CUCache.java

package blade.migrate.core;

import java.io.File;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;

import org.eclipse.jdt.core.JavaCore;
import org.eclipse.jdt.core.dom.AST;
import org.eclipse.jdt.core.dom.ASTParser;
import org.eclipse.jdt.core.dom.CompilationUnit;

public class CUCache {

	private static final Map<File, WeakReference<CompilationUnit>> _map = new WeakHashMap<>();

	public static CompilationUnit getCU(File file, char[] javaSource) {
		synchronized (_map) {
			WeakReference<CompilationUnit> astRef = _map.get(file);

			if (astRef == null || astRef.get() == null) {
				final CompilationUnit newAst = createCompilationUnit(file.getName(), javaSource);

				_map.put(file, new WeakReference<CompilationUnit>(newAst));

				return newAst;
			}
			else {
				return astRef.get();
			}
		}
	}

	public static void unget(File file) {
		synchronized (_map) {
			_map.remove(file);
		}
	}

	@SuppressWarnings("unchecked")
	private static CompilationUnit createCompilationUnit(String unitName, char[] javaSource) {
		ASTParser parser = ASTParser.newParser(AST.JLS8);

		Map<String, String> options = JavaCore.getOptions();

		JavaCore.setComplianceOptions(JavaCore.VERSION_1_6, options);

		parser.setCompilerOptions(options);

		//setUnitName for resolve bindings
		parser.setUnitName(unitName);

		String[] sources = { "" };
		String[] classpath = { "" };
		//setEnvironment for resolve bindings even if the args is empty
		parser.setEnvironment(classpath, sources, new String[] { "UTF-8" }, true);

		parser.setResolveBindings(true);
		parser.setStatementsRecovery(true);
		parser.setBindingsRecovery(true);
		parser.setSource(javaSource);
		parser.setIgnoreMethodBodies(false);

		return (CompilationUnit)parser.createAST(null);
	}
}