private List<ParentEntity> parents;
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----
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== Resources
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=== Documentation
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* https://docs.oracle.com/javaee/7/api/javax/persistence/FetchType.html[Java EE 7 API - FetchType]
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