Herman Ciechanowiec created SLING-12359:
-------------------------------------------
Summary: Extend records support
Key: SLING-12359
URL: https://issues.apache.org/jira/browse/SLING-12359
Project: Sling
Issue Type: Improvement
Components: Sling Models
Affects Versions: Models Implementation 1.6.4
Reporter: Herman Ciechanowiec
Fix For: Models Implementation 1.6.6
Java 14 introduced support for record classes, and Apache Sling 12 by default
runs with Java 17, allowing the use of records.
Although Apache Sling 12 supports record classes, the current latest version of
Apache Sling Models Implementation does not fully support injection in relation
to records. Specifically, for records, the Apache Sling Models Implementation
**does** support constructor injection similarly to a usual class if there is
an **explicit** constructor annotated with `javax.inject.Inject`:
```java
@Model(
adaptables = \{Resource.class, SlingHttpServletRequest.class},
defaultInjectionStrategy = DefaultInjectionStrategy.REQUIRED
)
public record StudentModel(String name, int age) {
@Inject
public StudentModel(
@ValueMapValue(name = "name") @Default(values = "unknown")
String name,
@ValueMapValue(name = "age") @Default(intValues = 0)
int age
) {
this.name = name;
this.age = age;
}
}
```
However, for records, Apache Sling Models Implementation **does not** support
constructor injection if there is an **implicit** constructor. Such a
constructor cannot be annotated with `javax.inject.Inject` and will not be
picked up during injection. Therefore, such a Sling Model will not be
instantiated at all:
```java
@Model(
adaptables = \{Resource.class, SlingHttpServletRequest.class},
defaultInjectionStrategy = DefaultInjectionStrategy.REQUIRED
)
public record StudentModel(
@ValueMapValue(name = "name") @Default(values = "unknown")
String name,
@ValueMapValue(name = "age") @Default(intValues = 0)
int age) {}
```
The above issue should be addressed by introducing support for injection in
records' implicit constructors.
Note:
1. For records, only constructor injection is supported since records cannot
have instance fields (code with such fields will not compile).
2. Apache Sling Models Implementation is currently based on Java 8 and may also
be executed in a Java 8 environment. Therefore, the records check should be
introduced via dynamic loading of the `java.lang.Record` class.
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