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  1. Jenkins
  2. JENKINS-57513

Split the large databound constructors into databound setters

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      Description

      Inside EC2 plugin there is a lot of constructors with a large set of databound constructors.
      Databound constructor should only be used for mandatory/final parameters

      Where databound setters should be used for optional parameters.

      https://jenkins.io/doc/developer/plugin-development/pipeline-integration/#constructor-vs-setters

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          casz Joseph Petersen (old) created issue -
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          casz Joseph Petersen (old) added a comment - - edited

          https://github.com/jenkinsci/configuration-as-code-plugin/issues/885
          https://github.com/jenkinsci/configuration-as-code-plugin/issues/381

          we also had several users on gitter ask for help debugging null pointers and it all leads to those large data bound constructors that assume null does not exist.

          Show
          casz Joseph Petersen (old) added a comment - - edited https://github.com/jenkinsci/configuration-as-code-plugin/issues/885 https://github.com/jenkinsci/configuration-as-code-plugin/issues/381 we also had several users on gitter ask for help debugging null pointers and it all leads to those large data bound constructors that assume null does not exist.
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          casz Joseph Petersen (old) added a comment - Matt Sicker Raihaan Shouhell
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          thoulen FABRIZIO MANFREDI added a comment -

          It is one of the things in backlog, now the plugin it is quite complex in term of options.

          Show
          thoulen FABRIZIO MANFREDI added a comment - It is one of the things in backlog, now the plugin it is quite complex in term of options.
          Hide
          jvz Matt Sicker added a comment -

          I'd also like to consider some form of data bound builder class feature so we can avoid using poor Java patterns. Let me give you an example from the Log4j plugin system. The more typical use of DataBoundConstructor is equivalent to PluginFactory in Log4j: https://github.com/apache/logging-log4j2/blob/a6b1cbfc9d4257baaa6760e58426f0f4dfa99b0f/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/FailoverAppender.java#L183

          In order to add new options over time, we used to deprecate a factory method, remove the annotation, and move it to the new factory method that contained default values for new parameters (as well as validation; you could return null instead of the plugin object to signify an error without throwing exceptions which was important in this part of our design, but I digress). This pattern was extremely brittle and is fairly similar to DataBoundConstructor. However, in order to follow Effective Java and other similar best practices, we'd still like to prefer that our objects are fully constructed and ready to use as soon as they're "created" whether that be via a constructor, a factory method, a builder class, or whatever. Having to call setters after creating the object leaves the object in intermediary states that typically don't have meaning, and this can cause runtime bugs in practice.

          This is getting a bit long, so let me wrap it up. My preferred approach would be what we did in Log4j with newer plugins via a builder class pattern: https://github.com/apache/logging-log4j2/blob/a6b1cbfc9d4257baaa6760e58426f0f4dfa99b0f/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/HttpAppender.java#L48

          As you can see, due to syntactical features of Java, it is much easier to add and rename things in a builder class over time independently from the implementation details of the plugin class itself. I'd also note that there was a time in Log4j history before there was automatic type conversion in the annotated factory methods, so some old code still have all string parameters with manual type conversion.

          Also, why do I bring this up in EC2 and not structs or whatever the appropriate plugin is? Good question, but a new issue should likely be filed about it linked back here.

          Show
          jvz Matt Sicker added a comment - I'd also like to consider some form of data bound builder class feature so we can avoid using poor Java patterns. Let me give you an example from the Log4j plugin system. The more typical use of DataBoundConstructor is equivalent to PluginFactory in Log4j: https://github.com/apache/logging-log4j2/blob/a6b1cbfc9d4257baaa6760e58426f0f4dfa99b0f/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/FailoverAppender.java#L183 In order to add new options over time, we used to deprecate a factory method, remove the annotation, and move it to the new factory method that contained default values for new parameters (as well as validation; you could return null instead of the plugin object to signify an error without throwing exceptions which was important in this part of our design, but I digress). This pattern was extremely brittle and is fairly similar to DataBoundConstructor. However, in order to follow Effective Java and other similar best practices, we'd still like to prefer that our objects are fully constructed and ready to use as soon as they're "created" whether that be via a constructor, a factory method, a builder class, or whatever. Having to call setters after creating the object leaves the object in intermediary states that typically don't have meaning, and this can cause runtime bugs in practice. This is getting a bit long, so let me wrap it up. My preferred approach would be what we did in Log4j with newer plugins via a builder class pattern: https://github.com/apache/logging-log4j2/blob/a6b1cbfc9d4257baaa6760e58426f0f4dfa99b0f/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/HttpAppender.java#L48 As you can see, due to syntactical features of Java, it is much easier to add and rename things in a builder class over time independently from the implementation details of the plugin class itself. I'd also note that there was a time in Log4j history before there was automatic type conversion in the annotated factory methods, so some old code still have all string parameters with manual type conversion. Also, why do I bring this up in EC2 and not structs or whatever the appropriate plugin is? Good question, but a new issue should likely be filed about it linked back here.
          Hide
          casz Joseph Petersen (old) added a comment - - edited

          Matt Sicker I agree with you but for JCasC we only really care about the lovely data binding

          I would like to point out this lovely PR which could solve all our data binding problem and jelly problems at the same time: https://github.com/stapler/stapler/pull/147
          https://github.com/jenkinsci/jenkins/pull/3669

          Show
          casz Joseph Petersen (old) added a comment - - edited Matt Sicker I agree with you but for JCasC we only really care about the lovely data binding I would like to point out this lovely PR which could solve all our data binding problem and jelly problems at the same time: https://github.com/stapler/stapler/pull/147 https://github.com/jenkinsci/jenkins/pull/3669
          Hide
          jvz Matt Sicker added a comment -

          I'd love to get that merged, though my Stapler street cred hasn't been enough yet to gain committership yet. I hope to change that over the next couple months, though.

