Shows how to rewrite Java source code

ASTRewriter.java

ICompilationUnit compilationUnit = null; // TODO - initialize
ICoreRunnable rewriteRunnable = new ICoreRunnable() {
	
	@Override
	public void run(IProgressMonitor monitor) throws CoreException {
		
		// TODO - create sub-monitors for different steps.
		
		ICompilationUnit workingCopy = compilationUnit.getWorkingCopy(monitor);
		try {
			Document document = new Document(workingCopy.getSource());
			// Get the compilation unit for traversing AST
			ASTParser parser = ASTParser.newParser(AST.JLS8);
			parser.setSource(workingCopy);
			parser.setResolveBindings(true);

			CompilationUnit compilationUnit = (CompilationUnit) parser.createAST(null);
			ASTRewrite rewrite = ASTRewrite.create(compilationUnit.getAST());
			
		    // Record modification - to be later written with ASTRewrite
		    compilationUnit.recordModifications();
		    

		    // Example of annotating and deprecating a method or a field
			IMember iMember = null; // TODO - initialize
		    String source = iMember.getCompilationUnit().getSource();
			String iMemberSource = iMember.getSource();
			int memberIndex = source.indexOf(iMemberSource);
			NodeFinder nodeFinder = new NodeFinder(compilationUnit.getRoot(), memberIndex, iMemberSource.length());
			ASTNode coveredNode = nodeFinder.getCoveredNode();
			if (coveredNode instanceof MethodDeclaration && iMember instanceof IMethod) {
				String cName = ((MethodDeclaration) coveredNode).getName().getIdentifier();
				String iName = iMember.getElementName();
				if (cName.equals(iName)) {
		            ListRewrite listRewrite = rewrite.getListRewrite(coveredNode, MethodDeclaration.MODIFIERS2_PROPERTY);
				    
				    // Create the annotation					            
				    MarkerAnnotation annotation = compilationUnit.getAST().newMarkerAnnotation();
				    annotation.setTypeName(coveredNode.getAST().newName("Deprecated"));
		            listRewrite.insertAt(annotation, 0, null);
		            
				    ASTNode comment = rewrite.createStringPlaceholder("/*\n * Some comment\n */"+System.lineSeparator(), ASTNode.BLOCK_COMMENT);
		            listRewrite.insertAt(comment, 0, null);
		            
				}
			} else if (coveredNode instanceof FieldDeclaration && iMember instanceof IField) {
				String[] cName = {null};
				
				((FieldDeclaration) coveredNode).accept(new ASTVisitor() {
															
					public boolean visit(VariableDeclarationFragment vdf) {
						if (cName[0] == null) {
							cName[0] = vdf.getName().getIdentifier();
						}
						return super.visit(vdf);
					}
					
				});
				
				String iName = iMember.getElementName();
				if (iName.equals(cName[0])) {
		            ListRewrite listRewrite = rewrite.getListRewrite(coveredNode, FieldDeclaration.MODIFIERS2_PROPERTY);
				    
				    // Create the annotation					            
				    MarkerAnnotation annotation = compilationUnit.getAST().newMarkerAnnotation();
				    annotation.setTypeName(coveredNode.getAST().newName("Deprecated"));
		            listRewrite.insertAt(annotation, 0, null);
		            
				    ASTNode comment = rewrite.createStringPlaceholder("/*\n * Some comment\n */"+System.lineSeparator(), ASTNode.BLOCK_COMMENT);
		            listRewrite.insertAt(comment, 0, null);
		            
				}
			}								
			
			TextEdit edits = rewrite.rewriteAST(document, workingCopy.getJavaProject().getOptions(true));
			edits.apply(document);
			String newSource = document.get();
			workingCopy.getBuffer().setContents(newSource);
			workingCopy.commitWorkingCopy(false, monitor);
		} catch (CoreException e) {
			throw e;
		} catch (Exception e) {
			throw new CoreException(new Status(IStatus.ERROR, "plug-in id here", "Error message here", e));
		} finally {
			workingCopy.discardWorkingCopy();
		}
	}
};

ResourcesPlugin.getWorkspace().run(
		rewriteRunnable, 
		ResourcesPlugin.getWorkspace().getRoot(), 
		IWorkspace.AVOID_UPDATE, 
		monitor);