Eclipse JDT AST：如何将生成的AST写入java文件？

Question

I am currently working with eclipse AST to generate source code. Other than in most examples, I am generating the source code from scratch and in a stand-alone application, as opposed to an eclipse plug-in.

When read in from an ASTParser, you can activate modifications by calling recordModifications() , but this doesn't work when the AST is created from scratch, eg by calling newCompilationUnit() .

Consequently, writing the source to file via a Document and TextEdit is not possible - there is an exception saying that modification recording hasn't been enabled.
Any experiences in generating AST from scratch and writing to file? Thanks!

Answer 1

Why not create the file first, then generate an AST from it, like this:

ICompilationUnit unit = JavaCore.createCompilationUnitFrom(file);
ASTParser parser = ASTParser.newParser(AST.JLS3);
parser.setKind(ASTParser.K_COMPILATION_UNIT);
parser.setResolveBindings(true);
parser.setSource(unit);
// Parse the source code and generate an AST.
CompilationUnit ast = (CompilationUnit) parser.createAST(null);

If the file is newly created and blank, then presumably the AST will be empty, You can then replace the root of the ast object and write it to the file. Also, if you are not tied to Eclipse, you could just do the same thing using the JSR199 standard and write that AST to a file in the normal way. See here for an introduction.

Answer 2

Thank you for your suggestions! In the meantime I found a way to emit the source code via an internal class "ASTFlattener", which creates a String representation of an AST. This works pretty well for me....

Answer 3

I've just been trying to find the answer to the same question. Based on the answers above, the most elegant solution I've found so far looks like:

ASTParser parser = ASTParser.newParser(AST.JLS4);
parser.setCompilerOptions(....);

Document document = new Document("");
parser.setSource(document.get().toCharArray());
CompilationUnit unit = (CompilationUnit)parser.createAST(null);
unit.recordModifications();

TextEdit edits = unit.rewrite(document, null);
edits.apply(document);

// now write document.get() to file

Answer 4

If you're generating the source from scratch, maybe you could write the minimal source able to be parsed to a temporary file, apply your modifications to the Ast, then write it back to that file as a text edit as you do otherwise. Then read the source. You could then transfer this to wherever you want.

There is probably a more elegant solution, but this may work.

Answer 5

After created a compilation unit from AST I'm doing:

AST ast = AST.newAST(AST.JLS4);    
CompilationUnit unit = ast.newCompilationUnit();

... fill Compilation Unit and then ...

package.createCompilationUnit(className + ".java", unit.toString(), true, null);

Where:
package = IPackageFragment
className = String (generated class name)
unit => CompilationUnit ast
true => force replace
null => progress monitor