Eclipse Architecture and Patterns. Mirko Stocker. Advanced Patterns and Frameworks May, 2015 IFS INSTITUTE FOR SOFTWARE

Transcription

1 Eclipse Architecture and Patterns Mirko Stocker Advanced Patterns and Frameworks May, 2015 IFS INSTITUTE FOR SOFTWARE

2 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

3 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

4 Eclipse History Origins 1999 Work begins on Eclipse inside IBM 2001 Eclipse 1.0 released as open source 2002 Eclipse 2.0 released 2004 Eclipse 3.0 released based on OSGi 2012 Eclipse 4.2 released with completely new fundament Mirko Stocker Eclipse Architecture and Patterns / 64

5 Eclipse History Eclipse 1.0 Mirko Stocker Eclipse Architecture and Patterns / 64

6 Eclipse History Eclipse 2.0 Mirko Stocker Eclipse Architecture and Patterns / 64

7 Eclipse Goals Open platform for application development to make building tools easier and to provide common tools Started as an IDE (-framework) but then became a general platform Integration and interaction of various tools and services based on plug-ins Platform independent but native widgets (SWT) The Eclipse platform itself is a sort of universal tool platform it is an IDE for anything and nothing in particular. Mirko Stocker Eclipse Architecture and Patterns / 64

8 Eclipse Components Figure: Source [GammaBeck03] Mirko Stocker Eclipse Architecture and Patterns / 64

9 Eclipse Components Figure: Source Eclipse.org Mirko Stocker Eclipse Architecture and Patterns / 64

10 Project Stats Over 250 projects under development at eclipse.org Yearly releases in June for projects that want to participate Figure: Source [Aniszczyk] Mirko Stocker Eclipse Architecture and Patterns / 64

11 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

12 SWT Building Cross-Platform UIs Native Widgets and mostly written in Java No performance impact from UI Native library and thin JNI layer for each toolkit SWT implementation per platform Why not AWT or Swing? Mirko Stocker Eclipse Architecture and Patterns / 64

13 JFace UI-Toolkit SWT provides basic components JFace builds on top of SWT: Actions, Menus, Dialogs, Wizards, Fonts Figure: Source Eclipse.org Mirko Stocker Eclipse Architecture and Patterns / 64

14 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

15 OSGi Open Services Gateway initiative Specifies a component and service model for Java Components (bundles) can be dynamically installed, started, stopped, and uninstalled Bundles define dependencies and export some of their packages (unlike a JAR) Similar to Java 9 (former 8) Modularization proposal Several OSGi implementations, Eclipse s is Equinox GlassFish, JBoss, WebSphere, IntelliJ, Netbeans, and many others are all based on OSGi Mirko Stocker Eclipse Architecture and Patterns / 64

16 OSGi Bundles Eclipse plug-ins are OSGi bundles! (since Eclipse 3) Packaged as JARs MANIFEST.MF file contains the bundle metadata Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Popup Plug-in Bundle-SymbolicName: com.example.myosgi; singleton:=true Bundle-Version: Bundle-Activator: com.example.myosgi.activator Require-Bundle: org.eclipse.ui, org.eclipse.core.runtime;bundle-version="4.2.0" Bundle-ActivationPolicy: lazy Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Export-Package: com.example.myosgi Mirko Stocker Eclipse Architecture and Patterns / 64

17 OSGi Services OSGi also offers services to connect bundles Service is a POJO and can be registered at a Service Registry at bundle start For historical reasons, Eclipse does not use OSGi services but Extensions and Extension Points Mirko Stocker Eclipse Architecture and Patterns / 64

18 Extension Points Extension Point collects contributions to the plug-in offering the Extension Point Extension contributes to an Extension Point Each plug-in contributes to at least one Extension Point Optionally declares a new EP Extension Points and Extensions are not part of the Manifest but separate XML files Figure: Source Eclipse.org Mirko Stocker Eclipse Architecture and Patterns / 64

19 Eclipse Plug-ins Plug-ins can add new Actions, Editors, Views, Menus, Perspectives, Preferences Each plug-in gets its own class loader Can only access specified dependencies Mirko Stocker Eclipse Architecture and Patterns / 64

20 Plug-in Example A plug-in has three interesting files: Manifest plugin.xml to wire up the Extension Class that implements the Extension Mirko Stocker Eclipse Architecture and Patterns / 64

21 Plug-in Example Mirko Stocker Eclipse Architecture and Patterns / 64

22 Eclipse Plug-ins Eclipse platform manages plug-ins: discover installed plug-ins from various disk locations builds the extension registry connects extensions and extension points only activates plug-ins when needed Mirko Stocker Eclipse Architecture and Patterns / 64

23 Plug-in Example Mirko Stocker Eclipse Architecture and Patterns / 64

24 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

25 Classical GoF Design Patterns Creational Patterns Factory Builder Singleton... Structural Patterns Adapter Bridge Composite Proxy Façade... Behavioral Patterns Observer Command Memento Strategy Visitor... Mirko Stocker Eclipse Architecture and Patterns / 64

26 Classical GoF Design Patterns Creational Patterns Factory Builder Singleton... Structural Patterns Adapter Bridge Composite Proxy Façade... Behavioral Patterns Observer Command Memento Strategy Visitor... Platform Singleton: getting Workbench, Plug-in Workspace Resources Proxy and Bridge: Accessing File System Composite: the workspace Observer: tracking resource changes Core Runtime IAdaptable and Adapter Factories: Property View SWT SWT Composite: composing widgets Strategy: defining layouts JFace Observer: responding to events Pluggable adapter: Connecting widget to model Strategy: customize a viewer without subclassing Command: Actions UI Workbench Memento: persisting UI state Virtual Proxy: lazy loading with E.P. LTK Template Method, Composite, Memento CDT Visitor: to traverse the AST Mirko Stocker Eclipse Architecture and Patterns / 64

27 Singleton Ensure that a class only has one instance, and provide a global point of access to it: PlatformUI.getWorkbench() Platform.getAdapterManager() ResourcesPlugin.getWorkspace() Mirko Stocker Eclipse Architecture and Patterns / 64

28 Singleton Ensure that a class only has one instance, and provide a global point of access to it: PlatformUI.getWorkbench() Platform.getAdapterManager() ResourcesPlugin.getWorkspace() Problem: coupling, code hard to test Mirko Stocker Eclipse Architecture and Patterns / 64

29 Proxy Files and Resources How can we represent an (external) resource in a progam? 1 Provide a handle for the resource 2 Handle acts as a proxy for the resource Mirko Stocker Eclipse Architecture and Patterns / 64

30 Proxy Provide a surrogate or place holder for another object to control access to it: Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

31 Proxy Files and Resources Advantages of the Proxy pattern approach: Small value objects Define behaviour but don t contain any state information Can refer to non-existing resource (file not yet created) Mirko Stocker Eclipse Architecture and Patterns / 64

32 Proxy Lazy Loading The Proxy pattern can also be used to implement lazy-loading: Eclipse only loads a plug-in when it s needed. UI actions are proxies for the real actions that are loaded when used the first time. Mirko Stocker Eclipse Architecture and Patterns / 64

33 Bridge Decouple an abstraction from its implementation so that the two can vary independently: Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

34 Bridge API interface is implemented by an internal class that delegates the calls to another implementation. Figure: Source [GammaBeck03] Both Proxy and Bridge patterns are used here. Mirko Stocker Eclipse Architecture and Patterns / 64

35 Adapter Adapt an interface for a class to make it compatible with another class: Figure: Source [DoFactory] Mirko Stocker Eclipse Architecture and Patterns / 64

36 Adapter Pluggable Adapters JFace uses the Adapter pattern prominently: IContentProvider to get at the contents of a domain object ILabelProvider for the text or image to display Figure: Source [IlyaShinkarenko] Mirko Stocker Eclipse Architecture and Patterns / 64

37 Observer Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. Figure: Source [IlyaShinkarenko] IWorkspace ws = ResourcesPlugin.getWorkspace(); ws.addresourcechangelistener(new IResourceChangeListener() public void resourcechanged(iresourcechangeevent event){ // handle change } }); Mirko Stocker Eclipse Architecture and Patterns / 64

38 Strategy Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

39 Strategy Strategy in SWT Mirko Stocker Eclipse Architecture and Patterns / 64

40 Strategy Strategy in JFace Filtering and sorting of elements in views are als handled by Strategies: Figure: Source [IlyaShinkarenko] Mirko Stocker Eclipse Architecture and Patterns / 64

41 Command Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support for undoable operations. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

42 Command JFace IAction IAction has a run() method encaspulating the code to be executed when it is called by the Invoker. More than just a function: stores additional data (label, icon, state). Can be used (attached) to multiple menus, tool bars, buttons. IAction action = new Action("Exit") public void run() { System.exit(0); } }; action.setdescription("exits the VM"); menu.add(action); Mirko Stocker Eclipse Architecture and Patterns / 64

43 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

44 LTK What is the LTK? Refactoring Language Toolkit (LTK) - a language neutral API for refactorings: Classes for constructing refactoring user interfaces (common L&F for wizards and dialogs) Refactoring wizard with diff preview Classes for modelling resource changes (e. g., "insert method foo into test.java at offset XY") Refactoring participant functionality Scriptable refactorings and refactoring history Used by Java Development Tools (JDT), C/C++ Development Platform (CDT), Eclipse Scala IDE and others Consists of two plug-ins: org.eclipse.ltk.core.refactoring org.eclipse.ltk.ui.refactoring Mirko Stocker Eclipse Architecture and Patterns / 64

45 LTK Refactoring UI Example: Specifying refactoring parameters Figure: LTK wizard for specifying refactoring parameters of "extract interface" Mirko Stocker Eclipse Architecture and Patterns / 64

46 LTK Diff browser: change 1/2 Figure: LTK diff view with change 1/2 of "extract interface" Mirko Stocker Eclipse Architecture and Patterns / 64

47 LTK Diff browser: change 2/2 Figure: LTK diff view with change 2/2 of "extract interface" Mirko Stocker Eclipse Architecture and Patterns / 64

48 LTK Refactoring Lifecycle Overview Figure: Source [Widmer06] Problem: How does the LTK provide a skeleton of this algorithm, while deferring some steps to subclasses? Mirko Stocker Eclipse Architecture and Patterns / 64

49 LTK Template Method Pattern Template method defines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

50 LTK GoF Patterns applied: Template Method public abstract class Refactoring extends PlatformObject { public R e f a c t o r i n g S t a t u s checkallconditions ( IProgressMonitor pm) { R e f a c t o r i n g T i c k P r o v i d e r p r o v i d e r = g e t R e f a c t o r i n g T i c k P r o v i d e r ( ) ; pm. begintask ( " ", p r o v i d e r. getcheckallconditionsticks ( ) ) ; R e f a c t o r i n g S t a t u s r e s u l t = new R e f a c t o r i n g S t a t u s ( ) ; r e s u l t. merge ( c h e c k I n i t i a l C o n d i t i o n s ( ) ) ; i f (! r e s u l t. h asfatalerror ( ) ) { r e s u l t. merge ( checkfinalconditions ( ) ) ; } pm. done ( ) ; return r e s u l t ; } public abstract R e f a c t o r i n g S t a t u s c h e c k I n i t i a l C o n d i t i o n s ( ) ; } public abstract Refac toringst atus checkfinalconditions ( ) ; Mirko Stocker Eclipse Architecture and Patterns / 64

51 LTK Applied code transformations with change objects After all preconditions have been checked AND no errors are detected, LTK calls createchange(iprogressmonitor) on the refactoring createchange yields a Change object Change is used by LTK to genereate a change preview (diff) and to apply the recorded change to the workspace There are different kinds of change objects, e. g.: TextChange: applies a TextEdit to a document MoveResourceChange: used to move a resource UndoTextFileChange: to perform the reverse of a TextFileChange NullChange: refactoring change that does nothing Most refactorings require several changes Changes can be composed to trees of changes Problem: How can we treat these compositions and the individual changes uniformly? Mirko Stocker Eclipse Architecture and Patterns / 64

52 LTK Composite Pattern Compose object into tree structures to represent part/whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

53 LTK GoF Patterns applied: Composite pattern Change perform(iprogressmonitor): Change dispose() 0..* Child fedit: TextEdit TextFileChange perform(iprogressmonitor): Change dispose() CompositeChange changes: List add(change) addall(change[]) perform(iprogressmonitor) dispose() 1 Parent Figure: Composite pattern with LTK s change objects Mirko Stocker Eclipse Architecture and Patterns / 64

54 LTK Participants A refactoring participant can participate in the condition checking and change creation of a refactoring processor Refactorings that change several source files may have impact on some of the other integrated tools Examples: Renaming classes in the Plug-in Development Environment (PDE) Setting breakpoints in a debugger Consistency of C function declarations and their JNI bindings Mirko Stocker Eclipse Architecture and Patterns / 64

55 LTK Refactoring History Refactorings that are intended to participate in the refactoring history and scripting service must implement a descriptor and a contribution object Two scenarios for scriptable refactorings: Reapplying refactorings on a previous version of a code base Composing large and complex refactorings from smaller refactorings Mirko Stocker Eclipse Architecture and Patterns / 64

56 LTK Scriptable Refactorings <?xml version= " 1.0 " encoding= "UTF 8"?> <session version= " 1.0 " > < r e f a c t o r i n g comment= " E x t r a c t i n t e r f a c e f o r class &apos ; Foo&apos ; " d e s c r i p t i o n = " E x t r a c t I n t e r f a c e Refactoring " filename= " f i l e : / tmp / TestLTK / t e s t. cpp " f l a g s = " 4 " name= " IFoo " p r o j e c t = " TestLTK " i d = " ch. hsr. E x t r a c t I n t e r f a c e R e f a c t o r i n g " replace=" t r u e " s e l e c t i o n = " 8,3 " / > < / session> Problem: How can we capture refactoring states externally so that they can be applied to code without user interaction? Mirko Stocker Eclipse Architecture and Patterns / 64