          Show
          jvz Matt Sicker added a comment - I'd love to get that merged, though my Stapler street cred hasn't been enough yet to gain committership yet. I hope to change that over the next couple months, though.
          oleg_nenashev Oleg Nenashev made changes -
          Field Original Value New Value
          Labels jcasc-compatibility
          jetersen Joseph Petersen made changes -
          Assignee FABRIZIO MANFREDI [ thoulen ] Joseph Petersen [ jetersen ]
          jetersen Joseph Petersen made changes -
          Assignee Joseph Petersen [ jetersen ] FABRIZIO MANFREDI [ thoulen ]
          jetersen Joseph Petersen made changes -
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          jetersen Joseph Petersen added a comment -
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          jetersen Joseph Petersen added a comment - EC2 is still going down a dark road as this is still happening. https://github.com/jenkinsci/ec2-plugin/blame/master/src/main/java/hudson/plugins/ec2/SlaveTemplate.java
          Hide
          jetersen Joseph Petersen added a comment -

          Raihaan Shouhell please take a look

          Show
          jetersen Joseph Petersen added a comment - Raihaan Shouhell  please take a look
          Hide
          raihaan Raihaan Shouhell added a comment -

          Hey Joseph, I agree we really need to fix this issue.

          The whole class(SlaveTemplate) needs a rework so that not everything is final so setters would work.

           

          Matt Sicker I'm not sure how builder patterns will help this since I don't think casc will support a builder

          Show
          raihaan Raihaan Shouhell added a comment - Hey Joseph, I agree we really need to fix this issue. The whole class(SlaveTemplate) needs a rework so that not everything is final so setters would work.   Matt Sicker I'm not sure how builder patterns will help this since I don't think casc will support a builder
          Hide
          jvz Matt Sicker added a comment -

          A builder pattern is the proper Java way to do it. Since nobody has implemented support for that in the JSON binding in Stapler, it seems like the suggested pattern is to use 90's-style JavaBeans with mutable getters/setters. Essentially, any data binding parameters that are required should be in the constructor, and any that are optional (i.e., every single new option added since the first release technically) should be added as setters so that the class can still be designed to work if that setter isn't invoked (i.e., providing default behavior).

          Show
          jvz Matt Sicker added a comment - A builder pattern is the proper Java way to do it. Since nobody has implemented support for that in the JSON binding in Stapler, it seems like the suggested pattern is to use 90's-style JavaBeans with mutable getters/setters. Essentially, any data binding parameters that are required should be in the constructor, and any that are optional (i.e., every single new option added since the first release technically) should be added as setters so that the class can still be designed to work if that setter isn't invoked (i.e., providing default behavior).
          Hide
          jbochenski Jakub Bochenski added a comment -

          Can you please leave the old constructors in place. I'm already using groovys scripts to configure the plugin.
          Splitting out into setters is a welcome change, but it sucks to have to update your scripts for a new release.

          Show
          jbochenski Jakub Bochenski added a comment - Can you please leave the old constructors in place. I'm already using groovys scripts to configure the plugin. Splitting out into setters is a welcome change, but it sucks to have to update your scripts for a new release.
          Hide
          jetersen Joseph Petersen added a comment -

          Why not offer a builder pattern and proper data bound setters, so that those in groovy can use the builder pattern and JCasC and stapler can use data binding.

          Show
          jetersen Joseph Petersen added a comment - Why not offer a builder pattern and proper data bound setters, so that those in groovy can use the builder pattern and JCasC and stapler can use data binding.
          Hide
          jvz Matt Sicker added a comment -

          The point of the builder pattern was to allow for a single (private) mega-constructor that continues to change as the class changes, but centralizing the configuration in its own builder class. Alternatively, if all these parameters are moved into their own anemic domain model class, then having everything be set up via getters and setters wouldn't be as painful. The general idea here is about setting up the state of the object by the time it's constructed so that you can avoid representations of invalid state.

          Show
          jvz Matt Sicker added a comment - The point of the builder pattern was to allow for a single (private) mega-constructor that continues to change as the class changes, but centralizing the configuration in its own builder class. Alternatively, if all these parameters are moved into their own anemic domain model class, then having everything be set up via getters and setters wouldn't be as painful. The general idea here is about setting up the state of the object by the time it's constructed so that you can avoid representations of invalid state.
          Hide
          raihaan Raihaan Shouhell added a comment -

          We might have to make a breaking change here since everything is public to give jcasc its databinding we need to remove the final keyword but since fields are public they now become directly modifiable. We probably should bite the bullet and change them to be private and provide setters / getters? WDYT: Matt Sicker FABRIZIO MANFREDI

          Show
          raihaan Raihaan Shouhell added a comment - We might have to make a breaking change here since everything is public to give jcasc its databinding we need to remove the final keyword but since fields are public they now become directly modifiable. We probably should bite the bullet and change them to be private and provide setters / getters? WDYT: Matt Sicker FABRIZIO MANFREDI
          Hide
          jvz Matt Sicker added a comment -

          Due to how many people already have pipelines referring to those constructors, it might be worth trying to deprecate that class entirely with a compatibility layer to the new class.

          Show
          jvz Matt Sicker added a comment - Due to how many people already have pipelines referring to those constructors, it might be worth trying to deprecate that class entirely with a compatibility layer to the new class.

            People

            • Assignee:
              thoulen FABRIZIO MANFREDI
              Reporter:
              casz Joseph Petersen (old)
            • Votes:
              1 Vote for this issue
              Watchers:
              8 Start watching this issue

              Dates

              • Created:
                Updated: