Embedding Groovy in a Java Application
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There are three main ways to embed Groovy in a Java application: 1) Compiling Groovy code to Java bytecode that can be referenced from Java code. This can be done with Maven or Ant. 2) Using the Bean Scripting Framework (BSF) or JSR 223 to execute Groovy scripts at runtime from Java. 3) Native embedding using the GroovyShell, GroovyClassLoader, or GroovyScriptEngine APIs to load and execute Groovy code from Java. Performance considerations include caching compiled scripts and reloading when dependencies change.
![GROOVYSHELL
GroovyShell
.evaluate(String) Object
.run(File, String[]) Object
Script
.parse(File)
.run()
.invokeMethod() Object](https://image.slidesharecdn.com/embedding-groovy-en-121207024824-phpapp02/85/Embedding-Groovy-in-a-Java-Application-7-320.jpg)
![GROOVYSCRIPTENGINE
GroovyScript
Engine GroovyScriptEngine(String[] roots)
.loadScriptByName(String) Class
.run(String, Binding) Object
Script
.createScript(String) .run()](https://image.slidesharecdn.com/embedding-groovy-en-121207024824-phpapp02/85/Embedding-Groovy-in-a-Java-Application-13-320.jpg)
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Embedding Groovy in a Java Application
- 1. EMBEDDING GROOVY IN A JAVA APPLICATION [email protected]
- 2. Java-Groovy integration Compiling Embedding (loading at run-time) BSF and JSR 223 Native embedding GroovyShell GroovyClassLoader GroovyScriptEngine
- 3. COMPILING MyClass.groovy MyClass.class Maven Ant Joint compilation: Java references Groovy and vice versa
- 4. BEAN SCRIPTING FRAMEWORK AND JSR 223 http://commons.apache.org/bsf/ http://groovy.codehaus.org/Bean+Scripting+Framework http://groovy.codehaus.org/JSR+223+Scripting+with+Groovy
- 5. NATIVE EMBEDDING GroovyScript Engine Scripts + GroovyClass classpath + Loader reload + Introduces the dependency GroovyShell concept of management classpath Simple isolated scripts
- 6. BEHIND THE SCENES... GroovyShell GroovyScriptEngine ScriptClassLoader dependency mgmt. GroovyClassLoader
- 7. GROOVYSHELL GroovyShell .evaluate(String) Object .run(File, String[]) Object Script .parse(File) .run() .invokeMethod() Object
- 10. BINDING
- 11. GROOVYCLASSLOADER GroovyClass Loader .addClassPath(“/home/groovy”) .loadClass(“com.manydesigns.Foo”) Class .parseClass(“/home/groovy/com/manydesigns/Foo.groovy”) Class
- 13. GROOVYSCRIPTENGINE GroovyScript Engine GroovyScriptEngine(String[] roots) .loadScriptByName(String) Class .run(String, Binding) Object Script .createScript(String) .run()
- 15. SCRIPT == CLASS Script run() def f() {} main() println “Hello world!” f()
- 16. IT MAKES SENSE TO DEAL WITH SCRIPTS AND CLASSES SEPARATELY } Classpath, packages, classes, reuse, engineering } Scripts, files, “spot” usage, hacking Groovy is groovy because it supports both perspectives!
- 17. GROOVY IN PORTOFINO 4 Classpath for common groovy classes Groovy actions
- 18. Groovy actions: URL structure same as directory structure One action.groovy per directory Packages are not required URL’s can be moved/renamed by moving/renaming the directories Nobody can depend on an action No refactoring is required Editable from browser or IDE Each action.groovy is self- contained. We treat it as a script.
- 19. Groovy classpath: A real classpath with packages and classes Contains beans, base classes for actions, utility classes invokable by actions Typically edited from an IDE Refactoring Groovy classpath: similar to a Java classpath but dynamically reloadable
- 20. CLASS LOADING ClassLoader Loads Java classes only parent classloader GroovyClassLoader Loads Java & Groovy classes
- 21. This is the main problem of embedding. If Groovy was compiled, Java and Groovy would live in the same class loader
- 22. CLASS LOADING: OGNL OGNL: %{@org.example.MyGroovyClass@myMethod()} ... does not work because OGNL uses the Java classloader and cannot resolve Groovy classes
- 23. CLASS LOADING: HIBERNATE In Groovy this works: From Java it works only if we retrieve Book from the GroovyClassLoader
- 24. PERFORMANCE: CACHING & RELOADING Test strategy: 1. “engine warm up” 2. measure the first run 3. measure the second run 4. “touch” the script 5. measure the third run
- 26. PERFORMANCE: CONCLUSIONS Caching Reloading GroovyShell.evaluate(String) No -- GroovyShell.run(File) Yes No GroovyClassLoader Yes No GroovyScriptEngine Yes Yes
- 27. DEPENDENCY RELOADING A A depends on B B is modified B is reloaded B Also A should be reloaded In theory, but until Groovy 1.8.8/2.0.4 there was a bug: http://jira.codehaus.org/browse/GROOVY-4975
- 29. THANK YOU! [email protected] http://www.manydesigns.com/