57 LTK Memento Pattern Capture and externalize an objects internal state without violating its encapsulation, so that the object can be returned to this state later. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

58 LTK GoF Patterns applied: Memento LTK s RefactoringDescriptor: Memento that captures the properties of a specific refactoring instance Contains unique refactoring ID, timestamp, description and further refactoring-specific data like selection, file path, chosen user arguments: protected R e f a c t o r i n g D e s c r i p t o r g e t R e f a c t o r i n g D e s c r i p t o r ( ) { Map< String, String > args = new HashMap< String, String > ( ) ; args. put ( CRefactoringDescriptor. FILE_NAME, filename ) ; args. put ( CRefactoringDescriptor. SELECTION, selectedregion. g e t O f f s e t ( ) + ", " + selectedregion. getlength ( ) ) ; args. put ( E x t r a c t C o n s t a n t R e f a c t o r i n g D e s c r i p t o r.name, i n f o. getname ( ) ) ; / / more r e f a c t o r i n g s p e c i f i c i n f o r m a t i o n return new E x t r a c t C o n s t a n t R e f a c t o r i n g D e s c r i p t o r ( p r o j e c t. g e t P r o j e c t ( ). getname ( ), " E x t r a c t Constant Refactoring ", " Create constant f o r " + t a r g e t. getrawsignature ( ), args ) ; } Mirko Stocker Eclipse Architecture and Patterns / 64

59 Outline 1 Eclipse Overview 2 SWT and JFace 3 OSGi Bundles and Eclipse Plug-ins 4 Eclipse Core Patterns 5 Language Toolkit LTK Patterns 6 C/C++ Development Tooling Patterns Mirko Stocker Eclipse Architecture and Patterns / 64

60 CDT Overview First release with Eclipse 2.0 in April 2003 Fully functional C and C++ IDE based on the Eclipse platform Features: Support for project creation and managed build for various toolchains (e. g., GCC, Clang) Standard make build Source navigation Type hierarchy, call graph, include browser, macro definition browser Code editor with syntax highlighting, folding and hyperlink navigation Source code refactoring and code generation Visual debugging tools, including memory, registers, and disassembly viewers Mirko Stocker Eclipse Architecture and Patterns / 64

61 CDT CDT s AST nodes In C/C++, a translation unit (TU) is a source file with all included headers The root node of CDT s abstract syntax tree (AST) has the type org.eclipse.cdt.core.dom.ast.iasttranslationunit In CDT, C and C++ AST nodes are separated (e. g., IASTUnaryExpression and ICPPASTUnaryExpression); C has ~60, C++ ~90 nodes org.eclipse.cdt.core.dom.ast.iastnode is the parent interface of all nodes in the AST The AST can be traversed by calling IASTNode s getparent() and getchildren() methods Calling child/parent methods can get cumbersome We want to decouple the data from the operations that process the data Solution: visitor pattern Mirko Stocker Eclipse Architecture and Patterns / 64

62 CDT Example of an AST Figure: Example of CDT s abstract syntax tree (AST) Mirko Stocker Eclipse Architecture and Patterns / 64

63 CDT Visitor Pattern Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates. Figure: Source Wikipedia Mirko Stocker Eclipse Architecture and Patterns / 64

64 CDT GoF Patterns applied: Visitor To create a visitor, subclass from ASTVisitor ASTVisitor has overloaded visit methods for each node type Each node class has an accept(astvisitor) method (defined in IASTNode) calls visit(this) Example visitor to collect all names: class ASTNameVisitor extends ASTVisitor { List<IASTName> names = new ArrayList<IASTName>(); { this.shouldvisitnames = true; public int visit(iastname name) { names.add(name); return PROCESS_CONTINUE; } } Mirko Stocker Eclipse Architecture and Patterns / 64

65 Bibliography I Erich Gamma and Kent Beck. Contributing to Eclipse: Principles, Patterns, and Plug-Ins. Addison Wesley, Marc Teufel and Dr. Jonas Helming. Eclipse 4: Rich Clients mit dem Eclipse SDK 4.2. entwickler.press, Ilya Shinkarenko. Design Patterns Used in Eclipse Bangalore, Eclipse Summit India Neil Bartlett. A Comparison of Eclipse Extensions and OSGi Services http: // Mirko Stocker Eclipse Architecture and Patterns / 64

66 Bibliography II Adapter Pattern Chris Aniszczyk. Ecipse Juno Released for Friends ecipse-juno-released-for-friends Tobias Widmer. Unleashing the Power of Refactoring. Eclipse Corner Articles, Michael Petito. Eclipse Refactoring. EE564, Various authors. The Architecture of Open Source Applications. Mirko Stocker Eclipse Architecture and Patterns / 64