Parsing java code and adding methods with AST (JDT Eclipse)

Question

I have a .java file which contains a class. I want to add a method to that class but I can't find a real useful "HOWTO" or examples around. I'm using Eclipse and its JDT plugin for AST. I tried a code that creates an ICompilationUnit from a project

IProject project = ResourcesPlugin.getWorkspace().getRoot().getProject("ProjName");
IJavaProject javaProject = JavaCore.create(project);
IPackageFragment package1 = javaProject.getPackageFragments()[0];
ICompilationUnit unit = package1.getCompilationUnits()[0];

then add a method with astrewrite. But it seems to work only if I run all as a Plugin Project and not a simple Java Application. I need to write an application in java that "simply" parse a java file and adds method to its class. What I supposed to do is: 1) Create an ICompilationUnit directly form the .java file I want to parse (eventually located in my own project's directory) 2) Using another way

Both case I can't go further. Anyone can help me?

alextsil · Accepted Answer · 2015-12-09 11:38:23Z

When you need to make a change by adding something to the compilation unit, you will have to use the functions provided by CompilationUnit to create new nodes.

To add a method to "unit" you will have to :

Create a MethodDeclaration node using your compilation unit :

MethodDeclaration md = unit.getAST().newMethodDeclaration();

Customize this method declaration to your requirements :

md.setName( unit.getAST().newSimpleName( "newMethod" ) ); md.setBody( unit.getAST().newBlock() );

this will produce : void newMethod() {}

Obtain the TypeBinding from "unit" :

TypeDeclaration typeDeclaration = ( TypeDeclaration )unit.types().get( 0 );

Add your newly created MethodDeclaration to the body declarations :

typeDeclaration.bodyDeclarations().add( md );

There's a method called getMethods() on TypeDeclaration but it doesn't return a live list of MethodDeclarations, therefore you can't modify that directly.

RokL · Accepted Answer · 2012-12-07 12:54:38Z

0

It's really easy to read the source file as text and replace the last } with the method declaration plus }. Obviously this doesn't work if someone puts multiple top-level classes in one file (which is extremely rare and I doubt you'll have a problem with that).

answered Dec 7, 2012 at 12:54

RokL

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1 Comment

user1847118 Over a year ago

I need to use AST (or similar) because I should not be forced to insert methods at the end of the code. For exemple it may be necessary to put the new method inside another already existing method. I proposed the simple goal in this post for learning just how to make it possibile with AST and then try by myself to use these informations for doing something more complicated.

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