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walkmod - JUG talk


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Barcelona JUG (Java Users Group) slides about walkmod, an open source tool to apply coding conventions. 6th March 2014.

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walkmod - JUG talk

  1. 1. walkmod a tool to apply coding conventions @walkmod
  2. 2. hello! @raquelpau @acoroleu
  3. 3. introduction how it works transformations query engine merge engine plugins roadmap
  4. 4. Introduction motivation • Don’t repeat yourself (DRY) principle. Multiple layer architectures contains lots of wrappers, which might be generated. E.g. Tests, DAOs, Facades.. • The application domain relevance. The business rules / domain logic can’t be generated (really?). We need to focus on this! • Code review of ALL contributors. Who fixes the code?
  5. 5. Introduction
  6. 6. Introduction What are coding conventions? “coding conventions are a set of guidelines for a specific programming language that recommend programming style, practices and methods for each aspect of a piece program written in this language.” wikipedia
  7. 7. Introduction examples • • • • Naming conventions Code formatting Code licenses Code documentation • • • • Code refactoring Apply programming practices Architectural best practices More..
  8. 8. Introduction examples
  9. 9. Introduction walkmod • automatizes the practice of code conventions in development teams (i.e license usage). • automatizes the resolution of problems detected by code quality tools (i.e PMD, , sonar, findbugs). • automatizes the development and repetitive tasks i.e: creating basic CRUD services for the entire model. • automatizes global code changes: i.e refactorings.
  10. 10. Introduction walkmod is open! • • • • • open source: feel free to suggest changes! free for everybody: tell it to your boss! extensible by plugins do it yourself and share them! DIY+S editor/IDE independent community support
  11. 11. introduction how it works transformations query engine merge engine plugins roadmap
  12. 12. how it works • All conventions are applied with blocks of transformations for each source file. • Transformations may update the same sources or creating/updating another ones. workflow
  13. 13. how it works overview • reader: reads the sources. i.e retrieves all files from a directory recursively. • • walker: executes a chain of transformations for each source. • writer: writes the sources. i.e using the eclipse formatter. transformation: updates or creates sources for the following transformation. Transformations are connected like a pipe through a shared context.
  14. 14. how it works reader • • • • Reads the sources. By default, reads the folder src/main/java. Works with multiple include/exclude rules. Creates a resource object, whose content is iterated from the walker. Works for sources of any programming language. The resource object could be a source folder, a parsed json file, etc..
  15. 15. how it works walker • Executes a chain of transformations for each object allocated in a resource. i.e all java source files of an specific folder. • merges the output produced by transformations with existent resources. • • invokes the writer with the final (and merged) output. analyzes and reports which changes have been produced by the chain of transformations in each object.
  16. 16. how it works transformations • • modifies or creates objects that will be written. There are three ways to design a transformation. Using: templates, scripts, or visitors.
  17. 17. how it works writer • writes each object allocated in a resource. i.e all java source files of a specific folder. • • Has include/exclude rules. There are useful writer implementations, such as the storage of the contents of a toString() object method or the eclipse formatter.
  18. 18. how it works remember
  19. 19. introduction how it works transformations query engine merge engine plugins roadmap
  20. 20. transformations why templates? • • • • Templates are used to avoid manipulating the AST directly. Generates dynamic content querying the AST. DRY compliance. groovy is the default template engine, but can be customized.
  21. 21. transformations template configuration <!DOCTYPE walkmod PUBLIC "-//WALKMOD//DTD" ""> <walkmod> ... <transformation type="walkmod:commons:template" > <param name="templates"> ["src/main/walkmod/templates/jpa-entities.groovy"] </param> </transformation> ... </walkmod>
  22. 22. transformations why scripts? • • • Scripts allow the design of inline transformations. Scripts should be used to apply simple modifications in source files. Support for multiple languages. Those which implement the standard Java scripting interface. i.e. groovy, javascript, python..
  23. 23. transformations script configuration ... <transformation type="walkmod:commons:scripting" > <param name="language"> groovy </param> <param name="location"> src/main/walkmod/scripts/fields.groovy </param> </transformation> ...
  24. 24. transformations why visitors? • • Visitors are developed and compiled in java. • Visitors should be used to apply complex modifications in source files. To include transformations as plugins to be shared inside the community.
  25. 25. transformations visitor transformations public class HelloVisitor extends VoidVisitor<VisitorContext>{ ... @Overwrite public void visit(MethodDeclaration md, VisitorContext ctx){ //TODO } @Overwrite public void visit(FieldDeclaration fd, VisitorContext ctx){ //TODO } ... }
  26. 26. transformations visitor configuration <!DOCTYPE walkmod PUBLIC "-//WALKMOD//DTD" ""> <walkmod> <plugins> <plugin groupId="mygroupId" artifactId="myartifactId" version="versionNumber"> </plugin> </plugins> ... <transformation type="mygroupId:myartifactId:my-visitor" > <param name="param1"> value1 </param> <param name="paramN"> valueN </param> </transformation> ... </walkmod>
  27. 27. introduction how it works transformations query engine merge engine plugins roadmap
