What's the advantage of using package-info.json vs. Export-Packages to define models to export Models? | Community
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Preston-3
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May 2, 2024
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What's the advantage of using package-info.json vs. Export-Packages to define models to export Models?

  • May 2, 2024
  • 2 replies
  • 1307 views

Recently I encountered a project with a complex model package structure and looked into how best to support this. I found documentation at WCM.io that indicated this. 

 

<!-- Export all non-internal packages by default --> 
Export-Package: !*.impl.*,!*.internal.*,\ io.wcm.samples.*

Replace io.wcm.samples.* with the topmost package from your project.

That got me wondering what the advantage was of using syntax like this vs. simply dropping package-info.json files into all of the folders that contained models. 

 

Additionally in the WCM.io documentation it mentions that for bnd plugin implementations Sling-Model-Packages should be moved into bnd configuration. 

 

<configuration>
   <bnd>
      Sling-Initial-Content: SLING-INF/app-root;overwrite:=true;ignoreImportProviders:=xml;path:=/apps/wcm-io/wcm/commons
      Sling-Model-Packages: io.wcm.wcm.commons
      Sling-Namespaces: wcmio=http://wcm.io/ns
      Import-Package: \
     <!-- For build compatibility with Java 11 -->\
     javax.annotation;version="[0.0,2)",\
     *
   </bnd>
</configuration>

Similarly why use this syntax vs just using the ModelScanner? 

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    Best answer by HrishikeshKagne

    Hi @preston-3 ,

    Using package-info.json versus Export-Package for defining models to export in OSGi bundles offers different approaches with varying advantages. Let's explore each and also delve into the usage of Sling-Model-Packages versus ModelScanner.

    Advantages of package-info.json:

    1. Granular Control:

      • With package-info.json, you have fine-grained control over which packages contain models and should be exported.

    2. Explicit Declaration:

      • It explicitly defines the packages containing models, making it easier to understand and maintain the export configuration.

    3. Modularity:

      • You can distribute model definitions across different packages, promoting modularity and organization in complex projects.

    Advantages of Export-Package:

    1. Simplicity:

      • Export-Package offers a simpler syntax for specifying which packages to export, especially for straightforward projects with fewer model packages.

    2. Coarse-Grained Control:

      • It's suitable for exporting entire packages or excluding certain patterns, providing flexibility in export configurations.

    3. Convention-Based:

      • It follows OSGi conventions, making it easier for developers familiar with OSGi to understand and work with.

    Advantages of Sling-Model-Packages:

    1. Explicit Configuration:

      • Sling-Model-Packages explicitly declares the packages containing Sling models, ensuring clarity and precision in the setup.

    2. Performance Optimization:

      • It helps in optimizing performance by specifying only the relevant packages to scan for Sling models.

    3. Compatibility:

      • Aligns well with Sling's architecture and best practices, ensuring compatibility and smooth integration with Sling-based projects.

    Advantages of ModelScanner:

    1. Automatic Registration:

      • ModelScanner automatically detects and registers models based on conventions or annotations, reducing manual configuration efforts.

    2. Dynamic Discovery:

      • It enables dynamic discovery of models during runtime, facilitating flexibility and extensibility in larger projects.

    3. Simplicity:

      • It simplifies the setup process by handling model registration automatically, suitable for projects where explicit configuration is not required.

    Example Java Code:

    Here's a simple example demonstrating how you can use ModelScanner in Java code:

     

    import org.apache.sling.models.annotations.Model; import org.apache.sling.models.annotations.injectorspecific.Inject; @Model(adaptables = Resource.class) public class MyModel { @Inject private String title; public String getTitle() { return title; } }

     

    In this example, MyModel is annotated with @Model, indicating that it's a Sling model. The ModelScanner will automatically detect and register this model based on the annotations and adaptability defined.

    2 replies

    gkalyan
    Community Advisor and Adobe Champion
    gkalyanCommunity Advisor and Adobe Champion
    Community Advisor and Adobe Champion
    May 2, 2024

    @preston-3 Interesting, I tried searching for this but didn't find a solid answer. I will look into this.

     

    Please let us know if you find an answer for this.

      HrishikeshKagne
      Community Advisor
      HrishikeshKagneCommunity AdvisorAccepted solution
      Community Advisor
      May 3, 2024

      Hi @preston-3 ,

      Using package-info.json versus Export-Package for defining models to export in OSGi bundles offers different approaches with varying advantages. Let's explore each and also delve into the usage of Sling-Model-Packages versus ModelScanner.

      Advantages of package-info.json:

      1. Granular Control:

        • With package-info.json, you have fine-grained control over which packages contain models and should be exported.

      2. Explicit Declaration:

        • It explicitly defines the packages containing models, making it easier to understand and maintain the export configuration.

      3. Modularity:

        • You can distribute model definitions across different packages, promoting modularity and organization in complex projects.

      Advantages of Export-Package:

      1. Simplicity:

        • Export-Package offers a simpler syntax for specifying which packages to export, especially for straightforward projects with fewer model packages.

      2. Coarse-Grained Control:

        • It's suitable for exporting entire packages or excluding certain patterns, providing flexibility in export configurations.

      3. Convention-Based:

        • It follows OSGi conventions, making it easier for developers familiar with OSGi to understand and work with.

      Advantages of Sling-Model-Packages:

      1. Explicit Configuration:

        • Sling-Model-Packages explicitly declares the packages containing Sling models, ensuring clarity and precision in the setup.

      2. Performance Optimization:

        • It helps in optimizing performance by specifying only the relevant packages to scan for Sling models.

      3. Compatibility:

        • Aligns well with Sling's architecture and best practices, ensuring compatibility and smooth integration with Sling-based projects.

      Advantages of ModelScanner:

      1. Automatic Registration:

        • ModelScanner automatically detects and registers models based on conventions or annotations, reducing manual configuration efforts.

      2. Dynamic Discovery:

        • It enables dynamic discovery of models during runtime, facilitating flexibility and extensibility in larger projects.

      3. Simplicity:

        • It simplifies the setup process by handling model registration automatically, suitable for projects where explicit configuration is not required.

      Example Java Code:

      Here's a simple example demonstrating how you can use ModelScanner in Java code:

       

      import org.apache.sling.models.annotations.Model; import org.apache.sling.models.annotations.injectorspecific.Inject; @Model(adaptables = Resource.class) public class MyModel { @Inject private String title; public String getTitle() { return title; } }

       

      In this example, MyModel is annotated with @Model, indicating that it's a Sling model. The ModelScanner will automatically detect and register this model based on the annotations and adaptability defined.

      Hrishikesh Kagane
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