  28. 28. query engine query engine • • Write less to do the same! • The default query language is gPath (groovy), but you can change it for your favorite language. • Common used large query expressions can be referenced from Alias. “TypeDeclaration.metaClass.getMethods = { -> delegate.members.findAll({it instanceof MethodDeclaration}); }” All queries have an object context and a query expression. By default, the context is the root element of a parsed source file.
  29. 29. query engine MethodDeclaration method = null; Collection members = type.getMembers(); Iterator it = members.iterator(); while (it.hasNext()){ BodyDeclaration member = (BodyDeclaration); if (member instance of MethodDeclararion){ MethodDeclarion aux = (MethodDeclaration) member; if(“execute”.equals(aux.getName()){ method = aux; break; } } } type.methods.find({“execute”)})
  30. 30. query engine queries from templates Using the query object: ${query.resolve(“expr”)}. import org.apache.log4j.Logger; public class ${query.resolve("")}{ public static Logger log = Logger.getLogger(${query.resolve("")}.class); } template to add Loggers
  31. 31. query engine queries from scripts accessing through a binding called query .. for( type in node.types) { def result = query.resolve(type, “methods”); ... } ... groovy script querying the type methods
  32. 32. query engine queries from visitors Implementing QueryEngineAware or extending VisitorSupport. public class MyVisitor extends VisitorSupport{ @Overwrite public void visit(TypeDeclaration td, VisitorContext ctx){ Object result = query( td, //context “methods.find({“foo”)})” //expr ); } } visitor code with a gpath query
  33. 33. introduction how it works transformations query engine merge engine plugins roadmap
  34. 34. merge engine why a merge engine? • To avoid duplicate results by transformations (i.e duplicate a method) in existing code. • Simplify transformations. Otherwise, transformations must check many conditions to avoid repeating code or overwriting it. • Sometimes, developer changes (i.e. adding a new method) must be respected by the engine.
  35. 35. walkmod merges outputs with existential sources
  36. 36. merge engine semantic merge • Code is merged according to the meaning of its elements instead of simply merging text. • Only elements with the same identifier are merged. Indentifiable element types must implement the interface mergeable.
  37. 37. merge engine previous concepts • • local object is the current version of an element. remote object is the modified version of an element generated by a single transformation. It may be a fragment to add in a local object.
  38. 38. merge engine merge policies Configurable and extensible merge policies for each object type. Object merge policy Finds the equivalent local version of a remote (and thus, generated) object and merge recursively their children. These objects must be identifiable to be searched and found. These policies should be applied for fields, , methods, , types … Type select which merge action do for local and remote objects which are merge not identifiable, although being instances of the same class. i.e policies policy for the statements of an existent method.
  39. 39. merge engine object merge policies • append policy only writes new values for null fields. Otherwise, these are not modified. • overwrite policy modifies all field values of a local object for those generated by a transformation.
  40. 40. merge engine type merge policies • assign policy only writes the remote values. i.e replacing the list of statements of a method for the generated list. • unmodify policy only writes the local values. i.e to respect the developer changes in the statements of an old transformation. • addall policy that appends the remote values into the local values.
  41. 41. introduction how it works transformations query engine merge engine plugins roadmap
  42. 42. plugins why and how to extend walkmod? • You can extend walkmod with new components or override the existing ones (visitors, readers, writers, walkers, merge policies…) • Creating new plugins (java libraries) and deploying them into a maven repository (public or private). See • All walkmod extensions need a plugin descriptor of their components in the META-INF/walkmod directory inside the jar library.
  43. 43. plugins plugin descriptor • Plugin descriptor is a XML file with the name walkmod-xxx-plugin.xml which follows the spring bean configuration. • New readers, writers, walkers or transformations must be specified with a unique name “groupId:artifactId:name” as a spring bean in the plugin descriptor. <beans> ... <bean id="walkmod:commons:import-cleaner" class="org.walkmod.visitors.ImportOrganizer" /> ... </beans>
  44. 44. plugins plugin usage (I) Plugins are declared into ${project}/walkmod.xml <walkmod> <plugins> <plugins> <plugin groupId="walkmod" artifactId="walkmod-commons-plugin" version="1.0"> </plugin> </plugins> <chain name="my-chain"> ... </chain> <walkmod>
  45. 45. plugins plugin usage (II) Beans declared in a plugin descriptor can be referenced from walkmod.xml using the type attribute. <walkmod> <plugins> <plugin groupId="walkmod" artifactId="walkmod-commons-plugin" version="1.0"> </plugin> </plugins> <chain name="my-chain"> ... <transformation type="walkmod:commons:imports-cleaner" /> ... </chain> </walkmod>
  46. 46. plugins plugins backend • Walkmod embeds apache ivy to download plugins from maven repositories in runtime. • Custom repositories are in ${walkmod-home}/conf/ivysettings.xml • All plugin jars and their dependencies are files loaded dynamically into a new classloader. • All beans used and declared in plugin descriptors are resolved by the spring source engine using the new classloader.
  47. 47. introduction how it works transformations query engine merge engine plugins roadmap
  48. 48. roadmap next steps • modularization: split the project in modules in GitHub and deploy them in a Maven public repository. • • Java 8 support (lambda expressions) • - less configuration: reutilization by inheritance / include rules of the XML elements. • saas: publish online services for running walkmod and all its plugins (also private). + plugins: Create and publish new plugins (e.g. refactoring or support for other programming languages).